Categories
WW2 US Prototypes

75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis

United States of America (1942-1943)
Tank Destroyer – 1 Converted

Created in January 1943 as a proof of concept, the 75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis was an experimental American light tank later designated as a tank destroyer. As the vehicle’s name would suggest, this project involved mounting the 75 mm Gun M3 in the turret of the 75 mm Howitzer Motor Carriage (HMC) M8. While initial testing at Aberdeen Proving Ground was promising, the tank destroyer’s numerous flaws were discovered during further testing by the Armored Force Board and the Tank Destroyer Board. As a result, the entire project was canceled in June 1943.

The 75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis in January 1943 at Aberdeen Proving Ground. ‘M8A1’ was Aberdeen Proving Ground’s unofficial designation for the vehicle. Source: Can Openers

Small Gun Problems

A destroyed M3 ‘Stuart’ of the British 7th Armoured Division in North Africa. Source: rommelsriposte.com

The most numerous American light tank available at the beginning of World War 2 was the M3 Light Tank, also known as the ‘Stuart.’ While the M3 was relatively reliable and agile, it lacked armor protection and firepower. The tank’s lack of armor was not unexpected, of course. To remain mobile, light tanks have to be, as the name would imply, light. In part, this is achieved by keeping armor to a minimum. The tank’s lack of firepower, however, was a much larger issue. The 37 mm Gun M5 of the ‘Stuart’ could handle lightly-armored targets, such as the Panzer II and early Panzer III, without many issues. However, combat in North Africa in late 1942 illustrated the obsolescence of the 37 mm gun rather clearly. Up-gunned and more armored tanks, especially Panzer IVs, were appearing more frequently and were proving to be much more resistant to 37 mm guns than earlier German tanks. In a frontal engagement, the M3 ‘Stuart’ stood almost no chance against the improved armor of contemporary German Panzers. In contrast, the larger 75 mm M3 gun used by the M3 and M4 Medium Tanks was still considered an effective anti-tank weapon despite the appearance of heavily armored German tanks. Therefore, in an attempt to increase the firepower of their previously poorly-armed light tanks, the United States began to pursue light tank designs mounting a 75 mm gun in a fully traversable turret.

The M7 Medium/Light Tank

The first attempt to create a light tank mounting a 75 mm gun began in July 1942 as a further development of the Light Tank T7. The T7 project was conceived in January 1941 as an improved replacement for the M2A4 light tank then in service. The tank was to feature frontal armor 1.5 inches (38.1 mm) thick, a vertically-stabilized 37 mm gun M6, a weight of 14 tons (12.7 tonnes), and a powerful engine, amid a slew of other improvements. However, by July 1942, the Armored Force requested that the 37 mm gun be replaced by a 75 mm gun to increase the firepower of the T7. The British 6-pounder (57 mm) anti-tank gun was also considered as a potential main armament but was dropped in favor of the 75 mm. This variant of the T7 was designated as the T7E5 and it featured the aforementioned 75 mm gun, a 450 hp engine, and cast armor up to 2.5 in (63.5 mm) thick.

The third production M7 medium tank. The vehicle’s visual similarity to the later ‘Stuart’ light tanks and the M4 Sherman is apparent. Source: Wikimedia

However, as a result of all the improvements made to the T7E5 design, this ‘light’ tank now topped the scales at 27 tons (24.5 tonnes), almost twice its predicted weight of 14 tons (12.7 tonnes). Now falling outside the weight requirements of a light tank, the T7E5 was standardized in August 1942 as Medium Tank M7. However, tests conducted in late 1942 revealed that the M7 was inferior to the M4 Sherman. Both vehicles were effectively equivalent in firepower and mobility, though the M4 offered more effective armor protection than the M7. The T7 project was promptly terminated and eventually declared obsolete in January 1944.

The T21 Light Tank

Despite the ongoing failure of the M7, the Ordinance Department and Armored Board were unperturbed. They wanted an up-gunned light tank design even if the M7 was a failure. In August 1942, they held a conference at Fort Knox to discuss the specifications of their ‘ideal light tank.’ As a result of the conference, a design based on the Medium Tank T20 was proposed. This light tank design would feature the 75 mm gun M3 (or a more powerful gun if the chassis could support it), armor capable of stopping .50 caliber armor-piercing rounds, and the suspension of the M7 medium tank.

No mock-up of the Light Tank T21 was ever produced. However, the vehicle bore a general resemblance to the Medium Tank T20, the mock-up of which is pictured here. Source: Stuart

By February 1943, the vehicle had been designated as Light Tank T21 and its specifications had been further refined. The predicted weight of the T21 was 23.5 tons (21.3 tonnes) and the vehicle was to be fitted with a 76 mm gun. A maximum top speed of 35 mph (56.3 km/h) and a cruising speed of 25 mph (40.2 km/h) were estimated. The vehicle’s impressive mobility was a result of keeping armor to a minimum, with the thickest plates on the tank being just 1.125 in (28.6 mm) thick. While the T21 promised to be an agile and well-armed light tank, Fort Knox had their worries. When final drawings of the tank were submitted in March 1943, the predicted weight of the T21 had increased by another 2 tons (1.8 tonnes). Afraid of making the same mistake twice, Fort Knox shortly canceled the T21 light tank project before months of wasted time and money could result in another ‘obese’ ‘light’ tank.

Development

Previous attempts to develop a successful light tank design featuring a 75 mm main gun were not very fruitful. The M7’s hefty weight made it unfit for its role and the T21 was in danger of following the same path. The experience in North Africa illustrated a desperate need for light tanks mounting larger guns, so an expedient light tank design was pursued. This expedient design was to be based on the chassis of the M3 or M5 light tank and mount a 75 mm gun in a turret. The usage of a reliable, standardized chassis would help keep the weight of the vehicle down.

A diagram of an M8 Howitzer Motor Carriage. The vehicle mounted a new howitzer-armed turret on the modified chassis of a M5 Light Tank. Source: lonesentry.com

To test if it was even possible to mount and fire the 75 mm gun M3 from the chassis of a Light Tank M3 or M5, the order was given in late 1942 to mount the 75 mm gun M3 on the chassis of the Howitzer Motor Carriage M8. The M8 HMC used the same chassis as the M5 and was chosen because its larger turret ring and open-top could accommodate the 75 mm gun much more comfortably than the smaller, fully-enclosed turret of a standard M5.

The 75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8. The vehicle was never given a shorter official designation, so both the Tank Destroyer Board and the Armored Force Board used their own nicknames for it. Source: warspot.net

For the conversion, a few modifications were made to both turret and gun. For the turret, the anti-aircraft machine gun and the small roof plate it was mounted on were removed to make more room for the turret crew. A hole was cut into the front of the turret to make room for the larger gun. However, this new opening was covered by the mantlet, meaning it was not visible in photographs taken of the vehicle. To ensure compatibility between the 75 mm gun and the recoil mechanism of the M8, a special adaptor was created and attached to the recoil system. However, this device prevented the breech block from closing automatically, slowing the gun’s rate of fire.

A view inside the turret of a restored M8 HMC. Note the rear roof plate and .50 caliber machine gun, both of which were removed on the converted M8 to improve crew comfort. Source: author’s own

With these modifications made and the 75 mm M3 mounted properly in its turret, the modified M8 HMC was delivered to Aberdeen Proving Ground on 30th January 1943 for trials. Before testing, the designation ‘M8A1’ was stenciled on the front corner of the vehicle’s hull. While the name ‘M8A1’ or ‘M8A1 Gun Motor Carriage’ has remained a common misnomer for the vehicle, it was never official.

The ‘M8A1’ at Aberdeen Proving Ground. Source: Can Openers

Tank Destroyer Board Testing

The trials at Aberdeen were so successful that a representative requested that the vehicle be delivered to the Tank Destroyer Board to be tested for service as a tank destroyer. In February 1943, the vehicle was tested by the Tank Destroyer Board to further evaluate its performance and compared to two standardized tank destroyers, the 3 in Gun Motor Carriage M10 and the 75 mm Gun Motor Carriage M3. During these tests, the vehicle was called ‘M8 Gun Motor Carriage’ by the Board.

From left to right, Gun Motor Carriages ‘M8’, M10, and M3. Source: Can Openers

The test results were mixed, with some positive aspects of the vehicle noted:

  • Cross-country performance was superior to that of the M3 GMC and road performance exceeded that of the M10 GMC.
  • Vehicle stability and handling were unchanged despite the larger gun.
  • Braking and accelerating capabilities were excellent.
  • The vehicle weighed 15 tons (13.6 tonnes), allowing it to use bridges and roads that the 30.5 ton (27.7 tonne) M10 GMC could not.

However, many shortcomings of the vehicle were also identified:

  • The limited turret ring size decreased crew comfort and resulted in crew injuries when driving over rough terrain or when making short, jerky movements.
  • The driver had limited vision.
  • The vehicle had a negligible advantage in cross-country performance compared to the M10 GMC and no superiority in road performance compared to the M3 GMC.
  • Only 44 rounds of 75 mm ammunition could be carried, which was considered inadequate.
  • Due to the fragility of the traverse mechanism, the gun had to be fixed over the rear of the hull when on the move. This decreased the vehicle’s responsiveness when entering combat.
  • The engines required 80 octane fuel, a fuel type not used by the M10 GMC or M3 GMC. This complicated logistics.
  • Most notably, the vehicle was generally inferior to the 76 mm Gun Motor Carriage T70 (M18), production of which was on track to begin within a few months.
“M8 GMC” (1943) M3 GMC (1941) M10 GMC (1942) M18 GMC (1943)
Weight 15.1 tons (13.7 tonnes) 10.0 tons (9.07 tonnes) 33.0 tons (29.9 tonnes) 18.78 tons (17.04 tonnes)
Engine & Horsepower 2x Cadillac Series 42
(220 hp)
White 160 (147 hp) GM Series 71 (375 hp) Continental R-975 C1
(350 hp)
Power/Weight Ratio 14.56 hp/ton
(16.06 hp/tonne)
14.70 hp/ton
(16.21 hp/tonne)
11.36 hp/ton
(12.54 hp/tonne)
18.64 hp/ton
(20.54 hp/tonne)
Max Speed 46 mph (74 km/h) 45 mph (72 km/h) 30 mph (48 km/h) 45 mph (72 km/h)
Fuel Capacity 178 gal (674 L) 60 gal (227 L) 167 gal (632 L) 165 gal (625 L)
Cruising Range 175 mi (282 km) 200 mi (322 km) 140 mi (225 km) 100 mi (161 km)
Suspension Vertical volute spring Leaf spring (front)
Vertical volute spring (rear)
Vertical volute spring Torsion bar
Height 90.5 in (2.30 m) 98.625 in (2.51 m) 97.5 in (2.48 m) 93.25 in (sans .50 cal)
(2.37 m)
Main Armament 75 mm Gun M3 75 mm Gun M1897A4 3 in Gun M7 76 mm Gun M1A1
Ammo Stowage
(Main Gun)
44 rounds 59 rounds 54 rounds 45 rounds
Horizontal Traverse
Limits
±180° -19° / +21° ±180° ±180°
Turret Ring Size 54.4 in (138 cm) n/a 69 in (175 cm) 69 in (175 cm)
Frontal Armor 1.125 – 1.75 in
(28.6 – 44.5 mm)
0.5 – 0.625 in
(12.7 – 15.9 mm)
1.5 – 2.25 in
(38.1 – 57.2 mm)
0.5 – 0.75 in
(12.7 – 19.1 mm)

*Data from afvdb.50megs.com and Can Openers

The Tank Destroyer Board concluded that the ‘M8 GMC’ was not fit for service, even as an expedient tank destroyer. By the time the vehicle’s many problems could be corrected and mass production could begin, the TD Board reasoned, the far superior T70 (M18) GMC would be ready for production.

In this photograph, the ‘M8 GMC’ has its gun locked over the rear of the hull in its ‘travel’ configuration. This was identified as a flaw by the Tank Destroyer Board, as the vehicle would be slow to respond to a combat situation. Source: Can Openers

Armored Force Testing

The ‘Motor Carriage M8 with 75 mm Tank Gun, M3’ arrives at Fort Knox to be examined by the Armored Force Board after the Tank Destroyer Board had run their course. Source: warspot.net

The Tank Destroyer Board was not the only group of evaluators to get their hands on the modified M8. The Armored Force also got their hands on the vehicle and performed their own tests to determine if the vehicle was suitable for service. Additionally, they also examined if there was a field requirement for such a vehicle. Unlike Aberdeen and the Tank Destroyer Board, the Armored Force did not give the vehicle a shortened name.

The Armored Force was able to compile a similar list of the modified M8’s faults:

  • Crew size was decreased from 5 to 4 when compared to a standard M8 HMC.
  • Firing, loading, and traversing the gun was made unnecessarily difficult as a result of poor ergonomics and mechanical failure.
  • The M8’s 75 mm gun M3 was not as accurate as the Medium Tank M4’s. This was due to the M8’s usage of a modified howitzer gun mount.
  • The turret was extremely off-balance.
  • Internal stowage facilities were disappointing.
  • No roof protection or anti-air capabilities.

The Armored Force bluntly concluded their assessment of the vehicle by stating that, as a result of multiple severe deficiencies, they considered the ‘M8 GMC’ to be entirely unfit for service.

However, as mentioned earlier, the Armored Force also sought to determine if there was any purpose to such a design. They reasoned that a light tank armed with a high-velocity 75 mm gun would be a vital asset, offering accurate and powerful fire from a maneuverable platform. As a result, they requested that the development and production of the Light Tank T24 (M24) be accelerated. The T24 was, of course, yet another light tank project to mount a 75 mm gun in the turret of a light tank. However, unlike its forefathers, the T24 would become a successful design, remaining firmly in the weight class of a light tank.

Coming to the same conclusion as the Tank Destroyer Board, the Armored Force requested that all development and consideration of the 75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis be halted. Faced with two very negative reports, the Ordinance Committee was left with a very easy decision. In June 1943, they requested that the project be scrapped. Later that same month, the request was approved. The modified M8 was sent back to Aberdeen Proving Ground and converted back into a regular M8 HMC.

Design

Firepower

Unsurprisingly, considering its extended designation, this vehicle was armed solely with the 75 mm gun M3. No machine guns were provided for anti-infantry or anti-aircraft duties. An unfortunate result of the modification process was that the gun breech no longer operated semi-automatically, decreasing the gun’s rate of fire. Another consequence of the expedient conversion was a comparative loss in accuracy. This was due to the use of a modified howitzer gun mount instead of a dedicated anti-tank gun mount. Firing tests between the modified M8 and an M4 ‘Sherman’ revealed that the M8’s accuracy was directly inferior to the M4’s.

A 75 mm Gun M3. Pictured here with the Mount M34, this cannon was mounted to early M4 Shermans. Source: theshermantank.com

The M3 gun could fire M72 Armor Piercing, M61 Armor Piercing Capped, M48 High Explosive, and M64 White Phosphorus rounds. The vehicle could carry up to 44 rounds of ammunition, slightly less than a standard M8 HMC’s 46 rounds of stowage.

A diagram of a standard M8 HMC’s ammunition stowage layout. Source: afvdb.50megs.com

>
A photograph of the bulkhead racks of the ‘M8 GMC.’ Source: Can Openers

The 75 mm gun was a significant upgrade over the 37 mm gun because it performed better against both soft and hard targets. Firing M61 APC rounds, the 75 mm M3 gun could penetrate a maximum of 2.4 in (60 mm) of rolled homogeneous armor (RHA) at a range of 500 yds (457 m) and a 30º angle. In comparison, the 37 mm M6 gun, firing its equivalent M51 APC round, could only penetrate 2.1 in (53 mm) of RHA under the same conditions. It should also be noted that the 75 mm armor-piercing shell kept more of its penetration at range and performed better against angled armor when compared to the 37 mm armor-piercing shell. Additionally, the 75 mm gun had an extremely effective HE round. The 75 mm M48 HE shell had a hefty 1.49 lbs (676 g) of TNT filler, while the equivalent 37 mm M63 HE shell had just 0.085 lbs (39 g) of TNT filler.

Armor-Piercing High-Explosive
37 mm M51 75 mm M67 37 mm M63 75 mm M48
Penetration @ 30° &
500 yd (457 m)
2.1 in (53 mm) 2.4 in (60 mm) Explosive Filler 0.085 lbs (38.6 g) 1.49 lbs (676 g)
Velocity 2,900 ft/s (884 m/s) 2,030 ft/s (619 m/s) Velocity 2,600 ft/s (792 m/s) 1,520 ft/s (463 m/s)
Projectile Weight 1.92 lbs (0.87 kg) 14.96 lbs (6.79 kg) Projectile Weight 1.61 lbs (0.73 kg) 14.7 lbs (6.67 kg)

Compared to the 37 mm guns of the M2, M3, and M5 light tanks, the 75 mm gun of the ‘M8 GMC’ had superior armor penetration capabilities and a much more powerful HE shell. With its powerful gun, the ‘M8 GMC’ would have been able to engage and destroy both armored and soft targets with ease.

Protection

Armor-wise, the vehicle was essentially unmodified. It retained the same armor profile as a standard M8 HMC. The only small armor modification was made to the frontal turret armor. A hole had to be cut into the front of the turret to make room for the larger 75 mm M3 gun. When viewing the vehicle from the front, this created an extremely small area behind the upper part of the gun mantlet that had no additional turret armor behind it. However, this minute weakness was so inconsequential that, for all intents and purposes, the modified M8’s armor was left untouched.


An overhead view of the vehicle’s turret. Note the hole behind the gun mantlet. Source: Can Openers

Mobility

Similarly, the mobility of the ‘M8 GMC’ was identical to that of a standard M8 HMC. Both vehicles shared the same vertical volute spring suspension (VVSS), ‘Hydramatic’ automatic transmission, and twin Cadillac Series 42 gasoline engines which produced a net 220 hp @ 3,400 rpm. Fuel capacity and cruising range were 178 gal (674 l) and 175 mi (282 km), respectively. Despite the added weight of the larger gun, the ‘M8 GMC’ had impressive mobility, with the vehicle performing well both on and off road.

A diagram of a standard M8 HMC showing most of its internal workings. Source: afvdb50megs.com

Crew and Ergonomics

For the modified M8, crew comfort and quantity were a point of contention. Standard M8 HMCs had a crew of four. The commander and gunner sat in the turret while the driver and assistant driver were in the hull. The ‘M8 GMC’ was no exception, with four seats for the four crewmembers. Both the Armored Force Board and the Tank Destroyer Board agreed that the vehicle’s two-man turret was a serious tactical shortcoming. Requiring the commander to load the gun in addition to his commanding duties was too overwhelming, they reasoned. However, while the Armored Force Board was content to test the vehicle as-is, the Tank Destroyer Board attempted to remedy this issue by adding an extra crewmember. Adding a dedicated loader to the turret would increase the vehicle’s effectiveness in combat, they argued. Executing this plan, however, was much easier said than done.


The Tank Destroyer Board tried multiple three-man turret crew configurations. The two pictured above were considered unsatisfactory. Source: Can Openers

Multiple changes were made to the vehicle in an attempt to squeeze in an extra crewmember. The gunner assumed a standing position made possible by removing parts of the hull floor. However, his arrangement was rather uncomfortable due to the close proximity of the traversing handwheels and recoil guard. Additionally, the gunner could only traverse the gun 90° to the left and 45° to the right. At first, the Tank Destroyer Board attempted to position the commander to the left of the gun, as seen in the above left photograph. However, this crowded the loader and interfered with his duties. The commander was moved to his ‘traditional’ location behind the gunner, which gave the loader enough space to effectively load the gun. At the end of their report, the Tank Destroyer Board concluded that placing three crewmembers within the turret of the ‘M8 GMC’ would inevitably have a negative impact on crew safety and efficiency.


A photograph of the gunner’s position. Source: Can Openers

Conclusion

The ‘M8 GMC,’ ‘M8A1,’ or even the long-winded 75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis, was a failure. Although the vehicle performed quite well during its initial trials, numerous serious flaws were eventually discovered. A two-man turret, mediocre accuracy, unsatisfactory ammunition stowage, poor crew ergonomics, and, most importantly, general inferiority plagued the vehicle. Taking the time to perfect a flawed, expedient tank destroyer when a superior light tank, the M24 ‘Chaffee,’ and a superior tank destroyer, M18 ‘Hellcat,’ were well into development would be wasteful. Although promising on paper, the ‘M8 GMC’ simply had no role to fill.


An illustration of the 75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis by Pavel Alexe. Original M8 ‘Scott’ illustration by Tank Encyclopedia’s own David Bocquelet.

75 mm Gun M3 on 75 mm Howitzer Motor Carriage M8 Chassis Specifications

Dimensions (L x W x approx. H) 14’ 6.75” x 7’ 4.5” x 7’ 6.5”
4.44 x 2.25 x 2.30 m
Weight 15.1 tons
13.7 tonnes
Armament 75 mm Gun M3 (44 rounds)
Armor Turret
Front: 38 mm
Gun shield: 38 mm
Side: 25 mm
Rear: 25 mm
Hull
Front: 28.6-44.5 mm
Side: 25-28.6 mm
Rear: 25 mm
Roof: 13 mm
Floor: 9.5-13 mm
Crew 4 (driver, assistant driver, gunner, commander) or
5 (driver, assistant driver, loader, gunner, commander)
Propulsion 2x Cadillac Series 42, 220 hp @ 3,400 rpm, 14.57 hp/ton (16.06 hp/tonne)
Fuel Capacity 178 gal
(809 l)
Top Speed 46 mph
(74 km/h)
Cruising Range 175 mi
(281.6 km)
Suspension Vertical volute spring
Total Production 1 converted

Sources

Can Openers – The Development of American Anti-Tank Gun Motor Carriages by Nicholas Moran
Stuart – A History of the American Light Tank by R. P. Hunnicutt
Seek, Strike, and Destroy US Army Tank Destroyer Doctrine in World War II by Dr. Christopher R. Gabel
M3 & M5 Stuart Light Tank 1940-45 by Steven J. Zaloga
HMC M8: Quick Support for Light Tanks | Warspot.net
British Army Staff AFV Situation Report No. 1 July 18th 1942
TM 9-732B 75 mm Howitzer Motor Carriage M8 January 1944
75mm HMC M8
75mm GMC M3
3″ GMC M10
76mm GMC M18

Categories
Has Own Video WW2 US Prototypes

75 mm Howitzer Motor Carriage T18

United States of America (1942)
Self-Propelled Gun – 2 Mild Steel Prototypes Ordered, 1 Built

With the onset of the Second World War in 1939, the United States began rapidly developing new self-propelled guns to modernize their antiquated ground forces, which were only equipped with towed guns. In early 1941, the Firestone Tire and Rubber Company submitted their proposal for a fully enclosed self-propelled gun based on the chassis of the M3 Stuart Light Tank. This vehicle was designated as the 75 mm Howitzer Motor Carriage T18. Two mild steel prototypes were ordered in 1942, but only one vehicle was completed before the termination of the T18 project.

A three-quarter view of the 75 mm Howitzer Motor Carriage T18 pilot. Source: tankarchives.ca

The Beginnings of American Self-Propelled Guns

In 1918, at the end of the First World War, the United States began developing domestic self-propelled guns. These vehicles were inspired by French designs of the time, such as the Canon 155 mm GPF sur affût-chenilles St Chamond, and based on Holt tractors. However, with the end of the war arriving sooner than expected, just a handful of these self-propelled guns were actually produced. These completed vehicles were used as a basis for future mechanized artillery development, but large-scale budget cuts in the early 1920s severely hindered any further experimentation.

French crewmen and their Canon 155 mm GPF sur affût-chenilles St Chamond. These St Chamond-based self-propelled guns arrived too late to see service in World War 1. However, the Americans took note of the design and began developing similar vehicles of their own. Source: landships.info
An American Holt-based Mark I SPG, one of three built for testing in 1918. The massive gun is the Vickers Mark VIII 8 in (203 mm) howitzer. Source: landships.info

American self-propelled gun development remained relatively stagnant for many years, with the United States’ first (and, until World War 2, only) mechanized artillery regiment, the 1st Battalion, 6th Field Artillery, being established in 1934. They were equipped with vehicle-towed 75 mm Pack Howitzer M1s, far from state-of-the-art. By the time World War 2 began, this was the only battalion of mechanized artillery in the United States Army.

A 75 mm Pack Howitzer M1A1 preserved at the American Military Museum in California. Source: author’s own

As war began in Europe, a rushed re-militarization effort began in the United States. A single battalion of towed light howitzers would be nowhere near enough firepower for the upcoming global conflict, so field artillery battalions were restructured, and modern designs for future self-propelled guns were pursued. Of course, it takes a not-insignificant amount of time to develop and produce an entirely new vehicle, so an expedient solution was chosen. This resulted in the 75 mm Howitzer Motor Carriage T30, an M3 Half-track mounting a 75 mm Pack Howitzer M1A1. The T30 was rushed into service while development of a proper self-propelled gun continued.

A T30 Howitzer Motor Carriage in the United Kingdom, 1943. Around this time, the T30 was being replaced in service by the M8 HMC. Source: public domain

75 mm Howitzer Motor Carriage T3

An early proposal for a self-propelled gun based on the Combat Car M1 was submitted in 1939. This vehicle, designated 75 mm Howitzer Motor Carriage T3, had a rather interesting design. The turret and upper hull of the Combat Car were removed and a short superstructure was constructed. The T3 HMC featured two guns: a 75 mm howitzer M1A1 in the right side of the superstructure and a .30 caliber machine gun located inside a modified M2A3 Light Tank turret on the top of the superstructure. Curiously, due to the lack of a proper gun mounting, a pair of doors could close around the howitzer to protect the crew. However, the doors had to be opened to traverse the gun, creating an opening in the casemate front. The vehicle’s armor was quite thin, at a maximum of only .625 in (15.9 mm) thick on the front of the machine gun turret and hull. Mobility was similar to the Combat Car M1, although the vehicle accelerated slower due to its increased weight.

The T3 HMC with its barrel-adjacent doors opened. Source: tankarchives.ca

The T3 HMC had a crew of three: gunner, loader, and driver. Even with a crew this small, the T3’s interior was still quite cramped. Issues reloading the howitzer and operating the machine gun were made apparent during testing. These poor crew ergonomics led to the T3’s eventual cancellation in 1940. With just a single prototype completed, the T3 Howitzer Motor Carriage was not considered successful. However, lessons learned during its development helped influence future self-propelled gun projects.

Development

In June 1941, after the cancellation of the T3 Howitzer Motor Carriage, guidelines for a new self-propelled gun were created. This new vehicle was to act as a close-support vehicle and would mount either a 75 mm or 105 mm howitzer. It was to be based on the chassis of the M3 ‘Stuart’ Light Tank. Almost immediately, the 105 mm howitzer was dropped as a potential armament. The limited size of the M3 chassis would make operating the gun difficult and the howitzer’s weight would cause the vehicle to be front-heavy. With the 105 mm howitzer off the table, two designs mounting a 75 mm howitzer were proposed and evaluated.

The M1E3 Combat Car. This tank shared a chassis with the T17 HMC. Source: tankarchives.ca

The first, designated 75 mm Howitzer Motor Carriage T17, was based on the chassis of the M1E3 Combat Car. This chassis was chosen because of its sizable internal space. However, rather predictably, the T17 was canceled because it did not use the requested M3 Light Tank chassis. The vehicle never left the drawing board. This left just one capable design; the Firestone Tire and Rubber Company’s proposal, the 75 mm Howitzer Motor Carriage T18.

Two views of the wooden T18 HMC superstructure mock-up. Source: Stuart – A History of the American Light Tank

While it might seem unusual that the Firestone Tire and Rubber Company was contracted to produce an armored fighting vehicle, they had a long history of producing various other goods, including tank parts, for the American military. They produced tank tracks, M5 Light Tank turrets, artillery shells, and 40 mm Bofors anti-aircraft guns, to name just a few. Therefore, it was not completely unexpected for Firestone to attempt to develop an entire armored vehicle by themselves.

Dozens of 40 mm Bofors anti-aircraft guns on the Firestone factory floor in April 1944. Source: washingtonpost.com

In October 1941, a wooden mock-up of the T18’s superstructure was produced by Firestone and fitted to an early M3 Stuart chassis. Suitably impressed and ready to suggest improvements, the Ordinance Committee approved the production of two mild steel pilot vehicles. The first pilot was delivered in May 1942, when testing could finally begin.

A front view of the T18 HMC mock-up taken in December 1941. Note the driver’s direct vision slit at the front of the superstructure and the sponson .30 caliber machine gun holes. Source: tankarchives.ca

The 75 mm Howitzer Motor Carriage T18’s Design

At a Glance

The T18 Howitzer Motor Carriage, from the lower hull down, was identical to a standard early production M3 Stuart. Both tanks shared the same lower hull design, suspension, drivetrain, engine, etc. However, the most striking visual change was the T18’s large cast casemate. The Stuart’s upper hull and turret were removed, replaced by the boxy fighting compartment designed to protect and contain the 75 mm main gun and three crew members.

Firepower

The T18 was, much like the T3 HMC before it, armed with the 75 mm Pack Howitzer M1A1. The howitzer was fitted to a modified version of the M3 ‘Lee’ Medium Tank’s 75 mm gun mount and located in the front right of the superstructure. Within the vehicle, 42 rounds of 75 mm ammunition could be carried. For the gunner, an M1 periscopic sight was installed on top of the mount. Gun traverse limits were 15° to either side and between 20° to -5° vertically. The M1A1 howitzer could fire an assortment of rounds, including the M48 High-Explosive shell, the M66 High-Explosive Anti-Tank shell, and the M64 White Phosphorus shell. The M66 HEAT shell would have given the T18 HMC a fighting chance in an engagement with enemy armor. However, with a velocity of just 1,000 ft/s (305 m/s), this shell would have been quite hard to aim at any targets beyond close range. The M66 HEAT shell could penetrate a maximum of 3.6 in (91.4 mm) of armor. This gave the T18 HMC’s howitzer similar penetration to the M4 Sherman’s 75 mm M3 gun. The M1A1 howitzer’s maximum rate of fire was about 8 rounds/min, but even a trained T18 crew would probably not have been able to maintain that volume of fire. Limited by the spatial confines of the vehicle, the crew’s achievable rate of fire would probably have been no higher than 6 rounds/min.

A scale diagram of the M66 HEAT shell. Source: Aerodynamic Data For Spinning Projectiles

To increase the firepower of the T18 HMC, two .30 caliber M1919A4 machine guns were placed in the vehicle’s sponsons. The machine guns were unable to traverse. Therefore, the only way to aim them was by turning the entire vehicle. The machine gun mountings and mounting locations were quite similar to those of the M3 Stuart. A maximum of 4,900 .30 caliber bullets could be carried within the vehicle. With its armament loadout, the T18 HMC could effectively fight as a direct-fire assault gun, neutralizing infantry with its machine guns, demolishing obstacles with high explosives, and even fighting tanks with its HEAT shell.

The T18 pilot and an early production M3 Light Tank. Note the sponson machine guns that both vehicles possess. Sources: tankarchives.ca and afvdb.50megs.com

Protection

The T18 was a reasonably well-protected vehicle. While the cast armor of the casemate was flat, it compensated with pure thickness. The front of the casemate was an impressive 2 in (50.8 mm) thick, which would have offered reasonable protection against 37 mm rounds from a distance. The sides and top of the casemate were 1.25 in (31.8 mm) thick and the rear was just 1 in (25.4 mm) thick. As for the lower hull of the T18 HMC, the armor was unchanged from the M3 Stuart the vehicle was based on. The lower side of the T18 was the same thickness as the casemate side, 1 in (25.4 mm). The heavily sloped upper front plate and cast lower front plate offered .625 in (15.9 mm) and 1.75 (44.5 mm) of protection respectively. Finally, the rear armor of the T18 was 1 in (25.4 mm) thick, while the floor armor ranged from .5 in (12.7 mm) thick at the front of the tank to just .375 in (9.53 mm) thick at the back. Overall, this armor layout was reasonably thick for its time, protecting the vehicle against many of its common threats frontally from a distance.

However, this armor profile had a few disadvantages. Despite its thickness, the T18’s casemate armor was completely vertical. While this design decision increased the available space inside the vehicle, it limited the actual protection the armor could offer. Sloped armor can deflect and deform armor-piercing rounds, helping prevent a penetration. Completely flat armor, however, offers no such benefits. Incoming armor-piercing rounds maximize their penetrative effects. Furthermore, the weight of the casemate’s heavy frontal armor placed significant strain on the vehicle’s suspension. When observing pictures of the T18, the overloaded suspension becomes apparent quickly. The vehicle had a noticeable frontal tilt, as the vehicle’s rather forward center of mass placed much more strain on the forward bogie than it did the rear. Similar issues of front-heaviness plagued other uparmored American tanks, such as the Assault Tank M4A3E2 ‘Jumbo’ based on the M4 Sherman chassis.

Side view of the T18 HMC pilot. Note the strain placed on the front suspension by the vehicle’s heavy frontal armor. Source: Ordinance Department

Mobility

The T18 HMC mounted the same Continental W-670-9A engine as the M3 Light Tank it was based on. This was a gasoline engine capable of producing 250 net hp at 2,400 rpm. Automotive testing of the T18 HMC was successful, revealing only slight differences in mobility between the T18 and a standard M3 Light. Both vehicles could reach the same top speed of 36 mph (58 kph) and had similar automotive characteristics. However, the slight difference in mobility was due to the T18’s increased weight of 14.88 tons (13.5 tonnes). For comparison, the standard M3 weighed only 14 tons (12.7 tonnes). Because of the weight disparity, the vehicles also had different power-to-weight ratios. The T18’s was 16.8 hp/ton (18.5 hp/tonne), while the Stuart’s was 17.86 hp/ton (19.69 hp/tonne). This difference was quite small and likely caused the T18 to accelerate slightly slower than the M3 Stuart. Regardless, having mobility only slightly worse than a very speedy light tank is still quite impressive and the T18 proved that it would have been able to maneuver around quickly and responsively.

A Continental W-670-9A engine. Source: advrider.com

Crew and Ergonomics

The T18 had a crew of just three, consisting of a gunner, driver, and commander/loader. To enter and exit the vehicle, two roof hatches were provided. While the T18 wooden mock-up had only one hatch, a second was added to the pilot at the request of Aberdeen Proving Ground.

Crew conditions inside the vehicle were likely poor. The driver’s only vision source was a single forward-facing periscope, severely limiting his ability to gauge his surroundings while driving. The vehicle did not have any pistol ports to peer through or a commander’s cupola, either. The only other source of precious situational awareness during combat was the gunner’s sight, which could only traverse as far as the gun could. The commander/loader did not have any source of vision at all, a very serious drawback. Understandably, the T18 would have been extremely vulnerable to flanking attacks during combat that it could neither see nor defend against. The vehicle’s lack of a dedicated commander combined with the limited vision of the crew would have resulted in a blind vehicle operated by overworked personnel.

Additionally, ventilation of the main gun was an issue. With no ventilation fans of any type, and a limited internal casemate volume, the vehicle surely would have filled with dangerous fumes when the main gun was fired continually. The only way to ventilate the crew compartment would have been to open the roof hatches, which created another problem. Driving around un-buttoned in the middle of combat is not generally considered to be a good idea, especially in close-quarters fighting. Crews would have been stuck between a rock and a hard place. Either they could try and ignore the gasses created by the howitzer or they could compromise their protection by opening the roof hatches. However, for the long-range indirect fire duties that T18 crews would have invariably found themselves participating in, opening the hatches would have been a much smaller issue. Far from the frontline and in much less imminent danger, opening the hatches to increase crew visibility and casemate ventilation would have been a no-brainer.

Top view of the T18 HMC pilot. Source: tankarchives.ca

Fate

While the T18 offered some advantages over its predecessors, including thick frontal armor and the usage of a standardized chassis, the project was doomed from the start. A month before the first pilot vehicle was delivered in May 1942, the Ordinance Department canceled the T18 program. Even without a physical vehicle, it was clear that the T18 had many intrinsic issues that made it unfit for service. The vehicle’s flat armor, front-heaviness, lack of vision, and poor gun traverse limits were cited as the main reasons for vehicle’s rejection. The fate of the prototype following this decision is unknown. A popular theory states that the pilot was kept on display at Aberdeen Proving Ground until it was destroyed in 1947. However, this remains unproven and the current location of the prototype, if it survives, remains a mystery.

This photograph of the T18 taken in February 1947 was its last sighting. What became of the vehicle after this is left to speculation. Source: Moose via pintrest.nz

Legacy

The 75 mm Howitzer Motor Carriage T18 was just a single stepping stone in the development of a 75 mm American self-propelled gun. Before the vehicle was even canceled, new development requirements were put forth by the Ordinance Department in December 1941. Reflecting the lessons learned from the T18 program, these requirements requested a self-propelled gun design based on the M5 Light Tank chassis and utilizing sloped frontal armor.

The T41 HMC (left) and T47 HMC (right) wooden mock-ups. The T47 was originally based on the M3 Light Tank chassis before the design was changed to use the M5 Light Tank chassis instead. Source: Stuart: A History of the American Light Tank

In an attempt to satisfy these conditions, two designs were proposed in April 1942. These were the T41 and T47 Howitzer Motor Carriages. The T41 was an open-topped turretless design on the M5 chassis and the T47 was a proposal mounting a new open-topped turret in place of the M5’s standard turret. The T47 was considered to be the best design and, as a result, the T41 was canceled almost immediately. The T47 was continually improved and developed, resulting in the now-familiar turret with the large barrel flash deflector and direct vision hatches in the front of the hull. This new turret combined with the slightly-modified hull of the M5 Light Tank was standardized in May 1942 as the 75 mm Howitzer Motor Carriage M8 ‘Scott,’ a vehicle that would see widespread service with the United States and its allies via the Lend-Lease program as a successful infantry support weapon.

 

The M8 HMC ‘Scott’ pilot during testing at Aberdeen Proving Ground in September 1942. Source: Stuart: A History of the American Light Tank

 

The T18 Howitzer Motor Carriage in olive green livery, complete with a white star decal on the side of the casemate. Original M3 ‘Stuart’ illustration by David Bocquelet. Modified by Freezer.

75 mm Howitzer Motor Carriage T18 Specifications

Dimensions (L x W x approx. H) 14’10” x 7’4” x 7’
4.53 x 2.24 x 2.13 m
Weight 14.88 tons
Armament 75 mm M1A1 Pack Howitzer (42 rounds)
2 x .30 caliber M1919A4 Machine Guns (4,900 rounds)
Armor Casemate
Front: 50.8 mm
Side: 31.8 mm
Rear: 25.4 mm
Top: 31.8 mm
Hull
Upper front: 15.9 mm
Lower front: 44.5 mm
Side: 25.4 mm
Rear: 25.4 mm
Engine deck: 12.7 mm
Floor: 12.7 mm to 9.53 mm
Crew 3 (gunner, driver, commander/loader)
Propulsion Continental W-670-9A, 250 hp, 16.8 hp/ton
Top Speed 36 mph (58 km/h)
Suspension Vertical volute spring
Total Production 1 mild steel prototype completed, 2 ordered

Sources

Stuart – A History of the American Light Tank by R. P. Hunnicutt
M7 Priest 105mm Howitzer Motor Carriage by Steven J. Zaloga
M3 & M5 Stuart Light Tank 1940-45 by Steven J. Zaloga
M3 Infantry Half-Track 1940-73 by Steven J. Zaloga
British and American Tanks of World War II by Peter Chamberlain and Chris Ellis
Aerodynamic Data For Spinning Projectiles by H. P. Hitchcock
Work on Sabot-Projectiles by the University of New Mexico under Contract OEMsr-668, and Supplements, 1942-1944 by J. W. Greig
Holt SPGs
Saint-Chamond SPGs
Firestone in World War Two
Tank Archives: T18 HMC: Quick Howitzer
Light Tank M3 Stuart

Categories
WW2 US Prototypes

Wallace Leaping Tank

United States of America (1942-1945)
Walking Pillbox – None Built

If someone tried to define the term ‘tank’ as a military vehicle, they generally would agree on the need for a turret, armor, and tracks. Whilst there are exceptions to each of these to one degree or another, the only real unifying point across definitions is the use of armor and this raises interesting possibilities, especially for Henry Wallace of Freeport, New York, USA. In 1942, Henry Wallace expanded the idea of what a tank can be to a vehicle with no tracks at all. In fact, Wallace did not even go for wheels for some wheeled tank/armored car, nor did he go the full way towards a legged machine. Instead, Wallace went for perhaps the most unusual method of transportation possible, a vehicle that walked on one leg, pushing what could be named as a tank to a new extreme.

The Man

The patent for this odd design came from Henry W. Wallace of Freeport, New York State, USA. He should not be confused with the US Secretary of State for Agriculture of the time with the same name. Freeport, New York, is not a large city but, as of 1940, there were just over twenty thousand people living there according to US Census Data. The only other patent from this man was filed in October 1940 and was for a flexible pen in the shape of a snake wrapped around the wrist. With a relatively common name and few other details to go off, there is insufficient information to be able to reliably identify the designer at this time.

Concept

There are inherent problems in a tank design that involve compromises. Whether operating on wheels or tracks, movement is limited to the direction the vehicle faces and a change in direction involves turning or reversing. Protection for the vehicle is concentrated forwards to protect from fire from the front, as it would be too heavy and impractical to add equivalent protection to the sides and especially to the rear. Thus, a conventionally laid out combat vehicle is more vulnerable from the sides and rear than the front. Any turning or change in direction by the vehicle might expose that weakness to an enemy. A vehicle on which all sides are equally armored does not have to worry about the direction of an enemy attack or even turn to face it.

The same is true for armament. With a vehicle carrying a turret armament, it has to be turned to target a specific threat, and, once more, the maximum of protection faces the enemy threat. Armor protection, as both weight and bulk have to be shared between the turret and hull, provides a challenge for a designer as to where to use the armor for optimal value.

With those two primary considerations in mind, the conventional vehicle cannot deliver equal protection and firepower all round – for Wallace, the solution was effectively a simple one. Create a vehicle that was symmetrical in defensive capabilities and offensive alike, and this meant a circular body. This body would make the tank especially valuable in a defensive situation, where it could simply ‘sit’ as a bunker to guard or control an area and then, when the job was done, move on.

The propulsion of such a vehicle could not rely upon tracks or wheels, as it would not be able to change direction quickly enough in the mind of Wallace. Instead, he opted for a single leg which was located in the center of the doughnut-shaped machine. With this, he felt, the tank would be able to “oscillate” to move, with all-round gun positions guaranteeing that firepower constantly faced the enemy. Thus, the vehicle could advance, retreat or move sideways without regard to enemy position or flanking attacks.

Layout

With a doughnut-shaped body resembling a pressure cooker or saucepan with a lid, the machine was certainly odd. The ‘handle’ of the lid was a small cabin that could be rotated in any direction and in which sat the driver of the machine, with a view slit for observation.

The driver’s cabin was located on top of the machine and could rotate within the machine.
Source: US Patent US2371368

The rest of the machine was circular, with 6 gun positions located at 60 degrees from each other. Each position had a field of fire of up to 45 degrees to each side, which managed to create small blindspots immediately alongside the vehicle between the guns.

Seen from above, the vehicle has no ‘weak’ side, as it is circular, with weapons equally spread around the circumference.
Source: Modified from US Patent US2371368 by Author

The smooth exterior of the vehicle was broken up by the 6 gun positions, but there would be no sign of the propulsion leg from the outside when the vehicle was ‘sat’ down as a pillbox. The leg itself resided in an octagonal area within the floor of the tank, with its gearing and hydraulic actuators around it to control its position and direction. The extension of the leg, however, was not done hydraulically but using compressed air or, as suggested by Wallace, by means of an explosive expansion of gas. This might have seemed like a good idea for a patent application, but was utterly preposterous for even this rather silly design. The automotive power was to come from a two-stroke fuel-injected diesel engine of an unspecified type. In a lengthy explanation of how the whole system was meant to work, Wallace explained that this explosive method was to work by releasing fuel into the top of the hollow extensible cylinders which formed the leg and that, with a single detonation of a cartridge into this cylinder, the explosive gases from this detonation would rapidly propel the vehicle upwards to get out of trouble or leap into action. Quite what effect this bounding kangaroo leap would have on the occupants is not explained and perhaps was never even considered as a possible issue or concern.

The octagonal central space is occupied by the propulsion leg and associated hydraulic pistons for controlling its position and movement. The driver sat directly over this central position.
Source: US Patent US2371368. Note this image has been digitally cleaned by the author.
Cross-section elevation of Wallace’s design showing the large central area for the propulsive leg and driver’s cab over the top of it.
Source: US Patent US2371368. Source: US Patent US2371368

The rest of the internal arrangement within the machine was relatively straightforward. Between the outer walls, with those 6 gun positions, was a raised fighting platform under which ran a lot of the mechanical equipment (such as pumps) to run the machine. The outer skin of the machine was supported at the top and bottom by supporting beams. Despite the size of the machine and the number of men within it, just one hatch is shown in the patent drawing, in the rotating cabin for the driver at the top.

In terms of crew, even assuming just one man per gun (x 6), a driver, and a commander would mean not less than 8 men to reasonably crew this vehicle.

Propulsion

Whilst there have been designs for walking machines before, they usually relied upon continual support by their legs even when not in motion. More than that, they also had to depend on at least 2 legs for bipedal stability or more in motion. Wallace eschewed such ideas or any concept of motion short of brachiation from nature and went instead for a system using one leg. It is obviously not possible to walk on one leg without a hopping motion, but the design did not produce some giant pogo stick type of movement. It instead had an unusual undulating step where the second ‘foot’ would be the vehicle itself.

Consisting of a giant doughnut shape, with the single leg occupying the central recess in the bottom, at rest, the vehicle sat on the ground as a giant round fort or pillbox. During this phase, the leg could move forwards to a position in the direction of movement and then lift the whole vehicle off the ground, bringing it upwards and in the direction of travel. Now having moved a short distance ahead or in any direction, the leg would collapse slowly bringing the vehicle back to rest on the ground. The process would then repeat for as long as may be needed to move from location A to B. At all times whilst sitting on the ground, the leg was completely enclosed by the body and the vehicle provided both maximum firepower and maximum protection in all dimensions simultaneously. Using four large wheels, one on each side of the leg, and an element of rotation within the housing for it, the leg could be prepositioned in any direction in anticipation of a move that would be unknown to anyone outside the machine by observing it.

There are, however, serious problems with this method of motion, not least of which are ground pressure, balance, and speed.

Firstly, with the entire weight of the vehicle concentrated onto just a single point of contact with the ground. As the leg extended hydraulically into the ground to raise the body, it would sink into anything other than a good hard surface. The result would potentially be the leg impaling the ground to an extent that it might not be easily removed. This would be the military equivalent of trying to walk on a beach in high heels. If this sinking happened when the body was off the ground, the result could be disastrous, as moving a point of balance beyond the lip of the foot would result in the machine flailing over.

This brings up the second point of balance. Not only could the machine potentially tip if the ground shifted or leg sank when moving, but this would be magnified as a problem moving on anything other than a flat surface. Whilst the foot itself had a semi-flexible coupling in the manner of an ‘ankle’ connecting it to the base of the leg, the foot allowed for a limited degree of flexibility. Measurements of the vehicle would indicate that it would become unstable past 10 degrees of any slope. This would render the vehicle unable to operate on anything other than ideal flat terrain. Wallace sought to correct this rather obvious deficiency with his idea by stating that it was to use a gyroscopic stabilization device located around the center of gravity and consisting of two oppositional gyroscopes.

Even allowing for the body to pivot and remain horizontal, once the vehicle gets past 10 degrees from vertical, it is unstable. Source: US Patent US2371368 digitally modified by the author.

The final major problem with the practicalities of the mean of motion for the vehicle is speed. Movement in the chosen direction is limited by the amount of movement available to the foot at the point when the body of the vehicle is on the ground. Moving the foot in the desired direction whilst on the ground (1), as the hydraulics push on the foot, the body gradually lifts off the ground and is righted to a new forward position (2) until reaching full height (3). The tank can remain at any elevation between ground level and (3) for combat, although this would expose the leg to enemy fire. Return to the ground starts from the elevated position (4) down vertically (5) to the new resting position (6), a short distance from point (1). To continue the motion, the leg is moved to the new forward position (7) and the vehicle rises (8) to a new elevation (9) and so on.

Movement through phases of elevation. Source: Author

One step beyond this slow move-lift-lower means of motion, Wallace drew an even more fanciful one. Here, the leg would do far more than even those rather absurd methods of movement, showing the tank literally jumping.

Even had the idea been a practical one, Wallace’s ridiculous concept for tank movement ensured that not only would the vehicle be very easy to see leaping above any cover but also that any crew inside would be in no fit shape to fight at the end of it.
Source: US2371368

This slow move-lift-lower process could be sped up to a ‘dragging’ speed whereby only enough pressure need be applied to the foot to raise the body from the ground far enough that the hydraulics for the leg movement could drag it forwards and then return to the body to rest as the foot moves again. It is surely this method that would have been the only practical way of moving the vehicle, although practical is not really applicable to such an implausible design.

‘Walking’ by dragging the lidded-saucepan-shaped vehicle would have been a bumpy and slow affair.
Source: Author

Wallace made no mention or estimate of the speed of this system of propulsion, but it was clearly not possible to combine a rapid bounding from the machine with a chance of the crew being in a fighting condition, even assuming the system had worked. The easiest, simplest, safest form of motion, the dragging method, would perhaps at best manage walking pace on a good surface.

Armor

As with many other features of this vehicle, little information can be discerned on which to judge the level of protection provided. No information is provided other than to say that protection was implied as being equal in all directions. From the approximate scale of the vehicle, the size of the seat, and space for the crew, the drawing would appear to indicate armor would have to have been metal (presumably steel) and not much more than bulletproof in thickness.

Armament

With 6 evenly distributed guns around the outside, it is unclear what sort of firepower Wallace had in mind. An enemy could be engaged at best by just two of the guns at any one time, leaving ⅔ of the firepower idle. Wallace could simply have had a rotating turret with a single large gun or multiple gun mountings, which would have obviated the need for so many crew and guns. Instead, unless the vehicle was totally surrounded, then all of the firepower could never be used at the same time and none of it when moving.

Conclusion

Weakly protected for a static pillbox, poorly protected for such a visible tank, and oddly armored for a fighting vehicle, the design was particularly bad when it came to motion. The single-leg concept, as drawn, was preposterous and unlikely to work even on a flat and hard surface, let alone a modest slope or wet ground. There, this tank would display the mobility of a lawn dart when moving and a house brick at other times, with less potential than either.

What Wallace was trying to secure as intellectual property with this design is clearly the single springing leg concept and a tank of equal protection and firepower. What he actually designed was perhaps one of the least practical, workable, or sensible systems of vehicular motion imaginable.

Trying to imagine what possible use this vehicle might have had to the US military or Allies in 1942, when it was submitted, is even less clear. Today, it can be seen as just one of those ideas from a well-meaning public eager to engage in and/or profit from the war by producing war-winning weapons and ideas. Sadly for Wallace, this was not one of them.

The Wallace Leaping Tank is probably the oddest military vehicle ever proposed. Or, at least, the oddest we ever found. Illustration by Yuvnashva Sharma.

Sources

US Patent US2371368 Vehicle, filed 16th October 1942, granted 13th March 1945
US Patent US2266942 Bracelet, field 24th October 1940, granted 23rd December 1941
US Decennial Census data https://www.census.gov/programs-surveys/decennial-census.html

Categories
WW2 Belgian Armor WW2 British Prototypes WW2 US Prototypes

Bechhold Tank

United States of America/United Kingdom/Kingdom of Belgium (1938-1941)
Light Tank – 1 Partial Prototype Built

Introduction

Many people interested in tanks have likely heard the name Walter Christie and are aware that he produced several prototype tanks during the period between WW1 and WW2. Whilst his vehicles had some good features, overall they were not a commercial success for Christie, who had amassed a lot of debt in developing and building them. The result was that some of his assets, his tank prototypes included, ended up being used to pay off his debts and his ‘high-speed tank’ was one of them.

Sold to pay off Christie’s debts, this vehicle ended up in the hands of a German-born American businessman, Siegfried Bechold. This new owner rebranded the tank, had some additional design changes made and then, at the start of WW2, tried to sell the ‘new’ design to both the Belgians and the British.

The Belgians needed tanks urgently but this design would come too late to help them. The British expressed interest as the light weight of the machine was suited to their need for a tank for airborne operations, and by 1940 the British Purchasing Commission was actively considering the vehicle for production. Nonetheless, the idea was over by 1941, when British attention switched to a vehicle with more armor and firepower than the ‘Bechold’ tank. Even so, this early design and the consideration of it adds to the story of how the British were trying to develop their own ideas for a new kind of mobile warfare and airborne operations.

The enigmatic Mr. Bechhold

The name Siegfried Bechhold means very little even to the most ardent tank enthusiast. However, just prior to WW2 and into its first years, Bechhold was one of the most prominent men involved in tank design and production in America, despite never having produced any tanks. This peculiar state of affairs takes some digging to get to the bottom of, as does the man himself, not helped by his name appearing variously as Bechhold, Bechold, and Buchhold.

Siegfried Bechhold appears to have been born in Bavaria, Germany in 1900, although a newspaper article from January 1941 puts his birthplace as Holland. This is likely one of those situations where people de-Germanized themselves to try and disguise their German ancestry, something which was a common occurrence at the time, especially with the switch from ‘Deutsch’ to ‘Dutch’ in terms of self-description. Another account of his early life (from April 1941) stated that he was born in Bavaria and lived in Germany until he was 11 – so maybe his family moved to Holland or maybe he was just hiding his background.

Bechhold recounted his story that, at the age of 16 (so ~1916), he was, like tens of thousands of other German boys, drafted into the German Army during World War One, although it is not known if he saw any active service or not. By 1922, with WW1 behind him but in a country ravaged by economic and social problems, he managed to make the transatlantic voyage to the United States, arriving in New York with just US$40 to his name.

His first jobs were very poorly paid but, by the late 1920’s, he was living as a tenant at 34 East 62nd Street between Madison and Park Avenues (this house was demolished in an explosion in July 2006). He had been learning English at night school and had managed to get a job as a salesman, which proved very successful for him. So successful was it, that this man, who had arrived in the USA just a few years before, could now afford to travel back and forth to Europe. He would later claim that he used these trips to pass on information about German rearmament efforts during the early 1930’s and that he believed that Germany was far ahead of other countries in weapons development, although this sounds more like his sales-speak for selling tanks than the serious recollections of an international spy.

What is known though is that during this time, he, like many others, saw the tanks of Walter Christie. These were very well covered in the newspapers and newsreels of the age with Christie’s penchant for publicity stunts. Seeing a potential business opportunity, Bechhold was interested in these tanks which were significantly faster than other tanks of the age, and in many ways the most advanced tanks in the USA at the time.

Bechhold later reported that he was encouraged in his interests by Congressman Ross Collins of Mississippi, although how these two men knew each other is unknown. It was, according to Bechhold, Collins who encouraged him to produce tanks in the United States but Bechhold was not a technical man nor an engineer despite being Vice President of the Bethlehem Engineering Export Corporation of Wall Street, New York. He was skilled in salesmanship and finance. He was, however, despite his lack of engineering skills, to be credited in the US press as coming up with the idea of putting lightweight aircraft engines into tanks in place of ordinary diesel or petrol engines, although this too sounds more like the pitch of a salesman, as Christie had already done this years beforehand.

As an aside to his tank work and to give a flavour of the way in which Bechold was trying to avoid being labelled as anything other than as a patriot, he embarked on a vigorous self-justification campaign in the media, making sure no one was in any doubt as to his loyalties. As a result, in June 1941, it was reported that Bechhold, a naturalized citizen and “intense” patriot, had refused to sell his tanks to the Russians at the time of the War against Finland. Furthermore, it was claimed that, in the new war against Hitler, he would only sell them when the Russians went to war with Hitler, even though there seems to be no evidence whatsoever for this claim.

The Tank Company

By the end of the 1930’s, Bechhold had his opportunity. Walter Christie, a man of undoubted technical gifts, was running short of investors who wanted to keep losing money on his tanks. One vehicle of his, a “high-speed tank”, had to be handed over to the partners of the Hempsted Welding Company of New York, William and Alfred Christ, as a lien against unpaid debts owed to them by Christie. Exactly which of Christie’s vehicles this was in unclear but as the M.1938 was later presented by a Mr. Bigley with some involvement from Christie suggests that Bechhold got hold of the M.1937 high speed tank from Christie as the basis of his design. However, whilst exactly which vehicle may not be known, Christie’s creditors were to be appeased with a tank available for purchase to pay his debts.

Bechhold had, through Bethlehem Engineering Co. been engaged in a commercial contract with Christie which started on 9th August 1938 whereby Bechhold and his company were granted exclusive rights to sell and manufacture the design from Christie for the princely sum of US$5,000 (just over US$91,000 in 2020 values). The idea of the partnership was simple. For this initial outlay of cash to Christie, Bethem Engineering would take the full blueprints of the design, market them globally and grant manufacturing licences for US$50,000 to each national licensee. This US$50,000 (US$915,000 in 2020 values) would be split 50:50 between Bethlehem Engineering and Christie for which the licence got not only the blueprints but also a master mechanic or draughtsman from Christie. This agreement simply fell apart not least in part to how appallingly badly written and complicated it was. In the words of the New York Second Circuit of Appeals in July 1939 ruling on whether to grant an injunction against Christie for breach of his contract:

This contract is so obscure, and, strictly taken, so incoherent, that nobody can be sure of its meaning, but so far as we can spell it out, this is what it was. The defendants made the plaintiff its exclusive agent to sell licenses to prospective manufacturers of their tank in foreign countries — perhaps also in this country as well, though apparently it was not included. The plaintiff was not free to sell such licenses generally, but only for those countries where the parties thought it “practical” to do so. The minimum license fee was to be $50,000, but the plaintiff was to try to get more, and the parties were to discuss the amount in advance: probably this implied that they should agree upon it.
105.F.2d 933 (2nd Cir. 1939)

With the case between them ending in confused acrimony, Christie and Bethlehem Engineering’s relationship was over. Christie had won that case due not least in part to how confusing the agreement was between them over rights and whilst he had retained his rights over his design he was also financially crippled.
Bechhold too had moved on and was no longer involved with the Bethlehem Engineering Expert Company and, instead, on 25th July 1939 (just 2 weeks after the ruling), formed the Armored Tank Corporation (A.T.C.), incorporated in New York. Initially, this company had just 100 shares of stock (30 Class A, and 70 Class B) at a value of US$50 each (Total nominal value US$5,000).

The purpose of the company was to acquire the Walter Christie high-speed tank from William and Alfred Christ. On 31st July 1939, this tank was purchased for an undisclosed sum along with 34 shares (Value US$1,700) in the new company (6 more were given to the attorney for their legal services). The Armored Tank Corporation (A.T.C.) of New York was now in possession of the Christie High-Speed Tank, the rights over which had fractured the relationship between Christie and Bethlehem Engineering. Bechhold now had the vehicle and also the more difficult task of making money from it.

Belgians

Within a few months of formation of the company and the purchase of this High-Speed tank, Bechhold was recruiting a draughtsman. Between December 1939 and January 1940, A.T.C.’s draughtsman prepared blueprints and drawings of this Christie tank with some modifications. During this time, a license agreement for the production of this modified Christie high-speed tank was acquired in Belgium. The Belgium firm, Ateliers de Construction de Familleureux, paid an advance royalty of US$10,000 for this license. Whatever plans there were in Belgium for this vehicle though are unknown, as the nation was overrun by the Germans in May 1940, with no Christie tanks produced.

Super Tanks

By the end of 1940, the first glimpse of what A.T.C. was working on can be seen. In November-December that year, it was advertising ‘Super-Tanks’ in the US Army Ordnance Magazine as being “built in all weights” by the Armored Tank Corporation at 30 Church Street, New York. This was formerly the location of numerous businesses such as the National Manufacturing Company, American Locomotive Sales Corporation, and the New York Railway Club (close to the site of the World Trade Center Complex today and now the location of the Century 21 Department Store). The same advert appeared that same month as being constructed by the Pressed Steel Car Co. as well.

Image of a Bechhold Tank
Image of a Bechhold Tank dated 1940, published November/December 1940. Source: Army Ordnance Magazine
Image of a Bechhold Tank
Image of a Bechhold Tank published early 1942. Source: Crismon

Although the tank was never built as shown in the 1940 image with the low cylindrical turret there was a photo of a mockup of the Bechold tank was circulated in the press by least the early part of 1942. This vehicle had the same distinctive rounded nose glacis and two hatches in the driver’s plate. Off-center to the left of the driver’s plate, next to the left hatch was a mockup of a gun of unknown type although it appears too large to be a simple machine gun. The gun is roughly in the same position as what appears to be a small machine gun on the 1940 artist’s impression. The most noticeable difference between the 1940 drawing and the mockup (other than the lack of turret on the mockup) is that 3 wheels can clearly be counted on each side along with what appears to be a pair of return rollers instead of 4 wheels with no return rollers. Also apparent is that whilst the return rollers appear to be real, the photo may have been editted to make the vehicle appear shorter than it was.

Based on the available photograph, the drawing, and information from the company’s advertising of it being “Built in all weights”, a brief analysis of the vehicle shown is possible.

Advert for Bechold’s Armored Tank Corporation of New York.
Advert for Bechold’s Armored Tank Corporation of New York. Source: Army Ordnance Magazine

In December 1940, Bechhold was reported to have been producing ‘Medium Tanks’ for the British and had also submitted a design for an airborne tank. This tank was at the time being reported in the press as weighing 10 tons (9.1 tonnes), 14 ½ feet (4.42 m) long, fitted with armor one-inch (25 mm) thick with a single 37 mm gun and a machine gun. Also noted was that it would carry two sub-machine guns, suggesting a crew of just 2 or 3. A final note is that it was designed to be carried under “a Douglas plane”.

This description is immediately reminiscent of the Christie promotional idea of an underslung high-speed tank from 1936. In that artwork, a 3-wheel Christie turretless high-speed tank was pictured being carried under an Air Corps bomber.

The idea for the rapid deployment of tanks by aircraft
The idea for the rapid deployment of tanks by aircraft appeared in Christie designs as early as 1936. Source: Popular Mechanics. May 1936.

An idea of quite how a system for carrying a tank in this manner under a plane would work can be found in a May 1941 Patent. This was filed by Alfred Anderson, assignor to the Armored Tank Corporation for a ‘Hook-on-and-Release-Mechanism for Fighting Tanks’. This invention describes an invention for attaching tanks to aircraft, specifically slung below the plane, and for dropping the tank when in flight. This is a different system to the one from Christie – that one used a pair of scissor arms to grab and retract the tank.

Instead, four upside-down triangular fittings would be attached on the underside of the fuselage of the aircraft. Each held a hydraulically controlled actuator with a large stud pushed out on a spring. When hydraulic pressure was applied, this spring would compress withdrawing the stud back inside the actuator. This would release the tank, as these four studs were attached via holes into the body of the tank. These would not be disengaged simultaneously, but in pairs. The rear pair would disengage first, allowing the bottom of the tank to hang down as the carrying plane swooped in suicidally low over the ground. At a suitable point, the front studs would also then be disengaged releasing the front of the tank. The back end of the tank was then supposed to hit the ground first from a lower height, with the front end following. This method was intended to overcome the turning effect on the vehicle. The dangers to the vehicle crew and to the aircraft performing this maneuver cannot be overstated; this was really a system designed to get the plane and its tank shot down. Even if it did work and the tank was deposited safely to the ground, one wonders how long it would take the crew to become operational after such an experience.

Hook on and Release Mechanism for a Fighting Tank.
Hook on and Release Mechanism for a Fighting Tank. US Patent US2310887 of 1941
Christie M-1950
A depiction of the gantry arrangement on top of what is supposed to be the ‘Christie M-1950’ (albeit with a different number of road wheels). The gantry could not only attach a tank, but also raise it within the fuselage of the aircraft. Source: Steel Steeds Christie

The vehicle shown in that 1936 promotion art for Christie is different from the vehicle in the 1940 ATC advert though. For sure, ATC got a Christie High-Speed Tank but its vehicle is much closer to a vehicle the size of the M3 Stuart or even the M1 Combat Car. What can be seen from the advertising image is that it was a small tank with a distinctive rounded back end to the hull running on four closely-spaced Christie type wheels (and presumably Christie spring suspension too). No track guards or mudguards at all are shown. The track itself is very similar to the flat plate track of the Christie tanks.

The nose lacks any indication of the pointedness of the earlier Christie High-Speed tanks but is uniformly rounded leading to a long glacis sloping up to a slightly inclined driver’s plate. Where the glacis meets the driver’s plate, there are two structures that appear to be mounts for fixed hull machine guns. In 1940, it should have been obvious that fixed, forward-firing machine guns were utterly useless but it was an easy way to add what was thought of as additional firepower to a design and many tanks subsequent and independent of this one retained this feature, including the M3 Grant, M4 Sherman, and Canadian Ram.

The driver’s plate featured two rectangular hatches, each with a vision slit. Out of the front of the left-hand hatch was what appears to be a heavy machine gun. From the position of the hatches and hull weapons, it would appear to have had a driver mounted on the right and hull machine gunner on the left. A third man, the commander, would most likely occupy the turret. The turret itself, as drawn, is very unusual, looking like an overturned cooking pot. On the roof was a full size (it occupies the entire roof) hatch in two parts, each opening sideways. A series of slits were placed around the exterior of the turret and at least two machine guns, one forwards and one to the left. In total, the firepower for this vehicle as drawn was 4 machine guns and one heavy machine gun.

Presumably, the part about being built in ‘all weights’ was to mean that different options in terms of fittings, armor, and weapons were potentially on offer. Certainly, the specifications and look of the vehicle were very up to date given the parlous state of US tank development at the time. The T4 medium tank, for example, from 1935/1936, was a very promising design but was 13.5 tons and capable of just 35 mph with 3 machine guns. The Bechhold tank was, at least on paper, better armed, better armored, smaller (about 50 cm shorter), and faster. No surprise then that it was an interesting prospect for investors interested in lucrative future army orders.

The 13.5 ton Medium Tank T4
The 13.5-ton Medium Tank T4 – at 13.5 tons (12.2 tonnes) this tank was armed only with machine guns and was not adopted. Source: Wiki

Investment

The potential of the A.T.C. tanks from Bechhold’s company had indeed gained attention. In June 1940, a British Purchasing Commission had arrived in the USA to look at the possibility of producing and purchasing tanks for the war effort. Great Britain had, of course, been at war since September 1939, and June 1940 was just after the evacuation of Dunkirk, a time when a lot of British armor had already been lost on the continent with the fall of France. Great Britain and its Empire now stood resolute against the Axis of Germany and Italy but it desperately needed tanks and arms to fight the war.

The same month, Bechhold managed to interest John MacEnulty, the President of the Pressed Steel Car Company, in tank production and a five-year contract (renewable for up to 2 years) was signed on 23rd July 1940. Under the terms of this contract, Pressed Steel would gain exclusive rights to the production of tanks from A.T.C. (notwithstanding that a non-exclusive Belgian production license had already been signed). Under the terms of the contract, Pressed Steel would pay A.T.C. a royalty of $750 for each vehicle of A.T.C.’s design ordered for production by the US or Foreign Governments at Pressed Steel. A.T.C. was to provide plans, drawings, technical advice and, if required, a skilled engineer to assist in production.

 John F. MacEnulty, President of Pressed Steel Car Company
John F. MacEnulty, President of Pressed Steel Car Company from 1937. Source: Railway Engineering and Maintenance Vol.34

On 25th October 1940. Pressed Steel entered into an agreement with the British Purchasing Commission for the production and delivery of 501 M3 Medium tanks. These were not tanks designed by A.T.C. but Bechhold did assist in the completion of the contract arrangement and the British sent an advance of US$500,000 to Pressed Steel. The next month, November 1940, Pressed Steel paid A.T.C. US$75,000 under the terms of the July 1940 contract with US$300,000 remaining to be paid.

It is not clear though why Pressed Steel paid this commission to A.T.C. as the vehicles being produced were Grant tanks and not the Christie-based tank design from A.T.C. Despite the huge sum paid to ATC, it was in trouble. Bechhold had finagled matters so that after October 1940, only he held all of the Class A shares in the company, and therefore had exclusive voting rights for A.T.C. He had also increased the number of shares available from 100 to 10,000 (3000 Class A and 7000 Class B) with a reduced value of just US$1 each.

British Interest

The desperate need for tanks meant that the British were rapidly building their own in industries repurposed from civilian work to war work, but they were also looking for American production too, as this would not be affected by the manpower shortage in Britain or by German bombing. As well as the order for the M3 tanks from Pressed Steel, various other options were being considered and the work of the Purchasing Commission continued into 1941.

One particular type of vehicle that the British were interested in was an airborne tank,namely a tank which could accompany parachute or glider-borne troops. The lightweight and compact Bechhold tank was obviously of specific interest. On 27th February 1941, on behalf of the British committee in charge of evaluating tank designs, a telegram was sent to the Consul General in New York regarding the tank situation. The British were clear on what they needed from an airborne tank:

3 man crew
37 mm gun and .30 calibre Browning in a 360 degree rotating turret (quite why a 37 mm gun was specified in preference to the 2 pounder which was already an excellent gun and fielded on the A.17 Tetrarch is unknown but it is probably to do with the 37 mm being easier to produce in the USA)
Space for a wireless
Maximum Speed 40 mph (64 km/h)
Radius of Action 200 miles (320 km)
Armor basis ‘preferably’ 40-50 mm on the front and turret. 30 mm thick sides
Weight about 9 tons (9.1 tonnes) (anything under 9 tons was felt to lack the fighting qualities required) (for reference: the A.17 Tetrarch weighed just 7.6 tonnes)
“Not very interested in dropping Tank from a height of two feet”

In other words, the idea of dropping the tank from a plane was not wanted at all. Either it had to be landed directly (some various schemes for adding wings to tanks were considered), or it had to be unloaded from an aircraft. Dropping it from underneath a plane was, quite rightly, seen as a terrible idea. These requirements exceeded those of the Bechhold tank from A.T.C. That vehicle lacked the armor and firepower required and was inferior to the available A.17 Tetrarch when what was wanted by the British was basically a better armored version of the Tetrarch. The British were also anxious to get an airborne tank as soon as possible and were hoping for interest from the USA in manufacturing the vehicle. The Bechhold tank was, therefore, not suitable for their needs as it was noted that a pilot model had not yet been built.

By the end of March 1941, British plans for “the Bechold [sic: Bechhold] Project” were over. Having analyzed the tank, the British reported that: “The tank will not have the essential fighting qualities for the operations in view” and would also divert production from heavy bombers. The matter was left in the hands of American authorities to pursue and oversee its development. In its place came consideration of a 9-ton (9.1 tonnes) tank to be carried by towed glider. A final comment on the matter, from 30th April 1941, was that it had become clear to the British that the “American War Department feel they have no capacity to devote to the development of air-borne tanks”. As the decision was that Bechhold’s tanks should be overseen in America rather than from Britain it was decided that no action be taken on the Bechhold tanks.

Sold Off

The British had not been convinced by Bechhold’s salesmanship. They had, after all, already been down the Christie suspension vehicle route with the purchase of a Christie M.1931 which became the A.13E1 in 1936/7 and they had extensive experience with light Cruiser type tanks already. They also had plenty of small light tank designs including the A.17 Tetrarch. They had been clear on what they wanted but Bechhold was either unable or unwilling to comply, or simply could not produce a prototype, which was required before a decision could be taken. With the British unconvinced and an already lucrative deal with Pressed Steel in place, Bechhold had other plans.

Shenanigans and Taxes

In February 1941, A.T.C. sold its original Christie tank for just US$3,500, (Bechhold had bought it for US$5,000 in 1939) and on 18th August that year, A.T.C. incorporated as a corporation in Delaware to avoid payment of New York franchise taxes. This was completed on 20th August and the shares changed to just 100 Class A and 9,900 Class B shares with Bechhold, of course, retaining all the Class A shares and the voting rights that went with them (he also held 6,400 of the Class B shares too). Between 2nd and 4th September 1941, A.T.C. signed over all assets and the July 1940 contract (with Pressed Steel) to a newly incorporated body in Delaware, meaning the New York ATC effectively disappeared, although it was not formally dissolved until 11th September 1941. Mr. MacEnulty of Pressed Steel wrote to Bechhold on 4th September 1941 informing him that the July 1940 contract was now canceled due to alleged misrepresentations by Bechhold and a legal fight ensued.

Bechhold was insistent that he was owed money from Pressed Steel and, despite being offered US$300,000 (the remaining balance from the British Purchasing Commission contract), Bechhold refused due to the tax liability involved. His counter-offer was US$1.5m and this was immediately rejected. Instead, Pressed Steel suggested it should buy all of the remaining shares of ATC for US$50 per share (10,000 shares at US$50 would mean a US$500,000 payday). This would mean the end of Delaware A.T.C, which would have to surrender all its designs including an “aero” (airborne) tank concept, a full size model of the hook and release mechanism for releasing a tank from an airplane, designs of various other tanks and flamethrowers, and cash. This offer was considered and changed on 3rd October 1941 with a value of US$37.50 per share (US$375,000), but this would be only the existing July 1940 contract, no other plans or designs. This was agreed to by the voting members of Delaware A.T.C., which was just Bechhold, who of course approved of this arrangement.

In order to facilitate this transaction, the Delaware incorporated A.T.C. was changed from any mention or use of Armored Tank Corporation to the ‘Illinois Tank Corporation’ (I.T.C.) on 14th October 1941. On this day, just as Armored Tank Corporation (Delaware) was bought out by Pressed Steel and changed to Illinois Tank Corporation, Bechhold started a new company in Delaware. He called this new company the ‘Armored Tank Company’ once more receiving all of the assets from the original A.T.C., other than the contract, which had now gone to I.T.C. The next day, the new A.T.C. handed over all of its shares to I.T.C. which was then distributed to the stockholders, which also included Bechhold.

From these corporate shenanigans, Bechhold netted himself a cool 100 Class A shares (100% of the voting power), and 6,400 Class B shares valued at US$243,750 in total. This 15th October 1941 payment of US$375,000 (tax year 1941-1942) was to have serious consequences for Bechhold and his creative accounting.

Following this 15th October takeover though, the original July 1940 contract was finished. Bechhold probably felt he had made enough money and the entire business of the Illinois Tank Company was wound up suggesting that what assets in terms of tank designs it might have had leftover had little to no value. I.T.C. formally dissolved on 22nd November 1941.

Certainty

The substantial pay-off which Bechhold had received was classed as personal income. He, and the other stakeholders, were found to be personally liable for taxes of this income. If there is one certainty greater than death and taxes, then it is taxation in time of war. Taken to court for non-payment of taxes, Armored Tank Corporation admitted an error in its tax liabilities and was assessed to be liable for the sum of US$390,144.91 (including US$78,028.98 in tax penalties on top of its original 80% tax liability of US$312,115.93).

This was not the end of it either, for the individual shareholders of the Armored Tank Corporation/Illinois Tank Corporation were also found personally liable for back taxes and penalties. Stockholders Philip Steckler and Hamilton Allen were found liable for US$33,750, and US$22,500 respectively, and Max and Siegfried Bechhold were found liable for US$243,750 and US$45,000 respectively. A massive combined penalty of US$735,144.91 (over US$12.8m in 2019 dollars) for not paying taxes on that US$375,000 (US$6.5m in 2019 dollars) income demonstrated the danger of trying to dodge taxes in wartime.

Accessories

A.T.C. did not just produce a tank design. One of the more unusual things it designed and produced was a trailer for vehicles. This design appears in a letter dated 19th May 1942 from the Office of the Chief of Ordnance to the Commanding General of Aberdeen Proving Grounds (A.P.G.). Confusingly though, the product in question was produced by the ‘Armored Tank Corporation’ of Jersey City, New Jersey, suggesting that Bechhold kept working on designs incorporated in a different state. It is unlikely to be a mistake as A.T.C. (NY) had ended in September 1941 and I.T.C. (DE) ended November 1941. It is undoubtedly the same firm reborn, however, as the person providing information to A.P.G. on behalf of A.T.C. (NJ) was none other than ’Mr. Bechhold’ himself.

Rota-Trailer Model 4
A.T.C.(NJ) Rota-Trailer Model 4 during testing at A.P.G., Summer 1941, hitched to the rear of a half-track. The tests did not go well. Source: The_Chieftain – WoT forum

The proposal to the military was not this time a tank, but a trailer capable of being used for hauling supplies, equipment, or fuel. According to Mr. Bechhold, the British were interested in this trailer and the report recommended that APG experiment with it over a 250 mile (402 km) course to assess its viability, showing it off to the army and British representatives respectively.

This trailer was known as the ‘ROTA-TRAILER’ and the name stenciled on the side during trials stated this was the ‘Model 4’, suggesting the other 3 models or designs were less well refined. This Model 4 trailer consisted of two large hollow wheels fitted with a 40 inch (101.6cm) rubber tire 5 inches (12.7cm) wide. The wheels were unsprung but could hold up to 60 imperial gallons (272.8 liters) of fuel, either petrol or diesel, and were covered in rubber to provide a ‘self-sealing’ effect if the wheel hub were punctured by ammunition up to .50 caliber. Between the two wheels was a large rectangular cargo compartment made from ⅛” thick (3.175 mm) thick welded steel. This large space inside could be fitted with an ammunition rack for tank or artillery shells (34 rounds of 75 mm or 108 rounds of 37 mm), small arms ammunition boxes, ration boxes, water or fuel cans, or other items that were required. A second, smaller compartment below this was specifically designed to hold four boxes of .30 ammunition.

Top-down view of the Rota-Trailer Model 4
Top-down view of the Rota-Trailer Model 4 from A.T.C. (NJ) with top cover open. It contained 3 specimen shells in a rack, two 5-US gallon (18.9 liter) ‘flimsies’ and three boxes of rations. Source: The_Chieftain – WoT forum

At the back of the trailer lay a third compartment, smaller than the first, and which contained a hand-operated fuel pump and supply hose long enough to feed the towing vehicle. Below this compartment lay a fourth compartment (just like the one at the front) which held stowage space for tools.

A.T.C.(NJ) Rota-Trailer Model 4
A.T.C.(NJ) Rota-Trailer Model 4 pictured during testing at A.P.G. Summer 1941. Source: The_Chieftain – WoT forum

Overall, the trailer was very complex containing many bespoke parts that made for complicated maintenance. The doors to access the items inside were fitted with wing nuts (butterfly nuts) but were overly laborious to unscrew to access the contents. This is something that could easily have been rectified in a production model.

Rear view of the Rota-Trailer Model 4
Rearview of the Rota-Trailer Model 4 from A.T.C. (NJ) with hand pump (top) and toolbox (bottom) open for inspection. Between the two is a towing hook for additional trailers. The narrow tires and very wide wheel hubs are apparent in this image. Source: The_Chieftain – WoT forum

The Rota-Trailer not only had these internal compartments for stowage but also the ability to have a multitude of items carried on top. A special frame was fitted which held three 5-US gallon (18.9 liter) oil cans, and various tie-downs allowed other accessories such as nets or tarpaulins or other stores to be lashed to the top of the trailer.

Testing

Despite looking good on paper, capable of extending the fighting range of a tank, the trailer had serious problems. It was tested by an M4 Sherman and two different half-tracks over a 26 mile (42 km) cross country course and 250 miles (400 km) of gravel roads and, whilst it was on a flat surface, like a road, it worked well with little bouncing. The trailer was heavy too: each wheel weighed 400 lbs (180 kg) empty and 800 lbs (360 kg) when full in addition to the weight of the other material carried. The weight of the trailer placed additional strain on the drivetrain of the towing vehicle and, during rough travel off-road, the stress and strain on the trailer risked serious damage. On top of this, the trailer reduced the maximum speed of the vehicle towing it because the instability of the load caused by the sloshing liquid in the wheels threatened to result in sideways skids at high speeds.

Even as it was, the semi-rough terrain traversed ended up with all of the cans of water inside or on top of the trailer becoming deformed and leaky but the trailer did at least provide self-floatation in mud due to the width of the fuel cells. Another downside was that the lower front compartment, just 8.75 inches (222 mm) from the ground had a tendency to become filled with mud which was forced into it.

A final problem with the trailer was that it made reversing more difficult. During testing with an M4, the trailer skewed to one side and the stress caused damage to the towing arm and the tank tracks rubbing against the trailer body.

Model 4 from A.T.C. (NJ) after testing, the twisted tow arm
View of the Rota-Trailer Model 4 from A.T.C. (NJ) after testing, the twisted tow arm and torn section of the front having been caused by contacting the tracks of the tank. Source: The_Chieftain – WoT forum

Overall, the tests of this A.T.C. product were a failure and the vehicle was not recommended for use. Its main faults were:
Difficult to reverse
Additional strain on the drivetrain of the towing vehicle
Reduces maximum possible speed of the towing vehicle
Too heavy to move easily by hand
Too little ground clearance
No suspension
Steel body is not resistant to small arms fire

None of these faults were to stop further ideas, designs, and experimentation with trailers for hauling fuel or stores by tanks, but the work from A.T.C. (NJ) on this matter was effectively dead. No more is known of A.T.C. after this time; possibly Bechhold’s resources had simply run out and this venture failed, although it is noteworthy that on 1st February 1943, despite the failings of the Rotatrailer, the British still ordered 600 of them anyway, although how many were finished or delivered is less clear.

In the Army

Siegfried Bechhold, aged 42, in October 1942 joined his second Army. His first was a German one in WW1, his second, an American one in WW2. He served as a private being sent to Camp Lee in Virginia. He is not believed to have been sent overseas.

Re-born once more?

The back end of the hull of the Bechhold Tank seen in the November/December 1940 advert is very similar to the vehicle shown to the US Army Ordnance Department in May 1942 known as the Bigley Gun Motor Carriage suggesting a possible link to that vehicle. Was, in fact, the Bigley GMC the M.1938 High-Speed tank from Christie, bought and modified by A.T.C. and then sold off, redeveloped and re-submitted by another firm? Or is it in fact the other Christie tank, the M.1937 sold off by his creditors to Mr. Bechhold. On the balance of the evidence, the former case appears to be correct.

Bigley GMC seen in May 1942
Bigley GMC seen in May 1942. Source: US Army Ordnance

By the end of WW2, Bechhold had left the field of tanks and the complications of military work. By 1948, he was living in Florida where he headed the Ribbonwriter Corporation of America, selling parts for typewriters. Siegfried Bechhold died in California in 1956.

A rendition of Bechhold’s tank, as shown in the ad published in the November/December 1940 issue of the Army Ordnance Magazine. Illustration by Adrielcz, funded by our Patreon campaign.

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US Patent US2310887(A). Hook-on-and-release mechanism for fighting tanks. Filed 6th May 1941. Granted 9th February 1943.
Weir J. D.G. Mech. E. (24th March 1941). Memo to Sir James Lithgow.
Weir J. D.G. Mech. E. (24th March 1941). Memo to Air Marshall Dawson.
Weir, J. D.G. Mech. E. (30th April 1941). Memo to A.R. 2 War Office via DAFV.
Wrynn, C. Major. (1st February 1943). Rota Trailers – Memo.. 1/Rel/ Equip Armd/1
The Chieftain’s Hatch 28th March 2014. Trailer, Ammunition and Fuel Part 1. 
Christie, J. (1985). Steel Steeds Christie. Sunflower University Press, Kansas, USA

Categories
Has Own Video WW2 US Prototypes

Light Tank T3

United States of America (1936)
Light Tank – 1 Prototype

Light Tanks T3 Source: AGF

The Light Tank T3, made in the late 1930s, occupies a period of time in US tank development history best described not so much as a dark age but more of a grey age. Lots of failed and somewhat obscure ‘T’ number designs were being developed to fulfill an unclear and poorly considered set of strategic goals at a time when an isolationist America was unprepared to wage a modern war.

This relatively unknown and obsolete-before-it-was-even-finished tank is remarkable only for its unremarkableness, and that it was inferior in almost every way to tanks of other nations such as Italy, whose 2-man turretless light tanks were also identified as having serious failings in combat. Perhaps, the only thing to distinguish the Light Tank T3 is that it marks one small step in the process of development which eventually led to one of the most successful light tanks of WW2, the Stuart.

The design

The US Light Tank T3 started life in 1936 as an idea by Rock Island Arsenal (RIA) to produce a tank lighter than the Light Tank T2, which was due to go into mass production that fiscal year. At this time, weight was king. The US Secretary of State for War had decreed in the Spring of 1933 that 7.5 US tons (6.8 tonnes) was the maximum weight allowable for a light tank, so the goal was to keep the weight as low as possible. RIA had already dropped the British Vickers 6-ton-style suspension in favor of a double-wheel volute spring bogie from the Combat Car T5 for the Light Tank T2 in 1934. Thus, the suspension which was to form the basis of numerous American designs for the next several years had already been selected when the Light Tank T3 came along. With an attempt to be less than half the fully laden weight of the already light Light Tank T2 (weighing just 7.5 US tons to 9.7 US tons/6.8 to 8.8 tonnes depending on the variant), severe design compromises would have to be made.

The most obvious of these changes was the removal of the turret, followed by a significant overall reduction in size and the switch to a crew of just two instead of four on the Light Tank T2. The two crew were simply the driver on the front left of the hull, and the commander on the front right. The commander also had to operate the sole armament. In an effort to further reduce weight, some aluminum components were also used inside. Finished in March 1936, the vehicle was shipped to Aberdeen Proving Ground (APG) in Maryland in April that year. Here, on 23rd April, the Light Tank T3 was unveiled for comparative testing with the pilot model Combat Car T5 (a tank in all but name).

Pilot model of the Light Tank T2 (no armament fitted) Source: Hunnicutt
The 7.5 US ton (6.8 tonnes) Pilot Combat Car T5 (no armament fitted) Source: Hunnicutt

Engine

The Light Tank T3 was powered by a single V8 Ford car engine. Capable of delivering 83 hp at 3,800 rpm, with differential steering and a 4-speed transmission, the Light Tank T3 could manage a credible 35 mph (56 km/h) on a road.

This Ford V8 was later replaced with a Menasco air-cooled engine and as such was renamed Light Tank T3E1.

Suspension

The Light Tank T3 used a pair of dual-wheel bogies with rubber volute springs of a very similar style fitted to a whole generation of US tanks in WW2. These volute spring units, however, were the result of comparative testing with an experimental rubber torsion suspension. Details on what that suspension actually looked like are unclear but it is known that it failed repeatedly during testing and would need redesigning to be usable. It was not and was abandoned. When the Light Tank T3 was upgraded with a Menasco engine as the Light Tank T3E1, the volute springs were finally selected as the preferred suspension.

The Armament

The Light Tank T3 was very poorly armed, just a single .30 caliber (7.62 mm) machine gun located in the front right of the hull. Mounted in a ball, the range of motion was acceptable but still ultimately as limited as other vehicles such as the Italian CV.3, it faced forwards so could not fire to the sides or rear.

Armor

As might be imagined in such a small and light vehicle, the armor was woeful. No part of the Light Tank T3 was thicker than ⅜” (9.5 mm), with most of the armor being just 3/16” (4.8 mm) thick, enough to protect against small arms from the front but vulnerable to even a burst from a machine gun or shot from an anti-tank rifle. With such poor armor, it is no surprise that an idea was floated to increase the armor thickness to an unspecified value in another variant known as the Light Tank T3E2, with the issuing of the tank to the National Guard in mind. This was never completed and the Light Tank T3E2 was never built. There was also a T3E3 version that got as far as a study but it is not known exactly what the study was about and whether it was armor or automotive related or something else.

US Light Tank T3 pictured during trials on 13th March 1936. No armament is fitted but it does have a very shiny single front headlamp on the glacis nose and what appears to be some kind of siren on the mudguard. Source: Hunnicutt

Variants

T3E1: upgraded T3 with a Menasco engine. 1 converted.
T3E2: T3 project with increased armor. None built.
T3E3: unknown study project

Conclusion

When the Light Tank T3E1 was abandoned, it was not wasted. Instead, the remaining vehicle was stripped of its armament and converted into an experimental tracked carrier named the Cross-Country Carrier T5. The sole contribution of the Light Tank T3 is perhaps to show the futility of a two-man tank armed with just a single machine gun. The cost of the vehicle and the poor combat potential meant that, despite moderately good mobility, it was still a failure. Of the variants attempted, the Light Tank T3E1 was at least an improvement with a better engine but the E2 with more armor was dropped before it began. The Light Tank Tank T3E3 got as far as a design study but how far and quite what they were even trying to study is not clear. The concept was a dead end. The vehicle was converted to a tracked utility carrier and quite rightly consigned to the dustbin of US tank design.

With a soldier for scale, the tiny Light Tank T3 shows really just how small it was. Source: Hunnicutt
The T3 light tank was tiny, armed with just a single machine-gun and seating two crew members in the front compartment. The rear rounded compartment housed the engine. Illustration by Yuvnashva Sharma, funded by our Patreon campaign.

Specifications

Dimensions 11.25’ x 6.75’ x 4.5’ (3.43 x 2.06 x 1.37 m)
Weight 3.54 US tons / (3.21 tonnes)
Crew 2 (Commander/gunner, and driver/radio operator)
Engine Ford V8 Petrol (T3), Menasco air-cooled (T3E1)
Max. speed 35 mph (56 km/h)
Armament 1 x .30 caliber machine gun
Armor ¼” to ⅜” (6.35 to 9.53 mm) (T3), slightly heavier armor (T3E2)

Sources

AFV Data Series
Crimson, F. (1992). US Military Tracked Vehicles. Crestline, USA
United States Army. The General Staff: Its Origins and Powers
AGF Board. (1947). Development of Armored Vehicles Vol.1: Tanks.
Hunnicutt, R. (1992). Stuart: A History of the American Light Tank. Presidio Press, USA

Categories
WW2 US Prototypes

Light Tank T21

United States of America (1942-1943)
Light Tank – None Built

Introduction

When the US joined the war in 1941, their primary light tank was the M3 Stuart and, while this vehicle was acceptable for that time, there was an interest in a new light tank. In January 1941, the US Army started the T7 Light Tank program, however, by August 6th, 1942, this tank had grown in weight and size and was now reclassified as the M7 Medium Tank. With no replacement for the Light Tank M3 in progress, the T21 Light Tank project was started.

While no T21 mockup would ever be made, this mockup of the T20 shows roughly what the T21 would have looked like. (Photo: Stuart)

Development

With the need for a new light tank, representatives of the Ordnance Department and the Armored Force held a conference at Fort Knox on August 18th, 1942. where it was decided that they should use the new T20 medium tank as a basis for the light tank. It would mount the M3 75 mm gun and feature armor capable of holding up against .50 caliber rounds while being within a 20-ton limit. It was decided that, if possible, the M3 75 mm gun would be replaced with a 76 mm higher velocity gun. It was proposed that it could use the Medium Tank M7’s suspension.

Following this conference and additional studies, an Ordinance Committee Minutes (OCM) was issued in February 1943 detailing the new light tank. It would have a crew of 5, mount a stabilized 76 mm gun, and would have a top speed of 45 mph (72 km/h). However, at this stage, the engine, suspension, and various other aspects were not finalized and its weight had been increased to 47,000 lbs (21,300 kg) or 21 long tons. Final layout drawings were finished during March and submitted. By this time the weight had been increased to 51,000 lbs (23,100 kg) or 22.8 long tons, with the new top speed being intended as 50 mph (80 km/h).

There was also a second variant which existed for a short time called the T21E1. This variant was to weigh 22 tons, later increased to 23 tons, and would have thicker armor than the normal T21 while being able to manage 50 mph (80 km/h). It seems likely that the T21E1 program was accepted as the new T21, as later sheets state the T21 as having almost the same figures as the T21E1.

T20 Pilot 1
T20 Pilot 1; the T21 with VVSS would have been almost identical to this. (Photo: Pershing)

Armor

The initial armor for this tank was designed to only resist .50 caliber fire, being 1 1/8th inch (2.85 cm) on the hull’s front and 1.5 inches (3.81 cm) on the turret face. The hull’s side and rear armor was 1 inch (2.5 cm) and 3/4th (1.9 cm) of an inch, respectively, the turret’s side and rear armor were 1 1/8th inch (2.85 cm). At a later point, the armor on the T21 increased to be the same armor basis as on the M5 Stuart. The T21E1 project was to have the same armor as the M5 Stuart as well.

Firepower

The T21 was to mount the 76 mm M1E1 or M1E2 gun – the primary difference between these 2 guns being that one had a tighter rifling twist rate than the other. The rounds used by that gun included M62 Armor Piercing Capped (APC) and M79 Armor Piercing (AP), additional rounds including High Explosive and White Phosphorus. The gun was to have elevation and depression limits of +25 and -10 degrees respectively, as well as being gyro-stabilized. It also was to mount two .30 caliber machine guns, one co-axially to the main gun and another in a bow mount in the hull.

Suspension and Tracks

While it was initially proposed in August 1942 to use the M7 Medium Tanks Vertical Volute Spring Suspension or VVSS, it was later decided to utilize torsion bar suspension instead. The tracks that were intended for it were the 18 inch T49 type. Whilst the exact layout is unknown, the T21 would have had, it can be assumed that due to it being just a lighter T20, it would have been the same or very similar as on the T20E3. The T20E3’s suspension had a torsion bar and initially had 3 track return rollers per side, however later on, 2 additional ones were added, bringing the total to 5 per side. an idler wheel was attached to the front wheel to compensate for slack in the track.

T20E3 Pilot
T20E3 Pilot, externally, the T21’s suspension would have been almost identical. Note the 3 return rollers (Photo: Pershing)

Engine and Transmission

The engine for both the T21 and T21E1 was to be the Ford GAN, which produced 500 bhp at 2600 RPM. The transmission for both was the same 5-speed manual transmission utilized in the M4A3. The location for the engine and transmission is unknown, but again, due to it being just a lighter T20, it is likely that it would have been in the same position as on the T20, in the rear of the tank.

Fate

In March 1943, the design and layout were presented at Fort Knox to the Armored Force. They came to the realization, from their experience with the M7 Medium Tank, that the T21’s weight would continue to increase in the future, resulting in another under-armored medium tank. They then suggested that the T21 project be terminated and Ordinance replied in July 1943 by killing the project. Up to this point, no mockup or pilot vehicles had even been started. The fate of the T21E1 is unknown, but it was almost certainly canceled along with the T21 if it was still in development at that time.

T20E3 showing the later change to 5 return rollers
T20E3 showing the later change to 5 return rollers. (Photo: Pershing)

Conclusion

This design, like many before it, was a good idea on paper, but operational realities and desires soon lead to a situation where, like the M7 before, it was doomed to become too heavy to fulfill the light tank role and too light to fulfill the medium tank role. The discontinuation of the T21 program in March 1943 was met with the start of a new project, the T24, which would not be deployed until 1944, which in turn forced the US to continue having to field the M3 and M5 Stuarts up until the end of the war, despite their growing inferiority.

The T21 Light Tank was very similar to the T20 Medium Tank from which it was derived. Illustration by Andrei “Octo10” Kirushkin, funded by our Patreon campaign.

T21 Light Tank Specifications

Dimensions (L-W-H) 5.76 m x 2.98 m x 2.48 m
Total weight, battle ready 20.98 tons (47,000lbs gross)(21.31 tonnes)
Crew Five (Driver, Co-Driver, Commander, Gunner, Loader)
Propulsion Ford GAN
Maximum speed 45mph (72kph) on road
25mph(40kph) on 3% grade
12mph(19kph) on 10% grade
Suspensions Torsion bar
Range 1150 miles at 25mph (40kph) on roads
Main Armament Gyro Stabilized 76mm M1E1 or M1E2 gun with 70 rounds
Secondary Armament Two .30 Browning M1919 machine guns with 6000 rounds
Armor 1 inch (25mm) to 1.5 inches (38mm)
Production None

Sources

Pershing: A History of the Medium Tank T20 Series, R.P Hunnicutt.
Stuart: A History of the American Light Tank, R.P Hunnicutt.
R.A.C British Army Staff (AFV) Situation Report No. 5,7,9

Categories
Has Own Video WW2 US Prototypes

Barnes Two-Man Heavy Tank

United States of America (1938)
Heavy Tank – None Built

Lt. Colonel Gladeon M. Barnes from the US Army’s Ordnance Department casts a long shadow over tank development in the USA in the period around the start of WW2. Barnes was an interesting man, but some of his ideas and designs were demonstrative of a disconnect between his thinking and military reality.

One such example came in 1938 with the idea for a small heavy tank armed with a single machine gun. Quite what role such a vehicle was meant to fulfill is hard to imagine years after other users of such vehicles had already accepted the serious inherent limitations of a similar type of vehicle.

Inspiration

Somewhat oddly, the inspiration for this idea came from the Spanish Civil War. Section G-2 (the department responsible for Intelligence in the US Army) examined that conflict for lessons in a report titled ‘Tank Lessons from the Spanish Civil War’. They concluded that tanks were too poorly armored, used in too few numbers, and that they were not maneuverable enough.
In that war, the primary tanks being used were the German-supplied Panzer I, the Italian CV.3 series light tank, and the Soviet-supplied T-26 light tank. During that war, as G-2 correctly pointed out, tanks tended to be used in small numbers or alone and both the CV.3 series and T-26 had thin armor, around 14 to 15 mm maximum, meaning both were just bulletproof.

The T-26 had an advantage over the CV.3 in the addition of a turret-mounted weapon, whilst the CV.3 was stuck with its only armament in a mounting on the front left of the hull facing forwards. Neither tank was able to demonstrate much speed even though the CV.3 was faster, just under 30 miles per hour (48 km/h) compared to just under 20 miles per hour (32 km/h) for the T-26, although the overall effect was slight. Both tanks were too slow, both suffered from narrow tracks and a relatively underpowered engine. Any reasonable and objective assessment of the use of tanks in the Spanish Civil War would reflect this.

The Italians, for example, understood from the conflict the severe limitations of the CV.3 for tank vs tank combat and undertook work on turreted light tanks with some urgency. The Germans and Soviets likewise looked and learned. Why then did the US see a solution lying in a vehicle with the same sort of layout as the CV.3 but with less armament is difficult to comprehend.

The outline of Barnes’ concept for a 2-man heavy tank.(Source: Armor Magazine)

The design

Barnes’ concept was for a small light tank, just 7 US tons (6.35 tonnes) or so and just 11 feet (3.35 m) long. For reference, the Italian CV.3 was less than half the weight, shorter, narrower, and lower, and the Soviet T-26 was heavier and slightly longer, wider, and taller.

With a crew of just two, both men would have their work cut out for them. One man had to drive the tank and operate its radio, almost certainly sat on the left just like on the Light Tank T3. The other crew member would have to both command the tank and operate the armament and would sit on the right, alongside the other man. This is a very similar arrangement to the Italian CV.3, except the crew position/roles were reversed. It could be considered that these reductions in size and capability were, in fact, simply the means to get the most tank possible for the least money. However, here Barnes trips-up once more. He provided a cost estimate of US$20,000. In 1938, US$20,000 was a huge sum of money, equivalent to over US$350,000 in 2020 values, or roughly half the cost of a far more potent and useful Sherman tank.

Comparison between Barnes’ design and the primary Spanish Civil War Tanks

The 2-man heavy German Pz.I Italian CV.3 Soviet T-26
Crew 2 2 2 2
Armament 1 x 37 mm / 1 x .30 cal MG 2 x 7.92 mm machine guns 2 x 6 mm machine guns 1 x 45 mm & 1 x 7.62 mm MG
Dimensions
L / W / H
11’ x 6.5’ x 4.5’
(3.35m x 1.98m x 1.37m)
4.02 x 2.06 x 1.72
(meters)
3.03 x 1.4 x 1.2
(meters)
4.65 x 2.44 x 2.24
(meters)
Weight 7 tons (US)
(6.35 tonnes)
5.4 tonnes ~3 tonnes 9.6 tonnes
Speed
(off road/on road)
20 mph / 35 mph
(32 km/h / 56 km/h)
25 km/h / 37 km/h 42 km/h 42 km/h
Armour
F / S / R
1.5”
(38 mm)
7 – 13 mm 14 / 8 / 8
(mm)
15 / 15 / 15
(mm)
Note No turret Turreted No turret Turreted

The Armament

The drawing of Barnes’ vehicle shows a single machine gun and the annotation states this to be a single .30 caliber (7.62 mm) weapon with 60 degrees of traverse, presumably 30 degrees to each side. An alternative armament was also proposed, a 37 mm gun. Once more, this was to be mounted in the front, seriously limiting its potential effectiveness. On top of this failing, operating a gun is a lot of work to load, aim and fire and, perhaps because of this, Barnes did propose that it could be automatically fed. Thus, the commander would have to ‘only’ command the tank, aim and fire the gun. Even so, the tank, limited by the traverse of its gun, would still be inferior to the Soviet T-26.

Armor

If the CV.3 and T-26 were unsuitable, with armor only 15 mm at most, then the goal would be to have more, presumably to make the tank protected against automatic cannon fire such as the potent 20 mm Breda cannon which was a proven armor-killer in Spain. It would also mean anti-tank rifles would be less useful against tanks, so more armor was not an unreasonable goal. Barnes wanted up to 1.5 inches (38 mm) of armor on this small heavy tank. For the purposes of reference, the Czech LT vz. 35 (better known as the Panzer 35(t) in German service in WW2), a tank which is possibly the preeminent and most modern turreted tank of the era, had just 25 mm across the whole front. What Barnes was indeed proposing was a tank the size of the diminutive American Light Tank T3, a little larger than the Italian CV.3 light tank, but with armor heavier than most of the tanks then in European service. All that, just to carry a single and rather limited machine gun, a task the even smaller CV.3 did more effectively with two machine guns mounted together.

tiny Light Tank T3
With a soldier for scale, the tiny Light Tank T3 shows really just how small it was. (Source: Hunnicutt)

Maneuverability

The speed and agility of the vehicles in the Spanish Civil War were seen as a failure because they were insufficient. Therefore, Barnes should have been looking for a vehicle able to exceed the speed of the CV.3. Instead, he managed to make a vehicle which even under ideal circumstances was larger, heavier, and slower.

The power to weight ratio of this design was to be 20 to 25 horsepower per ton and, with an estimated 7-ton (6.35 tonnes) weight, that would mean an engine of 140 to 175 hp. Ideally, this would mean a top speed of 20 mph (32 km/h) on a slight slope and 35 mph (56 km/h) on a road. On paper, this all sounded good, but paper-designs are like that and a magic engine can be produced from thin air with imaginary performance. When the design meets reality, things change and this is exemplified by the Light Tank T3.

Although Barnes did not specify which engine was going to be used, the Light Tank T3, produced two years earlier in 1936 gives a good idea of the problems. Both vehicles clearly use a pair of volute-sprung bogies, each with two wheels and a front-mounted drive sprocket meaning the transmission was in the front. The Light Tank T3 is very similar in size, suspensions, armament, and appearance to Barnes’ idea and was fitted with a 221 cubic inch (3.62 litre) Ford V-8 engine. Despite being slightly over 3.54 US tons (3.21 tonnes), this vehicle had half of the armor Barnes was proposing and yet had the same top speed. The Light Tank T3 was the same size as Barnes’ idea, with half the armor and half the weight, and yet the same desired performance meaning whatever engine Barnes was considering would have to be significantly more powerful and yet fit in the same space as available in the T3. This was no small order, although the Combat Car T5 of 1933 had managed to cram a 235 hp air-cooled Continental R-670 radial petrol engine inside, all for 6.29 US tons (5.71 tonnes), albeit with armor around just ½” to ⅝” thick (12.7 to 16 mm).

US Light Tank T3 of 1936
US Light Tank T3 of 1936. (Source: AGF)

The closest vehicle, perhaps to Barnes’ idea, was not the Light Tank T3, but the Light Tank T6. Built in 1939, one year after Barnes’s 1938 concept, the Light Tank T6 departed from the suspension of the Light Tank T3, using just a single 2-wheel bogey with a volute spring and the large on-ground trailing wheel at the back along with a separately sprung half-bogey. Once more, the driver was to be on the left in another two-man tank but this vehicle was not armed at all. With armor up to 1” (25 mm) thick and weighing in at 9.75 US tons (8.85 tonnes), the Light Tank T6 was roughly the same size and gives a good idea of a potential power plant for Barnes’s tank, namely a pair of 8-cylinder Buick petrol engines. However, even so, it was more than 2 tons heavier and still had armor no thicker than 1” (25 mm) and, importantly, no armament. Comparing Barnes’ idea to both Light Tanks T3 and T6 shows how unrealistic it really was.

US Light Tank T6
US Light Tank T6. (Source: AGF)

Comparison between Barnes’ design and the Light Tanks T3 and T6

Light Tank T3 The 2-man heavy Light Tank T6
Date 1936 1938 1939
Crew 2 2 2
Armament 1 x .30 cal MG 1 x 37 mm / 1 x .30 cal MG unarmed
Dimensions
L / W / H
11.25’ x 6.75’ x 4.5’
(3.43m x 2.06m x 1.37m)
11’ x 6.5’ x 4.5’
(3.35m x 1.98m x 1.37m
Approx. 11.25’ x 6.75’ x 4.5’
(3.43m x 2.06m x 1.37m)
Weight 3.54 tons (US)
(3.21 tonnes)
7 tons (US)
(6.35 tonnes)
9.75 tons (US)
(8.85 tonnes)
Engine Ford V8 Petrol unstated Twin Buick 8-cylinder Petrol
Speed
(off road / on road)
? mph / 35 mph
(? km/h / 56 km/h)
20 mph / 35 mph
(32 km/h / 56 km/h)
? mph / 30 mph
(? km/h / 48 km/h)
Armour
F / S / R
¼” to ⅜”
(6.35 to 9.53 mm)
1.5”
(38 mm)
⅜” to 1”
(9.53 to 25 mm)
Note No turret No turret No turret

Conclusion

It is hard to see any merit in Barnes’ idea. The armor certainly would have provided excellent protection from the relatively small caliber weapons then in service on a lot of tanks, but those were the previous generation. Against a 37 mm anti-tank gun, like the type used in numbers in Spain to good effect, even 38 mm of armor was not going to be much help, although it would certainly have made the little tank impervious to infantry which did not have access to a cannon. What then was Barnes’ really proposing? A small lightly armed and heavily armored tank may have some utility against infantry but, with the only armament in the front it would, as the Italians found to their cost, prove untenable. If, however, Barnes was really considering a small tank destroyer then why bother with the armor at all. Concealment and maneuverability would have been of far more use and he could reasonably have mounted the gun on top in an open-setting for a wider arc of fire and more space to carry ammunition.

Both ideas were also stymied by the selection of just two crew. There was simply too much for two men to do in combat, so a slightly larger chassis would also have allowed a third or fourth man to operate the gun, but would also have severely increased the weight and decreased the mobility.

Finally, Barnes’ concept of mobility was flawed. There was no way he was going to get even more armor and an automatic 37 mm anti-tank gun into a vehicle no bigger than the 9-ton Light Tank T6, along with a larger engine and still have the same performance. Likewise, he could not have allowed the weight to go over 7.5 tons (6.8 tonnes), as this was the limit set in 1933 by the Secretary of War for light tanks, suggesting a reason behind the ‘heavy’ part of the name, and that is before the eye-watering price-tag for the vehicle was considered.

Illustration of Barnes Two-Man Heavy Tank illustrated by Yuvnashva Sharma and funded by our Patreon campaign.

Barnes 2-man Heavy Tank specifications

Weight 7 tons (6.35 tonnes).
Crew 2 (Commander/gunner, and driver/radio operator)
Propulsion Type unknown, 140-175 hp desired
Desired Speed 20 mph off-road / 35 mph on road (32 km/h / 56 km/h)
Trench Crossing 4 feet (1.22 m)
Armament 37 mm gun or .30 caliber machine gun
Armor up to 1.5 inches (38 mm)
Total production None

Sources

Bellinger, J. American Hetzer. AFV news Magazine 37(2)
AFV Data Series
Crimson, F. (1992). US Military Tracked Vehicles. Crestline, USA
United States Army. The General Staff: Its Origins and Powers
Christie, J. (1985). Steel Steeds Christie. Sunflower University Press, Kansas, USA
AGF Board. (1947). Development of Armored Vehicles Vol.1: Tanks.
Hunnicutt, R. (1992). Stuart. Presidio Press, USA

Categories
WW2 US Prototypes

Mobile Pill-Box Fortress

United States of America (1940)
Mobile Pillbox – None Built

The early 20th century was dominated by new technologies being developed in large numbers. To capitalize on these rapid advancements, monthly magazines were published that focused on bringing these new technologies to the general public’s attention. This proved to be a great success. The most popular example of these magazines is Popular Mechanics, which published its first issue in 1902 and continues to be published today. Another popular example was Modern Mechanix, which went through several name changes since its first issue in 1928 before its final issue in 2001.

The technologies featured in these magazines varied greatly in their application. Power sources, home gadgets, farming equipment and flying machines are but a few examples of the kinds of inventions and concepts featured. Most notably, particularly during both World Wars, was the inclusion of conceptual weaponry and armored vehicles. These were rarely competently designed. Due to a total lack of practical insight into the use of military equipment, the end result was often a design more appropriate for a science fiction setting than a real battlefield. Some designs featured in these magazines are notable for their relative practicality however, at least when compared to the rest, and their intended usage is somewhat reasonable for being designed by illustrators as nothing more than magazine filler.

Firepower Required

Before the United States entered the War in 1941, it faced a distinct lack of dedicated tank destroyers. While it would not be until late 1941 when the US finally adopted such a vehicle – the 75 mm gun-armed M3 Gun Motor Carriage – designs already existed in the previously mentioned magazines that were intended to fill a similar role.

The November 1940 issue of Modern Mechanix features a drawing of a large armored truck with two guns in an even larger turret-mounted behind the cab. This Mobile Pill-Box Fortress, as it is referred to in the magazine, by virtue of having a single turret on a sensible and presumably existing truck chassis, is on the higher end of practicality regarding conceptual designs found in these magazines. No other name is given to the vehicle and no further information on it can be found despite supposedly being based on a prototype built by a truck manufacturer based in Los Angeles, California.

The single page showing the Mobile Pill-Box Fortress and its description. Note the inconsistency in scale between the crewmen in the cab and in the turret, making judging the size of the vehicle difficult. Source: Modern Mechanix, Issue November 1940.

Design

The Mobile Pill-Box Fortress is based on a large truck chassis with two single wheels at the front and two pairs of triple wheels at the rear. The reason for two pairs of triple rear wheels should be clear, as directly above them is a huge domed turret housing a pair of 6 inch (152 mm) guns, presumably naval in origin.

Turret

The turret can rotate a full 360 degrees, but gun elevation and depression are not known. Depression would inevitably be limited in the forward arc due to the roof of the cab and the bizarrely located headlight mounted to it. Ammunition for the guns is stored in two racks, one upper and one lower. The shells are stored nose-up in two racks that run the full circumference of the interior turret wall. This allows a large number of projectiles to be stowed despite their great size. It is not shown in the drawing where the propellant charges are stored. It is possible they are stored at the front of the turret or on the right side of the guns where they would be obscured, but the most likely explanation is either that they were never considered by the artist or the shells are one-piece. No access hatch or door is visible on the turret.

Due to the great recoil generated by such large guns, the vehicle features four large outriggers around the turret ring. These outriggers appear to be telescopic in extension and fixed in place with no articulation, apart from being capable of extending and retracting their feet up and down. The outriggers are an appropriate design choice for a vehicle that, as the name suggests, acts as a stationary pillbox instead of a more mobile vehicle, capable of quickly relocating during combat.

The turret’s gunner is located on the left side of the guns and has no seat. He has a direct vision telescope that is mounted unusually far back in the turret which is aiming through a thin visor in the turret’s mantlet. Even though the sight would most likely move with the mantlet, and stay lined up to see through it, the field of vision as a result of being mounted so far back would be incredibly narrow. Only two other crewmen are shown in the turret, those being the loaders, who are each loading their respective guns. As 6 inch guns, each projectile would have been very substantial, at likely 45 kg (99 lb) or more in weight. With the turret having a pair of guns, this means that each loader has to lift and load projectiles by himself, which during sustained fire would be incredibly tiring without any loading aides such as a winch or conveyor, neither of which are shown.

Cab

The cab is located at the front of the vehicle. The driver’s position is assumed to be on the right side due to the placement of the only seat visible in the drawing, an unusual choice for an American vehicle. However, due to the perspective of the drawing, the seat may actually be more centered in the cab. On the left side of the cab is the assistant driver who operates at least one of the two machine guns present in the vehicle, both of which are in the front corners of the cab. Ammunition for the machine guns is stowed above the engine in the center of the cab. Due to the placement of the driver, it is likely that he operates the right-side machine gun instead of the assistant driver having to move back and forth between the two guns. Like some tanks with an assistant driver, it is likely that he would be expected to take over driving the vehicle should the driver be injured. They may also alternate duties each day.

There are a number of vision ports around the cab. There are two ports on the front slope which can be hinged open. Similarly, there is a large hinged port on the sloped roof. It can be assumed there is a second port on the right side which is obscured, but what these upwards-facing ports would be for is not clear. Each of the two machine guns in the front corners had their own fixed vision ports above them, which, like that on the turret, would provide undoubtedly poor visibility for those operating the guns. There is a fixed port on the left side of the cab, again it is likely the right side has the same. Lastly, there is a vision port in what appears to be an access door in the back left corner of the cab. A step is present below it on the outside, as is a handle. What appears to be two hinges spanning the width of the cab roof are also present. It is not clear how these panels would open.

Armor

No specific armor values for the vehicle are given, but while the drawing is poorly scaled it is clear that the armor of the turret is supposed to be very thick by standards of the time. The turret armor is intended to protect against shells and bombs (no specific shell or bomb is described), whereas no such requirement is given for the cab armor, but it is reasonable to assume it would be at least capable of resisting small arms and shrapnel. The engine has its own armored housing within the cab, and it is not known if the covers over the wheels are simply mudguards or if they too are supposed to be armored.

Fate And Conclusion

While at its core the Mobile Pill-Box Fortress is reasonably designed by the standards of the magazine it was featured in, no information can be found regarding the claim that it was based on a real prototype that underwent four months of testing by the US Army. After the United States joined the war, a great deal of effort went into developing and testing trucks carrying anti-tank guns in a wide variety of configurations.

The purpose of these vehicles was to be fast and easy to manufacture due to being built on existing chassis, as well as fast on the battlefield, able to quickly respond to reports of enemy tanks in an area and move to engage them. This manufacturing and doctrinal need are incredibly similar to the description of the Mobile Pill-Box Fortress, a truck-based vehicle capable of traveling up to 65 mph (105 km/h) to any threatened area to counter both tanks and infantry, and afterward, relocate to any other area in need of anti-tank support. However, due to the great weight of the vehicle, it is reasonable to expect it to be incapable of reaching such high speeds outside of long straight roads.

The choice of a 6 inch gun would be questionable, let alone a pair of them. The incredible capability of such weapons against both tanks and infantry cannot be understated, especially for 1940, but their immense size and weight directly influences the size of the vehicle, which in turn condemns it as almost entirely impractical. For the vehicle’s time, it can be argued quite easily that no practical advantage comes with having such large weapons in a vehicle like this, simply because far smaller and lighter anti-tank guns already existed that were perfectly capable of defeating any tank of the period. At the very least it would be easy to invent a more sensible gun for the drawing.

Despite the similarities between the purpose of the Mobile Pill-Box Fortress and the actual tank destroyers the United States would come to use, the sheer unwieldiness and weight of the vehicle would undoubtedly restrict it to roads only, greatly limiting its application as a strategically mobile weapon. The design, like so many from these magazines, is a great example of theory detached from reality and it is no surprise that none were ever built – this vehicle was purely for the readers of the magazine rather than actual use.



Representation of the ‘Mobile Pill-Box Fortress’ produced by the Author, Mr. C. Ryan, funded by our Patreon campaign.

Specifications

Crew At least 5 (Driver, Assistant Driver, Gunner, Two Loaders)
Speed 65 mph (105 km/h)
Armament Two 6 inch (152 mm) guns, Two machine guns

Source

Modern Mechanix, November 1940

Categories
Has Own Video WW2 US Prototypes

G-3 Light Tank Destroyer

United States of America (1941-1942)
Tank Destroyer – None Built

The G-3 Light Tank Destroyer was the product of the disorganized state of US tank design at the start of WW2. The United States of America formally declared war on Japan, one of the three main Axis powers, on 8th December 1941, following the attack of the US naval base at Pearl Harbor, Hawaii the day before. This was followed, on 11th December, by a declaration of war against Nazi Germany and Italy. The US had been selling arms to the United Kingdom for some time before this though and had started its own military build-up as well, increasing its army strength from just over ¼ million men in 1940 to nearly 1.5 million by the time of entering the war. Nonetheless, it would be some time before the American war machine was in full swing and it had squandered the honeymoon period from the war’s beginning in 1939 to do exactly the development work it needed to deliver an effective tank destroyer. The G-3 Light Tank Destroyer is emblematic of this failure by the US military as the design fails to accommodate the needs of the Army in a new era of tank warfare.

The Americans entered WW2 with a serious shortage of armor, just 8 battalions of tanks for the entire Army in 1940. The Army had been hamstrung by the determination that tanks were only there to support the infantry in tackling machine guns, leading to a lack of attention to the actual problems associated with knocking out enemy tanks with their own tanks. The speed of the German advance and destruction of the most powerful tank force in the world, France, in 1940 came as a further body blow to the US military, which realized it had a serious shortfall in capability to overcome. The US Army needed large numbers of powerful anti-tank guns quickly and this was a problem considering the main anti-tank weapon in service was the 37 mm towed gun which had only entered service in 1939. The Army, in fact, had not even started work on a dedicated anti-tank gun until 1936, and despite men like General McNair having pushed for mobile anti-tank battalions within Infantry Divisions, little had actually been done.

The Start

With little done in the run-up to declaring war and despite the bad news from France in 1940, it was not until April/May 1941 that General Marshall (Chief of Staff of the US Army) decided that a solution was needed to meet the shortfall in anti-tank capability. He instructed the Army’s G-3 Section, responsible for Operations and Training, with this task and, within G-3, this responsibility fell onto the shoulders of Lt. Col. Andrew Bruce. Specifically, Lt. Col. Bruce was tasked with dealing with “such unsolved problems as measures against armored force action”. This was the start of the tank destroyer branch and, at this time, nearly 6 months into the war, there were simply no vehicles for it. The most powerful gun on a tank at the time was mounted in the sponson of the M3 Medium Lee, the 75 mm M2 gun, a less than ideal solution.

The Requirement

G-3 quickly developed a list of requirements for a lightweight tracked vehicle. Fast and maneuverable, these vehicles were to be able to respond to actions where enemy tanks were encountered and then engage them. This required speed, but also a powerful gun. The one thing which was not a particular need was armor. Protection would be sacrificed to the need to bring a gun to the battle faster.

The Fast Tank

How do you get a tank to go quickly? – by taking away all unnecessary weight, such as all but the bare minimum of armor, just bulletproof would have to suffice. The turret could also go if necessary, saving a lot of weight directly, as it would not need turret traverse motors or a turret ring, but also indirectly as the gun could use mounts in the hull and be substantially lower, meaning a smaller vehicle. Maneuverability also meant the vehicle would need a powerful engine, and all of this would have to be carried on a suspension system capable of traveling quickly over rough ground. In 1940/41, there was a clear leader in this regard in the US, the ‘Christie’ system.

The essential elements of the Christie-type system relied upon large diameter wheels carried on a short arm connected to a large coil spring. It was already in extensive use by the British on their Cruiser tanks and by the Soviets on the BT series of tanks. The US, however, had said no. They had already closely examined and rejected the Christie design several years beforehand in favor of volute springs.

Volute springs had two large advantages over the Christie system. Firstly, they were more compact, and secondly, they removed the need to deal with the obnoxious Mr. Christie. So bad, in fact, was Christie’s reputation within US armor circles that, despite his designs having several advantageous features, the Army simply would not consider the vehicles. This attitude persisted even after Christie had divested himself of his designs, selling the rights off to a man named Bechold, who, in turn, would later sell them on to a man named Bigley. Both of those men (Bechold and Bigley) would learn the sting that Christie’s work carried with it and found no success either.

This need for a fast tank-destroyer though, meant a re-appraisal of the Christie system was needed regardless of the previous history between the establishment and the man. The volute-spring system worked but was simply not capable of dealing with the speeds that G-3 wanted. What this meant was that, by December 1941, G-3, through Lt. Col. Tharp, a G-3 General Staff Officer and strong advocate for the Christie-suspension tank destroyer concept, had managed to gain a small amount of interest in it, sending G-4 (responsible for supplies) their recommendation.

This recommendation was for a fast tank using Christie-suspension and carrying a 37 mm anti-tank gun. That vehicle would see development on the old Christie tank chassis owned by William Bigley. By the start of 1942, Tharp’s pressure had led G-3 to develop their own ideas for a fast tank-destroyer based on the now ‘Bigley’ chassis.

With the US entry into the war, the development of armored fighting vehicles required coordination and, to this end, a board was set up to manage things. This board, known as the Armored Vehicle Board (A.V.B) was chaired by Brigadier General William Palmer and often simply referred to as the ‘Palmer Board’. By October/December 1942, the Palmer Board was considering 15 different designs for tank destroyers, amongst them this design using the Bigley chassis. Of note is that one of the competing designs was what became the T49 from Buick.

Christie Airborne Gun Carrier Chassis
Difficult to read, the label says ‘Christie Airborne Gun Carrier Chassis’. Source: Armor Magazine

Engine

No engine is mentioned on the plans. It may be assumed that the engine inside was the same one that had originally been used in the Christie design, the 750 hp Hispano Suiza V12. With this engine the tank could, in theory, manage up to 60 mph (97 km/h) fully laden on a good road, although this would be lower off-road and also a dangerous and impractical speed to consider ‘the norm’. Nonetheless, the speed of the Christie design was undeniable and would likely be reflected within the thinking behind this G-3 concept.

Armament

The initial recommendation was to use the standard Army 37 mm anti-tank gun, but by the time the development work had begun on the Bigley chassis, the move towards a bigger gun was already underway.

By way of illustration, one of the rival designs, which went through a series of substantial changes, ended up as the T42. Even that vehicle did not meet requirements and was then redesigned once more (and redesignated as T49) by April 1942. When it did so, it was being considered for it to mount an American-made British 57 mm gun (6 pounder) instead of the original 37 mm gun considered suitable for anti-tank warfare at the start of the process. That decision was followed in July 1942 by the selection of an American 75 mm gun instead for the T49, ready for assessment in October/December that year. The T49 was later redesignated as T67.

As a turreted vehicle, the T42 (T49) mounting a 6 pounder or 75 mm gun was substantially more effective than the 37 mm proposed on the Bigley chassis and the result was obvious. The Bigley idea was shelved and the only known remaining drawing of the vehicle concept clearly shows it with a small-caliber gun. Whether the armament planned for the T42 was being mirrored by ideas to uparm the Bigley to match it is simply not known. If it was not changed, then it can be speculated that the Bigley tank-destroyer idea was dead sometime in the middle of 1942, when there was the switch to the British 6-pounder. Indeed, this would match with the death of the parallel idea, that of utilizing the Christie suspension taken from the Combat Car T4 to re-equip the T9 Light Tank chassis during the development of the 37 mm-armed GMC T42 in April 1942. That, in turn, had led to an unsuccessful Christie trailing-arm suspension concept for the first pilot model T49, although that too was dead by October, along with a myriad of other proposals to fill this fast tank destroyer role.

Even if heavier armament options had been considered for this G-3 concept, all hope for the Bigley was definitely over by the end of 1942 with the approval of the far more capable T49 platform. And, if any doubt remained, the selection of a 75 mm gun as the weapon of choice in January 1943 for the project put the final nail in the coffin.

Name Confusion

With all of the talk of Christie, Bechold, G-3, and Bigley, it is understandable how hard it is to keep track of what the actual name of the vehicle was. If that is not hard enough, the book ‘Steel Steeds Christie’ by Walter Christie’s son J. Edward Christie makes the matter worse. Here, a suspiciously similar tank using the hull shape of the tank (albeit with 5 return rollers) is being referred to as the ‘M-1943 Christie Tank’ and also as the ‘M-1950’, which is recorded in US Archives as the Bigley Motor Carriage when it had the 4 large road wheels.

The 'M-1943 Christie Tank'
The ‘M-1943 Christie Tank’ also known as the ‘M-1950’ as shown in Steel Steeds Christie by J. Edward Christie.
comparison between G-3 vehicle and M-1943
Reverse (from L to R, to R to L) image allows for a straightforward comparison between the vehicle considered by G-3 and the vehicle claimed by Christie as the M-1943
M-1936 Modified into Christie Tank M-1938
With its unmistakably similar lines, this vehicle is recorded by US Archives as the Bigley Gun Motor Carriage yet by ‘Steel Steeds Christie’ as the ‘M-1936 Modified into Christie Tank M-1938’: Armor Magazine

Comparing the vehicles it is clear that they share several common features such as the lines of the hull indicating a connection between the designs. However, the caption on the G-3 drawing shows Christie’s level of involvement with the name sticking with the suspension rather than the designer of this vehicle per se, despite the efforts of J. Edward Christie to postscript claim the design as his own.

Suspension

A real question mark though has to be considered as to what the final G-3 proposal was even to look like. Clearly, the suspension is the same type of angled ‘Christie’ units with a wheel on an arm controlled by an angled cylinder with a spring. Undoubtedly, this was a very good suspension system but was not without its faults either. Primarily, the problem with the suspension was that the springs took up valuable width on the vehicle. Four of the wheels, each relatively small, were on these arms and a fifth wheel at the back was attached in the reverse-position to the same axis as the drive sprocket. On top of this was a second balanced arm connected to the rearmost return roller which also served to feed the track at the correct angle to the drive sprocket whilst simultaneously pushing up on the track to keep it tight.
One additional note on the return rollers is that the lead-most roller is also drawn as if it was meant to be able to move. There is no springing or return arrangement for it to move back into its original position but a sprung return roller would also assist in keeping the track tight. The mechanism by which it was to do this is, however, not clear.

The sprocket too was a Christie-design leftover. This was not the normal kind of tank sprocket with a toothed wheel pulling a track around via gaps in the end connector of the track plates. This was actually patented by Christie in January 1937 in conjunction with Morris Commercial Cars of Birmingham, England and used a series of rollers mounted on a sprocket. These would draw the track by means of the central guides on the track plates and also move with them as the track is drawn over them to reduce wear.

A further arm was fitted to the front of the tank and appears to be connected to a short arm connected to a central pivot about which the arm could rotate. On each end of this arm was a bearing with a roadwheel. This arrangement was clearly sprung, but only on the top part of the arm. The spring was yet another of the cylindrical springs and was angled back just as sharply as the other ones. This arrangement was perhaps best considered to be in the manner of a see-saw (teeter-totter) where, as one side moves up or down, the arm rotates and the other side moves in the other direction. Balanced by a coil-spring to the top part of this arrangement it meant that regardless of the position of the arm and wheels relative to each other, that they would remain in contact with the track and help keep it taut.

 


Drive Sprocket and Double ArmsAngular Sprung Suspension Unit

Left: The unusual and ingenious system of drive sprocket and double arms with one arm for a sprung road wheel, and the other for a sprung-tensioning return roller. Right: An angular sprung cylinder suspension unit for a road wheel. Source: Steel Steeds Christie

Roller-Type Drive SprocketTrack Plates Designed by Christie

The roller-type drive sprocket and track plates designed by christie. Source: UK Patent GB474714 of January 1937

Layout

The basic hull shape was the same as the original Christie machine, that much is clear but the rest is not. The drawing from G-3 clearly shows some kind of superstructure on top. The superstructure would certainly increase the profile of the vehicle, but it doesn’t appear to be part of the actual tank itself. Instead, this frame appears to be part of a gantry system as used to attach the tank slung underneath or drawn up inside an aircraft, a particularly favorite pastime of Christie to suggest.

Gantry Arrangement on Top of Vehicle
Depicting the gantry arrangement on top of what is supposed to be the ‘Christie M-1950’, (albeit with a different number of road wheels). The gantry allowed not only to attach a tank but also to raise it within the fuselage of the aircraft. Source: Steel Steeds Christie

The small size of the wheels and the spacing between them would seem to indicate this was going to be a very light vehicle too, with the engine and transmission in the rear. Crew-wise there is little information other than that which can be inferred from the design. In the raised section on the hull, there was originally just a small raised cupola from which the commander/driver could observe the surroundings. There would also be space for a second man, presumably to operate the gun. There would still be sufficient space, albeit maybe not very comfortable considering ammunition storage and the breech of the gun, for another crew member, meaning a crew of 2 to 3 men.

Armor

Like all of Christie’s designs, armor was secondary to speed. In fact, for Christie, almost everything was secondary for speed. His designs were either bulletproof or barely bulletproof. In its original form, before being sold off to Mr. Bechold, the hull is reported to have been just ¼ (6.35 mm) to ½” (12.7 mm) thick. Speed, not armor, was to be the protection for the G-3 Tank Destroyer if it kept the same armor values.

Conclusion

It is not hard to see why this G-3 concept failed. It was not a future-looking design but a quick glance back to a past image of a tank in which the figure of Walter Christie loomed large. Undoubtedly, the Christie suspension was innovative with many desirable features but a barely-bulletproof, casemate-gun-mounting tank-destroyer armed with a 37 mm gun was hardly a reasonable competitor to a vehicle as capable as the T49 with a 75 mm gun. It would not be until July 1943 that the first actual descendants of this process, the M18 Hellcat started to roll off the production lines – the product of an unnecessarily long process started too late.

Illustration of the G-3 light tank destroyer, showing the very small size and the odd running gear. Illustration by Pavel ‘Carpaticus’ Alexe, funded by our Patreon Campaign

G-3 Light Tank Destroyer Specifications

Crew 2-3
Dimensions
Armor bulletproof (roughly 0.25″-0.5″ or 6.35mm-12.7mm)
Armament 37mm gun
Engine Possibly Hispano Suiza V12 750 hp petrol
Speed Theoretically 60mph (97 km/h)

References

UK Patent GB474714 ‘Improvements Relating to Track Laying Vehicles’, filed 7th January 1937, granted 5th November 1937
Armor Magazine, November-December 1991. Christie’s last hurrah.
Armor Magazine, March-April 1992. The Origins of Torsion Bar Suspension.
Gabel, C. (1992). The US Army GHQ Maneuvers of 1941. Center of Military History, United States Army, Washington D.C., USA
United States Army. The General Staff: Its Origins and Powers
Christie, J. (1985). Steel Steeds Christie. Sunflower University Press, Kansas, USA

Categories
WW2 US Prototypes

Chrysler’s Improved Suspension M4A4

United States of America (1942)
Medium Tank – Blueprints Only

The Medium Tank M4A4 Sherman was an improved variant of the M4A3. The goal of the tank was to increase the speed of production of the M4 by using a new multibank engine and with a hull made from 5 pieces instead of seven. The longer and more complex engine would mean an increased length of track on the ground for improved performance of the M4A4 on soft ground, yet despite this, the M4A4 was not adopted by the US Army for use overseas. Early in the development of the M4A4, consideration was given to making us of the longer hull to improve the suspension. This led to the idea of using the ‘Christie’-style suspension from the T4 Medium Tank on this new Sherman. Whilst the M4A4 was built in large numbers and saw extensive service during World War 2 and later, the idea of using this ‘big-wheel’ suspension never left the drawing board.

M4A4 Sherman with the Vertical Volute Suspension System (VVSS) which Chrysler were investigating the replacement of with an improved big-wheel form. Photo: Mark Nash

Development

The design of the M4A4 began in February 1942. This new Sherman was going to be more mobile than the M4A3 by using the 435 hp Chrysler A57 multibank petrol engine. The selection of what was actually 5 engines fitted together created a crowded space within the engine bay, which necessitated a slightly longer hull than the M4A3. This was considered a tradeoff that could add a large number of tank engines into the supply chain which would aid in meeting their production targets. Further, the hull of the M4A4 was simplified, as it was made in fewer parts than the M4A3 (5 instead of 7), and featured a 3-piece final drive housing on the front instead of the single-piece final drive housing on the M4A3. This would improve the speed of repairs and maintenance on the tank although, initially, the complex engine arrangement had been unreliable.

Lengthening the hull by 11 inches (279 mm) in order to accommodate the engine also meant that the suspension would have to be lengthened. The M4A3 had used three pairs of volute spring suspension (Vertically Volute Suspension System – VVSS) and these could be spread out more along the slightly longer sides of the M4A4 or a new suspension system could be considered instead. This prompted a very short study by Chrysler, the design agent for the M4A4, to try and improve the performance of the tank by way of an improved suspension system. The system to be investigated was a modified version of that trialled on the T4 Medium Tank.

Rather than refit the three VVSS units, spaced out along the side, the idea was now to use five large road wheels connected on horizontal crank arms. Springing for the wheels was delivered by means of vertical coil springs mounted on the outside of the lower hull. This has been described variously online as being a ‘Christie Sherman’ or ‘Christie suspension’ but it really is not. The Christie patent for his system had already been sold off by then as well as licensed off to countries like Great Britain and the Soviet Union. One of the dominant features of Christie’s suspension design was the suspension springs operated within a double-wall cavity along each side of the tank. This system was adopted and adapted for use in tanks such as the British A.13 and Soviet BT-5 and remained in use on some tanks through to the end of World War 2. The British Comet, for example, was the last British tank to use a version of this system. This was not the case for this M4A4. Here, the springs would be mounted externally.

Christie, by February 1942, was almost a dirty word in US armor circles and had no formal involvement with the US Army. His last official contact had been with the Ordnance Department in March 1939 and ended when he had stormed out of a meeting in a tantrum when his demand for large orders for his tanks was rejected. He had stomped off saying he would go and see President Roosevelt and with that had ended any prospect of formal consulting work.

Consequently, attributing his name to this design would be incorrect. If there is any doubt on the matter, the somewhat awful book ‘Steel Steeds Christie’ published in 1985 by his son Edward and which makes numerous fallacious claims, makes no claim to this design. The T4 suspension design was certainly based on the work of Christie, but the first conceptualized drawings for a sprung suspension-arm suspension for the M4, prepared by the Ordnance Office in February 1942, had already departed from this arrangement.

T4

The T4 Medium Tank, built by Rock Island Arsenal in 1935 and 1936, weighed just 13.5 tons (12.2 tonnes). Different versions of the T4 were trialed between 1935 and 1940 when it was declared obsolete, but the key feature of the design was the four large road wheels on each side. The suspension of the T4 was certainly based on the suspension designs from Christie, but it did not use Christie’s patents. The track for the T4 was also a short-pitch type track 12 inches (305 mm) wide.

Medium Tank T4 showing the 4 large road wheel design with no return rollers. Source: Hunnicutt

The T4 weighed just 13.5 tons (12.2 tonnes), whereas the M4A4 would weigh 34.9 tonnes (31.6 tonnes), more than double the weight of the T4, so using the same suspension required changes. The T4 used just 4 wheels on each side, which would be inadequate for the extra weight of the M4. Thanks to the longer hull of the M4A4 though, 5 of these large-diameter wheels could be fitted on each side. The second change came about after the initial drawings from the Ordnance Board. Those drawings had shown the five, closely positioned wheels, each mounted on an individual arm with a corresponding spring cylinder angled forwards. To meet the increased weight of the M4, these springs had to be changed too. The solution here was to adopt heavier coil springs and to mount these vertically along the outside of the lower hull of the tank under the sponsons.


First plans for a T4 Medium tank-style suspension on the M4 Sherman, circa February 1942. Note the suspension springs are angled forwards rather than vertical. Source: Hunnicutt

Tracks

The adoption of the T4 style wheels was also met with the choice of a wider version of the T4 track. This single-pin track was 18.5 inches (470 mm) wide, wider than the standard M4A4 track and the original T4 track, and used a center guide to prevent lateral slippage. With 93 track links per side (compared to 85 on the T4) and the larger, heavier wheel, this new M4A4 was significantly heavier than the original volute-suspension M4A4 by 3,080 pounds (1,397 kg).

The volute-suspension M4A4 used either the T48 or T51 83-link 16.56 inch (421 mm) wide track with a ground contact length of 160 inches (4,064 mm), which was substantially longer than the M4A3 at 147 inches (3,734 mm). Using this T4 style suspension, the track length on the ground was only fractionally longer than that of the M4A3, at just 148 inches (3,759 mm), yet despite this shorter length of track in contact with the ground than the volute-suspensioned M4A4, the wider track made up for this and kept ground pressure to just 14 psi (96.5 kPa).

Front view of the Chrysler sprung swing-arm suspension M4A4 shows the width of the external springs on the sides of the outer lower hull (left), and with the additional width of the spring highlighted in pink (right). Source: Hunnicutt and Author respectively

With the new spring system fitted to the outside of the lower hull, this meant a lot of space was taken up under the sponson on each side. Consequently, the tracks and wheels would be further out than they would be if it had retained the VVSS system. This would have posed some additional issues regarding the transportation of the tank due to its increased width, about 450-470 mm wider than the M4A3 due to the projections of the track and the lack of space in which to add grousers to the inside of the track.

With the new spring system fitted to the outside of the lower hull, this meant a lot of space was taken up under the sponson on each side. Consequently, the tracks and wheels would be further out than they would be if it had retained the VVSS system. This would have posed some additional issues regarding the transportation of the tank due to its increased width, about 450-470 mm wider than the M4A3 due to the projections of the track and the lack of space in which to add grousers to the inside of the track.

M4A4 with VVSS (left) compared to M4A4 with T4 Style Suspension (right) showing the additional width of the M4A4 (not to scale). Source: Hunnicutt
M4A4 with VVSS (top) compared to M4A4 with T4 Style Suspension (bottom) (not to scale). Source: Hunnicutt

One final note of difference between the suspension systems on the M4A4 are the return rollers. Easily overlooked, the VVSS system used a small return roller angled back from the suspension bogie which served to hold the track off from fouling on the top of the bogies. No such rollers were drawn on the T4 suspension units to support the track. The angle of the track, as it descended from the front sprocket to the rear idler, would likely contact the top of the last roadwheel but other than that it was unsupported .

The final product. Five large diameter T4-style road wheels and vertical coil spring suspension on the M4A4. Note that the mantlet is misdrawn and should be further back, towards the turret front. Source: Hunnicutt

Conclusion

Despite the fact that the T4-style suspension was found by engineers at Chrysler to be workable, it was not pursued. The volute system was not ideal but it was simple and reliable. In the short-term, the volute-spring system was retained, although work on improved suspension for the M4 continued. No versions of the Chrysler vertical coiled spring suspension M4 were ever built. Despite 7,499 M4A4s being built, it only saw limited service with the US Army anyway, restricted mainly to training duties. It did, however, find extensive use overseas particularly with the British, where it was known as the Sherman V.



Illustration of Chrysler’s improved suspension M4A4. Illustration by Andrei Kirushkin, funded by our Patreon Campaign.

Specifications

Dimensions 6.06 m x 2.62 m (hull, 3.07 m to 3.09 m wide over tracks) x 2.74 m
Total weight, battle ready 72,780 pounds (36.29 US tons) (33 tonnes)
Crew 5 (commander, driver, co-driver, gunner and loader)
Propulsion 435 hp Chrysler A57 multibank petrol engine
Speed (road) 35 mph (56 km/h)
Armament M3 75 mm gun in M34 mounting
.50 calibre M2 AA machine gun
2 x .30 calibre M1919A4 machine guns
Armor 1.5 inches (38.1 mm) – 3 inches (76.2 mm) – 107.95mm

Sources

Armor Magazine, November-December 1991. Christie’s last hurrah.
Christie, E. (1985). Steel Steeds Christie. Sunflower University Press, USA
Gabel, C. (1992). The US Army GHQ Maneuvers of 1941. Center of Military History, United States Army, Washington D.C., USA
Hunnicutt, R. (1977). Sherman – A History of the American Medium Tank. Presidio Press, USA
Icks, R. (1969). The Fighting Tanks 1916-1933. We Inc. USA