Categories
Cold War American Other Vehicles

Crawler-Crusher, or “The Monster”

USA (1968-1969)
Civil Engineering Vehicle – 1 built

Background – The Cross Florida Barge Canal: “The Ditch of Dreams”

As far back as 1565 with Governor Pedro Menéndez de Avilés, when Florida was ruled by Spain, people have dreamed of cutting a waterway across it to shorten the voyage to the Gulf of Mexico from the east coast of America and from Europe. United States territorial governments in Florida first started considering a canal in the 1820s, with the first legislation being the Canal Memorial sent to Congress in 1825. Andrew Jackson (President of the United States, 1829-1837) had supported the idea of a canal during his tenure as Governor of Florida in 1821, but he did not condone the use of taxpayers’ money for the project as President, and the project was rejected as unfeasible.
The next attempt to build a canal across the width of Florida after the failed 1820 motion, was during the Great Depression. Calvin Coolidge’s River and Harbor Act of 1927, which ordered the US Army Corps of Engineers to carry out surveys, the cost of which had been determined two years prior, would form the basis for the project which would see the first breaking of ground on a cross-Florida canal. After extensive lobbying and political squabbling, in 1935, President Franklin D. Roosevelt approved the use of 5 million dollars to construct the Atlantic-Gulf Ship Canal, which would provide jobs as part of his New Deal program.
Route 13B was chosen as the path for the canal. It would run from Palatka to Yankeetown via the St. Johns, Ocklawaha, and Withlacoochee rivers. The St. Johns River, and to a lesser extent, the Ocklawaha River, had been important transport and trade routes for much of Florida’s history. The St. Johns is a wide river providing access from the Atlantic Ocean to the cities of Jacksonville and Palatka. The Ocklawaha River is a much smaller, winding tributary of the St. Johns, which feeds into the latter just north of Lake George. The Ocklawaha meanders its way further inland before turning South and continuing all the way to Lake Griffin, near Leesburg. Before railways were built, the Ocklawaha had been the route connecting Lake Apopka with Jacksonville and the ocean. The Withlacoochee is on the other side of Florida; emptying into the Gulf of Mexico near Yankeetown. It runs inland and then south to Green Swamp. Green Swamp also happens to feed the Ocklawaha, though indirectly. Had the canal been finished, the two halves would have come together south of Ocala, Florida.

Map of the would-have-been Cross Florida Barge Canal, made in January 1971 Source
Construction began in 1935. The canal was to be a sea level canal, meaning it would cut straight through any mountains or hills along its path, and would not require any locks to change ships’ elevation. Due to political opposition from Secretary of the Interior Harold Ickes, who claimed that a sea level canal would destroy Florida’s aquifers, work on the canal was cancelled within a year. Other political factors also contributed to the cancellation of the Atlantic-Gulf Ship Canal, such as a need for disaster relief elsewhere in Florida, and pressure from the railroads and the city of Miami. The Depression Era canal attempt ended with only a few miles of ditches dug, some abandoned structures, and $5.4 million in wasted federal appropriations.
The cross-Florida canal idea was revisited in 1942 as World War II was in full swing and thousands of tons of shipping were being lost to German U-boats off the coast of Florida. The canal was proposed as a means for ships to avoid the U-boat infested waters of the Atlantic when making trips from the US East Coast to the Gulf of Mexico. Construction of the canal was approved as a wartime defense measure, however, Congress was still divided on it, ending in a tie that was only settled in favor of the canal by Vice President Henry Wallace. Despite being approved, the canal was never funded; unsurprising considering the mixed response from Congress in the first place. Political pressure also influenced this decision, as there was concern that had a canal been built it would rob port traffic from Palm Beach, Fort Lauderdale, and Miami. However, the men who served in World War II, and saw the loss of life at the hands of the U-boats first hand, would remember the government’s indifference to what they saw as a life-saving measure. Some of them would go into politics and would ascertain the third and final attempt at a canal in the 1960s.
Approved in 1963 by President John F. Kennedy, work started in 1964 under President Lyndon B. Johnson, the Cross Florida Barge Canal project was born out of a political struggle much too in depth to cover here. The project would run from 1964 to 1971 and follow much the same route that the 1930s canal would have. It was intended that the canal would benefit central Florida militarily, economically, and recreationally. The US Army Corps of Engineers was put in charge of construction of the canal and broke ground in February, 1964.
Only two locks, Buckman and Inglis, were completed on the Cross Florida Barge Canal, with a third, Eureka, left unfinished. The first lock built was originally known as the St. Johns Lock, but was renamed Henry H. Buckman Lock, or simply Buckman Lock. Buckman Lock is the closest lock on the canal to the St. Johns River. It sits on a man-made portion of the canal connecting Rodman Reservoir and the St. Johns, bypassing the lower Ocklawaha. Buckman Lock is less than two miles (about 3 kilometers) from the St. Johns River and 4.75 miles (7.64 km) from Rodman Reservoir. Construction began in 1964 and was completed in 1968. Buckman Lock is the lock for Rodman Reservoir, despite being some distance away from it.
Work on Rodman Dam and Eureka Lock and Dam began about the same time in 1966. Rodman Dam is roughly 7 miles (11.25 km) from the St. Johns River. Eureka Lock and Dam, named for the nearby town of Eureka, is 21 miles (33.8 km) upstream from Rodman Dam. Eureka Lock and Dam was entirely complete apart from a 400 foot (122 meter) section of the 4,000 foot (1,220 meter) wide earthen dam that was never filled in.
Work on Rodman Dam and Reservoir was conducted by the Army Corps of Engineers from 1966 until September 30th, 1968, when the dam was closed and the reservoir filled. Rodman Dam is about 7,200 feet (2,200 m) long, 300 feet (91 m) wide at the base, and 30 feet (9 m) wide at the top. It has a four gate spillway, each gate measuring approximately 40 feet (12.2 m) wide by 15 feet (4.6 m) tall. The gates can be lifted above the spillway to increase flow. The top of the dam is 28 feet (8.5 m) above sea level and 22 feet (6.7 m) above the surrounding natural ground elevation. The spillway crest is only 6 feet (1.8 m) above sea level. The spillway’s ‘apron’ (the flat, sloping, concrete path where the water leaving the spillway flows) is 100 feet (30.5 m) long, about 160 feet wide (48.8 m), and ranges in elevation from 3 to 15 feet (0.9 to 4.6 m) below sea level. The spillway discharge channel is nearly a mile long, has a depth of between 8 and 20 feet (2.4 to 6.1 m) depending on flow, and narrows from about 300 feet (91 m) to about 150 feet (46 m) before meeting what remains of the Ocklawaha River. The Ocklawaha meanders for another 11.6 miles (18.7 km) and then empties into the St. Johns south of the canal exit.
The only other completed lock is on the Gulf coast of Florida, near Yankeetown. The Inglis Lock and Dam is located on the Withlacoochee River, and holds back Lake Rousseau. Inglis Lock is the only portion of the Cross Florida Barge Canal to have seen use besides Rodman Reservoir. The lock has since fallen into disrepair and has not operated since 1999.
In total, the Cross Florida Barge Canal would have been 107 miles (172 km) long when completed. However, construction work was slow, and quickly fell behind schedule, probably not least in part due to lack of unified enthusiasm for the canal and public backlash. In an age when environmentalism was on the rise, seeing ancient forests destroyed and thousands of species of plants and animals threatened to make way for “more recreational waters” and a barge canal that was not really needed angered and divided the population. Marjorie Harris Carr, for whom the greenway that now spans the would-be area of the canal is named, led the public protest efforts against the canal for much of the losing battle. In the end, however, public outcry was too much to ignore, which led President Richard Nixon to sign an executive order to halt construction of the canal on January 19th, 1971.

The Monster from Fern Gully

Part of creating the aforementioned dams and the artificial reservoirs that would be held behind them was clearing the area of trees and other ground clutter. The goal was to have a central channel through the reservoir, of sufficient depth (12 feet / 3.65 m) to accomodate barge traffic. The area the channel would be cutting through on the Rodman and Eureka Reservoirs would be the general path once run by the flowing Ocklawaha. Area around the channel, which would soon be underwater if it wasn’t already marshland, would also need to be cleared to prevent underwater obstacles being swept into the barge lane, and to keep the area open for recreational pleasure craft. The task of clearing the swamp that occupied the area that was slated to become the Rodman Reservoir was especially daunting, in some places the swamp water was up to 6 feet (1.83 m) deep.
With this in mind, the Army Corps of Engineers asked for bids from civilian firms to do the clearing work. The barge channel was to be 400 feet (122 m) wide and 16.5 miles (26.55 km) long in Rodman Reservoir alone. 5,617 acres of land were to be cleared, 708 acres of that figure representing just the channel. The heavily forested section of Rodman Reservoir comprised 6,325 acres of ancient swamp forest. The time allotted for clearing the reservoir was a mere 445 days.
F. Browne Gregg, head of the company Gregg Gibson & Gregg, put in a very low bid; far too low in hindsight. With a bid 1 million dollars less than the next lowest bidder, Browne Gregg easily won the contract from the Army and was awarded $4,191,047. Soon though it was abundantly clear that doing the work traditionally of felling and removing thousands of acres of swamp and forest on the budget that the bid had given them would run the company a major loss. To get around this, Gregg came up with a novel solution; he would build a massive tracked vehicle, capable of going on land or water, that could be filled with water to increase its weight. The vehicle would weigh so much, and be so large, that with its sheer bulk it could push over trees up to 6 feet (1.83 m) in diameter, drive over them, stripping them of their branches and crushing the trunk and branches into the mud, where they would remain. Gregg hoped that this machine would save over a million dollars in clearing costs. The Crawler-Crusher was designed in only a few hours and perfected over only one weekend. It was designed to clear swamp at a speed of only half a mile per hour (0.8 kph), slightly slower for clearing dry land.
“I literally woke up from a sound sleep with ideas running through my head. I wasn’t thinking in words in my sleep but in moving pictures of machines and how I would utilize the equipment. I got up and went to the kitchen to brew myself a pot of coffee. By the time I had a hot mug in my hand, I knew what my first sketch would be. I had a draft board with a target light set up in my bedroom and I went to work.
I stayed at it, working on what I called the Crawler Crusher night and day. I was obsessed by the thing. I was oblivious to [my friend] Fred and his pal Jeff Cherry coming in and out of the bedroom. Jeff kept asking me, “What’s that you’re drawing, Mr. Gregg?” I ignored him as I was concentrating. He looked over my shoulder and watched what I was doing. He spoke right up and said, “Mr. Gregg, you forgot to put the hole on the top for the man to crawl into.” He was right and I told him I would get to it later. And sure enough, a few hours later, the boys were back, checking up on me. To them it was just a nifty army tank I was drawing for our military.”
-F. Browne Gregg on designing the Crawler-Crusher, taken from his autobiography Progress Through Innovation.
US Patent 3418961A, plainly entitled “Swamp Clearing Machine”, was filed by Frederick Browne Gregg of Leesburg, Florida, on behalf of Gregg Gibson & Gregg, Inc. on March 17th, 1967 and issued on December 31st, 1968, the machine itself having been completed at least several months prior. The dates surrounding its construction and operation are not known.


Crawler-Crusher patent Figures 2 and 4 respectively, showing the right side and right side cutaway of the machine. Source
In summary, the Crawler-Crusher is described by the patent as follows:
“It is a very large machine consisting of two large, hollow, watertight track pods. These pods can be separated for transport, and contain pumps that facilitate filling and draining them of water to control the weight of the vehicle. The design builds upon the armored, amphibious tree clearing machines in use by the US Army in Vietnam at the time. The Crawler-Crusher is superior to the Army’s tree clearers because it is fully amphibious and can regulate its ballast. While the Army’s tree clearers are at home on hard ground, sand, or open water, they struggle to operate in mud and marsh, where they bog down and cannot gain sufficient traction.”
The Crusher’s left and right track pods were mirror images of each other, but otherwise were identical. Each pod by itself measured roughly 50 feet (15.2 m) long, 12 feet (3.65 m) wide, and 12 feet 6 inches (3.8 m) high. Including the operator’s cabin, the entire machine stood 22 feet (6.7 m) high. For comparison, the largest tracked tank ever built (albeit unfinished), the K-wagen, measured 42 feet 8 inches (13 m) long and 19 feet 8 inches (6 m) wide.
Structurally, the Crawler-Crusher’s track pods were constructed and reinforced with hundreds of I-beams. Sixteen I-beams were oriented widthwise along the bottom of the pod, above the area containing the track rollers and their supports. The I-beams near the front and rear of the pod were tilted to follow the curvature of the bottom of the pod. There were two rows of short, vertical beams running down the center of the bottom of the pod between the two track roller channels, these supported the above mentioned 16 I-beams.
Above each of the 16 horizontal I-beams were 4 beams arranged diagonally which resembled a “W” shape when viewed as a cutaway from the front. The outermost arms of the “W” were placed in front, with the inner arms following immediately afterward. Each of these cross-beams was half the width of the I-beam they rested on, meaning they were all fully supported. In the center of each “W”, of which there were 16, one for each supporting I-beam, was another, shorter, vertical beam that separated the “W” in half. There were also occasional vertical I-beams placed directly against the inner and outer walls of the track pod, on either end of the “W”s; it is unclear from the blueprints whether these were continuous down the entire length of the track pod, if there were 16 of them and they were attached to the “W” frames, or if there was only a couple that were placed in specific areas.

Crawler-Crusher patent Figure 3, showing the vehicle from the front, the right side pod cutaway back to the partition wall midway down the length of the vehicle. Source
The four beams of the “W”, the central vertical beam, and the side vertical beams all supported a framework inside the pod that formed a floor, or “inner deck”. The height of the inner deck was at approximately 40% of the pod’s total height. Above the inner deck, extending to the roof, were over 100 vertical I-beam supports. There were 18 or 19 rows lengthwise down the pod, each row consisting of 7 beams widthwise. The outermost two beams in each row were placed directly against the outer and inner walls respectively. At the top of the pod, supported by the aforementioned vertical beams, was another framework of I-beams that support the roof and return rollers.
Entrance to the pod was via a side hatch, which was watertight and could be locked with two dogs (small, solid pieces of metal that are hinged on one side and can be flipped out to secure the door). The side entrance doors were hinged on the side facing the rear of the vehicle and opened outwardly. The entrance hatches were between rows 10 and 11 of the vertical I-beams (counting from the front). Directly across from the two exterior doors, on the inner walls of the pods, were two more doors. These allow travel and communication between the two pods when the machine is assembled. The inner doors were virtually identical to the outer doors, also being watertight and having locking dogs, but they are presumed to open inwardly. When the right side inner door is viewed from the inside, the hinges were on the right; the left side inner door is not illustrated or seen in any photos. The inner deck was partitioned off at beam row 10, dividing the interior of the pod into two large sections. Access to the forward compartment was via another hatch, identical to the side access hatch; it was placed between beam columns 3 and 4 (counting from outboard to inboard). For the right side pod, this hatch was hinged on the side facing outboard; again, the hatch in the left side pod is not seen in the blueprints.
Entrenched in the bottom of each pod were two channels containing the support rollers for the track. There were 188 rollers in total; the rollers themselves were the type normally used on Caterpillar D8 bulldozers. Each roller axle was supported by a pillow block bearing on either side, meaning there was no suspension at all. The roller itself was a cylinder with an enlarged band in the middle and flanged ends, this arrangement created two channels on the roller in which the track’s guide horns rested.
The return rollers on the top of the machine were nearly identical in construction to the support rollers, except for the fact that their ends had smaller flairs, and that the channels they rested in were not continuous along the entire vehicle. Each return roller had its own “well”, a recessed area it rested in. Each return roller well had a drain plug at the bottom underneath the roller, to let out rainwater. There were 4 top return rollers per channel, meaning 8 per pod, and 16 in total. At the back of the pod, above a small slanted rear roof section, were 2 more return rollers per channel, meaning 4 per pod, and 8 total. In total there were 12 return rollers on each track pod; 41 support rollers for each channel, 82 on each pod, and 164 total. For comparison, the TOG II* tank, known for its size and length, had only 32 support rollers in total.
The track links themselves were 11½ feet wide (3.5 m) and were made from a special steel alloy used by Caterpillar. Each track had a grouser of approximately 5 inches (127 mm) long, tapering from approximately 2.5 inches (63.5 mm) to 1.5 inches (38.1 mm) in girth. These long grousers gave the Crawler-Crusher a means of propulsion in the water, acting like paddle wheels. “Skids or wear strips” were placed along the bottom of the pod near the ends of the track links to support the outer length of the track and prevent them from bending and warping under the machine’s weight.
Propulsion for each track pod was provided by a Caterpillar D432 diesel engine, taken out of a Cat D8H bulldozer. Each engine produced 270 horsepower at the flywheel, for a total of 540 (FW) hp. Each engine, mounted on a support beam above the inner deck of its respective pod, drove a driveshaft that went through the rear wall of the pod, into a differential that took up the entirety of the rear of the pod beyond the rear wall. On either side of the differential was a large drive sprocket. The clutch for the differential was pinned in place, as it was only driving one large track instead of two smaller ones, and moving one sprocket more quickly than the other would be catastrophic. The patent remarks that even though the machine being built is powered by internal combustion, the design could accommodate any means of heavy-duty propulsion, such as hydraulic or electric drives.
At the front end of the vehicle, the toothed idler wheels were supported on sliding members that were mounted on top of support beams that jutted out through the front wall of the pod. The idler wheels were each connected to a tensioning piston that was connected to a double-acting cylinder, mounted on the same support beam but on the interior of the pod. This support beam was held strongly in place and continued all the way back to beam row 4.
Each track pod weighed approximately 200,000 pounds (90,700 kg) and could be increased by 100,000 additional pounds (45,400 kg) by filling the area below the inner deck with water. An inlet pipe was mounted directly on top the inner deck between beam rows 12 and 13; it carried water from a small, screened opening on the side of the pod to near the middle of the pod, where it made a 90° turn downward, dumping through the roof of the lower compartment. A solenoid valve was mounted along the pipe immediately after it entered the pod from the outside, this could be controlled by the operator of the machine remotely to start or stop filling the ballast.
A 4 inch (101.6 mm) ballast pump was mounted atop the inner deck next to the front of each of the engines. The pump was driven by a belt from the engine; itself driving a shaft that went to an impeller on the end facing the front of the pod. The patent again remarks the pump can be hydraulic, electric, or even a separate combustion engine if desired. A header pipe came out the front of the impeller housing and made an immediate 90° turn downward through the deck. The header pipe met a cross-joint at the same level as the I-beams that lay widthwise across the roller channels. The cross-joint split the pipe into three separate pipes, one continued straight down, while the other two traveled out to the sides of the pod before making 90° downward turns. All three of these sump intakes were held at only about an inch or two (~25 to 50 mm) above the bottom of the pod. Attached radially to the top of the impeller shroud, the outlet pipe went directly out to the side of the pod, passing through a one-way valve before going out the side wall behind and above the inlet pipe. The sump tubing was contained between beam rows 13 and 14.

Crawler-Crusher patent Figure 5, showing the right side pod cutaway back to the sump, just in front of the engine. Source
A feature outlined in the patent that does not seem to have been used on the actual machine is the vent line. Mounted on the inner wall, just behind beam row 9, the vent line seems to have been a safety feature of dubious necessity, perhaps for if the ballast tank became overfull, or somehow became pressurized. The vent line would be opened and closed by a wheel valve mounted at about chest height. It continued from below the inner deck, up and out through the top of the pod, rising to just under the bottom of the control cab, before making a quick 180° curl outward, to prevent rain from getting in. An optional auxiliary vent line could be built off the main one, extending from under the wheel valve, back through the partition wall at beam row 10, making a 90° turn downward and going through the floor. The auxiliary vent line could have a blow off valve mounted on top of it, underneath the wheel valve on the main vent line, should it be so desired.
The track pods were attached together by multiple sets of splined recesses, or sockets, that were inlaid into the inner walls of each pod. A splined shaft is fitted between each of these sets of sockets so that they line up, and then can be pushed together. (This is very similar to how Lego axles, or “stick” pieces are attached together). A heavy duty bolt is fed through the end of one socket, through the middle of the joining piece, and out the other socket, where it is secured by a nut.
When fitted together, the two-track pods form two vertical sockets between them which the 8 inch (203 mm) thick support posts for the operator’s cabin fit into. The two support posts were cross-braced to each other; the overhanging portion of the cabin was supported on the four corners by diagonal supports coming off the support posts. In the patent, the cabin is shown as a simple box, the bottom half of which is solid (presumably wood or metal) and the top half wire mesh, with a flat roof. The real machine had a cabin of less crude construction, with glass replacing the wire mesh, and a tall, curved roof.
Behind the sockets for the cabin supports, each track pod also had a long, shallow recess that when fitted together created a vertical “letter slot” extending from behind the cabin nearly to the end of the vehicle. This slot was divided with vertical separators into a forward section, a small middle section, and a rear section. The front section was connected to ductwork running along the roof of the right side track pod, providing air to the engine. The rear section of the open-air slot likewise, but providing air to the left side engine. Both engines exhausted into the center section.


Crawler-Crusher patent Figures 1 and 6. Figure 1 shows the entire vehicle as seen from above. Figure 6 shows the rear half, with the engine compartments, final drives, air intake ducts, and exhausts outlined. Figures 7 and 8 show the method of attaching the two track pods together by splined sockets and shaft, and Figure 9 shows a side view of several track links. Source
At the front of the vehicle, there was a large pusher-bar for pushing over trees. The concrete-filled pusher bar extended 5 feet (1.5 m) forward of the vehicle, and towered approximately 15 feet (4.57 m) off the ground. The pusher bar was supported by two A-frames, one on either side of the machine. The top leg of each A-frame was connected by a pin to a support bracket on the top corner of the respective track pod. The bottom leg of the A-frame was also connected to a bracket by a pin, the bracket being supported by a structural beam coming off of the lower side of the track pod. Diagonal struts reinforced the corners of the pusher bar. The patent mentions the possibility of making the top A-frame brackets into pivots and replacing the bottom ones with hydraulic pistons to raise or lower the pusher bar, but this seems highly unnecessary.
The difficulty of transporting 50 foot (15.24 m) long, 12 foot (3.66 m) wide track pods, as well as the machine’s other accessories is quickly glossed over in the patent. It is claimed the track pods, when separated, can be moved to or from a job site by barge, railway flat car, flatbed truck, “or any other known manner”; however, while the length of the apparatus will fit on a railcar or semi-truck, the width would be a major problem. At 12 feet (3.66 m) wide, just one Crusher track pod would be an exceptionally oversize load, requiring escort vehicles and advanced planning to move. The height of 12 feet 6 inches (3.8 m) would not be much of a problem, provided it was taken on a low load trailer, which it certainly would need be; weighing 200,000 pounds (90,000 kg), or 100 US tons (90.7 metric tons) dry, just one track pod is over four times the weight limit of even a modern flatbed trailer. It would require a specialized heavy trailer to move. The weight would not pose such an issue for movement by rail, but the width would be an even bigger issue than on the road. The track pod would overhang by several feet on either side of the railcar, meaning that all oncoming traffic would need to be stopped and rerouted, or put into a siding while the train carrying the Crusher parts passed, for fear of collision with the wide load. The same problem is encountered when trying to transport exceptionally large tanks, such as the French Char 2C, or the German Panzerkampfwagen Maus or Karl-Gerät by rail.
Once at a job site, the track pods were to be placed in a swamp so that they were easier to manipulate. The splined shafts were fitted in the sockets on one pod and the other pod is mated to it. They were bolted in place, and then the cabin supports and cabin could be dropped in from above. Electrical connections from the cabin were connected to the pods, the intakes and exhausts to the central recess, and the pusher bar was mounted.
The main points and key features of the design that are claimed in the patent were thus:

  • An amphibious vehicle with two independent, watertight propulsion units consisting of two sets of very wide tracks having only a narrow space between them, and the ability to fill with or pump out liquid to increase or decrease mass to the desired level.
  • Such a vehicle with the control cabin placed centrally on narrow supports between the two propulsion units.
  • Such a vehicle that has separate engines for each of the propulsion units.
  • Such a vehicle with a bar for pushing over trees.
  • Such a vehicle intended for crushing trees and undergrowth.
  • Such a vehicle with channels on the underside that contain support rollers for the use of tracks.
  • Such a vehicle that is joined together using the splined socket-and-shaft method.

Crawler-Crusher Specifications

Dimensions 58 x 24 x 22 ft (17.7 x 7.3 x 6.7 m)
Total weight 306 US tons
Crew 1+ (driver-operator, mechanic)
Propulsion 2x Caterpillar D432 270 hp Diesel Engines, 540 hp total
Suspension None
Total production 1
For information about abbreviations check the Lexical Index


The Heaviest Tracked Amphibian Ever Built

At 306 US tons (277.6 metric tons) fully loaded and 204 US tons (185 metric tons) dry, the Crawler-Crusher is the fourth heaviest amphibious vehicle of all time. It is surpassed only by the Aist-class LCAC hovercraft at 302.8 metric tons fully loaded, the Saunders-Roe N.4 Mk.III passenger hovercraft, at around 320 metric tons, and the Zubr-class LCAC hovercraft, which can weigh over 500 tons when fully loaded. The Crawler-Crusher is by far the largest and heaviest tracked amphibian of all time, vastly surpassing all other conventionally- (non-hovercraft) powered amphibious vehicles. For such a heavy vehicle, the Crawler-Crusher was surprisingly buoyant, able to float in just 7 feet 10 inches (2.38 m) of water. In terms of overall dimensions, the Crawler-Crusher was 58 feet (17.7 m) long, 24 feet (7.3 m) wide, and 22 feet (6.7 m) tall.

Source
It is not known precisely when the Crawler-Crusher was constructed, but we do know that it went into operation in April 1967. It cost $700,000 to build and employed many of the companies in Leesburg and the surrounding area. The Jacksonville Shipyard constructed the two-track pods, and most of the assembly work was done by Tucker’s Heavy Equipment Service (now Tucker’s Machine & Steel Service, Inc.) in Leesburg, Florida, with assistance from Leesburg Welding & Machine Company. Adams Air & Hydraulics from Tampa, Florida, did the hydraulic work, and Rozier Machinery Company, at the time a Caterpillar dealership, assisted in the construction by supplying Caterpillar parts.
In was not recorded as to what extent the built vehicle differed from the vehicle outlined in the patent, but there are some observations that can be drawn from photos. Most noticeably, the pusher bar is more heavily reinforced between the top legs of the A-frames. As already mentioned, the cabin is more competently built, and the vent lines do not appear to have been implemented. The controls for the engines and transmissions were electronically-operated hydraulics. Hydraulic pumps and generators were carried in the engine compartments, while the electronic equipment, spare parts, tools, and fuel was carried in the forward compartments.
During testing, the Crusher was found to overheat when it was especially hot out or the machine was worked continuously. Murray Tucker Sr. was discussing the issue at dinner one night when his son Charles Tucker overheard. Being a student at the Southern Technical Institute in Georgia, he asked his professor for help, who in turn assigned the problem to the class. They came up with the idea of running copper pipes down into the ballast water at the bottom of the machine; the engine coolant would be run through these pipes to disperse the heat into the ballast water. Charles informed his father about the solution.
“He acted like he knew it all along. He got the guys in the shop on it right away. He never did tell Mr. Gregg.” – Charles Tucker

F. Browne Gregg (left) and Murray Tucker Sr. (right) standing atop the Crawler-Crusher as the cabin is lowered into place by crane. Notice that the front face of the cabin is smooth and lacking the equipment that can be seen in other photos. Source: “Progress Through Innovation” by F. Browne Gregg
The completed Crusher was first demonstrated for a crowd of 300 people off of State Route 19, 15 miles (24 km) south of Palatka, Florida. Husebo Advertising & Public Relations organized the event that brought in news reporters from across the United States and Europe. The Crawler-Crusher exceeded every expectation, clearing 5 acres of land during the 1-hour demonstration — far more than the half-acre it was expected to accomplish. In both flooded swamp and dry land it left behind a smooth, clean surface.
The Crusher’s first and only job would be to clear the area behind Rodman Dam that would be known as Rodman Reservoir, Rodman Pool, or Lake Ocklawaha. The field supervisor from Gregg, Gibson & Gregg that saw over the use of the Crusher was a man named Jack Perko, the superintendent for the clearing overall was Andy Crabb. The Crawler-Crusher did its work extremely quickly, said to have been able to clear an acre or two of land an hour at a sustained rate. For it to clear 4,500 acres (7 square miles; 18.2 square kilometers) took between just 18 and 27 weeks.


“The Monster” and “The Tree Killer” were some of the creative nicknames given to the Crawler-Crusher by those who opposed the canal. Source
Able to mow over trees up to 6 feet (1.8 m) in diameter, or as many as eight 2 foot (0.6 m) diameter cypress trees at once, the Crawler-Crusher worked with such astonishing efficiency that it served as a rallying point for environmentalists. The Crusher exemplified to the public that the canal was not a long, drawn-out project that would be in the background for years, but was laying waste to the Ocklawaha on an unprecedented scale. Indeed, less than 15% of the trees in the area cleared for Rodman Reservoir were exploited; most were simply doused in diesel fuel and burned, or smashed by ‘Big Charlie’, as the Crusher became known by its operators.

Orange Springs Ferry was one of the first areas to be crushed.Source
Interestingly, one of the Crusher’s assigned jobs was to perform “mosquito control”. It did this by driving around the perimeter of the reservoir (or what would be the perimeter of the reservoir when the water level was between 20 and 21 feet above sea level) and mashing down the swamp forest so that pest control people could spray for mosquitos there. One founding member of the Environmental Defense Fund, which was formed to oppose the canal, was spurred to join the fight against the canal when on one of these mosquito patrols the Crawler-Crusher flattened Cause Springs, one of many natural sources of groundwater around the Ocklawaha, which he had been using as a personal pool!
Erika Ritter, a lifelong resident of the Ocklawaha, witnessed the destruction of the forest on the reservoir first hand when she was a child. Though she wasn’t old enough at the time to play a major part in the environmental movement to save the canal, since 2006 she has run pontoon boat tours on the Ocklawaha and Rodman Reservoir to educate the public about the impact of the canal. She recounts her experience with the Crusher as such:
Once we were in our small wooden boat watching the monster move along the river bank when its weight was too much for the bank and it caved into the river sliding sideways. The operators jumped out and climbed up top and it must have been full of water for maximum crushing weight as soon water started pumping out from various point in a large strong streams! The wave it caused across the river almost swamped our little craft as we cheered for its doom! It crushed everything in front of our house that we loved, I.e. springs, Creek Indian mounds, and [our] favorite fishing hole. They would park it in front of our place for safe keeping since it was an isolated area. We were informed not to come out in the canal clearing when the machine was moving due to the frequent busting off of bolts at a high rate of speed. The tracks had so much pressure on the bolts and breakage was common enough for safety concerns.

Erika Ritter, age 12, standing in front of the Crawler-Crusher while it was undergoing track repairs, October 20th, 1968. Source

Source
5,500 acres (8.6 square miles; 22.25 square kilometers) of land was cleared by the autumn of 1968, when Rodman Dam was completed on the 30th of September, and the reservoir was allowed to fill. Immediately, there was a problem. The trees that had been crushed into the mud by the weight of the Crawler-Crusher, intended to never be seen again, started floating to the surface. There had been a massive oversight during the design of the Crusher; the feasibility study that had been conducted used northern hardwood trees, while the trees along the Ocklawaha were primarily softwoods: gum, bay, pine, cedar, and cypress. The fact that it had been an unusually dry season, and thus the ground being harder than expected, was also cited by the Army Corps of Engineers as a reason for the tree crusher failing to work. Work continued with the tree crusher attempting to stomp the trees back into the muck, but they always came back up.
Despite this massive setback, which rendered the Crawler-Crusher useless as a means of making trees “go away”, work continued on clearing the canal and reservoir to the greatest degree possible. Some effort was expended with a barge-mounted crane and tugboat collecting the floating logs and burning them. The Crusher ran a methodical pattern, clearing a section 400 feet (122 m) wide and 12 feet (3.65 m) deep which would serve as the barge canal. On other portions of the reservoir, trees were left standing to serve as habitat for game fish. Meanwhile, the Army Corps of Engineers had been at work clearing trees from the banks of the Ocklawaha up to 20 miles (32.2 km) upstream from Rodman Reservoir in preparation to excavate and widen the stream to continue the canal.

The Crawler-Crusher wading through a field of floating trees on Rodman Reservoir, February 1969. Note that the pusher bar has been removed. Source
Rodman Reservoir was intended to be kept, under normal operation, at 20 feet (6.1 m) above mean sea level (note, this is not the same as 20 feet in depth), with a maximum of 22 feet (6.7 m) above sea level and an operational minimum of 18 feet (5.5 m) above sea level. At 20 feet, the reservoir covered about 13,000 acres (20.3 square miles; 52.6 square kilometers) of land and was 16 miles (25.7 km) long. At minimum draft, the reservoir covers about 9,200 acres (14.4 square miles; 37.2 square kilometers) and measures 15 miles (24.1 km) long and almost 2 miles (3.2 km) at its widest. The reservoir has been kept at 18 feet above sea level since 1969, with only brief periods of low water to prevent gunk from accumulating on the bottom.
In total, 5,500 acres (8.6 square miles; 22.25 square kilometers) of land was cleared and the rest of the reservoir was left standing; probably because attempting to clear it with the tree crusher would have only created more flotsam. To add insult to injury for the environmentalists that had opposed the canal the whole way, Rodman Reservoir was given the 1969 Army Corps of Engineers “Conservation of Natural Beauty Award” for leaving 5,500 acres of “natural wetlands” go uncleared, and merely putting them underwater. Of the roughly 7,500 acres (11.7 square miles; 30.35 square kilometers) of land that was not cleared, up to 2,000 acres (3.1 square miles; 8.1 square kilometers) have since drowned, leaving only decaying stumps where forest once stood.

Source
But Marjorie Harris Carr and her movement to save the Ocklawaha had one final ace in store. David Anthony was a biochemist from the University of Florida who had been in the field since World War II. With David’s scientific reason as backing, the Environmental Defense Fund (EDF) filed a suit in the United States District Court for the District of Columbia, seeking to halt all work on the Cross Florida Barge Canal. On January 15th, 1971, Judge Barrington D. Parker ruled in favor of the EDF, citing lack of statement regarding environmental impact, as required by the brand new National Environmental Policy Act. On January 19th, Richard Nixon formally ended the canal project. There was much political squabbling after the cancellation of the canal, with the invested parties attempting to reverse the decision, however, the canal project could never regain momentum, and no further work was done beyond finishing several bridges that were in the middle of construction.
In an ironic way, the symbol that had represented everything the environmentalists found wrong with the Cross Florida Barge Canal, the Crawler-Crusher, was a big part in their ultimate success at stopping it. The Environmental Defense Fund used the imagery of the Crusher to such great effect as ‘propaganda’, that it effectively turned public opinion against the canal itself.

Lasting Effects of the Canal and Fate of the Crusher


Press photo of the Crawler-Crusher near to or after the cancellation of the canal. Notice the damage done to the side panels and the bow in the tracks. Also notice the different exhaust structure; at some point it seems to have been rebuilt and extended forward past the cabin for some unknown reason. Source
With Rodman Dam and Reservoir completed, it very quickly became apparent that the environmentalists’ warnings were correct. What hardwood trees remained around the area died off due to being overwatered. Hydrilla and common water hyacinth, highly invasive aquatic weeds, flourished in the shallow, still water. At 18 feet (5.5 m) above mean sea level, the level at which Rodman Pool has usually been held at since its construction, the dam causes a backwater effect (water in a river being held higher than it normally would be) for about 2 miles (3.2 km) downstream, and, though there is debate, about 0.5 miles (0.8 km) upstream as well.
Work on Eureka Dam continued until it was halted in 1970 just shy of completion. It is unknown if there had ever been talk of using the Crawler-Crusher at Eureka as well, but after its utter failure to crush trees effectively at Rodman, it is more likely to have been kicked off the project.
Apart from Rodman Dam (later renamed George Kirkpatrick Dam), the aforementioned Eureka and Inglis Dams, and Buckman Lock, there are three bridges over the Ocklawaha that were built as part of the Cross Florida Barge Canal project that still exist today. These are: the bridge that carries State Road 19 over the canal between Buckman Lock and Rodman Reservoir, the bridge that carries County Road 316 over the Ocklawaha south of Rodman Reservoir, and the Bert Dosh Memorial Bridge on State Road 40 near Silver Springs. All three of these are “high bridges”, meaning they are high enough that barge traffic would have been able to pass underneath. Often thought to be part of the Cross Florida Barge Canal, concrete bridge supports that were poured in the 1930s as part of the Atlantic-Gulf Ship Canal still exist in the wooded area where U.S. Route 301 splits around the Marion County Sheriff Office south of Ocala, Florida.
Even though nearly 50 years have passed since the Crusher finished its work on Rodman Reservoir, its influence can still be seen today. One half of the reservoir is dotted with the stumps of trees drowned out by the raised water level, as well as what patches of forest have managed to cling on, while the other is an endless maze of splintered, floating, and half-sunken trees. These are the same trees that felt the weight of the tree crusher all those years ago, unable to be removed or crushed, they were left in the water, and have posed a hazard to boat traffic for the entire history of the reservoir. This desolate swampland has become suitable habitat for water birds, such as egrets, ibises, grackles, and anhingas, but does not make up for the destruction of the forest and river that was once home to many more species of birds, amphibians, and fish.


Photos of Rodman Reservoir taken during a “drawdown” by Raymond Powers in 2016. Source
The remains of the Cross Florida Barge Canal, especially Rodman Reservoir, remain a hotly debated topic, with people on both sides unwilling to waver in their convictions that the dam should come down or remain up. While it was never used as a shipping lane, or as a recreational lake, Rodman has become a competitive fishing hotspot, known for being chock full of prized largemouth bass. Undoubtedly, the fishing industry holds some sway over Rodman Dam’s continued existence.
As for the Crawler-Crusher, whether it inspired horror or awe, it left a lasting impression on the people of Central Florida, and many wondered what became of it once the canal was canceled. Like many grand machines, whether you agree with its purpose or not, it represented man’s ingenuity and accomplishment, and, like in the story of HMS Warspite making a break for the North Sea, people don’t want to see those accomplishments go gently into the dark night. There were several rumors as to what happened to the Crusher; some people said it went to Texas, or to South America, and was being used there to clear areas for reservoirs and canals; some people believed it had been moved out to Flagler Beach to work on the Intracoastal Waterway, and was abandoned on a spoil island somewhere; and others claimed it went to Vietnam, to support the war effort there. The real fate of the Crawler-Crusher is much less glamorous; with no work left to do, it sat disused for about a year and was scrapped circa 1971. No remnants of “The Monster” are known to exist, save for the thousands of acres of broken trees where it once trod.
One user on heavyequipmentforums.com claims that a friend of a friend was in Florida at an unspecified time and came across massive track links, 10 feet (3 m) wide, in a scrapyard there. There are very few vehicles in history, let alone in Florida, that had tracks that fit this description. In fact, the Crawler-Crusher exceeds this guesstimate, having tracks 11½ feet wide (3.5 m) wide, indicating that at the very least, Big Charlie’s tracks may have hung around for a while even after the machine itself was gone.
In his autobiography, F. Browne Gregg claims that Joe Rozier, the owner of the Caterpillar dealership that helped in building the Crawler-Crusher, was able to put Gregg in touch with the United Nations. He says that at the time the UN was anticipating a famine that would occur in Asia within three to five years. The UN’s interest in the Crusher was to use it to prepare rice paddies in Indonesia.
Gregg met with UN representatives in Hong Kong, where he was offered a contract to produce 500 Crushers in 18 months. In addition to a “mighty tempting” amount of money, he would be allowed to take tax-free ownership of the manufacturing facilities in three years. Even though each Crusher would sell for about 2 million dollars, Gregg passed on the offer due to the work being too momentous, and because it would have taken time away from his other businesses and his family. Perhaps this was the origin of the rumor that the Crawler-Crusher escaped to Vietnam.

The Man Behind The Monster

Frederick Browne Gregg was born on August 13th, 1922, in Lake Junaluska, North Carolina, to William Carter Gregg and Myra Lees Browne Gregg. He suffered from severe dyslexia as a child, something that shaped his life and forced him to think differently from most people. His family moved to Leesburg, Florida, when he was only a year or two old. Frederick graduated from Leesburg High School and started college at The Citadel in Charleston, South Carolina. When Frederick was 20 years old the United States entered World War II. On August 7th, 1942, he applied to the US Army Air Corps in San Antonio, Texas; then went on to pilot a B-26 Marauder, fulfilling his dream of flying. He would fly 37 missions, despite being shot down twice; he earned five Air Medals and was awarded a Silver Star in Paris for engaging with an Me 262 jet fighter. Frederick’s plane, B-26 serial number 43-34190, tail number KX-N, was leading a formation of 108 bombers when they were jumped by an Me 262 of KG(J) 54, supposedly flown by jet ace Heinrich Bär. The 262 downed the flight’s deputy lead aircraft, killing all but one of the crew, and heavily damaged Gregg’s B-26, counting it as a probable kill. With the Silver Star in 1945 he was promoted to the rank of Captain. After the war, Gregg came home to the States aboard RMS Queen Mary.
On January 1st, 1946, he was married to Juanita Osborne. He invested his military savings, about $4,000, into starting an outdoor furniture manufacturing business out of his parent’s garage. Later, Frederick Gregg, his brother Bill (William) Gregg, and their friend Brunson Gibson, with some help from the third Gregg brother, James Gregg, formed Gregg Gibson & Gregg Inc., a construction-oriented business that produced sand and concrete products and provided trucking and dredging services. This would set the tone for the remainder of the business ventures Frederick would undertake in his life.
Under Gregg Gibson & Gregg Inc. was where Frederick would make his most radical inventions; the Crawler-Crusher, and The Triton, the latter being the world’s largest dredge at the time. The Triton was constructed in 1968 around a surplus World War II destroyer engine to fulfil a $5 million excavation contract issued by the Army Corps of Engineers, the largest ever issued in Florida at the time. Gregg sold the company in 1969.

The Triton dredge. Source
In 1971 he purchased Camp Concrete Rock Co., a small mining operation; out of this was formed Frederick Gregg’s most famous company, Florida Crushed Stone. As the Florida Crushed Stone Company grew, it acquired several other companies, including Consolidated Minerals Inc., which still survives today. Florida Crushed Stone became central Florida’s leading producer of construction aggregates (quite literally, crushed stones; aggregates include concrete and sand).
During the 1980s, Frederick Browne Gregg and Florida Crushed Stone undertook the project they are remembered for best in the construction industry. This was reengineering Central Power & Lime of Brooksville, Florida, as the world’s first integrated power, cement, and lime plant. The rebuild of the plant cost $250 million and involved rebuilding and moving a disused coal-fired electric power plant from Illinois to Florida. The plant’s primary innovation though, was the fact that it operated almost entirely off of waste materials.
In 1994, Browne Gregg was involved in a plane crash that broke his neck and collarbone. Within months, he was skiing with his family in Colorado, despite having to wear a neck brace and being 72 years old.
Not all of his business ventures were successful; he caught criticism from local Floridians for his involvement in the Lake County incineration plant, which, despite being paid for by public funds, remained a private entity. Gregg sold his interests in the plant to Covanta Energy, which still operates it today.
Frederick sold most ownership of the Florida Crushed Stone Company to CSR America in 2000, though he retained some of its operations and combined them with his other businesses as Consolidated Minerals Inc. Today, Consolidated Minerals also owns CL Industries, the largest American manufacturer of pool finishing materials.
Frederick Browne Gregg’s wife Juanita passed away in 2000; he later remarried to Victoria McDonald Gregg. Frederick himself passed away on October 10th, 2014, at the ripe old age of 92. Arrangements were made by Beyers Funeral Home and Crematory. He was laid to rest at Hillcrest Memorial Gardens Cemetery in Leesburg, Florida, on October 15th, 2014, following a funeral at the Morrison United Methodist Church.

Source
F. Browne Gregg is remembered as a kindhearted and enthusiastic inventor and businessman. He and his companies have won many awards, including the Ernst & Young Entrepreneur of the Year Award, Socially Responsible Award, Florida Region for 1995; the Junior Achievement Mid-Florida Business Hall of Fame in 1998; an induction to the Texas Panhandle Veterans Hall of Honor; and several appointments to the Florida Council of 100. He was a benefactor of children’s education and medicine, and made regular contributions to Camp Boggy Creek, Junior Achievement of Central Florida, and Green Isle Children’s Ranch.

Probably the most famous photo of the Crawler-Crusher, showing its destructive power. Gregg’s wife Juanita created an oil painting copy of this photo that hung in Gregg’s office until his death. Source

Sources

“From Exploitation to Conservation: A History of the Marjorie Harris Carr Cross Florida Greenway” by Steven Noll and M. David Tegeder
“Cutting Through Paradise: A Political History of the Cross-Florida Barge Canal” Doctoral Dissertation by Sallie R. Middleton
“Ocklawaha River Cross Florida Barge Canal Structures” Webpage Report, Paul Nosca, 2015
“‘Our Lady of the Rivers’: Marjorie Harris Carr, Science, Gender, and Environmental Activism” Doctoral Dissertation by Margaret F. MacDonald
Summer 2004 Issue of The Florida Historical Quarterly
Pure Florida Blog’s entry on Rodman Reservoir
River be Dammed.org’s page on the history of Rodman Reservoir
US Patent 3418961A for Swamp Clearing Machine
“Progress Through Innovation” by F. Browne Gregg
Popular Science, April 1968
Heavy Equipment Forums.com
Consolidated Minerals Inc. Page on F. Browne Gregg
Frederick Browne Gregg’s Obituary
Contractors and Engineers Magazine, March 1970 Issue
The author would like to express thanks to Erika Ritter for supplying photos and for recounting her memories of the Crusher.


Illustration of the gargantuan Crawler-Crusher – otherwise known as “The Monster”, produced by Andrei ‘Octo10’ Kirushkin, funded by our Patreon Campaign.

Categories
Cold War American Other Vehicles

Self-Propelled Flame Thrower M132 ‘Zippo’

U.S.A. (1959)
Armoured Flame Thrower – 351 Built

Since its appearance in the late 1950s, the Armored Personnel Carrier (APC) M113 has continued to be one of the most versatile and universal armored vehicles to have ever existed. It has spawned numerous variants in its long service life, from mobile command posts and Self-Propelled Anti-Air Guns (SPAAGs) to firefighting vehicles.

One of the less well-known variants was the Self Propelled Flame Thrower M132. Entering service in 1963, the M132 – along with the Flame Thrower Tank M67 ‘Zippo’ – would be one of the last armored or ‘mechanized’ flamethrowers to see service in the United States Military. Whereas the M67 would serve in the US Marine Corps (USMC), the M132 would serve with the US Army. The vehicle saw action during the long years of the Vietnam War (1955-75), but its time in service was, however, short-lived. This is mostly due to the fact that, after Vietnam, flame throwing vehicles began to fall out of favor.

One of the first things the article will address is its unofficial ‘Zippo’ nickname – named after the lighter brand – which it shares with the M67. Its origin is somewhat mysterious. Just like the M60A2 tank and its ‘Starship’ name, a concrete source cannot be stated as to when this name came into use. It was likely given by the crews or infantry that operated with the vehicle. There is a suggestion, however, that the name originated from this particular lighter being used to ignite the napalm fuel when the electrical igniters failed.

The M113-based Self-Propelled Flame Thrower M132 ‘Zippo’. Photo: Hunnicutt Bradley

The M113

The M113 is one of the most famous Armored Personnel Carriers ever built and continues to serve in not only the US Military but also in the inventory of many of the world’s militaries. The vehicle has been in service for 60 years, making it one of the longest-serving armored vehicles in history.

Developed and built by the Food Machinery Corporation (FMC), the M113 is a basic vehicle, little more than an armored box on tracks. It is 15 ft 11.5 in (4.8 m) long, 8 ft 9.7 in (2.6 m) wide, and 8 ft 2 in (2.5 m) tall. The vehicle’s structure is almost completely fabricated from aluminum, including the armor which is between 0.4 and 1.4 inches (12 – 38 mm) thick. The vehicle started out with a Chrysler 75M petrol engine, although this would later be changed to a General Motors 6V53 diesel type. The power plant is located at the front of the vehicle with the transmission. The vehicle is supported by a torsion bar suspension connected to five road-wheels. The idler wheel is at the rear with the drive sprocket at the front.

The APC has a crew of two, a Driver and a Commander, who are located at the front of the vehicle, with a passenger compartment taking up the rear of the vehicle. Eleven passengers can be carried by the vehicle. The APC’s usual armament would be a single Browning M2 .50 Cal (12.7mm) heavy machine gun, located at the commander’s position.

Development & Background, the CRDL

In June 1954, the Chemical Research and Development Laboratories (CRDL) began a study, conceptualized by the US Army Chemical Corps, looking into the conversion of serving tanks and armored vehicles into armored/mechanized flame throwers. As a result of this study, the E31-E36 flame thrower kit was developed. The nomenclature, which was unchanged from its debut in the Second World War, denotes that this is the combination of the E31 fuel and pressure unit and the E36 flame gun. The idea behind this kit was that it could be installed on serving vehicles with minimal effort.

One of the M59 prototypes during a demonstration for President Kennedy in 1961 at Fort Bragg. Photo: LIFE Magazine

Three E31-E36 kits were produced and tested on the M59 APC, the predecessor of the M113. In the M59, flame-fuel capacity was 400 gallons (1,818 liters) providing a total firing time of 70 seconds. Following the tests, improvements were made to the weapon and it received the new designation E31R1-E36R1. The modifications to this version of the weapon were intended to allow its installation not only on the M59, but also the brand new M113 APC.

Diagram showing the internal arrangement of the flame thrower system inside the M113. Photo: Hunnicut Bradley

Prototypes

In the summer of 1959, a contract was signed for the construction of three E31R1-E36R1 units and their installation aboard three M113s. The newer, and larger, M113 was found to be a far more suitable vehicle than the M59 and, as such, all work on an M59 based flame thrower ceased. This is despite the M59 having better flame fuel capacity, and as such, a longer firing time*. Logistically, however, it was only prudent to develop the vehicle on a new type which was then entering service. This would allow a degree of commonality, making it easier to manufacture and allowing spare parts to be shared between vehicles.

The three prototypes had the E36R1 installed inside an M1 Cupola – the machine gun armed cupolas found on the M48 and M60 tanks – with a coaxial machine gun. This cupola was then mounted over the commander’s position, with the fuel and pressure systems installed in the personnel compartment. Initially, the coaxial machine gun consisted of the .50 Cal (12.7mm) M85, this was later changed to the .30 Cal (7.62mm) M73.

Production artwork of the M132. The configuration of the flame projector in the cupola with the coaxial machine gun is clearly visible. Photo: Hunnicutt Bradley

Testing of the prototypes took place in 1961 at Fort Benning, Georgia, and Fort Greely, Alaska. In March 1962, the E31R1-E36R1 was standardized by the Chemical Corps Technical Committee (CCTC) as the M10-8. This nomenclature denoted the M10 fuel and pressure unit, and the M8 flame gun or ‘Cupola Group’. A year later, in 1963, the United States Army Materiel Command (AMC) officially type-classified the vehicle as the Self-Propelled Flame Thrower M132. In December of 1963, a new Diesel powered version of the M113 was nearing the end of its development, this would become the M113A1. The natural progression for the M132 was for it to be built on the hull of the new M113A1. The new version was classified by the AMC as the M132A1. The M132A1 was also known as the ‘Standard A’ with the earlier M132 version known as the ‘Standard B’.

Overview of The M132

In total, the Food Machinery Corporation (FMC) would produce 351 vehicles, consisting of 201 M132s, and 150 M132A1s. The M132 was operated by a two-man crew consisting of the driver, front and left, and the flame gunner/commander, located behind the driver in the center with the flame gun. Overall, the dimensions of the M113 chassis were unchanged. It remained 15 feet 11 ½ inches (4.8 meters) long and 8 feet 9 ¾ inches (2.6 meters) wide. Due to the flame cupola, it is 2 ¼ inches shorter than the standard M113 at 7 feet 11 ¾ inches (2.4 meters) in height. This is due to the lack of a mount for a machine gun. The M132 retained the M113’s top speed of 42 mph (68 km/h).

Flame Equipment

In the cupola, the M8 flame projector is mounted on the left with the coaxial M73 .30 Cal (7.62 mm) machine gun on the right. The barrel of the projector is flat with a sausage-like aperture. The cupola is traversed by hand and has a 360-degree arc of rotation. Both the machine gun and flame gun share a vertical traverse of +55 to -15 degrees. The cupola was equipped with 4 vision blocks and an M28D sight for the flame gunner/commander.

Front view of the M8 cupola group atop the M132. Note the M73 7.92mm machine gun on the left, and the flame gun on the right. The flame gun has a flat barrel, with a sausage-like muzzle. Photo: Public Domain

The flame gun is fed by the M10 fuel and pressure unit, located in the rear of the vehicle in what would be the personnel bay of the standard M113. The drop ramp was retained on the M132 to allow easy access and refueling to the weapon systems. The M10 unit took the form of four snowman-like structures, consisting of a large, spherical 50 gallon (227 liters) pressurized fuel tank with a smaller, spherical compressed air tank on top. The fuel tanks were pressurized to 325 pounds per square inch (23 kg/cm²), with the air tanks pressurized to 3,000 pounds per square inch (210 kg/cm²). The fuel tanks are connected in series, with the last one connected to the rotating joint of the cupola group. The air tanks are also connected together and provide pressure for the flame gun and fuel tanks. The tanks were placed in a removal rack system to allow easy maintenance for both the tank system and the internal components of the vehicle.

Diagram of the snowman-shaped fuel and air units located in the rear of the M132. The large balls on the bottom contain the flame fuel, the smaller balls on top contain pressurized air. These components were all mounted to a single rack system to allow easy removal. Photo: Hunnicutt’s Bradley

In total, the M132 could carry 200 gallons (909 liters, *the dropped M59 version could hold 400 gallons/1818 liters) of thickened, gasoline-based flame fuel. This fuel could be propelled to ranges of 12 to 218 yards (11 to 200 meters).

Service

Where its bigger brother, the M67, found service almost exclusively with the United States Marine Corps (USMC), the M132 would enter service with the US Army, specifically in Armored Cavalry units. Based on ensuing combat experiences, the Army Concept Team in Vietnam (ACTIV) advised that four M132s and two regular M113s be attached to each regiment. Headquarter companies of U.S. Armor and Cavalry units were all assigned at least one M132. Also, armored regiments of the Army of the Republic of Vietnam (ARVN, Viet: Lục quân Việt Nam Cộng hòa) were all assigned four M132s. The M132s were not limited to the US Army, however. Specific tactics were drawn up for operations with both the Army and Marine Corps, but also for the Navy.

Close up of the flame gun in action. This photo was taken with the Vietnam version of a ‘selfie-stick’. This being a camera attached to a metal pipe slotted over the coaxial M73 machine gun. Photo. LIFE magazine

Standard combat procedure for the M132 was thus: 1) the M132 would advance on a target, using the coaxial M73 machine gun to suppress the target. 2) continuing to fire, the vehicle will move into flamethrower range of the target. 3) the flame gun is fired. In some instances, this may first consist of a “wet burst” of unlit fuel, which would then be ignited by a second ignited burst. The “wet burst” method had been in use since the Second World War. Flame tanks, whether it be the Churchill Crocodile or POA-CWS H1 Sherman, would fire unlit fuel at defensive positions, allowing it to ‘soak’ into the structure. The second lit burst would then ignite the first burst, burning out the defenders. Due to the location of the flame gun behind the driver’s position, it was recommended that the driver keep his hatch closed in combat, for obvious reasons.

Due to the vehicle’s thin, aluminum armor, it was relegated to a strictly support role, operating only with the protection of infantry or armored support. Even so, the vehicle was a valuable asset to convoys. It served as protection against hidden attackers in the heavily vegetated roadsides of the Vietnamese jungle. There is also a recorded example of an M132 knocking out a Vietcong 57mm recoilless rifle team with a 3-second flame burst during the Battle of Ap Tau O in 1966.

M132 of 1/4th Cavalry “The Quarterhorse”, 1st Infantry Division “Big Red One” during Operation Cedar Falls. This M132 is burning a field in the “Iron Triangle” region of Ben Suc, January 1967. Photo: Jerzy Krzemiński

Unfortunately, not too much more is known about individual battles or skirmishes the M132 may have taken part in. The Vietnam War would be the only conflict that the M132 saw service in. The small paragraph below from the US Army report ‘Mechanized and Combat Operations in Vietnam’ published in March 1967, gives a little detail on the vehicle’s use in the conflict:

The M132 mechanized flame thrower has been successfully employed in offensive and defensive operations in Vietnam. In search and destroy operations, they are normally employed in pairs against bunkers and densely foliaged enemy-defended areas containing antipersonnel mines and booby traps. Flame directed at such areas may not destroy a protected enemy, but heat detonates mines and defoliates the area. In defensive positions, the flamethrower is employed to fill gaps not covered by direct fire weapons and to illuminate the area. During movements, the M132s can provide close-in flank protection to the column…

When being used in Naval operations, M132s would be backed onto Armored Troop Carriers (ATC, converted LCM-6 vehicle carriers) accompanied by a 2 ½ ton refueling truck. The M132s would fire over the sides of the vessel at targets on the river bank. There is at least one recorded example of this taking place on the Mekong River.

An Armored Troop Carrier (ATC) on a Vietnamese River, note the M132 in the cargo area at the front of the vessel. Photo: Photo: NHHC Photograph Collection, L-File, Vietnam
An M132 unleashes its firey breath at a river bank from the deck of an ATC. Photo: Quora.com

An Unquenchable Thirst

In operations, the M132 was accompanied by a specially adapted variant of the M548 Cargo Carrier. This was the Flame Thrower Service Vehicle XM45E1. As the M132 had such a small flame fuel capacity, it had a short burn time of just 32 seconds (*the dropped M59 version had a 70 second firing time). The XM45E1 was designed as a refueler for mechanized flamethrowers. The vehicle could mix and transfer thickened flame fuel. It also had an air-compressor to replenish air tanks and carried spare flame system parts. As well as the M132, the XM45E1 also supported the M67, but to a lesser extent.

The Flame Thrower Service Vehicle XM45E1. Photo: Hunnicutt’s Bradley

Fate

The M132 was a successful vehicle. Modified versions of its M10 flame turret even went on to be used on some smaller naval vessels. Despite its success, the M132 would share the same fate as the M67 Flame Tank, being one of the last mechanized flamethrowers to serve with the US Military. The M132 and M67 would be completely phased out by the early 1980s, by which point the controversial weapons had largely fallen out of favor in many of the world’s militaries due to humanitarian reasons. Flamethrowers were controversial with the operators as well as those on the receiving end. They were dangerous to use and the injuries caused by them were horrific. The United States officially stopped using all flamethrower types in 1978 and continued to phase them out after that date. The reason stated at the time was: “flamethrowers were not effective in modern combat scenarios”.

One of the later ATC that had turrets from the M132 installed. Photo: Michael Moore

A few M132s survive to this day. One can be found in Vietnam at the War Remnants Museum in Ho Chi Minh City (formerly Saigon). One of the only surviving examples in the US can be found at the United States Army Chemical Corps Museum at Fort Leonard Wood, Missouri.

Surviving M132 at the War Remnants Museum in Ho Chi Minh City, Vietnam. Photo: Wikimedia Commons


Illustration of the Self-Propelled Flame Thrower M132 ‘Zippo’, produced by Andrei ‘Octo10’ Kirushkin, funded by our Patreon campaign

M113 APC specifications

Dimensions (L-w-H) 4.86 x 2.68 x 2.50 m (15.11 x 8.97 x 8.2 ft)
Total weight, battle ready 12.3 tonnes (24,600 lbs)
Crew 2 (Commander/Gunner, Driver)
Propulsion Detroit 6V53T, 6-cyl. diesel 275 hp (205 kW) P/w 22.36 hp/tonne
Transmission Allison TX-100-1 3-speed automatic
Maximum speed 42 mph (68 km/h) road/3.6 mph (5.8 kph) swimming
Suspensions Torsion bars
Range 300 miles/480 km
Armament Main: M10-8 Flame thrower system.
Sec: Coaxial M73 .30 Cal (7.62mm) Machine Gun
Armor Aluminum alloy 12–38 mm (0.47–1.50 in)
Production 351

Sources

R. P. Hunnicutt, Bradley: A History of American Fighting and Support Vehicles, Presidio Press
Michael Green, Images of War: Armoured Warfare in the Vietnam War, Pen & Sword Publishing
Captain John Ringquist, U.S. Army Flamethrower Vehicles Part 3, Army Chemical Review
Fred W. Crimson, U.S. Military Tracked Vehicles, Motorbooks International
Armored Fighting Vehicle Data Base
www.globalsecurity.org
www.revolvy.com


Categories
Cold War American Other Vehicles Improvised AFVs

Medium Tank M4A3 (105) HVSS ‘Porcupine’

U.S.A. (1950-53)
Communications Tank – 2-5 Converted

Ever since the earliest days of tanks and armored vehicles, special radio communications variants have been produced. After all, communication is, perhaps, the most important aspect of any military operation. Whether between infantry, airforce or armor, communications are key to a successful operation and maximizes coherence between various units. The earliest of these vehicles was the ‘Wireless Communications Tank’ based on the British Mk. I tank used in the First World War. In the Second World War, more appeared such as the German Kleiner Panzerbefehlswagen based on the Panzer I, and the Japanese Shi-Ki based on the Type 97 Chi-Ha.
In the Korean War (1950-1953), communication was key with Allied forces spread all over the ‘Land of the Morning Calm’, as it was called by the Korean people. With friendly forces always on the move, units realized there was a need for compact and mobile radio communication stations.
By the time of this War, the Medium Tank M4 was a largely outdated and plentiful vehicle to base such a vehicle on. This conversion became known as the ‘Porcupine’ after the multiple antennae that protruded from the tank. It was an extremely rare vehicle, and it is believed that only two to five of these field-conversions were produced.

Porcupine ‘Y53’, south of Panmunjom on 27th June 1952. Photo: Presidio Press

Medium Tank M4A3 (HVSS)

By the time of the Korean War, the M4 series had evolved into its final form, often referred to as the M4A3E8. To the Marines in Korea, they were known as the “Old Reliables”. Entering service late in the Second World War, this model featured an improved Horizontal Volute Spring Suspension (HVSS) that replaced the iconic Vertical Volute Spring Suspension (VVSS) of earlier models. This suspension allowed for a wider track, improving grip and lower ground pressure on softer ground.
Propulsion was provided by the Ford GAA all-aluminum 32-valve DOHC 60-degree, 525 HP, V8 gasoline/petrol engine. This could propel the tank to a top speed of 40 – 48 km/h (25 – 30 mph). Armor on the vehicle was up to 76 mm (3 in) thick. The tank had a crew of five, consisting of a commander, driver, co-driver/bow machine gunner, gunner, and loader.
Although a large number of the newer, 90mm gun armed M26 Pershings and M46 Pattons were dispatched to the Korean Peninsula, multiple variants of the E8 were also used in the Korean War. These included the regular M4A3(76)W HVSS, which was armed with the 76mm Tank Gun M1A1 or M1A2, the M4A3(105) HVSS, armed with the 105mm Howitzer M4, and finally, the POA-CWS-H5. This was a specialist version armed with both a 105mm Howitzer, and a coaxial flamethrower.

Choice of Tank

It would appear that every one of these converted M4s were 105mm howitzer armed M4A3(105) HVSSs. This highlights an interesting choice as there were not that many 105mm howitzer armed M4s deployed in Korea. There are few viable arguments to suggest why these tanks were used though.
In the Second World War, most M4 105s did not have power-traverse or elevation gears. By the time of Korea, these gears were added to most of the Howitzer M4s, but not all. This made the M4 105 turret extremely roomy, with more that enough space to add extra radio equipment. There is an element of redundancy in this argument however, as the August 1948 “Medium Tank Status” report stated that there were 1398 M4A3(105)s with HVSS and power traverse in the Army’s Inventory. An additional 521 M4A3(105)s with HVSS, but without power traverse were also listed. It is likely that the US Military would’ve prioritised the updated 105s, and taken them to Korea, albeit, in very small amounts.
However, another theory suggests that it was simply a matter of availability. In reality, the turret of the 76mm gun armed M4s was the larger of the two. M4A3(105) tanks would have been a logical choice as there was a potential surplus of the vehicles that would’ve have been available for conversion to utility vehicles such as this. This is possibly the most likely reason behind the vehicle choice.

One of the more extensive modifications with 8 Antennea. Photo: Public Domain

Specifications

Dimensions (LxWxH) 7.54 (without gun) x 2.99 x 2.97 m (24’7″ x 9’8″ x 9’7″)
Track width 0.59 m (1’11” ft.in)
Total weight, battle ready 30.3 tonnes (66,800 lbs)
Crew Possibly 5
Propulsion Ford GAA all-aluminum 32-valve DOHC 60-degree, V8 engine, 525 HP, V8 gasoline petrol engine
Maximum speed 40 – 48 km/h (25 – 30 mph) on road
Suspension Horizontal Volute Spring Suspension (HVSS)
Range 193 km (120 miles)
Armament None, all dummy or removed
Armor Maximum 76 mm (3 in)


‘Porcupine’ Y53, Korea 1952. Illustration by Tank Encyclopedia’s own AmazingAce, based on work by David Bocquelet.

Modifications


The above image and following information was provided by the “Sherman Minutia” website.
The photo shows one of the Communication Tanks and two M4 Dozer Tanks of the Provisional Tank Platoon on November 19, 1950, navigating the hazardously narrow road near the Funchilin Pass which was the 1st Marine Division Main Supply Route (MSR) to the Chosin Reservoir.
1, 2 & 3: At first glance the Communication Tank appears to be a conversion of a rare M4A3(75) HVSS tank due to the standard 75mm mantlet visible (1), but closer examination reveals the canvas mantlet cover attachment points (2) and the gun travel lock mounted lower on the glacis (3) both of which are characteristic of 105mm armed tanks. All of the Porcupines had dummy guns in an effort to look like regular gun tanks. To be precise, only the breech and other internal components were removed. The actual barrel of the gun remained intact and was fixed in place, either permanently resting in the travel-lock or rigidly facing forwards. The extra internal space was used for installing map tables and additional radios. All other armaments, such as the coaxial and bow-mounted machine guns, possibly even the cupola mounted .50 Cal (12.7mm) were also removed. Making them difficult to distinguish from regular tanks was part of their protection. The enemy had a harder job identifying a command vehicle to knock out.
4, 5, 6 & 7: A number of external modifications were made to the vehicle. These include a handrail added to the side of the turret (4) and an armored door added to the side of the hull (5). A large antennae mounting bracket was added to the side of the turret (6), as well as other points on the hull, for instance next to the driver’s hatch (7). The arrangement and amount of antenna added to the tanks appears to be unique to each vehicle. At least one of the Porcupines had as many as eight antennae.

Radio Equipment

The Radios added to the M4 were used for long-range communications. This included communication with Naval Vessels, aircraft, infantry units, and artillery batteries. A significant drawback of the high-amperage radios installed in these tanks was that they required a positive ground contact. As such, the radios could not be operated while the tank was on the move. When stopped to transmit, a steel stake connected to the earthing cable would be driven into the ground during operation.
Radio equipment may have included the AN/VRC-3. The AN/VRC-3 was simply a vehicle-mounted version of the SCR-300 which had an approximate range of 3 miles (4.8 km). Looking at photos, at least one of the tanks used an AB-15/GR antenna.
In reference to the fact that some of the vehicles were adorned with up to eight antennae, the tank acquired the unofficial nickname of “Porcupine” after the spine-covered mammal.

Service

Not much is known about the Porcupine’s career in the Korean War. It is hard to say when exactly they appeared in US Marine Corps. One of the earliest reported sightings of a Porcupine was between the 14th and 19th November 1950. That night, a Porcupine with the designation ‘Y51’ was documented as passing along the Marine’s treacherous main supply route (MSR) through the Taebaek mountains, accompanied by the entirety of the 9-Tank-Strong 1st Marine Division Flame Tank Platoon, a command tank and a recovery tank of the Headquarters and Service Company, First Tank Battalion.
In March 1952, the Marines began to relocate from the East coast of the Korean Peninsula to the West. To do this they would travel to the small port town of Sokcho-ri where LSTs (Landing Ship, Tank) were waiting to take them around the Korean coast to the Port of Inchon which had previously been taken earlier in the War. A Porcupine (ID number unknown) was recorded as being loaded onto an LST identified as No. 1138, with the nine tanks of the 1st Flame Platoon, three M4 Dozers and a Company of M4A3 (76) HVSS tanks of the Korean Marine Corps (KMC).
The next known location of one of the Porcupines, identified as ‘Y53’ was south of Panmunjom, (the future site of the signing of the Korean Armistice Agreement) on 27th June 1952.
Unfortunately, more is not known about this tank and its part in the Korean War. As it is an extremely rare vehicle, photographs and documented information are hard to find. It is highly unlikely that any of the vehicles survive today.

M46 ‘Porcupine’

An even rarer vehicle is the Porcupine variant of the Medium Tank M46 Patton. No pictures seem to survive of this vehicle, but there is a report of at least one in action as part of Operation Clambake on the Jamestown Line on the 3rd February 1953. The tank was under the command of Captain Clyde Hunter. It was equipped with six-radios.

An article by Mark Nash

Links & Resources

www,radionerds.com: (1) (2)
Brian Branson, US Military Radio enthusiast.
Pierre Olivier and Joe DeMarco of the ‘Sherman Minutia
Presidio Press, Sherman: A History of the American Medium Tank, R. P. Hunnicutt.
Turner Press, Hearts of Iron: The Epic Struggle of The 1st Marine Flame Tank Platoon: Korean War 1950-1953, Jerry Ravino and Jack Carty

Categories
Cold War American Other Vehicles

Flame Thrower Tank M67 Zippo

U.S.A. (1953)
Armored Flamethrower – 109 built

The United States Marine Corps (USMC) was no stranger to the use of flamethrower equipped tanks. The Corps strongly advocated for the deployment of such vehicles. American early flame-throwing tanks, such as the M3A1 ‘Satan’ and variants of the M4 Sherman, were used to great effect against the heavily entrenched Japanese forces in the Pacific in WW2.
With the outbreak of the Korean War, the Marines were practically begging for a new flame-throwing tank. All that they had at that time were the M42B1 and B3, flame throwing tanks built on the chassis of the out dated M4 Sherman. This led to a request for a new, up-to-date flame tank. The answer to this request was the M67, also known as ‘Zippo’ (after the popular brand of lighters), based on the 90mm Gun Tank M48 Patton III. It would, however, arrive too late to see action in Korea.

M67 in action near Da Nang. Photo: Wikimedia Commons

History

In the final stages of the Second World War, the United States Military, fighting the Japanese in the Pacific, realized the effectiveness of tank-based flamethrowers, particularly in dealing with a well-dug-in enemy force. They would first be deployed in the shape of field expedient modifications of the M3 Light tank (resulting, for instance, in the ‘Satan’). Such vehicles would then progress further into serialized developments of the Medium Tank M4A1 and A3. These were designated M42B1 and B3.
Post War, development continued on flame-throwing tanks on newer chassis. The M26 Pershing was first tested for conversion in October 1945 as the T35. This went through a few designs, including mounting the flame equipment in the turret, replacement of turret with a casemate structure, and finally a trailer configuration similar to that of the British Churchill Crocodile. None of these designs were accepted for production or service, and the T35 project was canceled in 1948. Believing that tanks with a flamethrower main armament had a limited infantry support role on the battlefield, the US Military wasn’t keen on developing a vehicle with such a configuration.
The United States Marine Corp (USMC) however, disagreed. The Marine Corps’ primary use of tanks was in a close infantry support role and the effectiveness of flame tanks was already demonstrated to them in fighting against the Japanese. Come the time of the Korean War, the Marine Corps were effectively pleading for a new flamethrowing tank to replace the outdated M42B1 and B3s which they had no choice but to use.

An early M67 based on one of the earlier models of M48 with the shallow engine bay. It is seen here in action alongside an M50 Ontos. Battle of Hue’ City, 1968. Photo: SOURCE
Following this, work began on a flamethrowing tank based on the 90mm Gun Tank T42, which was supposed to be America’s next medium tank. With the complications that arose from the T42, the project was moved onto the 90mm Gun Tank M47 Patton II. (This was the combination of the T42’s turret with the M46’s hull. The famous answer to the ‘Korean Tank Panic’). This variant was designated the T66, with the flame projector mounted in the turret in place of the 90mm gun. Only one prototype of this tank was produced before the project was canceled, due to the fact that by the time this single vehicle had been built, the M47 itself was being replaced by the new M48.

M48 Patton III

The M48 Patton III was the third in the line of tanks named after the World War Two American General George S. Patton. Entering service in 1953, the M48 replaced the rushed, but well serving, M47 Patton II, and was one of the last tanks in US military history to carry a 90mm main armament.
The tank weighed about 50 tons, with armor of up to 110mm thick. The tank was powered by a 650 hp Continental AVSI-1790-6 V12, air-cooled twin-turbo gasoline engine. This would propel the tank to a speed of 30 mph (48 km/h).
The tank served with the US Military up to the 1990’s, despite being mostly replaced by the next tank in-line, the M60. While in service, the M48 went through systematic upgrades including a new engine, internal systems and the eventual up-gunning with a 105mm gun.

Pilot, the T67

In Autumn 1954, work began on basing a flamethrower tank on the M48. It would be designated as the T67. Main armament would consist of the E28-30R1. This stood for Experimental E28 fuel and pressure system, with 30R1 flame gun. This configuration was later serialized by the Chemical Corp Technical Committee as the M7-6 Mechanised Flamethrower. The component parts were designated as the M7 fuel and pressure unit and the M6 flame gun. The complete system, including the turret, was designated Flamethrower Turret T7. For the prototype, this was assembled inside an M48 turret with the Low-Profile Chrysler commander’s cupola with external .50 cal. machine gun mount.

The T67 pilot vehicle based on the early M48 model with low engine deck. Photo: Presidio Press
This turret was lowered onto an M48 hull, with the low engine deck housing the early Continental AVSI-1790-6 V12. With the deletion of the standard gun, there was no need for a loader and the number of crew members was dropped to three. This position was taken up by a large, 398 gallon (US) fuel tank for the flamethrower. The Commander and Gunner remained in their traditional positions on the right-hand side of the turret. The only ingress and egress point in the turret was the commander’s hatch as the remaining loader’s hatch was completely blocked by the flame thrower’s fuel tank. As such, the hatch was used to refuel and maintain the equipment.

Flame Equipment

The thickened fuel for the flamethrower was stored in the large 398 gallons (US) central tank. This was the maximum capacity of the tank, but a bit of leeway was given for expansion and other losses or spillages. As such, usable capacity was closer to 365 gallons (US). There was a secondary 10.2 gallon (US) fuel container which supplied un-thickened gasoline to the atomiser, it also coated the main-fuel for ignition in cold weather. The system was pressurized to 325 psi (2240.8 kPa) allowing a 55 second burst with the ⅞ inch (22.22mm) nozzle, and 61 seconds with the ¾ inch (19.05) nozzle. Maximum range for the flame gun was 280 yards (256 meters).

Cross section of the M67’s turret. Note the huge fuel tank in place of the loaders position. Photo: Presidio Press.
The fuel was ignited by 24,000 volt spark plug igniters in front of the nozzle inside the firing tube. A carbon dioxide snuffer system was also employed at the nozzle to extinguish any residual fuel burning the gun itself after it was shut off.
The M6 flame gun was housed in a shroud designed to mimic the appearance of the 90mm T54 gun equipped on the standard M48 Patton in an effort to disguise it as a standard gun tank. The shroud was noticeably wider in diameter and 21-inches (53.34cm) shorter, though it did include a faux tubular ‘T’ shaped muzzle break. This dummy gun barrel had holes in the side allowing the circulation of air necessary for combustion. There were also holes and drip shields at the bottom for drainage. There was a removable cover in the center of the barrel, allowing access to the ignition systems and the whole system was attached to the standard gun shield found on M48’s, and the tube for the fuel pivoted on the same trunnions. Though the system shared as many elevation and traverse components as the standard M48, the M6 Flame gun and complicated shroud made it muzzle heavy. A hydraulic equilibrator device was introduced to balance the weapon which operated throughout the M6’s whole +45 to -12 range of elevation. As well as the flame gun, the gunner also operated the coaxial .30 cal. Browning machine gun as normal.

M67A2 taking part in fire trials. Photo: Presidio Press

Hull Modifications

The introduction of the T7 Flamethrower turret and accompanying weaponry necessitated a number of minor, but important, modifications to the M48 hull. The depression angle of the M6 Flame Gun was greater than that of the 90mm gun main armament of standard M48’s, as such, the brush guards of the bow head lights were flattened to allow clearance. The ammunition racks for the 90mm ammunition on the left and right of the driver were removed and replaced by stowage bays for the storage of tools, spare parts for the flame equipment, and ammunition for the machine guns.The auxiliary engine muffler, which was located on the M48’s rear deck, was relocated to the right-rear fender. This was a preventative measure to give clearance to the flame-thrower fuel tank vent which protruded from the left-bottom of the turret bustle.


M67A2 ‘Zippo’ from the 1st Tank Battalion, US Marine Corps. Illustration by Tank Encyclopedia’s own David Bocquelet

Standardisation, the M67

The T67 was now two-years late for action in the Korean War, but work carried on. After going through a number of tests and trials with the Marines, 56 complete T67s were delivered to the Corps, in addition to 17 T7 Flamethrower turrets. All of these were based on the M48A1’s with the large M1 Cupola that has the integral .50 cal machine gun mount. The spare 17 turrets were mated with the modified hulls of M48A1s. The T67 Pilot was also upgraded to M48A1 standard, bringing the total number of tanks to 74 units. On the 1st of June 1955, the T67 was standardized as the Flamethrower Tank M67. At the same time, the T7 turret was designated as the Flamethrower Tank Turret M1. When the M48A2 appeared (with the larger engine compartment and radiator grill) the M1 turret was introduced to the new chassis. This turned the M67 into the M67A1.

M67A2 during trials at Aberdeen Proving Grounds. Photo: Presidio Press
Along with the chassis changes, the M7 fuel and pressure system was upgraded to US Army standards and redesignated the M7A1. Following this, the Chemical Corps redesignated the whole system as the M7A1-6. Chrysler built 35 M67A1s at their Delaware plant between 1955 and 1956. These were the only M67’s to ever see service with the United States Army, but this was only for a very short period.
Further upgrades to the M48 tank soon resulted in the M48A3 with its powerful 750 hp Continental AVDS-1790-2 V12, air-cooled twin-turbo diesel engine. With this upgrade to the gun tank, the Marine Corps requested that their M67’s be upgraded to the same standard. Funds were provided for the Marines to have 35 of their M67’s upgraded to M48A3 standard. On the 1st of February 1962, a pilot of the upgraded vehicle was completed at the Detroit Arsenal. It was designated the M67E1. It featured a number of upgrades also found on the M48A3. These included a new gun shield cover, new fire control systems and the replacement of the coaxial .30 cal. (7.62mm) Browning machine gun with an M73 machine gun. On the 25th of June 1962, the M67E1 was officially serialized as the M67A2. In total, 73 vehicles would be converted to M67A2 standard. The upgrade work would be done at the Anniston and Red River Army Depots alongside the M48A3 upgrade program. In total, the USMC would receive 109 M67’s altogether.
The Chrysler Company also developed the T-89 flame thrower kits. This allowed a team of mechanics to turn a standard M48 gun tank into a flamethrower in around eight hours.

Service

Actual combat history of the M67 is not very well recorded and is, at best, patchy. This is due to a general lack of record keeping at troop level. This is a common occurrence in the history of many of the tank actions in Vietnam, as described by Oscar E. Gilbert in his book ‘Marine Corps Tank Battles in Vietnam’. With the assistance of such literature, the following section will highlight the known actions in as much detail as possible.
The M67A2 conversion program would be complete in time for the vehicle to see deployment in Vietnam with the US Marine Corps, though it would be accompanied by small numbers of the other models including the M67 and M67A1. The M67 was one of two armored flamethrowers used in the Vietnam War. The other was the Self-Propelled Flame Thrower M132. This was a modification of the M113 Armored Personnel Carrier fitted with similar flame equipment to the M67. This vehicle was used by the Army in armored cavalry units.

A Later M67 modeled on the M48A2-A3 hull with larger engine deck in service in Vietnam with the 1st Tank Battalion during Operation: Doser. Photo: Wikimedia Commons
In deployment, the M67 would often be accompanied by 2 ½ ton trucks equipped with special equipment to keep the tank in action. One would carry and refuel the tank’s Napalm supply, while the other would recharge the compressed air system. This was, of course, a drawback. Because of the necessity of keeping the resupply equipment relatively nearby, the M67’s were restricted in what operations they could take part in.
An unforeseen problem with the flamethrower was the noise created by the equipment when it was fired. Such was the level of internal noise that the gunner and commander could barely hear each other even when using the intercom. To deal with this, the commander, to his own risk, would often operate head-out. This would improve the audio enough for the crew to understand each other. Some commanders even went as far as haphazardly mounting the intercom outside of the tank, near the hatch.
The M67’s first combat came in the August of 1965 with Operation: Starlite, also known as the Battle of Van Tuong. This was the first major US action of the war. The objective was to hold and defend the Chu Lai Air and command base. During this battle, in map zone An Cuong (2), a resupply convoy of Amtrak’s and a 3-tank section of M67s was ambushed and almost completely destroyed by Viet Cong forces.
The action around An Cuong (2) was one of the only recorded in any great detail. We do know that the M67 took part in actions such as Operation Dozer and the Battle of Hue. In the Battle of Hue, two M67’s accompanied by M48’s were the first tanks to enter the city. The guerilla nature of the Vietnam War was no hindrance to the M67. It was often used to incinerate any patch of jungle that may look like an enemy position in so called “Rods of Flame” attacks.

Fate

The M67 would be the last flame thrower tank deployed by the United States military. The tank would stay in service with USMC until its retirement in 1974. In the 1960 World War II film ‘Hell to Eternity’, a number of M67’s were used to represent M4 based flamethrowers during the Battle of Saipan.

A M67 in a still from the film ‘Hell to Eternity’. Photo: IMFDB
A few of the tanks have survived. Before its recent closure, one was on display at the US Army Ordnance Museum at the Aberdeen Proving Grounds, Maryland. The tank has since been relocated to Fort Benning, Georgia. Another can be found outside the Engineering School, Fort Leonard Wood, Missouri.

The surviving M67 at Fort Leonard Wood. Photo: Mark Holloway

Zippo?

The tank’s unofficial nickname name, “Zippo” (after the lighter brand, as stated in the introduction), is somewhat mysterious. Just like the M60A2 and it’s “Starship” name, a concrete source cannot be stated when this name came into use. It was likely given by the crews or infantry (Grunts to the USMC) that operated with the vehicle.

An article by Mark Nash

M67 ‘Zippo’ specifications

Dimensions (L-W-H) 20’10” x 11’9″ x 10’10” ft.in
(6.4m) x 3.63m x 3.08m)
Total weight, battle ready 48.5 tons (96 000 lbs)
Crew 3 (Commander, Driver, Gunner)
Propulsion Continental AVDS-1790-5A V12, AC Twin-turbo gas. 810 hp.
Transmission General Motors CD-850-3, 2-Fw/1-Rv speed GB
Maximum speed 30 mph (48 km/h) on road
Suspensions Torsion bars
Range (Fuel) 80 miles/130 km (878 Liters/ 232 US Gal.)
Armament Main: M7-6 Flamethrower, 365 gallonso of fuel.
Sec: 1 cal.50 M2HB (12.7 mm)+ 1 cal.30 (7.62 mm) coaxial Browning M1919A4
Armor Max: Nose glacis/turret 110 mm (4.3 in)
Total Production 109
For information about abbreviations check the Lexical Index

Links, Resources & Further Reading

Presidio Press, Patton: A History of the American Main Battle Tank, Volume 1, R.P. Hunnicutt
Casemate Publishing, Marine Corps Tank Battles In Vietnam, Oscar Gilbert
Concord Publications, Armor at War Series, Vietnam Armor in Action, Gordon Rottman & Donald Spaulding

Categories
Cold War American Other Vehicles

90mm Self-Propelled Anti-Tank Gun M56 Scorpion

U.S.A. (1959)
Self-Propelled Anti-Tank – 325 built

Introduction

The M56 began life in the heads of an Anti-Tank Panel in Fort Monroe, 1948. They soon developed the idea of a self-propelled, high-velocity small caliber anti-tank vehicle that could be air transportable and deployable.
This idea was put forward to the Army Airborne Panel later the same year, who in turn forwarded the idea to the Ordnance Department. The department didn’t develop the project, under the designation of T101, until 1950. Cadillac was given a contract to build 2 prototypes.
The T101 project ran for 6 years, finally culminating with the 4-crew SPAT (Self-Propelled Anti-Tank) M56 Scorpion.

Development

As the T101/M56 was in development, so was the SSM-A23 Dart Anti-Tank Guided Missile (ATGM). The Continental Army Command did not want to spend the time and money on two projects that effectively fulfilled the same role. This postponed the original 1957 delivery date of the vehicles to troops. A case was argued that the Dart would not be serviceable for another 2 years. Because of this, it was finally agreed that Scorpion would go into production. It finally started being delivered to troops in 1959.
Built by Cadillac Motor Car Division of General Motors for use by US airborne forces, The M56 was designed to be airdropped by heavy assault gliders and cargo aircraft. In later years, it was able to be dropped via helicopter.
m56recoil
This photo of the M56 demonstrates the effect of the recoil. Source: – live.warthunder.com

Design

Due to it being lightweight, it was an extremely maneuverable vehicle on every ground type. It was powered by a Continental AOI-402-5 high-octane gasoline engine. This sent 200 hp through the Allison CD-150-4 transmission to the forward mounted drive wheels, powering the vehicle cross country at a respectable 28 mph (45 km/h). The M56 featured a unique track and suspension. The track was lightweight and rubber connected with metal grousers. It had a torsion bar suspension, connected to all 6 wheels, including the drive wheel and idler to assist with recoil stresses. The road wheels were pneumatic with 7.5×12 tires that could be run even if punctured. Pneumatic road wheels were chosen because they are much lighter compared with the standard solid-steel.
The airborne deployment and weight restrictions associated with it demanded sacrifices, one of which was that the Scorpion was a completely open vehicle. It had nothing that could be considered armor whatsoever, bar a 5 mm gun shield, and reinforcing brush protection bars on the front of the tank. Indeed, the only protection the crew had was the 5 mm gun shield, this only covered the driver and gunner’s positions. Other than that they were completely open to the elements or any fragmenting explosives.
Though the crew probably would’ve enjoyed a bit of armor, the lack thereof wasn’t too much of a downside. The Scorpion, like it’s namesake, was an ambush predator. It was able to fire and scuttle back to cover extremely quickly or engage targets at ranges up to 1000 m. The sting in this Scorpion’s tail was the M54 90 mm gun, which was specially designed for the vehicle. It was originally going to be mounted with the T119 90mm cannon, but it wouldn’t fit onto the tank. Its standard ammo was the M3-18 Armor Piercing round. It could punch through 190 mm of armor at 1000 m. It could also fire the entire range of 90 mm ammunition of the day, including HVAP and APCR-T. Ammunition was stored in a rack at the rear of the vehicle. It carried 29 rounds, in 3 stacked rows, 2 rows of 10, one of 9.
The gun, though it operated and performed as designed, was also somewhat of a problem. The force of the recoil was amplified on the vehicle because it was so light, to the extent that it would lift the vehicle almost 3 feet off the ground. Firing with the gun straight forward was not a problem, bar the intense recoil. However, should the tank need to engage a target to the extreme left or right of the gun’s traverse, it ran the risk of severely injuring either the driver, commander or the gunner himself. Indeed, if the commander stayed in his seat with the gun aimed to the right, he would receive a recoiling breech block to the face. As such, it was recommended by a manual that all unnecessary crew abandon the vehicle when the gun is fired in this way.

M56 Scorpion SPAT
Tank Encyclopedia’s own rendition of the M56 Scorpion SPAT by David Bocquelet.m56 in service
Scorpions operating in Vietnam. Source: – bemil.chosun.com (Korean)

Service life

The M56 saw limited combat service. During the Vietnam War, it was deployed by the 173rd Airborne Brigade, the only brigade to do so. They used it mostly in a supportive role.
The M56 was not popular with the USMC who favored the Recoilless-Rifle equipped M50 Ontos, which was used in the same role but had an armored fighting compartment. The vehicle was effectively replaced in the field by the better armed and armored M551 Sheridan in 1970.
The M56 was exported to The Republic of Korea, Spain and Morocco. Morocco was the only other nation to use the vehicle in anger. It served in combat against Sahrawi rebels during the Western Sahara War.

An article by Mark Nash

M56 Scorpion Gallery

M56preparing for air-drop.m56trainingEarly Prototype.M56 in Vietnam

M56 Scorpion Specifications

Dimensions 4.55 m x 2.57 m x 2 m (14’11” x 8’5” x 6’7”)
Total weight 7.1 tons
Crew 4 (driver, gunner, loader, commander)
Propulsion 200 hp, 6 cylinder, AOI (Air cooled Opposed Cylinder Fuel Injection) 402-5
Suspension torsion bar
Speed (road) 45 km/h (28 mph)
Armament M54 90 mm cannon
Armor 5 mm gun shield
Total production 325

Links & Resources

Osprey Publishing, New Vanguard #153: M551 Sheridan, US Airmobile Tanks 1941-2001
Osprey Publishing, New Vanguard #240: M50 Ontos and M56 Scorpion 1956–70, US Tank Destroyers of the Vietnam War
The M56 on tanknutdave.com
The M56 on Wikipedia
The M56 on militaryfactory.com

Categories
Cold War American Other Vehicles Coldwar Canadian Other Vehicles Dutch Armor

M113 C/V Lynx

USA (1963)
Reconnaissance vehicle – 424 built

The 113-and-a-half

By 1963, the US army had adopted Cadillac’s M114 to serve as a command and reconnaissance vehicle. However, the vehicle had proven troublesome and it elicited no interest from abroad for any export. Seizing this opportunity, the FMC Corporation (nowadays United Defense LP), prepared a reconnaissance and command vehicle of their own. FMC had also designed the world famous M113 APC, and used it as a basis for the new AFV.
The result was the M113 ½, which shared many features with it’s bigger brother. The Netherlands and Canada bought almost four-hundred in total, and some of them still serve to this day. They served with reconnaissance units and as command vehicles, being fast and with good cross-country mobility.

General design of the M113 ½

While similar in appearance to the original M113, the new vehicle was modified heavily for its new purpose. The troop compartment was completely removed. The same 6 cylinder General Motors engine which was on the M113 was placed at the rear. The crew compartment was at the front of the vehicle, and housed the driver, the commander and the observer. It was described as cramped. While the suspension from the M113 was kept, one roadwheel was eliminated, leaving only four on each side.
A Dutch M113 C&V with the Oerlikon turret
A Dutch M113 C&V with the Oerlikon turret – Photo: Ulrich Wrede, as taken from Panzerbaer
The aluminum armor was also taken from the M113, with a maximum thickness of 1.75 in (44.5 mm) on the lower front part, and a minimum of 0.75 in (19 mm). While these thicknesses may seem large, aluminum does not offer the same level of protection as steel. The armor could only protect the crew from machine-gun fire and shrapnel.  An easy way to differentiate the M113 ½ from the M114 is that the front of the former is 3-sided, while that of the latter is a simple slope.
The Lynx was narrower (2.4 m vs 2.68 m), shorter (4.6 vs 4.86 m) and significantly lower (2.17 vs 2.52 m) than the M113. Of course, this also meant that the vehicle was lighter (8700 vs 11,300 kg). It retained the amphibious capabilities of its forerunner, but necessitated some quick preparations. A trim vane had to be erected (a part at the front which kept water from coming over the vehicle), bilge pumps started (remove water from inside the vehicle) and some covers put in place. Once in the water, the vehicle was propelled by the movement of its tracks, being able to reach a modest 6 km/h (4 mph).
Also, being significantly lighter, the 6 cylinder 212 hp diesel engine allowed it to reach speeds of up to 71 km/h (44 mph). The range, when going only on roads, was above 500 km (325 mi).

The Dutch M113 C&V

The Netherlands was the first customer for the new vehicle, buying 250 vehicles. In Dutch service, these were known as the M113 C&V (Commando & Verkenningen, literally Command & Reconnaissance). Sometimes, they are also called C&R. The driver was seated in the front left of the vehicle, with an infrared periscope mounted on his hatch and four normal ones on the roof of the vehicle. To his right sat the radio-operator, who also had four periscopes at his disposal. The commander was seated at the back, under a large cupola.
A 12.7 mm (0.5 in) M2TTHB machine-gun was mounted on top of the vehicle, being operated by the commander. Another 7.62 mm (0.3 in) machine-gun could be mounted in front of the radio-operator’s hatch.
However, in 1974, the Dutch army decided to replace the commander’s cupola and armament with an Oerlikon Contraves GBD-AOA turret, armed with a 25 mm (0.98 in) KBA-B cannon. The C&V was eventually replaced by the Fennek.
Some of the Dutch vehicles have been sold off to Bahrain (35) and Chile (8).

The Canadian Lynx

Canada was the second operator of the type, having bought some 174 vehicles in 1968. The Canadian vehicles differed in the arrangement of the crew. The driver takes the same position, but the radio operator is placed at his back. The commander sat on the right side of the vehicle, with the same M26 cupola. He operated the 12.7 mm heavy machine-gun, and could fire it from inside the vehicle. However, reloading had to be done externally.
The Canadian Lynx were removed from service in 1993, replaced by M113A2s which had been stationed in Germany and returned after the fall of the Soviet bloc and AVGP Cougars. In 1997, the role was taken over by the Coyote vehicles. Most Lynxes were scrapped or became range targets. A fair few are spread in museums all over Canada.
A Canadian M113 Lynx at the Ontario Regiment Museum
A Canadian M113 Lynx at the Ontario Regiment Museum – Photo: Samuel Richardson, private communication

Links & Sources

On Army-Guide
Specification sheet on AFV Database
Photos in Bahraini service
Thanks to Anthony Sewards for the information he provided

M113 Lynx specifications

Dimensions 4.6 x 2.4 x 2.17 m (15’1” x 7’9” x 7’1”)
Total weight, battle ready 8460 kg (18,650 lbs)
Crew 3 (driver, comander, radio-operator)
Propulsion General Motors 6V53, 6 cylinder, 212 hp
Suspension Torsion bar
Speed (road) 74 km/h (44 mph)
Range 520 km (325 mi)
Armament 0.5 in (12.7 mm) M2TTHB machine-gun
Armor Aluminum, 19-45 mm (0.75-1.75 in)
Total production 424

Lynx-Dutch
A Dutch M113 C&V, before the addition of the Oerlikon turret.
M113-Lynx-Oerlikon-Barhain
A Bahraini M113 C&V, with the 25 mm turret, during Exercise Peninsula Shield 9. Bahrain bought 35 vehicles from the Netherlands.
Lynx-Canadian
A M113 Lynx from the Ontario Regiment Museum.
Canadian Lynx recce
Canadian Lynx recce armored vehicle in the 1970s.

Gallery

Bahraini M113 C&Vs on a shooting range during Peninsula Shield 9
Bahraini M113 C&Vs on a shooting range during Peninsula Shield 9 – Photo: Bahrain News Agency, as taken from the MilinME blog
Canadian M113 Lynx of the 4th Mechanized Brigade, 1986 - Credits: Wolfgang Igert
Canadian M113 Lynx of the 4th Mechanized Brigade, 1986 – Photo: Wolfgang Igert, as taken from Panzerbaer
A Canadian Lynx used as a monument
A Canadian Lynx used as a monument – Photo: Taken from Army Recognition