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WW2 German prototypes

15/17 cm Sturmgeschütz auf E100 Fahrgestell

Nazi Germany (1944) Tank Destroyer – None built

The E100, a 100-tonne experimental chassis developed by the firm of Adler using the Krupp 130-tonne Tiger-Maus design, was never finished. Partially complete at the end of the war, it was recovered to the UK for testing and evaluation and the ‘tank’ part of its history has, since the war, remained centred on this aspect of it. The design was a complicated and drawn out process and the use of the hull went further than just a tank concept.

When Krupp’s Tiger-Maus was abandoned in January 1943, the design was surplus, as development effort went into the Porsche-Maus instead. However, Ernst Kniekampf (Panzer Kommission) did not throw out Krupp’s design. Instead, and regardless of whatever reservations he may have expressed later about heavy tanks, he handed off the plans to the firm of Adler by the end of June 1943. Adler then worked on the design, making changes to it but keeping the essential design. The only substantive change, in fact, was the switch from Tiger II-style torsion bar suspension to externally-mounted Belleville-Washer-type spring suspension. Very little, other than collecting parts, took place with the E100 until March 1944, when Krupp became aware of its existence.

Considering it was their original work, they were likely unhappy at having been sidelined on the matter, but they obligingly provided assistance to Adler in the construction of the E100 anyway. When, in May 1944, the opportunity to work on a new vehicle mounting a 15 cm or 17 cm gun came up, there were two hulls optioned for it: the Maus (designed by Porsche and built by Krupp), and the E100 (designed by Krupp, added to by Adler, and to be built by Krupp). Krupp, therefore, embarked on another task, how to fit the huge 15 cm or 17 cm gun onto their as yet unbuilt, and untested E100 chassis.

Conception

If the idea of a 15 cm or 17 cm gun in a fixed casemate on a Maus hull is not hard enough to visualize, then it is worth bearing in mind that mounting a gun of this size on an E100 chassis is even more so. Specifically, because the E100 chassis was so much lighter, under 90 tonnes fully laden for the chassis.

On 9th May 1944, representatives from Porsche and Krupp met to discuss a new heavy type of self-propelled gun. Drawings were presented at this meeting of ideas by Krupp for how to mount the 15 cm L/63 or 17 cm L/53 gun on the Maus chassis as a direct competitor to a similar idea from Adler (Adlerwerke) for mounting these guns on the E100. Both designs were to use a fixed casemate structure (Sturmgeschütz Aufbau) in which to mount the guns.

These ideas were considered at a meeting held at Porsche’s plant on 17th May 1944, and it was here that Krupp expressed their earnest desire to do anything to avoid having to try and use the 15 cm gun in preference to the 17 cm one, likely as a result of the size and weight of the gun and its shells. Obering Hendel, the officer dispatched to ensure production quotas were being met by tank factories, considered both Maus and E100 ideas. His conclusion was not in favor of the Maus. The Maus hull was too high for a new fixed casemate to still fit within the rail loading gauge (assuming a normal railcar), whereas the E100 hull, being significantly lower, was much more suitable.

The Maus-plan was over, it was not a suitable platform and was abandoned as an idea. Instead, the E100 was selected, and on 28th May 1944, Krupp was requested to produce a 1:5th scale wooden model of their design. The purpose of this model was to get a better insight into how the vehicle could be organized internally for crew and ammunition. Importantly, both the 15 cm and 17 cm guns were to be shown, and the design was known as 15/17 cm Kanone auf E100 Fahrgestell (15 or 17 cm gun on 100-tonne experimental chassis).

Development to Termination

Although the E100 chassis had shown more promise, primarily as a result of being lower and lighter than the alternative chassis (Maus), this success was short-lived. Just under two months after being told to produce this model, all work was stopped. Wa Prüf 6 (Waffen Prüfen 6 – the design office responsible for motorized equipment) forwarded to Krupp a copy of the letter from Reichsminister Albert Speer dated 10th July 1944. In the letter, Speer, on Hitler’s orders, required all work on heavy guns on tank chassis to cease. There was a model, however. Krupp must have finished or at least prepared a model by this date as the letter ended that they were to take the model of the Sturmgeschutz 15 cm L/68 to General Guderian.

Guderian was not a fan of these heavy tank projects and had scuppered plans for Maus production a year earlier. There was little-to-no likelihood that he would suddenly change his mind on this type of project seeing just a wooden model of it. Nothing more is heard of the project after this point as it met the same fate as the 15/17 cm Sturmgeschütz auf Mausfahrzeug before it.

Plans for the mounting of the 15 cm gun still survive, at least for mounting it on the front of the turret for E100, but there is no trace of the 1:5th scale wooden model. Nonetheless, it is worthwhile considering what this machine might have looked like, aside from the fantasy creations of model makers and computer game companies, which may be designed more for the ‘cool’ factor than from a basis in engineering.

Layout

The primary consideration over what a 15/17 cm Kanone auf E100 Fahrgestell would look like begins with a look at the E100 hull. As it was was, the E100 hull featured a conventional layout with the engine at the rear, transmission at the front, and a centrally-mounted turret. There were plans for a modified layout on the E100, but as of 1944, when these plans were being considered, these had not progressed, and the original E100 hull had still not been finished. It remains open to question as to whether or not the 15/17 cm Kanone auf E100 Fahrgestell being proposed was to use the first hull or this later modified hull, but as this was future planning it is possible it was to be based off the second, improved hull. Further, it remains open to question as to whether the layout would be fundamentally altered with a casemate placed at the rear with the engine in front of it, like the Elephant/Ferdinand, or if it would simply occupy the space previously filled by the turret and basket.

Regardless of which E100 hull was to be used, the turret, and therefore the casemate, could only be fitted centrally or just forward of centre. Mounting anything else on the already heavy front end, such as in the manner of a Jagdpanther, would simply overwhelm the suspension.

Assuming a central position for the casemate, in roughly the same manner as the Jagdtiger, would mean that no changes would be made to the engine and transmission layout in either hull and keep the front driving position (front left) able to access the main crew compartment. Moving to a rear casemate system would separate the driver from the fighting compartment. A rear casemate would also suffer from the additional problem of having the gun over the engine bay which would greatly complicate access to the engine compartment for maintenance, a serious consideration in the design of the Jadgtiger and a primary reason for adopting a central-casemate layout.

Armor

It is assumed that the basic armor of the E100 hull, including the removable side armor sections, would be maintained and also that the armor on the casemate would approximately match the same protection levels offered by the E100 turm. That turret weighed just 35 tonnes with 200 mm of armor on the front, 80 mm on the sides, and 150 mm on the rear. Being a fixed casemate would mean there would be little scope for manoeuvering to avoid being hit in the sides but, just like the Jagdtiger, which had over 200 mm on the casemate face and 80 mm on the sides, the casemate on a 15/17 cm Kanone auf E100 Fahrgestell would likely be done in a similar way, except that the rear turret armor planned (150 mm thick) would not be required. On the turret, it added a degree of protection to accidental friendly fire from behind but much more importantly, acted as a counterbalance to the enormously heavy front of the turret. No such counterweight was needed on a fixed casemate so the armor could, if so desired, be greatly reduced in that area. Although it makes sense to reduce weight, the rear of the lower rear hull would still be 150 mm thick.

Jagdtiger blueprint
Manufacturing scheme for the Jagdtiger, showing the massive casemate front armor to good effect and a possible approximation of the layout envisaged for mounting a heavy gun on the E100 chassis. Source: Frohlich

Gun

The two guns in consideration for mounting on the E100 chassis were the 17 cm Stu.K. L/53 and the 15 cm Stu.K. L68. The 17 cm gun was, as of 22nd March 1944, still only a paper design and was unlikely to be available anytime soon given the demands of gun production already being very high. The second gun, and by far the preferred option of the two, was the 15 cm Stu.K. L/68 gun and the design for this piece was finished on 4th July 1944, just 6 days before Hitler killed the project.

Fragment of an official German drawing showing the proposed installation of the 15 cm Stu.K. L68 on an E100 chassis. Source: Warspot.ru

Given the enormous size of the 17 cm gun, its huge breech, high weight, and the size of its ammunition and the date of the design for the 15 cm gun, it seems likely that Krupp did everything they could to avoid using the 17 cm gun. Both guns, however, had to meet the requirements set by General Guderian (Inspector-General of Panzer troops) in April 1944 to be able to defeat up to 200 mm of armor at 4,000 meters, leaving no doubt as to a key intended purpose of this vehicle, the destruction of increasingly well-armored enemy tanks at long range. Of note too is that there is no comment as to secondary weaponry. Not a machine gun, but a second, tank cannon, like was originally intended for the Maeuschen program with a 15 cm or 12.8 cm gun paired with a 7.5 cm gun. Only using this single large gun would free up significant space inside the casemate for this E100-based vehicle as well as providing additional stowage space for the 15 cm ammunition. Just as with Maus and E100, it could be expected that a machine gun (either M.G.34 or M.G. 42) would be mounted independently on the left-hand side of the main gun to be operated by the gunner.

One last note on the casemate is the use of a rangefinder. The two rangefinders considered for the Maus II and E100 turm rangefinders were coincidence type devices fitted across the width of the turret. Both types were around 2 m long (1.9 and 2.1 m wide) and there seems to be little doubt that the 15/17 cm Kanone auf E100 Fahrgestell would also have to have a rangefinder, especially given the 4,000 m ranges at which it was going to be expected to deliver accurate fire against enemy tanks and structures. Given the common positioning of the rangefinder on the Maus II and E100, it is reasonable to assume a similar arrangement of a similar size/type of rangefinder would also have to have been used on the 15/17 cm Kanone auf E100 Fahrgestell.

Crew

Regardless of which layout the 15/17 cm Kanone auf E100 Fahrgestell took, it would need a crew and it is hard to envisage this vehicle operating with a crew of fewer than 6. At a minimum, the vehicle would need a driver, a radio operator, a loader, a gunner, and a commander, which totals 5. The Maus required the sixth man in order to operate the secondary 7.5 cm gun, and whilst it was likely that no such gun was to be on the 15/17 cm Kanone auf E100 Fahrgestell, the use of a second loader was all but essential, unless some kind of loader-assist system was planned, considering the size and weight of the 15 cm ammunition. A unitary (one piece) 15 cm shell, for example, weighed in excess of 34 kg and possibly over 40 kg depending on what ammunition might have been chosen. Moving those shells around would rapidly exhaust a single loader, so a second loader is almost essential just to make the machine viable.

Conclusion

Although the idea of the 15 cm or 17 cm gun using the Maus chassis had failed after a brief spark of interest in May 1944, with the E100 being selected in preference, it was not much of a loss. The E100 was to suffer the same fate. On 10th July 1944, Hitler canceled all of the work on these heavy guns on heavy tanks and the 15/17 cm Kanone auf E100 Fahrgestell became yet another failed project in what was a very long list of such projects.

Although it is not known what the 15/17 cm Kanone auf E100 Fahrgestell would have looked like and much of this article has been speculative about the shape and look of the vehicle, it is important to consider the design in order to gain an understanding of the challenges involved in mounting very large guns on very large chassis.

For Germany in mid-1944 to be considering these weapons though was pure folly. It would take months to get such a machine into production and longer still to get crew trained and units issued and deployed to combat. At a time when Germany was on the retreat and the war was a foregone conclusion, to focus precious and ever-dwindling resources on these machines was wasteful. It did nothing more than hasten the end of Germany.


What-if illustration of a Sturmgeschütz auf E100 with a centrally-mounted fighting compartment sporting the 15 cm Stu.K. L/68 gun in a Dunkelgelb finish.


What-if illustration of a Sturmgeschütz auf E100 with a centrally-mounted fighting compartment sporting the 17 cm Stu.K. L/53, lacking the E100 side skirts and with only a layer of Rotbraun primer paint.

Both illustrations by Mr. C.Ryan, paid for through our Patreon campaign.

Specifications

Dimensions (L-W-H) est.39.3 feet x 14.6 feet x 11 feet (12 x 4.48 x 3.37 meters)
Weight est. 127 long tons (130 tonnes)
Crew est. 6 (commander, gunner, 2 x loaders, driver, radio operator)
Propulsion Maybach HL 230 P30 V-12 Petrol delivering 700 hp
Maybach HL 234 V-12 Petrol delivering up to 1,200 hp
Suspension Hortsmann
Speed (road) <23 km/h (road) (HL 230), up to <40 km/h (road) (HL 234)
Armament 17 cm Stu.K. L/53 alternatively 15 cm Stu.K. L68
7.92 mm M.G.34 or M.G. 42 machine gun
Armour Casemate:
Front – est. 200 mm
Sides – 80 mm @ 29/30 deg.
Rear – est. 80 mm
Roof – 40 mm @ 90 deg.
Hull:
Front – Glacis – 200 mm @ 60 deg.
– Lower front – 150 mm @ 50 deg.
Track guards –
Sponson floor – 30 mm @ 89 deg.
Side – 120 mm @ 0 deg.
Rear – 150 mm @ 30 deg.
Floor – front – 80 mm @ 90 deg.
Floor – middle and rear – 40 mm @ 90 deg.
Roof – 40 mm @ 90 deg.
Trench est. 9.5 feet (2.9 m)

Sources

Porsche, F. Bericht Uber die Werksorprobung des Typ 205/1 in Böblingen von 11.1 – 3.2.1944
British Intelligence Objectives Sub-Committee. (1945). BIOS report 1343: German Steel Armour Piercing Projectiles and Theory of Penetration. Technical Information and Documents Unit, London.
British Report on ‘Experimental Super Heavy Tank ‘Mouse’ (Pz.Kpfw. Maus)’ – May 1945
CIOS Final Evaluation Report 153. (28th June 1945). Interrogation of Herr Stiele von Heydekampf.
Datenblatter für Heeres Waffen Fahrzeuge Gerät W127. (1976).
Frohlich, M. (2016). Panzerkampfwagen Maus’. Motorbuch Verlag, Germany
Frohlich, M. (2015). Schwere Panzer der Wehrmacht. Motorbuch Verlag, Germany
Jentz, T., Doyle, H. (2008). Panzer Tracts No.6-3 Schwere Panzerkampfwagen Maus and E 100.
Ludvigsen, K. (2018). Professor Porsche’s Wars. Pen and Sword Publications
Ogorkiewicz, R. (1991). Technology of Tanks. Janes Information Group, Surrey, England
Sawodny, M., Bracher, K. (1978). Panzerkampfwagen Maus und andere deutsche Panzerprojekte. Odzun-Pallas-Verlag, Friedberg, West Germany
Pasholok, Y. (2015). Heavyweight Paper Tank Destroyers at Warspot.ru https://warspot.ru/4351-sverhtyazhyolye-bumazhnye-istrebiteli-tankov
Pasholok, Y. (2016). Heavyweight Paper Tank Destroyers at Warspot.ru https://warspot.ru/5659-bronetehnika-iz-taynyh-podvalov
Spielberger, W. (1998). Spezialpanzerfahrzeuge des Deutschen Heeres. Motor Book Verlag
Spielberger, W., Milson, J. (1973). Elefant and Maus. AFV Weapons Profile No.61.
US Army. (1953). Technical Manual TM9-1985-3 German Explosive Ordnance (Projectiles and Projectile Fuzes)
US Army. (1946). Intelligence Bulletin March 1946. The German Mouse.
US Navy. (September 1945). Technical Report 485-45 – German Powder Composition and Internal Ballistics for Guns. US Naval Technical Mission in Europe Report.
War Office. (25th October 1944). 12.8cm A.Tk. Gun Pak.44 on Pz.Jag. Tiger (Pz.Kpfw. Tiger B Chassis) Sd.Kfz.186 JAGDTIGER. Appendix D War Office Technical Intelligence Summary, No.149 1944.
War Office. (25th April 1945). Technical Intelligence Summary Report 174 Appendix C
War Office. (4th June 1945). Technical Intelligence Summary Report 178 Appendix E
War Office. (27th June 1945). Technical Intelligence Summary Report 180 Appendix D
War Office. (26th July 1945). Technical Intelligence Summary Report 182 Appendix F and G
War Office. (11th October 1945). Technical Intelligence Summary Report 186 Appendix A
War Office. (20th December 1945). Technical Intelligence Summary Report 188 Appendix

6 replies on “15/17 cm Sturmgeschütz auf E100 Fahrgestell”

I think casemate should be placed at the back. According to the source (https://warspot.ru/4351-sverhtyazhyolye-bumazhnye-istrebiteli-tankov) “In addition, according to CIOS, the engineers redesigned the layout. The transmission, along with the drive wheels, was transferred from the bow to the stern. Alas, the Sturmgeschutz E-100 drawings were not preserved, but judging by what alterations were carried out, the self-propelled gun became more like a Ferdinand. “

It specifically says there is no proof of that, it is merely an educated guess, the same way that the author of this article hedges the educated guess that the casemate was likely center mounted. For the casemate to be in the rear the engine would necessarily have to be up front anyway. It is impossible to have a rear transmission, rear engine tank with a rear casemate or turret.

The source you linked is cited only for the original documentation it provides, the information it presents should not be valued more highly than other proper sources, and some of what is written there is incorrect.

It is possible to have a gearbox at the rear, and the engine in the middle of the body is similar to the Ferdinand self-propelled guns. A large self-propelled gun like the Sturmgeschütz auf E100 has a lot more room than the Ferdinand self-propelled guns. So this option is possible.

What’s up with these time stamps?
VRIL posted July 9, 2020 at 19:27 and Harold Biondo answered July 9, 2020 at 19:27. So Harold read the post AND the linked article AND wrote his answer within 60 seconds of VRIL posting?
And Kindabruhlol posted July 11, 2020 at 19:27, and I read his post July 11, 2020 at 19:22, 5 minutes before it will be written…

I have the feeling that the website doesn’t use one consistent time zone, for some inexplicable reason.

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