Thanks muchly good Sir, much appreciated! 👍🎂👍
Unfortunately, the decorative candles look more like a fire storm these days!! 😳😉🤣
Alternative History Armoured Fighting Vehicles Part 4
- Thread starter Claymore
- Start date
Unfortunately, the decorative candles look more like a fire storm these days!! 😳😉🤣
What were the length and height of the S35 engine?
I'm wondering if a mid-1930s US gasoline engine, such as the Hall-Scott "400" truck/bus-market version of the "Invader" marine straight 6 (310 peak hp in 1937-38) or "Defender" marine 60° V-12 (about 1000 hp in a 1940 supercharged version), would have fit into the engine bay.
If so, then once the French British Purchasing Committee was started up, SOMUA might have bought powertrains from USA as a fast way to leapfrog their tank design toward greater mobility and an ability to carry the weight of more armor and armament.
I'm wondering if a mid-1930s US gasoline engine, such as the Hall-Scott "400" truck/bus-market version of the "Invader" marine straight 6 (310 peak hp in 1937-38) or "Defender" marine 60° V-12 (about 1000 hp in a 1940 supercharged version), would have fit into the engine bay.
If so, then once the French British Purchasing Committee was started up, SOMUA might have bought powertrains from USA as a fast way to leapfrog their tank design toward greater mobility and an ability to carry the weight of more armor and armament.
No exact data, but a quick pixel measurement using the 120mm bore of the engine on its schematic would give roughly 1165mm length and 1045mm height without accessories.
France wasn't short of powerful tank engines however, especially not for the Somua series of which only 36/month were expected towards late 1940. The Hall Scott Defender would be far too big at nearly 2000 cu in ( 36L engine!), while the 17-18L Invader would probably be bigger (longer anyway given it has 6 cylinders in line) than the Somua V8. And at this size, France had better specialized tank engines well advanced in development in 1940 (a 350hp Renault straight-6). Even just lengthening the Somua V8 to a V12 (apparently suggested for a SOMUA G1 offering) would give an engine of comparable displacement to the Invader, but in a more efficient V12 configuration and with a bit more power. US engines could mostly help with numbers, but not really with performance at this point.
Thanks mate! Just watch the news for a massive wild fire starting in the North of Scotland! 🤣
What a quality cake! (62 years young by the way…) 👍
The Defender and Invader were ~ the same length; the Defender was created by joining two Invader cylinder banks to a common crankshaft housing in V-form, with of course a slight cylinder offset.
The (possible) advantage of an engine like the Invader over an engine in "advanced development" would be that the former had a number of years of real world proof of ruggedness and absence of issues and problems, in relatively high numbers since it was primarily a commercial truck and bus engine, in addition to the related marine version. Hall-Scott as a significant US engine manufacturer for heavy over-the-highway trucks, marine uses, fire equipment, mining equipment, crawler tractors, engine-powered railcars and the like produced two orders of magnitude more engines than the expected SOMUA tank production.
Yes, but again comparing a theoretical solution to a proven one in (moderate) volume production and heavy duty usage every day for many years.
Yes, not arguing that Hall-Scott's technology was advanced. Certainly it was not. But, their mid-to-late-1930s engines had impressive track records for ruggedness, durability, drivability and maintainability. Their higher torque and therefore much-flatter power curve, compared to an equal-displacement diesel or to most other spark-ignition engines of even 25% more displacement, made them easy to drive in challenging situations with less shifting, and allowed use of simpler transmissions without sacrificing performance.
As a side note, the Invader / 400 series also existed in well-proven flat versions, i.e. a straight six laying on its side, originally for use in underfloor mounts for snub-nosed, rear-engine buses. Such an engine configuration could be utilized to create a medium tank or assault gun that, while wider, could be much lower than the late-1930s norm. That wouldn't have been relevant to the S35, but could have been to a future project.
Fair enough. On a second glance, the Defender is actually very modern for a commercial engine of the time, and it could have been a credible powerplant for one of the long-hull Shermans or preferably a US heavy tank, since as a boat engine, it runs constantly at its peak rpm of 2100. In a tank it would not always run at peak so you could up the maximum regime to get a bit beyond 600hp. And it would be overall a much more compact powerplant for the M6, which could allow sufficient size reduction to be viable even at around 600hp. Or you can keep the supercharged 900hp version. In the former case, the Defender appears as an engine of somewhat similar output to the late-war Chrysler A-65 project, but with a greater displacement and thus even better torque curve for heavy tanks.
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I have once again updated part 2 of photodump after a visit to the french archives: https://photos.app.goo.gl/5tnqr7DG7vhBrVRB9
Haul was less successful than I hoped, but still interesting.
The documents I aimed for this time mostly concerned Franco-British exchanges regarding tanks in 1939-40. The French sent a mission lead by engineer Dupuy in 1939 and 1940 to see British tanks. At this point in time, most new British tanks were prototypes or had barely entered production. The French didn't find much of interest other than the Christie suspension of the A13, and the Liberty engine was a very powerful engine by early war standards, matching the French Panhard autorail engine. They noted that the armor of the Matilda II didn't follow French principles for armor distribution in that the roof and floor were quite thin and the main armor had weakened zones because the angled parts were too thin when accounting for the real orientation of the tank in normal movement. The British testing grounds were thought to be insufficient to properly test mobility on difficult terrain, and the French may well have been right as Matilda II proved to have poor mobility on wet french ground in 1939, which delayed its complete deployment in the BEF.
They also got to study what appeared to be the very late A20 before the A22 specification was issued. The British used weird armor arrays where a thin cemented plate was stacked over a thin RHA plate (20mm over 20mm at the front, angled, 25 over 18mm spaced away from another 18mm RHA plate for the sides). The British methodology was flawed as only 2pdr AP was used, which was notoriously poor against cemented plates, and they did not compare the side array to a 60mm cemented plate of comparable weight. The British hoped to uprate the 350hp engine (Meadows or Bedford at this point) to 450hp for a tank which was expected to weight 45 tons, but was more likely to reach 50 tons. The French were very concerned about the future of the A20 and offered joint production of B1 tanks until a suitable replacement (French, British or unified) is obtained.
Overall, the French concluded that the British were behind them in certain technical areas (welded assemblies) and in mass production, and offered their expertise and their testing grounds at Vincennes, Satory and elsewhere for British tanks. Meanwhile, Sir Albert Stern of the TOG enquired the French in late 1939 to discuss with local specialists about the unification of both countries' designs, the development of a superheavy tank, and suitable AT weapons for tanks (the French having more designs available at this point). In any case the French still found the A13 and Matilda II to be interesting and encouraged mass production of both types. They found the Nuffield tank factory at Birmingham to be spacious and well-equipped, on par with the AMX factory at Issy-les-Moulineaux, and estimated that a production rate of 24 A13s per month could be obtained if the full capacity was used. At this point, the limit on the utilisation of this factory was allocation of material, the scale of British mobilization and requirements.
I also found a few reports from the various French tank inspectors from 1931 to 1938. The main takeaways are:
- continued development of diesel engines for tanks was recommended as early as 1931,
- the FCM 36's engine could be easily uprated from 90 to 100hp in 1938 with some tuning of the injection system as the cooling system could now cope with the extra power. The tank inspectors once again deplored that orders for tanks such as the D2 and FCM 36 were too small to incentivize mass production measures in the factories.
Haul was less successful than I hoped, but still interesting.
The documents I aimed for this time mostly concerned Franco-British exchanges regarding tanks in 1939-40. The French sent a mission lead by engineer Dupuy in 1939 and 1940 to see British tanks. At this point in time, most new British tanks were prototypes or had barely entered production. The French didn't find much of interest other than the Christie suspension of the A13, and the Liberty engine was a very powerful engine by early war standards, matching the French Panhard autorail engine. They noted that the armor of the Matilda II didn't follow French principles for armor distribution in that the roof and floor were quite thin and the main armor had weakened zones because the angled parts were too thin when accounting for the real orientation of the tank in normal movement. The British testing grounds were thought to be insufficient to properly test mobility on difficult terrain, and the French may well have been right as Matilda II proved to have poor mobility on wet french ground in 1939, which delayed its complete deployment in the BEF.
They also got to study what appeared to be the very late A20 before the A22 specification was issued. The British used weird armor arrays where a thin cemented plate was stacked over a thin RHA plate (20mm over 20mm at the front, angled, 25 over 18mm spaced away from another 18mm RHA plate for the sides). The British methodology was flawed as only 2pdr AP was used, which was notoriously poor against cemented plates, and they did not compare the side array to a 60mm cemented plate of comparable weight. The British hoped to uprate the 350hp engine (Meadows or Bedford at this point) to 450hp for a tank which was expected to weight 45 tons, but was more likely to reach 50 tons. The French were very concerned about the future of the A20 and offered joint production of B1 tanks until a suitable replacement (French, British or unified) is obtained.
Overall, the French concluded that the British were behind them in certain technical areas (welded assemblies) and in mass production, and offered their expertise and their testing grounds at Vincennes, Satory and elsewhere for British tanks. Meanwhile, Sir Albert Stern of the TOG enquired the French in late 1939 to discuss with local specialists about the unification of both countries' designs, the development of a superheavy tank, and suitable AT weapons for tanks (the French having more designs available at this point). In any case the French still found the A13 and Matilda II to be interesting and encouraged mass production of both types. They found the Nuffield tank factory at Birmingham to be spacious and well-equipped, on par with the AMX factory at Issy-les-Moulineaux, and estimated that a production rate of 24 A13s per month could be obtained if the full capacity was used. At this point, the limit on the utilisation of this factory was allocation of material, the scale of British mobilization and requirements.
I also found a few reports from the various French tank inspectors from 1931 to 1938. The main takeaways are:
- continued development of diesel engines for tanks was recommended as early as 1931,
- the FCM 36's engine could be easily uprated from 90 to 100hp in 1938 with some tuning of the injection system as the cooling system could now cope with the extra power. The tank inspectors once again deplored that orders for tanks such as the D2 and FCM 36 were too small to incentivize mass production measures in the factories.
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