Alternative History Armoured Fighting Vehicles Part 4
- Thread starter Claymore
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According to this tank archives article, a soviet document claimed they managed to crowd ten submachine gunners into the standard M3- don't ask me how! And the standard Kangaroo APC OTL also fit 10 (or more) troops onto the same hull (effectively). So given the small size of the M3's turret, fitting 6 into this mod should be doable.
Les obus de 37mm français
Bonjour, Pour faire le point sur cette vaste famille de munitions, et afin de proposer un petit guide d'identification et de compatibilité avec les nombreuses p
atf40.1fr1.net
TL
R is that the longer gun could use full bore 37mm mle.38 APC (700 m/s), the same APCR as the short gun (37mm mle.35 at 705 m/s, but sadly not as fast as it should probably be considering it's lighter than the full bore round), 37mm mle.38 HE.Short gun was normally issued with mle.35 APCR at 600 m/s and 37mm mle.37 HE, and otherwise old WW1-era rounds. I have documents which show both were designed by Brandt (even the patent for the APCR). At the start of the Battle of France, AP usually represented only 1/5th of the load or as low as 12 rounds, which was increased to 2/5ths later. In practice the French noted they might as well have loaded almost only APCR at some point because they were facing so many tanks.
Re R40, most had the long gun so would have used full bore rather than APCR, which was worse anyway given it had the same velocity. APDS was not yet in mass production and was not issued to any tanks, though the short guns would have had priority.
Speaking of which, I have done a last visit to the archives for a while. The bulk of the findings are reports from the metallurgical laboratory at Satory which was tasked with armor and AP projectile research. Nothing really special other than the fact they would have got a lot of extra scientific equipment around June of 1940 if not for the Fall, and were working with steel foundries (in particular Cail), to develop new 75mm AP ammo. In this case capped APHE. Tungsten cores were mostly expected for infantry weapons because tungsten was still felt to be too rare and expensive to be used in mass in bigger guns.
The other stuff was a long report from March 1941 from General Keller, the tank inspector in 1939-40, about the lessons from the battle. There is also another officer suggesting a post-June 1940 armored force in the event it is reconstituted again, either through successful negociations with the Germans, or following a liberation.
The lessons learnt are hardly surprising and many officers of tank units, and Keller himself had noted this before the battle.
Mostly that the existing doctrine of largely tying tanks to the infantry and having a large amount of independent tank battalions was simply beyond the means of the French army in 1940. The infantry didn't understand modern tanks enough (for good reasons: there weren't many in service until 1939-40), so they tended to hoard them, to strip them away from the recent DCR and DLM tank divisions, and to not follow the tanks close enough after they captured terrain. All this lead to the tank force being eroded away in small unsupported packets with insufficient concentration of numbers to face German armor concentrations or tough defenses.
The doctrine deemed that tanks could not operate away from the infantry because antitank guns were just as lethal to them as MGs were to the infantry in WW1. An excessive statement since AT guns were harder to move and fired more slowly, so were simply not the same kind of threat. Additionally French tanks had sufficient armor to face AT guns at range and hunt them, and then assist the infantry.
The conclusion was that France should not use independent tank battalions until they can produce enough tanks to do so, and should instead focus on armored divisions. This would allow the French to finally outfit them with a reasonable amount of powerful and light tanks and reserves. They also mention improvements to make to the accompanying infantry and their APCs, and there is a strong focus on providing sufficient support vehicles and personnel for maintenance, recovery, repair and resupply (1940's DCR had been too hastily formed to have a sufficient support structure). Increased number and better use of radios (they note the system on Char B1s worked just fine). Crews should be young, well trained and very active, and there should be replacement crews when the main one is too exhausted.
For tank design, they don't need to change the future programs that much , but they emphasize some things still:
- easier maintenance obviously
- 2 men at least in turrets with powerful tank guns (de facto already the policy for long 47 and 75, but not sure they include the short 47 in this). Observation setup more similar to German tanks (or derived from FCM 36) with a hatch, a cupola with vision devices, and the forward part could rotate to reveal a hole to use goggles at long distances under armor, much like the umbrella position in modern tanks. Something which was noted and German tanks and already suggested before the battle by the French for future turret studies was to put the recoil buffers on the sides of the gun and put the gun as far out as possible, with no independent traverse from the turret and with mechanical elevation. This would allow lower but still roomier turrets, and more accurate aiming of the main gun. The coaxial MG would remain independently shoulder-aimed for use on the move.
Light tank turrets would follow these principles but still have 1-man for weight control reasons, but would need to be much more suitable than the APX-R which proved insufficiently comfortable to operate for 12 to 18 hours.
- the future light tank with 60mm of armor and a short 47mm turret would try to achieve a 40kph top speed to also replace Hotchkiss tanks and Somuas and reduce the number of tank types. It would ideally use an halved version of the battle tank's engine for commonality.
- if the light tank and the future battle tank can't achieve what is required of them within the required weight limited, it might be necessary to make specialized derivatives (say battle tank with AT-focused gun and a variant with an HE-focused gun, and a fast tank alongside the light tank). Diesel engines could assist in achieving the goals without specialization because of the volume of fuel and thus weight of armor they could save.
- A vehicle based on a light tank with a mortar and an observation turret with a rangefinder would help hunt AT guns.
- a fast casemated TD with 20mm of armor and a bigger gun than the long 47 would be needed
- a cheap light armored car bound to roads only, and a heavy armored car with good offroad mobility
The other officer's armored div proposal suggested the following new vehicles:
- an armored car
- a fast light tank with a 37mm autocannon, otherwise similar to the Hotchkiss H39
- literally a Somua S40 with a 2-man 47mm turret
- the same tank, but with thinner armor (likely 30mm) and instead a 3-man 75mm turret with good observation and targetting equipment for fire support
- a heavy tank with a 2-man 75mm turret (very reminiscent of the B40 with a 75mm turret or the ARL 30t clandestine tank project)
- a TD with the shortened 90mm CA 39 with medium armor
- a short 105mm unarmored SPH
- portee 20 and 25mm AA guns
That is how both m3 lee and m4 sherman came to be.
They wanted a 75mm gun in a turret, but didnt have a turret capable of it.
Because of that they made the m3 as a stopgap, as soon as the turret design was done they switched to that.
Would the M3 Lee hull been able to support said turret with some modifications?
Something like this.
The Canadian Ram tank was based on the M3 chassis. Mk1 Rams were armed with a 2pdr in a turret, Mk2s with a 6pdr, apparently an experimental "Mk3" was armed with the QF 75mm gun (which makes sense given the QF 75mm was just a bored out 6pdr, so all the dimensions would remain the same, requiring no alterations to the Mk2 tank to accept this alternate armament.
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The follow-up to the prototype you described was intended to be a 3.7 inch (or, after they tested how well the hull could stand the recoil with the AA version, a 17-pounder) mounted on a Sexton in place of the 25-pounder, which makes a lot more sense as a dedicated TD.
Yes, this could indeed happen, but what you have created is a vehicle that is much, much taller than it needs to be - the hull is still that of a standard M3 which is designed to carry a side, sponson-mounted 75mm gun. Without that sponson-mounted 75mm, the hull height can be reduced, the crew numbers can be reduced and therefore the need for a roomy hull. What do you end up with? Not surprisingly, something very much like the original M4! As already stated by others here, that is essentially what happened for real…
Yes, other major changes had long been on the "fix this in the next design iteration" list from when the M3 Medium was designed, including eliminating the riveted armor and heavy subframe, and replacing them either with a cast hull or a welded monocoque design, or a blend of the two, all of which would be both significantly lighter, and better performing, *and* cheaper to build. Once the big-enough-for-75mm turret production-capability question was resolved, it made sense to leave the M3 Medium design behind and proceed with the M4 Medium.
The M3 Medium was designed without much focus on manufacturability. The M4 Medium was designed with manufacturability entirely in mind. The final-assembly factories in Grand Blanc (Fisher Tank Arsenal) and Warren (Detroit Tank Arsenal) were specifically optimized to build the M4 Medium and vehicles like it.
The M3 Medium was designed without much focus on manufacturability. The M4 Medium was designed with manufacturability entirely in mind. The final-assembly factories in Grand Blanc (Fisher Tank Arsenal) and Warren (Detroit Tank Arsenal) were specifically optimized to build the M4 Medium and vehicles like it.
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Re the Mediums...
In 1934, Ordnance officer George H. Rarey, the same guy who patended a turret and convertible medium tank analogue to the T5/M2 Medium also wrote a piece on preferable special designs of engines for fighting tanks.
I will sum up the conclusion:
It is interesting to note that the author deemed the horizontally-opposed (that is flat engine or 180° Vee) engine to be the better one, rating reduction of height as more important than the length reduction offered by radials, which come after the flat and generally Vee engines due to the fact they are still quite small and especially light for their power.
Assuming this ideal engine had been designed for the 1934 specifications of tanks in the US, a 7.5 ton light tank and a 15 ton medium tank, they would have needed engines with respectively 187.5-225hp and 375-450hp respectively, weighing less than 937.5-1125 pounds and 1875-2250 pounds respectively. The lucky consequence of the fact the light tank must weigh half the weight of the medium is that they could derive the light tank engine from the medium one by simply cutting the amount of cylinders, such as using a V12 and a V6. It is interesting to note that these power figures are very much those that WW2 US light and medium tanks would use.
The other advantage of the ideal flat engine is that the driveshaft mounting would likely be very low and thus preclude the need for a transfer case to drop it low enough.
The ideal engine would certainly have been very useful for US WW2 tanks. It would combine both a low driveshaft and low powerpack height, completely circumventing pretty much all height issues US tanks had (bar the fact they still need a driveshaft and aren't rear-drive tanks). The diesel operation would help quite a bit with fuel consumption. It would be much lighter and more compact than the GM 6046 which weighed in the region of 4000 pounds. Since the medium engine would likely be a flat 12, it would be a little longer than a radial, so US tanks would be a bit longer, which is preferable since they were a bit short and not as stable as they could be.
5 pounds per hp was eventually achieved by the Soviet V-2 series a few years later, so it was not an impossible feat with a decently funded Army engine program. Ironically a lot of the developments of the US Hyper engine program (flat engines and relatively light high output engines) would have been useful here.
In 1934, Ordnance officer George H. Rarey, the same guy who patended a turret and convertible medium tank analogue to the T5/M2 Medium also wrote a piece on preferable special designs of engines for fighting tanks.
I will sum up the conclusion:
It is interesting to note that the author deemed the horizontally-opposed (that is flat engine or 180° Vee) engine to be the better one, rating reduction of height as more important than the length reduction offered by radials, which come after the flat and generally Vee engines due to the fact they are still quite small and especially light for their power.
Assuming this ideal engine had been designed for the 1934 specifications of tanks in the US, a 7.5 ton light tank and a 15 ton medium tank, they would have needed engines with respectively 187.5-225hp and 375-450hp respectively, weighing less than 937.5-1125 pounds and 1875-2250 pounds respectively. The lucky consequence of the fact the light tank must weigh half the weight of the medium is that they could derive the light tank engine from the medium one by simply cutting the amount of cylinders, such as using a V12 and a V6. It is interesting to note that these power figures are very much those that WW2 US light and medium tanks would use.
The other advantage of the ideal flat engine is that the driveshaft mounting would likely be very low and thus preclude the need for a transfer case to drop it low enough.
The ideal engine would certainly have been very useful for US WW2 tanks. It would combine both a low driveshaft and low powerpack height, completely circumventing pretty much all height issues US tanks had (bar the fact they still need a driveshaft and aren't rear-drive tanks). The diesel operation would help quite a bit with fuel consumption. It would be much lighter and more compact than the GM 6046 which weighed in the region of 4000 pounds. Since the medium engine would likely be a flat 12, it would be a little longer than a radial, so US tanks would be a bit longer, which is preferable since they were a bit short and not as stable as they could be.
5 pounds per hp was eventually achieved by the Soviet V-2 series a few years later, so it was not an impossible feat with a decently funded Army engine program. Ironically a lot of the developments of the US Hyper engine program (flat engines and relatively light high output engines) would have been useful here.
Ordnance had pretty good technical officers, but quite insufficient funding and Cavalry/Infantry branch support. Rarey, Colby, and Barnes.
I haven't yet found cases of armor and armament specialists and their suggestions bar a passing comment about a 75mm armament in 1935-late 30s, but if there had been funding for all three mentionned officers' suggestions from 1934, the US would have been highly competitive in terms of automotive components.
One complexity of weight-per-unit-power comparisons is assuring that you're including the weight of all the same ancillary equipment, and measuring output the same way.
For instance, the specs for the Guiberson radial diesel used in some US WWII light tanks state that it weighed about 2 pounds per HP. Obviously that has an apples-and-oranges problem. https://airandspace.si.edu/collecti...es-4-radial-9-diesel-engine/nasm_A19880410000
In the early 1940s, the pre-eminent US heavy-earthmoving-equipment maker Caterpillar was very interested in getting into the tank business. In particular, they had a large number of good powertrain engineers with a great deal of experience with high-reliability, low-maintenance diesel powerplants. They pitched the War Department on their capabilities, and were asked to bid on a larger version of the aforementioned Guiberson radial diesel, to be used in the M4 medium. They were so confident in their capabilities, and so committed to being involved, that they began building a new engine factory before they even got the development contract. Their engine aced out the Guiberson version for use in the M4A6, but just as the design and the new factory were ready, that program was cancelled, due to the War Department's loss of interest in dieselization.
WWII Caterpillar Diesel American 7-cylinder, Tank
WWII Caterpillar Diesel American 7-cylinder, Tank ..The original order was for 775 M4A6 to be built starting in late 1943.
www.dieselworldmag.com
My guess from what historical information I've been able to find is that Caterpillar wasn't at all wedded to the radial form-factor...its weight advantages were offset by its size and packaging issues...but weren't given any design freedom by the War Department in that regard. Caterpillar argued hard against that choice, but to no avail. Caterpillar would have been much happier to develop a diesel flat-12 or flat-8, which would have had much more technical usefulness in future earthmoving equipment and potentially in heavy trucks. In the end, there were considerable recriminations at Caterpillar regarding their commitment and investment having been for naught after their design advice was overruled.
It's more complicated when the necessary right angle transfer case (to re-direct the vertical crankshaft to horizontal, so the driveshaft can connect it to the transmission) is considered. If that transfer case has to go under the engine, so that the top of the engine remains unobstructed for cooling and particularly for the gear-driven cooling fan, then the engine has to be removed for maintenance of the transfer case...which will need oil changes, so that's a required engine removal each time.
There's also the power loss in that transfer case, and its own height, and its weight, and its cost.
There's also the power loss in that transfer case, and its own height, and its weight, and its cost.
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Then-Captain Rarey first appears in the Army's difficult attempts to come to grips with tanks and mechanization in 1926-27, as a staff member at the fledgling Tank School.
Driftless
Donor
Sounds like potential "What if Captain Rarey....." timeline on the order of Allan Cameron's "Sir John Valentine Carden Survives"
It's interesting that US Infantry-branch observers of European thinking mainly seized on that of the Germans and French. That of the British--i.e. that infantry support tanks could be slow but had to have dominant armament, including for engaging enemy tanks, and plenty of armor--was much more congruent with where 1920s US Infantry doctrine could go without requiring brain-resets for the commanders and staff, and if adopted would more rapidly have led to useful tanks in service.
It's also unfortunate that US Cavalry doctrine couldn't have evolved in coordination with that of the Infantry. US Cavalry tank doctrine much like that of the French (i.e. that Cavalry tanks should be both fast and sufficiently armed and armored to fight enemy cavalry tanks...and not just light tanks) would have been a helpful pointer to the doctrinal need...at least per British and French thinking...for Infantry tanks to be much more heavily armed and armored than any of the light tanks of that time, in order to be able to fight enemy Infantry tanks...thus helping to cut short the time wasted in USA on light-tanks-are-what-we-need wrong thinking.
Sure, just as with the British, there eventually would have had to be a reckoning that separating the infantry and cavalry tank concepts was a mistake, and they should converge into a single battle tank design concept with enough armor, armament and mobility to do both jobs. But, as long as the resources were available in the 1920s to build both concepts...and for USA they were...it would have been a step forward to move in the two-concepts direction, and relegate light tanks to the more sensible recon and screening roles in both the Infantry and Cavalry forces.
The many MGs of the then-current M3 Light as USA entered WWII clearly were a holdover of that 1920s Infantry-force doctrinal wrong turn.
It's also unfortunate that US Cavalry doctrine couldn't have evolved in coordination with that of the Infantry. US Cavalry tank doctrine much like that of the French (i.e. that Cavalry tanks should be both fast and sufficiently armed and armored to fight enemy cavalry tanks...and not just light tanks) would have been a helpful pointer to the doctrinal need...at least per British and French thinking...for Infantry tanks to be much more heavily armed and armored than any of the light tanks of that time, in order to be able to fight enemy Infantry tanks...thus helping to cut short the time wasted in USA on light-tanks-are-what-we-need wrong thinking.
Sure, just as with the British, there eventually would have had to be a reckoning that separating the infantry and cavalry tank concepts was a mistake, and they should converge into a single battle tank design concept with enough armor, armament and mobility to do both jobs. But, as long as the resources were available in the 1920s to build both concepts...and for USA they were...it would have been a step forward to move in the two-concepts direction, and relegate light tanks to the more sensible recon and screening roles in both the Infantry and Cavalry forces.
The many MGs of the then-current M3 Light as USA entered WWII clearly were a holdover of that 1920s Infantry-force doctrinal wrong turn.
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