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If one had made no diesel engine worth speaking about, and the fuel flow was more or less unproblematic, then keeping it with the gasoline-powered tanks was a no brainer
Aside from Russia the other 'major' uses of diesel engines in tanks were the Japanese and Italians.
The Italians tended to bounce back and forth. They wanted diesels but an useable diesel was not always available and they resorted to petrol engines while they sorted out higher powered diesels. How good the 1943 higher powered diesels were may never be known. Not many were built and conditions were not good.
Japanese had started making diesels in very early 30s but getting powerful diesels may have taken a while. Powerful is relative. Japanese were using a 21.7 liter air cooled diesel of 170hp in 1941 in their 15ton (roughly) medium tank at that time. They got 240hp from the engine later (1943?)
The late war Czech diesel used the later 8 wheeled armored cars was 14.8liters and gave 220hp and was air cooled.
In the late 30s Diesels may not have given the power to weight ratios or power to volume ratios that were wanted.
Soviet V2 was powerful, it was also large, and it may not have been very long lived. The Soviets may have accepted the trade-offs. Other countries may not have.
I previously posted these US Army memos on their plans diesel engines in tanks.The Japanese appear to have made the worst tank diesels from a power-to-displacement standpoint. The 21.7 L engine on the Chi-Ha had been rushed (barely tested) before approval. The Type 100 employed on the Chi-He and Chi-Nu had got the time to be better designed, hence the 240 hp (1940).
The Type 4 on the Chi-To developped from 1942-43 onwards initially made 412 hp out of 37.7 L and 500 hp when supercharged, which was still mediocre compared to V-2 analogues, but more or less acceptable.
Italian diesels started worse than even some commercial British ones (save for the more convenient V8 form factor). Some were derived into petrol versions in emergency but as they were not built for this fuel from the start, they were not very efficient (as opposed to the gasoline engine made for the Sahariano tank which was efficient). The SPA 242 in the P26/40 did do 330 hp out of 24L which was respectable, and was to be pushed to 430 or 460 hp in the SPA 342 or 343 mooted for faster versions of the tank, but killed by Italy's fall. There was a large 700 hp diesel in development, but displacement is unknown.
Daimler-Benz set for itself the target of getting a very modern and efficient diesel tank engine in 1938 which led to the MB 809. However, they trended towards making a smaller engine rather than keeping displacement the same and increasing power: they went from 400 hp at 24 L to 360 hp at 17.5 L and 300 hp at 14.8 L. The marine MB 507/517 family mooted for the Maus and VK-3002 (DB (800 hp naturally aspirated and 1200 supercharged at around 42-44 L) was also efficient, if a bit large. MAN also worked on a diesel before 1942 but just like the 809, couldn't be upscaled to meet the needs of the VK-3002 program. But from 1942 onwards, almost all new engines in development in Germany were diesels, with only Maybach continuing development of the existing gasoline engines. Even then, they also moved to diesels derived from the HL 230 family towards the end of the war. The issue here was not performance, but simply that it was too late and that the engine couldn't be expected to enter production until late 1945/46.
Britain employed commercial diesels early in teh war which were on the inefficient side but still better than Japanese and Italian early models. Work on (allegedly purpose-made) tank diesels happened some time around 1940-41 but they were made for no more than 350 hp, so unsuitable for the needs of the new tank programs by then. Harry Ricardo briefly worked on a family of H16/24 and I6/8 diesels from 1939 onwards which were quite efficient and could deliver up to 560 hp unsupercharged and 720 supercharged (not even mentionning TOG's Paxman Ricardo), but Ricardo was too busy on aircraft engines and the Army focused more on the Meteor.
America was very unlucky as the Guiberson radials tried before the war were fundamentally flawed and Buda/Guiberson was not actually interested enough to redesign them accordingly. The Detroit Diesels were good but it was too late to expand production enough to make a real surplus, considering these engines were in very high demand for naval assets. Caterpillar diesel radials and half-radials were too late. George H Rarey, an officer involved in tanks in the interwar period, recommended diesels (albeit with a rather ambitious desire for 5 hp per pound of engine weight), especially in flat and radial forms. Ironically, the target power ouputs (25-30 hp per ton on the US interwar tanks) translated to 375-450 hp for the medium tank and 187.5-225 hp for the light tank, which was right in the class needed for the main US tanks fielded during the war.
French tank inspectors were quite interested in diesels ever since 1929 or so, with some in development for Renault FT and FCM 2C modernizations. The B2, B3 battle tanks and BB fortress tank all employed dedicated tank diesels, half or more of the light tank entries in 1933-35 used diesels (but were not adopted for unrelated reasons), the ARL and AMX 45t fortress tanks used diesels (commercial and dedicated alike), and AMX went with only diesels ever since it started working on new tanks. Dedicated engines (instead of commercial/aircraft engines until then) for 65 octane gasoline remained the norm for the new developments of 1939-40 - as by this point, mass adoption of diesels in a sea of gasoline engines would face an uphill struggle just like in the US.
The USSR was unique in that
- it was used to high output tank engines so the V-2 was suitable for the entire war, while even dedicated engines designed elsewhere could well have been too small and weak to serve the entire war (in tanks at least)
- V-2 development started all the way back to 1932, so that the engine was already well-developped (if a little short-lived still) when Barbarossa happened
- the state of the Soviet gasoline process industry and civilian road economy was such that road gasoline engines were not particularly important, unlike certain Western countries.
Even then, Harry Ricardo noted that before WW2, the British had moved on to diesel engines for heavy trucks, such that there weren't many high power gasoline engines in use.
So other than the Soviets, most belligerents had not made a serious dieselization effort (with dedicated, high output designs) until they were already too deep in WW2 to transition.
How much the Germans have 'slept' on the captured 47mm stuff. Once outfitted with the cored ammo, the Czech 47mm ATG used 642g of propellant, the French 47mm used 560g of propellant, while the short 50mm used 557 g of propellant.
(sorry for the lousy quality of the Czech/German PzGr40 cartridge)
Respective shot weights were 800g for the Czech gun, 825g for the French gun, and 900g for the 5cm gun.
That was the French AT gun. The tank gun was weaker, as you know.Use of the French 47mm is a lot more debatable. I am assuming that this is the tank 47mm gun.
Agreed all the way.The Germans certainly did not make good use of the Czech 47mm.
The Germans had over 1 1/2 years to figure out what to do with the Czech guns/equipment before the attack on France.
Now they have the time between France surrendering and the Attack on Russia to figure out what to do with the French stuff. Under one year? and they could use that same year to figure out more to do with the Czech stuff. They also could figure out what to do with their own short 50 vs long 50 problem.
Germans were handing out AP40 shot like a drunk buying drinks in bar. Everybody get's some. Few people had enough.
When did they figure out they didn't have enough to go around?
When did they figure out that the Somua 35 had no business in the front line in Russia?
Old book, could be in error. The Pak 38 used a 2050 gram projectile and 882grams of propellent for the PzGr39 and a 850 gram projectile and 688 gram propelling charge for the AP40 shot.
Perhaps the Germans could have used the towed French 47mm gun to greater effect. But fooling around with captured French guns for ballistics (different projectiles/powder charges) is time that is not being spent on other things.
Could have started even earlier, with the Polish 75mm.But making something, especially self-propelled, with the French 75mm guns ASAP would've yielded them a lot more.
Thank you, I had forgotten how short and fat the tank cartridge was.That was the French AT gun. The tank gun was weaker, as you know.
Stick the French 75s on French chassis and forget about them.The most useful French stuff for them was probably the classic 75mm gun. The 105mm howitzers were probably also useful.
Small French yes. the sooner the Germans divorce themselves from the Pz-II the better.. Or even on the Pz-II or the small French tanks.
SeeThe 47mm ATG is in the 3rd place IMO. The 47mm tank gun if out-bored for the Czech or the ATG ammo would've been also very useful. Or, out-bore it for short 50mm ammo?
The Somua 35 was a worse tank than the Pz-38 (t) in Russia. Even with a German radio it still had the crappy one man turret and lousy vision to the outside.As for the Somua 35 for Russia, we can recall that Germans were badly in need for any useful tanks in any year of the war. The S35 makes more sense in Russia than the Pz-38(t) the Germans used there.
Not out of their wheelhouse.It is too much work, you have to take off the Breech block, cut over 300mm off the back of the barrel for the French AT gun (over 150mm for the tank gun) rechamber it and modify to the breechblock and extractors and then put the breech block back on. And them modify the recoil systems and make new gun sights.
In small arms it is quite easy to rechamber some guns for a longer cartridge or both longer and fatter. It is possible to rechamber and gun from a 'standard' bolt face like 12.01mm (NATO or old 7.9mm Mauser or host of others) to the 'magnum' bolt face, most belted magnums. But you have to open up the bolt face and modify/replace the extractor.Later upgrades were designated as the Pak36(r), and:
- Were rechambered for the more powerful German Pak40 cartridge - which was nearly twice as long as the Soviet one (715 mm vs 385.3 mm) and also wider (100 mm vs 90 mm), resulting in 2.4 times the propellant load; and
- Had recoil mechanism adjustments to accommodate the new recoil characteristics.
For beyond 1940 and beyond France, I'd prefer the Pz-II chassis.Small French yes. the sooner the Germans divorce themselves from the Pz-II the better.
It is too much work, you have to take off the Breech block, cut over 300mm off the back of the barrel for the French AT gun (over 150mm for the tank gun) rechamber it and modify to the breechblock and extractors and then put the breech block back on. And them modify the recoil systems and make new gun sights.
Boring out the 47mm guns to 50mm is even more work.
Use them for training, Atlantic wall defenses or send them for scrap.
The Somua 35 was a worse tank than the Pz-38 (t) in Russia. Even with a German radio it still had the crappy one man turret and lousy vision to the outside.
It doesn't matter what kind of of gun you stick in the turret or what kind of ammo you give it if the the tank commander/gunner cannot identify a target to shoot at. Or can't find the enemy until 1/2 of his company is already going up in flames.
The Pz 38(t) had a two man turret. The loader was an after thought and vision for him, like most loaders, was also an after thought. However the commander/gunner had the cupola with 4 vision slots/blocks so he could ride head out,(could not shoot). ride with head in the cupola (still couldn't shoot unless at very very close range?) or with body/head inside the turret and using the either the periscopic sight going through the roof (traverse was?) or the gun sight next to the gun.
Not out of their wheelhouse.
You could rechamber a German Pac 40 to take Soviet ammo (or a composite soviet cartridge case and a German 75mm projectile but you would need to cut off about 700-715mm of the rear end of the barrel to get rid of the larger diameter chamber. OR ream out the chamber over size and insert a liner, except you would have no rifling for about 330mm from the shorter case to the start of the old rifling. Now perhaps you could rifle the the part of liner you stick in the old tube but you have to figure out a way to align the new section of rifling with the old rifling.
You can do all sorts of things. Should you?
The 38(t) carried some of the ammo in the turret. Most below, It turned out they could squeeze the extra crewman into the existing turret. French had looked into 2nd crewman for the APX turret (same turret used in the Char B1bis) and figurered they needed a larger/heavier turret. The French tanks stowed few or no ammo in the turret. Germans, with hundreds of Somua 35s and Char B1s never got a 2nd man into the turret. If it was a simple as taking out a couple of ammo bins why didn't they do it?As designed as as originally produced, the future Pz 38(t) have had a 3-men crew. Germans found the way to have an extra crew member to fit in the turret, sacrificing some ammo load. They did the same with the Pz 35(t).
Do the same with the S35.
OK, we are dealing with several different things here. One of them is actual gun construction.A short list of the guns Germans over-bored and never looked back includes the 5cm Pak into 7.5cm (to make the Pak 50), Soviet 76 and 85mm AA guns into 88mm, inter-war naval 105mm gun into 127mm, as well as, indeed, the F-22 into the pak 36(r); granted, the latest received over-boring just of the chamber area. British over-bored the 6pdr into 75mm to be used as tank guns.
So they not just could, but also reckoned that they should, and they did.
Good knows that Germans were making a whole host of 75mm guns that were begging to be installed in the tanks. Barrel lengths (to make the best use of the ammo 'power') from 26, 34, 36, 40.8, and 60 calibers were made before ww2, while the ww2 saw the L43 and L48 sharing the same ammo, and the 46 cal (pak 40) used the ammo of similar dimensions to the L60 Flak weapon. Even the L54 weapon was made in a few dozens. Then we have the ~75mm guns from Czechoslovakia and from Poland, and, indeed, the L70 weapon for the Panther.
Still, it took Germans an eternity to move up from the short 75mm gun. Even the M36 mountain gun and the FK 18 were more powerful than the Kwk 37, with muzzle energies being some 25-30% greater.
Making a real effort to up-gun the Pz-III with a good 75mm gun would've netted the Germans with a tank comparable (if slower) to the early Cromwell, but years earlier. And a much better tank than the 75mm gunned Valentine.
(turret ring diameter was 1530 mm on the Pz-III, 1450mm on the Cromwell)
How hard have they tried it?Germans, with hundreds of Somua 35s and Char B1s never got a 2nd man into the turret. If it was a simple as taking out a couple of ammo bins why didn't they do it?
The Pak 50 was a bored-out Pak 38. From here:1, the Pac 50 was NOT a bored out Pak 38. It was a shortened Pac 40 barrel and breechblock mounted in a Pac 38 carriage.
2. A lot of bigger gun barrels were constructed in pieces. A series of tubes places inside of each other and often the inter tube with the rifling was made replaceable so the gun could be relined when the rifling wore out. Cheaper and easier than building new barrels. I don't know if the soviet 76mm AA gun needed to bored out to take a bigger liner or if an 88mm liner could be slid into the existing outer tube/s. The 85mm gun might have just accepted an 88mm liner. This is also what the Germans did with the 10.5cm to 12.7cm change over.
3. The British never bored out an existing 57mm gun to make a 75mm gun. They either bored out a gun during manufacture or they designed a 75mm gun barrel to fit the existing 57mm mounts/recoil system and kept just about the same over all length.
And as always, if you are doing this sort of work, what else isn't being done?
Not true. Tanks are not constantly on the move. In fact they spend a lot of time idling waiting for the enemy to show up. There is also a big difference in fuel consumption when running cross country vs on roads.Diesels get much better mileage running under light load...but tanks are rarely run under light load (tracks don't just roll down the road) - you rail/transport them to the front, fight your battle, then rail them to the next location. So, 100s of km, not 1,000s. As a result, the difference for tanks isn't as significant as say trucks. Mixing petrol for you trucks with diesel for your tanks will result in some logistics issues.
Not true. Tanks are not constantly on the move. In fact they spend a lot of time idling waiting for the enemy to show up.