Victor Semensi Posted May 2, 2001 Share Posted May 2, 2001 Maybe you grogs out there can answer these questions I've had since my Panzerblitz days. Why did the Russians settle on diesel engines for their tanks instead of petrol? How did they keep them running in the winter without the fuel hardening as it does up here in New England? T34's didn't seem to lack for speed so why didn't the Germans use diesels? How did the diesel powered Shermans compare to gas powered ones in performance? Personally I'd take a performance hit if it reduced the chance of my burning to death. Am I right in assuming that a barrel of crude oil will yield more diesel fuel than gas. If true it further begs the question of the lack of diesels in German tanks. Link to comment Share on other sites More sharing options...
Guest Babra Posted May 2, 2001 Share Posted May 2, 2001 One “average” barrel of crude = 40% gasoline; 30% diesel/jet fuel; 20% lubricant; 10% asphalt. I suppose ideally, an efficient military force would have a 3:4 ratio of diesel powered vehicles to gasoline powered. I am not sure what the performance differences are, but considering race cars use gasoline, I would presume the better performance is to be had from that, though diesel would likely give great gobs of low-end torque, which might be better for a tank overall. Link to comment Share on other sites More sharing options...
Stalins Organ Posted May 2, 2001 Share Posted May 2, 2001 I believe the secret to the Russian diesel engine was the ability to make an aluminium crank case. This allowed the engine to be light enough at the size for the required power. Even when the Germans captured the engines they still couldn't make the crank cases. sowhy use it? Well that's 30% of the barrel that you can't use otherwise, so you're getting better efficiency from your barrel of crude! Also diesel's tend to be heavier than comparable petrol engines, so are less use in lighter vehicles due to weight. Also diesel is less flammable than petrol, and the engines do not require electrical ignition systems, which makes them a little simpler. as to why their diesel didn't harden? I did read somewhere that it did, but they were better prepared for it - keeping their engines warmed and/or out of the cold and/or making plans that didn't require them! [ 05-01-2001: Message edited by: Mike the bike ] Link to comment Share on other sites More sharing options...
offtaskagain Posted May 2, 2001 Share Posted May 2, 2001 I believe there was a discussion about this before. The main reason I believe is diesel doesn't explode very easily. You can actually put out cigarettes with it. Diesel engines are much less complex than gas engines as well. The low-end torque is indeed the most desirable for tanks as high RPMs burn a lot of fuel. Link to comment Share on other sites More sharing options...
Jeff Hays Posted May 2, 2001 Share Posted May 2, 2001 In all actuality, diesel engines are much more complex than gasoline engines. It is the fuel delivery system that requires precision where a gasoline engine in the 1940's was carbureted for the most part (some exceptions). A diesel engine would have less horsepower than a diesel but what really matters is how much horsepower in the form of torque is delivered to the ground via the tracks and the power systems of the AFV. Also a high HP gasoline engine must have large displacement for high HP and torques and a diesel could provide a high torque value at a lower displacement in engine size. As for the Russian use of diesels I believe it was used in vehicles due to the fact that high quality (octane) gasoline was in short supply. Also to counter this though a well engineered gasoline engine can be quite powerplant. If you look at all major powertrains in use today in most equipment it has a diesel engine. Of course the M1 Abrams series has a gas turbine! diffrent animal all together!!! Link to comment Share on other sites More sharing options...
Kanonier Reichmann Posted May 2, 2001 Share Posted May 2, 2001 My very basic understanding of the diesel engine is that it has to made to much higher tolerances compared with the petrol engine due to the diesel fuel being under very high pressure for it to vaporise. In this case it really does beg the question why the Soviets went for diesel engines as I would have thought alot of their production processes (due to forced mass evacuation eastwards to the Urals etc.) wouldn't have cut the mustard in terms of consistently manufacturing engine blocks and associated bits to withstand the high tolerances required for a reliable diesel engine. If some trained engineers want to shoot me down in flames on this one you're more tham welcome to. Regards Jim R. Link to comment Share on other sites More sharing options...
Gyrene Posted May 2, 2001 Share Posted May 2, 2001 Diesel engines do require higher tolerances, especially in the fuel pump and piston rings. One big advantage of diesels is fuel economy, and in the Eastern Front this was no small matter. The problem with diesels is that they can't spin as fast as gasoline engines, so horsepower numbers are lower for diesels than gas engines of the same size. I could go into why diesels can't rotate as fast as gasoline engines, but its beyond this topic. Diesels do produce more torque at lower RPM's than gasoline engines due to the much higher compression ratios they run at (7.5:1 for a typical 1940's gas engine compared to 14:1 for a low-end diesel). Torque is a good thing if you trying to move a heavy object like a truck or tank around. Aircraft engines were much more efficient than Tank engines because they are optimized to run at a set RPM and they usually had the benefit of supercharging and higher octane gas available (Higher compression possible). The same radial engine found in some Shermans would put out upwards of 300 more HP in aircraft trim. Jim R. probably has it right, diesels tend to be much more reliable and along with the fuel economy benefits it was attractive enough to the Soviets to put with the extra hassle in making them. Gyrene Link to comment Share on other sites More sharing options...
Skipper Posted May 2, 2001 Share Posted May 2, 2001 The only part of the diesel that has to be high tolerance is the high pressure fuel pump and the injectors. Both are very simple to replace and do not require much of any tuning after replacement. And it goes without electric ignition - which is the major maintenance PITA in an old petrol engine. Besides, diesel oil vapour doesnot explode. Diesels are also more fuel-efficient. Afaik, germans did not go with diesels for the simple reason that they lacked diesel oil. They used synthetic fuels for their tanks etc, and all the diesel they could make from their sparse supply of oil went for the Kriegsmarin (sp?). About the use of engines in winter, it always amused me that in Russian Far North (where I used to live) everybody would get up in the morning, pull a car battery out of closet, put a flame under engine, maybe use a lighter to unfreeze the lock on the door, and go to work. Otoh, if anything close to that temperature would happen in Cyprus (where I live at the moment), no car will start, thousands will die and it will generally be a disaster of epic proportions. Link to comment Share on other sites More sharing options...
Skipper Posted May 2, 2001 Share Posted May 2, 2001 > benefit of supercharging No such thing in a WWII plane engine. Link to comment Share on other sites More sharing options...
Jeff Hays Posted May 2, 2001 Share Posted May 2, 2001 Reichman, you are correct in your assumption. Diesels have to be manufactured with stronger blocks, pistons, rods, crankshaft. As for precision, machining tolerances and such, the soviets were up to the task. All engines depending on their design and application must have exacting tolerances. the unique thing about diesels is that you can engineer them to run on just about anything. In college in one of my courses we rigged up a small John Deere 4 cylinder diesel to run off of oil that had been filtered straight out of the fryer vat (french fries!). It ran of course and the engine was forgiving until the injectors were coated with soot from the wrong combustion temperature. But this proved a point in alternative fuels and the diesels ability to withstand punishment. As for the previous question of diesels "gelling" in the winter. All the soviets would have to do would use a more viscous fuel or what is known in north america as #1. There are also additives that can be used in the fuel to prevent the fuel seperating into solids. Link to comment Share on other sites More sharing options...
Gyrene Posted May 2, 2001 Share Posted May 2, 2001 <BLOCKQUOTE>quote:</font><HR>> benefit of supercharging No such thing in a WWII plane engine. <HR></BLOCKQUOTE> I'll let you reconsider that statement and do some research. Gyrene Link to comment Share on other sites More sharing options...
Jeff Hays Posted May 2, 2001 Share Posted May 2, 2001 I do believe the Germans fielded a bomber that had diesel engines and I think the HE111 replaced but I can't remeber the desingation right now...JU86's!!!! thats them!!! they used these up in desperation to resupply stalingrad from the air. And yes superchargers rule gas engines and probably helped win the war in the pacific. But oh lets not forget turbocharged diesels!! oops that wasnt till the early 50's! Link to comment Share on other sites More sharing options...
Jeff Hays Posted May 2, 2001 Share Posted May 2, 2001 I cant remember but do any of the WWII tanks from any nation have superchargers? I know some american vehicles had water injection to cope with varying levels of octane but I can remember about the superchargers except in planes (Wildcats) Link to comment Share on other sites More sharing options...
Skipper Posted May 2, 2001 Share Posted May 2, 2001 > I'll let you reconsider that statement and > do some research. Put it this way, it was not usual at all (if we are talking about the same thing - ie, compressor on the air intake). Turbines for these things were tough to make at the then state of metallurgy. Link to comment Share on other sites More sharing options...
Gyrene Posted May 2, 2001 Share Posted May 2, 2001 Skipper, supercharger, forced induction systems which achieve higher than ambient pressure in the intake manifold: Engine driven (Via belt, direct to crankshaft etc) or exhaust driven (i.e. Turbochargers) were very common, all late war fighters and bombers had them, the P39 was a failure as a fighter because it did not have one. If you are thinking of Power Recovery Turbines (PRT) like some later model R-3350's had they are not what I am talking about. I am a licensed Aircraft Mechanic, and part of my education was devoted to large piston engines, both inline and radials, I don't want to sound like an a-hole, but I can assure you that WWII engines did have superchargers. Gyrene Link to comment Share on other sites More sharing options...
Stalin's Organ Posted May 2, 2001 Share Posted May 2, 2001 Skipper's probably talking about turbo-charging, wher exhaust gasses are used to drive a turbine that drives a compressor in the inlet. Americans sometimes call thus turbo-supercharging. Supercharging (direct mechanical drive from the engine to the compressor) was absolutely common - the Allison B-1710 originally fited to the Mustang suffered from only having a 1-stage supercharger, whereas the merlin eventually fitted had a 2-stage. The American radial engines might have either super or turbo-charging - eg the P47 had a turbocharger behind the cockpit, while the C47 engines had a supercharger. The Diesel engine fitted to the Ju-86 was unusual in that it had 2 pistons in each cylinder, and a separate crankshaft at each end of hte cylinder - the pistons compressed the charge by moving towards each other, and a gearbox merged the power from the 2 crankshafts. This did away with the need to have a strong, heavy cylinder head for each cylinder and was a major reason why hte engine could be made light enough for aircraft use. Link to comment Share on other sites More sharing options...
Gyrene Posted May 2, 2001 Share Posted May 2, 2001 Stalin, Turbos were used only towards the end of the war (P38's had them) and they did have lots of maintenance problems due to heat cracking. I had heard of double piston per cylinder diesels but didn't know of any examples, thanks! Gyrene Link to comment Share on other sites More sharing options...
Skipper Posted May 2, 2001 Share Posted May 2, 2001 Ahh, yes - it was a turbocharger that I was talking about. Link to comment Share on other sites More sharing options...
Stalin's Organ Posted May 2, 2001 Share Posted May 2, 2001 Gyrene turbos were used quite early on - the P47B had one, and they were fitted to P-38's from 1943. The A-20 (Boston II) had turbochargers, as ordered by France at the start of the war & delivered to the UK, replaced by superchargers on the A20A (BD-1), various marks of the B-24 Liberator had turbo's asa well as superchargers. The P38 ones gave trouble, never heard of any hassles from the P47 ones though. Stalin, also a LAME! Link to comment Share on other sites More sharing options...
Gyrene Posted May 2, 2001 Share Posted May 2, 2001 Stalin, one of my instructors at A&P school here in the US (Airframe & Powerplant, the FAA name for a mech's license) is a USAAF veteran, he joined in 1937 got out in 1969 (32 years!) he served in WWII, Korea and Vietnam. He served with a P39 Squadron in Guadalcanal, and later with a P38 Squadron in the Pacific. He's just retired from the school, lots of great stories from him, he was merciless with ex-servicemen, really held us to a higher standard. You're right about the early turbos. Wasn't one of the problems with Spitfires the lack of a pressured carb? Gyrene Link to comment Share on other sites More sharing options...
Stalin's Organ Posted May 2, 2001 Share Posted May 2, 2001 Yes it was - they couldn't nose over in a dive too hard or the float would stick to the top of hte bowl and cut out hte fuel supply! The problem was with all early marks of hte Merlin, so affected the Hurricane and Defiant too. I did an apprenticeship with the local airline, including time on R1830's and Gipsy Majors - now I work for the local feds! Link to comment Share on other sites More sharing options...
Stacheldraht Posted May 2, 2001 Share Posted May 2, 2001 FWIW, Stewart Wilson's Aircraft of WWII states that the P-38 was the first (military) plane "anywhere with turbocharged engines." Link to comment Share on other sites More sharing options...
Victor Semensi Posted May 2, 2001 Author Share Posted May 2, 2001 Thanks for all the info. I constantly amazed at the wealth of information a single question can generate on this forum. Link to comment Share on other sites More sharing options...
Gyrene Posted May 2, 2001 Share Posted May 2, 2001 <BLOCKQUOTE>quote:</font><HR> I did an apprenticeship with the local airline, including time on R1830's and Gipsy Majors - now I work for the local feds! <HR></BLOCKQUOTE> An airline running round motors? Jeez, how long ago was this? I did mostly helicopter stuff, all kinds of Bells and Sikorskys and I did a stint at Generous Electric O/H'ing CF6's. Got laid off from that easy gig and went off to try my luck in graphics. Gyrene Link to comment Share on other sites More sharing options...
Marnix Posted May 2, 2001 Share Posted May 2, 2001 <BLOCKQUOTE>quote:</font><HR>Originally posted by Victor Semensi: Thanks for all the info. I constantly amazed at the wealth of information a single question can generate on this forum.<HR></BLOCKQUOTE> You can say that again! I really enjoyed reading this one, thanks guys. OB Diesel: How Stuff Works on Diesel Engines Link to comment Share on other sites More sharing options...
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