Reluctant Poster
Tech Sergeant
- 1,656
- Dec 6, 2006
The suspension of a Churchill precluded high speed. More power would just waste fuel
Napier keeps making liquid-cooled engines in 1930?
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Shortround6
Major General
True but a 3-71 didn't make enough power for a tank................of any size.
Using two engines.
You wouldn't waste much fuel before you broke the suspension/track
Everything has to work together.
You can't stick a Panther engine in a MK IV and get very far
Sure, everything has to be matched together to work. I'm sure designers at the time were well aware of that.
As for a diesel Churchill, the twin 6-71 used in the Sherman produced around 400 hp, which is quite similar to the 350 hp the historical Churchill engine had. So that might have been an option (though the twin 6-71 was a bit of a rush job).
In general, I think not vigorously going for diesel powered tanks (and other AFV's and why not trucks as well) in the pre-war era was a mistake almost every one of the major combatants did. Except for the Russians.
As for a diesel Churchill, the twin 6-71 used in the Sherman produced around 400 hp, which is quite similar to the 350 hp the historical Churchill engine had. So that might have been an option (though the twin 6-71 was a bit of a rush job).
In general, I think not vigorously going for diesel powered tanks (and other AFV's and why not trucks as well) in the pre-war era was a mistake almost every one of the major combatants did. Except for the Russians.
As for air cooled diesels for tanks, Germany was working on that though never entered use. The US apparently also liked the concept, and they eventually got there in the AVDS-1790, though much too late for WWII. But it became the engine in some later variants of the M47/M48 and in the M60 (apparently still used in some vehicles based in the M60, like recovery vehicles etc.).
Reluctant Poster
Tech Sergeant
- 1,656
- Dec 6, 2006
the 6-71 was used in buses in 1938
Reluctant Poster
Tech Sergeant
- 1,656
- Dec 6, 2006
The AVDS-1790 started out as the AV-1790 gasoline engine. The US army finally realized the advantages of the diesel in the mid 50s and began retrofitting M-48s with the diesel version in late 1956.
Incidentally the gasoline version used the Simmonds fuel injection system which was a license built version of the fuel injection system developed by Rolls Royce for late model Merlins.
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Reluctant Poster
Tech Sergeant
- 1,656
- Dec 6, 2006
Attached is brochure describing later diesel versions of the AV-1790.
Shortround6
Major General
Trouble was that you needed a different logistics train.
Germans used, at time, captured civilian motor fuel in France. Poland didn't have enough to say so.
Of course with MK I and MK II tanks you could top up a number of tanks from one filling station, MK IVs not so many
The US Marines got most of the Diesel powered Shermans that the US kept. They foisted the rest onto the British and the Soviets. US Marines and Navy already had quantities of diesel for landing craft and aux generators on ships.
There just weren't that many Diesel engines available in the late 1930s to chose from for either tanks or trucks. And Diesels were heavy. A 6-71 went about 2200lbs. You needed two replace the radial engine in the early M-4 tank. You also needed to extend the hull about 1 ft in length to fit them in.
In the US there were around 480 different models of Stock, Industrial, Marine and commercial vehicle/automotive engines being cataloged in 1940. does not include aircraft.
from 6hp to over 600hp. Darn few were suitable to tanks.
It took quite a while in the 1950s for the US to switch to diesel fuel for transport. Trying to switch to diesels in WW II ???
The US could use or adapt a number of existing engines in short order for special uses. Waukesha for example supplied thousands of large (like 779 cu in) six cylinder engines for large trucks and tractors either using exiting models or slightly modified ones.
Tanks also needed room around the engines to work on them, they hadn't figured out how to pull engines for routine maintenance
There was a lot more to consider than just getting an engine had the required power.
These used a 210hp Waukesha engine, 6 cylinders, 779 cu in. 1800lbs and the basic engine was in production 1940. These industrial engines were sometimes rated in different ways.
In the High speed tractor they were rated at 210hp 2100rpm. but the basic engine was rated at 168hp at 1800rpm. They were sometimes rated at full load, intermittent load (90%) and continuous load (80%) depending on manufacturer.
This is just an example.
The number of motor vehicles that the US used was staggering. And the US did a much better job of standardizing things than most other armies. A least those that made more than 2 types of trucks (Soviets).
Diesels in WW II were example of the "The Best is the enemy of good".
The Soviets had 1 diesel that they used in the bigger tanks.
14,000 of these used a pair of car engines running on gasoline, as did the vast majority of wheeled Soviet vehicles.
So they needed both diesel tank trucks and gasoline tank trucks to supply armored units.
Sure, but one of the big advantages of diesel vehicles at the time was roughly 30-40% better fuel economy, so the total size of the logistics train would be smaller (how much smaller depending of course on how big a portion of the total usage would be diesel vs. motor gasoline).
A more or less completely diesel powered army like in modern times is maybe a bit too much to ask for WWII.
And in Russia they ran into the opposite problem of being unable to use captured Russian diesel. Plus ça change..
Obviously not feasible, or at least very difficult, to switch in the middle of WWII. So it would have to be prepared before the war and before setting up all the production lines for the war production.
Shortround6
Major General
It was too much to ask.
In France they were using fuel from civilian gas stations. French tank forces had also used civilian fuel on occasion. In Russia there were no civilian cars/trucks. Horse feed doesn't work in tanks
The Stalinets 60 tractors ran on gasoline. The 65s ran diesel
Very few soviet trucks ran on Diesel.
The US simply used already existing engines, transmissions, axles and other other parts.
trying to design and build even a 1/2 dozen small diesels to huge numbers to suit military trucks would have been very costly.
They built about 382,000 of the Dodge small trucks using standard Dodge 6 cylinder gas engines.
and you can go through every other class of trucks similar adaptations. You might have been able to simply things a bit but then you need to equip and tool up a lot of factories to make a lot (millions) of diesel engines. It was a lot easier to try to use different existing gas engines and try to standardize them in classes/categories.
US also tried to standardize by using certain manufactures for export/lead lease so the US units would have fewer different models to deal with.
US didn't even have dedicated gas tank engines and were using 3 different sizes of radial aircraft engines for tanks. Trying to set up a large number of diesel engine plants for military vehicles/trucks was beyond what the US could do, unless you cut out something else, Like new navy ships?
Reluctant Poster
Tech Sergeant
- 1,656
- Dec 6, 2006
The attached collection of US army memos shows that was a lot of effort made to dieselize but eventually gasoline was preferred.
All of the M10 the Army used were 6-71 powered, the M10A was Ford GAA powered.
The M10A didn't go overseas, most stayed in the US for training
