Early Western adoption of AFV diesels after WW2?

[Elan Vital]

Hi everyone,

Historically the Western powers didn't seriously push for AFV diesels until the late 50s (or early 50s in the US), with those entering service in the early 60s. But the tools required for good AFV diesels (beyond 200hp at least) and the factors favoring it already existed in 1945, which means that postwar engine developments could have been diesels from the start.

First of all, superchargers, if not turbochargers, were now small enough for use in tanks, and were indeed even used by the US on some early postwar engines (AVSI-1790-8, AOS-895), and tested by the UK in 1944-45 and contemplated in France. The switch to forced induction favors diesels even more than gasoline engines since the former can throttle superchargers well even at low RPMs, get much better mixing thanks to the good flow of air which massively improves performance at all regimes, and they can get much higher boosts than low octane AFV gasoline since they do not knock. This greatly bridges the gap in volumetric power density between diesel and gas.

Secondarily, the Western powers already knew in WW2 that diesels were workable and better, and pursued them extensively even if they couldn't make the switch due to wartime constraints. You have the US still testing the GM 8-184 diesel, Caterpillar offering twin radial diesels cut in half, US and Canadian experiments with diesel Ford V8 and Meteor, and Harry Ricardo in the UK designing a family of I and H-type diesels with superchargers in the 1940-43 period. France meanwhile preferred diesel Shermans, and wanted that engine type in postwar tanks in 1945 plans. AMX M4 briefly had a Swiss diesel compete with the HL295.

Thirdly, the West was already making half the step in the 40s and 50s with fuel-injected gasoline engines.

There is also the fact that with the jet age already in sight after 1945, the aviation would soon stop using gasoline.

So how about the Western powers actively work towards diesels in 1945 already? The US postwar air-cooled engines would have particularly benefitted from being supercharged diesels from the start. A backup/alternative supplier would be General Motors through Detroit Diesel, by designing Vee variants of their 2-stroke engines earlier instead of in the 50s (and possibly with some refinements for military use, like the features the Japanese had in their tank 2-strokes in the Type 74).
France can leverage Mercedes-Benz or ask Maybach for a diesel derivative of HL295 (already fuel-injected).
The UK can listen to Ricardo for once.

What do you think about this?

 

[GTX]

The problem with this is that right after the war, the western powers were awash with equipment that had just been proven and were trying to cut back spending. To do this would go contrary to that.

 

[Fluff]

The problem with this is that right after the war, the western powers were awash with equipment that had just been proven and were trying to cut back spending. To do this would go country to that.

Thats what I was going to say. Korea was fought with basically the kit from 1945 with a few jet aircraft added. Most aircraft were WW2 props.

of course the russians had got to a diesel tank engine since the mid 30's.

 

[Elan Vital]

The problem with this is that right after the war, the western powers were awash with equipment that had just been proven and were trying to cut back spending. To do this would go country to that.

I was talking about changing the existing postwar programs, not expanding on them.

 

[Fluff]

The problem with this is that right after the war, the western powers were awash with equipment that had just been proven and were trying to cut back spending. To do this would go country to that.

I was talking about changing the existing postwar programs, not expanding on them.

I'm not sure I'm following you.

After WW2 no-one really designed(or actually built in numbers) anything new, for a few years. Of course American and British designers knew of diesels, and will have also had the captured german heavy tanks to play with. But we had thousands of comets, M4 etc. Even centurion was built with the meteor petrol engine. After that the diesels started arriving.

I'd also suggest standardisation comes into this, if the 1946 british army is built around petrol, its a big ask to change over or to now run 2 fuel logistics systems.

 

[Elan Vital]

The problem with this is that right after the war, the western powers were awash with equipment that had just been proven and were trying to cut back spending. To do this would go country to that.

I was talking about changing the existing postwar programs, not expanding on them.

I'm not sure I'm following you.

After WW2 no-one really designed(or actually built in numbers) anything new, for a few years. Of course American and British designers knew of diesels, and will have also had the captured german heavy tanks to play with. But we had thousands of comets, M4 etc. Even centurion was built with the meteor petrol engine. After that the diesels started arriving.

I'd also suggest standardisation comes into this, if the 1946 british army is built around petrol, its a big ask to change over or to now run 2 fuel logistics systems.

The US had AV-1790 in development since 1943 with time to reorient it, and AOS-895 was in development in 1946. The British had fuel-injected Meteor variants in development for A45/FV201. The R&D was already going on in 1945-46.

Again, I am strictly speaking about the engines developped for vehicles slated for the 1950's period in 1940's planning. Not about immediately replacing late war vehicles in the second half of the 40s.

 

[Fluff]

The problem with this is that right after the war, the western powers were awash with equipment that had just been proven and were trying to cut back spending. To do this would go country to that.

I was talking about changing the existing postwar programs, not expanding on them.

I'm not sure I'm following you.

After WW2 no-one really designed(or actually built in numbers) anything new, for a few years. Of course American and British designers knew of diesels, and will have also had the captured german heavy tanks to play with. But we had thousands of comets, M4 etc. Even centurion was built with the meteor petrol engine. After that the diesels started arriving.

I'd also suggest standardisation comes into this, if the 1946 british army is built around petrol, its a big ask to change over or to now run 2 fuel logistics systems.

The US had AV-1790 in development since 1943 with time to reorient it, and AOS-895 was in development in 1946. The British had fuel-injected Meteor variants in development for A45/FV201. The R&D was already going on in 1945-46.

Again, I am strictly speaking about the engines developped for vehicles slated for the 1950's period in 1940's planning. Not about immediately replacing late war vehicles in the second half of the 40s.

Your getting firmly into the period when USSR was seen as the current or future adversary, and the biggest tank issue was that they had 122mm guns, and we had 80-90mm guns. So the $$ went on the guns first.

I’d grant that there was an anomaly that the ussr had diesels in 37, and the west only ‘discovered’ it was preferable to brew up in a diesel, many years later.

To force the issue, in your AH, Needs NATO to push diesel very early on.

 

[Elan Vital]

I’d grant that there was an anomaly that the ussr had diesels in 37, and the west only ‘discovered’ it was preferable to brew up in a diesel, many years later.

To force the issue, in your AH, Needs NATO to push diesel very early on.

The USSR had a pretty good reason at the time considering that it had a very limited refining industry to produce gasoline. I think they only really noticed the inherent benefits of diesel (outside of low fuel consumption) after V2 testing in BT-7s however. Also, the USSR was naturally more thorough in military R&D at the time compared to peacetime Western powers that relied more on off-the-shelf tech.


In any case, seems like I need to have extensive Western use of diesels in WW2 then to really make the point. The US is probably out since good diesel engines simply weren't available in the numbers needed for its military buildup, but both Germany and the UK could make greater use of them. Germany since some were pushing for diesels in 1940 already (Daimler-Benz, MAN) and then in 1942-43 wanted to use them to exploit Navy stocks of fuel and the greater production of diesel in artificial fuel factories. One would just have to break the monopoly of Maybach sooner.

For the UK, listen to Leslie Little and get Valentine with diesel from day one (maybe it was even suggested for A9/A10? no info), finally get the diesel intended for A22 Churchill and support Ricardo's I and H engine family for Cruisers or prospective designs.

 

[riggerrob]

" ... For the UK, listen to Leslie Little and get Valentine with diesel from day one (maybe it was even suggested for A9/A10? no info), ... "

Perhaps install American-made diesels in the Valentines built by Montreal Locomotive works. Most of those Canadian-made Valentines went straight to the USSR under Lend-Lease Agreements.

 

[riggerrob]

Remember that the Rolls-Royce Meteor was a de-rated version of the wartime Merlin airplane engine. It was de-rated to run on 80 octane pool petrol while RAF Merlins ran on 100 or 120 octane aviation gasoline.
During WW2, the USA sent a bunch of tanker ships to the USSR, loaded with tetra-ethel lead to allow Soviet petro-chemical refineries to up the octane rating of Soviet produced aviation gasoline.

Octane rating is irrelevant for diesel engines since they will burn almost any flammable liquid that can be pumped through injectors. The other advantage of diesels is that they tend to "brew up" much slower when hit by bazookas, HESH, APFSDS, etc.

 

[Elan Vital]

" ... For the UK, listen to Leslie Little and get Valentine with diesel from day one (maybe it was even suggested for A9/A10? no info), ... "

Perhaps install American-made diesels in the Valentines built by Montreal Locomotive works. Most of those Canadian-made Valentines went straight to the USSR under Lend-Lease Agreements.

Already the case, but using AECs in British-made Valentines from the start would be nice too.

 

[JWilly]

One consideration in the mid to late 1930s in regard to the desirability of diesel vs. gasoline engines for the heavy equipment of the time was that individual deposits of crude oil have different chemistries, and...especially with the refining technology of the time, which was mostly just filtering and distillation plus final-product blending...the preponderance of then-developed Americas crude fields (mostly Texas/Oklahoma, Pennsylvania, Caribbean, Venezuela areas) gave much greater yields of gasoline than of light (i.e. motor vehicle type) diesel. Refineries also were designed for particular products so tended to be crude-source-specific if they were to be operated at greatest efficiency.

And, Army logistics efficiency was maximized when most engines ran on a limited range of fuels, and most Army non-combat vehicles were adapted from civilian vehicles that ran on gasoline.

So, a broad change of heavy land military equipment in the late 1930s to diesel would have had multiple effects on resource production, fuel manufacturing, and distribution.

But it could have been done. In the mid 1930s Caterpillar in the U.S. was the largest manufacturer of diesel engines (by total rated horsepower) in the world. Their lead diesel engine designer, Art Rosen, was excellent. They certainly understood heavy-offroad-vehicle applications, and how to build relatively powerful engines in large numbers. They could have been funded to build more factories, just as GM, Chrysler and Ford later were funded to build military-production factories. What was missing was only an Army visionary who could foresee, and convince his peers, that such a disruptive change to not-yet-powerful-and-small-enough diesel engines, not yet available in great enough numbers, requiring major changes to the motor fuels industry, in a few years would have benefits in combat vehicle survivability and performance that no one yet had ever considered.

 

[JWilly]

Note that Germany didn't have good options for broad dieselization. Romanian crude is no longer available on the world market, but my understanding is that it was medium-weight and high in sulfur...not good characteristics for diesel fuel, which if high in sulfur tends to form acids during combustion and progressively destroy the engine. And, coal-to-motor-fuel processes (Fisher, etc.) produce mostly aromatics. Diesel fuel must be about 75% aliphatics, 25% aromatics. Gasoline on the other hand can be much higher in aromatics, though only if contact with natural rubber is strictly avoided since aromatics rapidly degrade natural rubber.

Urals crude made excellent diesel fuel, and of course the Soviet Union was broadly dieselized. I think Iranian crude makes good diesel, too. But if Germany had tried to dieselize more broadly, they'd have been stopped even farther from the Urals and Persian oil fields.

 

[Elan Vital]

Note that Germany didn't have good options for broad dieselization. Romanian crude is no longer available on the world market, but my understanding is that it was medium-weight and high in sulfur...not good characteristics for diesel fuel, which if high in sulfur tends to form acids during combustion and progressively destroy the engine. And, coal-to-motor-fuel processes (Fisher, etc.) produce mostly aromatics. Diesel fuel must be about 75% aliphatics, 25% aromatics. Gasoline on the other hand can be much higher in aromatics, though only if contact with natural rubber is strictly avoided since aromatics rapidly degrade natural rubber.

Urals crude made excellent diesel fuel, and of course the Soviet Union was broadly dieselized. I think Iranian crude makes good diesel, too. But if Germany had tried to dieselize more broadly, they'd have been stopped even farther from the Urals and Persian oil fields.

If I recall they had substantial diesel reserves from the navy that the navy itself had barely tapped into in WW2. But are you sure they couldn't get more diesel than gasoline out of the Fischer process?

 

[JWilly]

Well, I'm an engineer by background, not an organic chemist. My chemistry knowledge is mostly basic. But my understanding is that historically the Fischer-Tropsch process as implemented in Germany during WWII, with the catalysts available to them, tended to produce a considerable overweight of aromatics and therefore to be much more suitable for production of gasoline than diesel.

Historically, we know that Fischer-Tropsch outputs made up about 9% of overall hydrocarbons used by Germany during WWII, but about 25% of its gasoline.

spelling correction: "German" --> "Germany"

 

[Pioneer]

Maybe, the U.S. Army pushes for diesel engines as a consequence of combat experiance during the Ardennes Offensive. The cold weather, causing deteimental engine starting and seizures issues for U.S. Army armoured and soft-skin vehicles alike.
On top of this is the wartime appreciation that diesel fuel is less combustible and offering better range and endurance, gives the U.S. Army the incentive to 'harden' it's existing armoured and soft-skin fleet under the economic restraints of Post-War budgets.
In doing so, the U.S. Army is able to sensibly utilise almost brand new war production vehicles, with their existing gasoline engines and fuel systems be replaced by that of diesel systems, in an effort to gain operational improvements, whilst appeasing Congress.
At this same time, the U.S. military, trying to rebuild Western Europe's defence against the perceived Soviet threat, sees such a transition from gasoline to diesel as a window of opportunity to form a standardisation of fuel when establishing the NATO military alliance.
This standardization to diesel within the NATO system also derives it's own little economic and education stimulus with the war ravaged post-WWII NATO counties.........

This initiative, although not without it's criticism from elements within both U.S., Britain and France's government's and militaries themselves, is quickly forgotten with the unforseen advent of the military crisis on the Korean Peninsula and the harsh and debilitating winters that would ensue......

Sorry, just a thought

Regards
Pioneer

 

[JWilly]

...the U.S. Army is able to sensibly utilise almost brand new war production vehicles, with their existing gasoline engines and fuel systems be replaced by that of diesel systems...

Direct replacement of heavy equipment gasoline engines with diesels in the 1940s period would have required consideration of transmission suitability as well...particularly in regard to tanks with manual transmissions.

Gasoline engines of that period for such applications...large displacement, low-revving, larger bore than stroke, relatively low compression ratio...typically had a useable RPM range of 2:1 or more and, if provided with a manual transmission, generally were matched to a transmission with say four or five forward ratios; and because such engines had moderate torque at low RPMs, clutch torque capability typically was not a problem.

By comparison, diesel engines of that period typically had narrower useful RPM ranges and therefore required more transmission ratios, and had much more torque at low RPMs so required clutches with a much greater torque capability. So probably redesign of such a tank to utilize a diesel engine also would have entailed replacement of the transmission.

Tanks with automatic transmissions faced different complications. Transmissions incorporating "torque convertors" generally have an upper limit to the torque they can transmit. Automatic transmissions designed for heavy-duty-diesel-engine applications often incorporate so-called lockup features to avoid torque-limit and slippage issues.

 

[Elan Vital]

...the U.S. Army is able to sensibly utilise almost brand new war production vehicles, with their existing gasoline engines and fuel systems be replaced by that of diesel systems...

Direct replacement of heavy equipment gasoline engines with diesels in the 1940s period would have required consideration of transmission suitability as well...particularly in regard to tanks with manual transmissions.

Gasoline engines of that period for such applications...large displacement, low-revving, larger bore than stroke, relatively low compression ratio...typically had a useable RPM range of 2:1 or more and, if provided with a manual transmission, generally were matched to a transmission with say four or five forward ratios; and because such engines had moderate torque at low RPMs, clutch torque capability typically was not a problem.

By comparison, diesel engines of that period typically had narrower useful RPM ranges and therefore required more transmission ratios, and had much more torque at low RPMs so required clutches with a much greater torque capability. So probably redesign of such a tank to utilize a diesel engine also would have entailed replacement of the transmission.

Tanks with automatic transmissions faced different complications. Transmissions incorporating "torque convertors" generally have an upper limit to the torque they can transmit. Automatic transmissions designed for heavy-duty-diesel-engine applications often incorporate so-called lockup features to avoid torque-limit and slippage issues.

That said, American cross-drive postwar transmissions were designed basically alongside the engines in development at the time and didn't require excessive mods to be mated to diesel engines. Sherman's transmission also appears to have worked well with very different engines. So there shouldn't be much of an issue on the US side if the decision had been taken in 1944-45.

Dunno if France wanted a different transmission for that, but AMX M4 initially was supposed to use a diesel engine and the 1945 plans noted the Army's preference for diesels and automatic transmissions so there was the lead time to develop a proper combination in time.

Even Sweden was recommended diesels in the 35L and 670hp category for their postwar tank project from 1946 when they invited a Czechoslovak engineer (who was working on the TVP project with high displacement X and H diesels). However they didn't want to design one themselves and no suitable engine was found on the export market. So if more countries had done high power diesels the Swedes would also take one. One could also argue that Czechoslovakia could have spread the technology around if its military programs hadn't been suddenly shut down in 1949 by the new communist government.

Arguably the want was there but a powerful and rich first customer was required.

 

[Nicknick]

Diesel engines have higher cylinder pressures and are therefore heavier than gasoline (“Otto”) engines. Because of that and because of the injection system which needs high precision components, Diesel engines are also more expansive. Shortly after the war, gasoline was still very common even as truck fuel (especially in the US), so that Diesel engines would have required a second fuel infrastructure. Fuel cost were not a big issue in the military and combat vehicles usually will never see high milage. With this boundary conditions, investing in Diesel engines didn’t make a lot of sense, especially for the Americans which of course were the most important player in the Nato.

With jets replacing the piston engine powered military planes, the NATO became very interested in Dieselization, there have even been research programs for Diesel powered motorcycles. The idea was, that in wartime Jet fuel could be used as universal fuel for all types of engines (generators, cars, planes, boats, tanks….).

Military Custom Kawasaki KLR650 Converted to Run on Diesel Fuel | DriveMag Riders

Smaller engine displacement, designed to use diesel fuel and army spec

riders.drivemag.com

 

[1635yankee]

Note that Germany didn't have good options for broad dieselization. Romanian crude is no longer available on the world market, but my understanding is that it was medium-weight and high in sulfur...not good characteristics for diesel fuel, which if high in sulfur tends to form acids during combustion and progressively destroy the engine. And, coal-to-motor-fuel processes (Fisher, etc.) produce mostly aromatics. Diesel fuel must be about 75% aliphatics, 25% aromatics. Gasoline on the other hand can be much higher in aromatics, though only if contact with natural rubber is strictly avoided since aromatics rapidly degrade natural rubber.

Urals crude made excellent diesel fuel, and of course the Soviet Union was broadly dieselized. I think Iranian crude makes good diesel, too. But if Germany had tried to dieselize more broadly, they'd have been stopped even farther from the Urals and Persian oil fields.

If I recall they had substantial diesel reserves from the navy that the navy itself had barely tapped into in WW2. But are you sure they couldn't get more diesel than gasoline out of the Fischer process?

Marine diesel fuel is quite a bit different in its physical properties from the sort of diesel one uses in an AFV diesels. To burn it in those tank diesels, one would need to add quite a bit of auxiliary machinery, like a system to heat the fuel. Marine diesel has about the consistency of roofing tar.

 

[Nik]

Been a while, but I remember being aghast at the weight and complexity difference between a 'white van' with comparable petrol and diesel engines.

The diesels were much, much heavier due to their higher pressures, auxiliary rotating whatsits etc etc. Plus the 'gotchas' such as up-graded starter motor, much bigger starter battery, the pre-heat etc etc. And, yes, different gearing due torque curves...

Of course, if you had a fleet of diesel trucks, you probably had the 'grok' for diesel-powered 'white vans', too...

Logistics, logistics, logistics: I'm reminded there were sundry other-wise worthy designs not fielded by Wallies due to complication of logistics. Also, how the French Resistance notoriously complicated German ammunition supplies by eg train workers switching crate labels between similar but incompatible types....

 

[1635yankee]

Been a while, but I remember being aghast at the weight and complexity difference between a 'white van' with comparable petrol and diesel engines.

The diesels were much, much heavier due to their higher pressures, auxiliary rotating whatsits etc etc. Plus the 'gotchas' such as up-graded starter motor, much bigger starter battery, the pre-heat etc etc. And, yes, different gearing due torque curves...

Of course, if you had a fleet of diesel trucks, you probably had the 'grok' for diesel-powered 'white vans', too...

Logistics, logistics, logistics: I'm reminded there were sundry other-wise worthy designs not fielded by Wallies due to complication of logistics. Also, how the French Resistance notoriously complicated German ammunition supplies by eg train workers switching crate labels between similar but incompatible types....

French workers had a number of clever ways of sabotaging stuff being produced for the Germans, such as deliberately mis-sizing rivet holes. This subtly causes failures in aircraft.

 

[Nicknick]

Marine diesel fuel is quite a bit different in its physical properties from the sort of diesel one uses in an AFV diesels. To burn it in those tank diesels, one would need to add quite a bit of auxiliary machinery, like a system to heat the fuel. Marine diesel has about the consistency of roofing tar.

No, marine oil (MDO) is much more like conventionel Dieseloil used in land vehicles. Marine oil is a special quality mainly for military ships and completely different than heavy fuel oil (HFO)