Best tank engines of WWII

[z42]

We've had several recent threads about aviation engines spin off into discussions about tank engines. Which isn't entirely off topic, as many WWII tank engines were adapted from aviation engines, but still.

Some references to previous discussions (I tried to find the initial message in each thread, further follow-up messages I haven't copied separately):

• Best piston engine(s) for fighters of 1945?
• Radial engines more favored in Germany, 1935-45?
• Other liquid cooled aero engines with tank potential?
• Radial engines more favored in Germany, 1935-45?

About diesel power. Diesel has several advantages, like

• About 30% lower fuel consumption. Mean longer range, and 30% less fuel logistics volume.
• Much less flammable than gasoline. Though catastrophic fires in tanks where crewmen were incinerated were usually due to the ammo cooking off. For a fuel fire, even a petrol one, there was usually time for the crewmen to get out of the tank.
• Easier and cheaper to refine than gasoline.

Of course there were disadvantages to diesel as well:

• Heavier and more expensive engines.
• Need to supply two different fuels. Converting the entire army to diesel is the solution to this, this was done post-WWII, but in the WWII the vast majority of trucks, jeeps etc. were definitely petrol powered. A diesel powered army in WWII is an unrealistic fantasy.

Some famous(?) WWII tank diesels were the Kharkiv V-2, which powered most Russian tanks, and the Detroit Diesel twin 6-71 which powered some Sherman variants. The British also had some diesel powered tanks early in the war, though it seems they gave up on that.

Germany was working on diesel engines for tanks, but they didn't get anything out the door before the war ended: How the Wehrmacht's Diesel Stalled and SGP Sla 16 (Porsche Type 203) X-16 Tank Engine

So, which was 'the best' WWII tank engine?

• Meteor, based on the RR Merlin?
• The above-mentioned Kharkiv V-2 diesel?
• The Ford GAA V-8 used in the Sherman?
• Something else?

And for a what-if question, what should various nations have done instead of what the historically did? E.g. in some of the above threads there is the suggestion that the UK should have gone with an adaptation of the RR Kestrel, which would have saved them from their rather sorry state of affairs wrt tank engines all the way until the Meteor eventually entered service?

 

[bf109xxl]

About diesel power. Diesel has several advantages, like

• Much less flammable than gasoline. Though catastrophic fires in tanks where crewmen were incinerated were usually due to the ammo cooking off. For a fuel fire, even a petrol one, there was usually time for the crewmen to get out of the tank.

Theoretically - yes. Practically it depends on the tank design and manufacturing quality. According to the results of the Battle of Kursk, the T-34 was not better (or even worse) than the T-70 in terms of fire safety. Apparently, the main reason was the presence of insufficiently sealed fuel tanks in the crew compartment and the poor fabrication of the fuel lines.

 

[bf109xxl]

About diesel power. Diesel has several advantages, like

• The above-mentioned Kharkiv V-2 diesel?

Why only V-2? Why not V-4 (a half-V-2 for T-50 manufactured in Leningrad) as well?

 

[tomo pauk]

Why only V-2? Why not V-4 (a half-V-2 for T-50 manufactured in Leningrad) as well?

Has anyone forbidden you making the suggestions?

 

[SaparotRob]

Hey B bf109xxl , the same suggestion was made about me too.

 

[marathag]

And for a what-if question, what should various nations have done instead of what the historically did? E.g. in some of the above threads there is the suggestion that the UK should have gone with an adaptation of the RR Kestrel,

Had the UK decided on higher than Pool Petrol octane for AFVs, they could have used the Lion, that while barely newer than the Liberty, was a more advanced, more compact design, and in product as the SeaLion thru 1939 compared to the Liberty, that Lord Nuffield had financial interest in.
They didn't want to spend money for a detuned Lion to run on the near kerosene that was Pool Petrol, while the Liberty could run on it without much change. Despite plentiful engines in RAF stock being able to acquired at surplus over to the Army

Crystal Ball would have showed that the Liberty would need redesigning twice, and never got decent reliability(see Centaur), and the USA would be shipping only 80 octane gasoline to the UK.

the Books _Rude Mechanicals_ _Death by Design_ _The Business of Tanks_ and _Great Tank Scandal_ makes for sad reading on the UK AFV effort.

Biggest downside on the Kestrel, was Roll Royce was spread too thin, and seems they weren't that willing to license designs out before the War.

 

[marathag]

Theoretically - yes. Practically it depends on the tank design and manufacturing quality. According to the results of the Battle of Kursk, the T-34 was not better (or even worse) than the T-70 in terms of fire safety. Apparently, the main reason was the presence of insufficiently sealed fuel tanks in the crew compartment and the poor fabrication of the fuel lines.

model kit, but shows the T-60 interior pretty well.

Firewall, Bah.
That's for weak, running dog capitalists, not stronk followers of STALIN

 

[z42]

Had the UK decided on higher than Pool Petrol octane for AFVs

I found this POOL PETROL (STANDARD) (Hansard, 13 November 1950) from 1950 where the UK house of commons rejected increasing the octane of road fuel to 80 octane, as increased TEL content would have caused problems for engines, and also it would have resulted in a reduction of volume. I would suspect the same argument would have held before or during the war; increased volume was considered more valuable than higher octane.

It mentions that before the war there were three grades of gasoline, 68, 75, and 80 octane ("very few vehicles used 80 octane"). I'm not certain, but I believe the "pool petrol" that was the mainstay of WWII auto petrol was the 68 octane variety.

I guess increased octane only became viable once refineries started adding some of the modern gasoline production reactors such as isomerization, alkylation, catalytic cracking etc.

they could have used the Lion, that while barely newer than the Liberty, was a more advanced, more compact design, and in product as the SeaLion thru 1939 compared to the Liberty, that Lord Nuffield had financial interest in.
They didn't want to spend money for a detuned Lion to run on the near kerosene that was Pool Petrol, while the Liberty could run on it without much change. Despite plentiful engines in RAF stock being able to acquired at surplus over to the Army

Crystal Ball would have showed that the Liberty would need redesigning twice, and never got decent reliability(see Centaur), and the USA would be shipping only 80 octane gasoline to the UK.

the Books _Rude Mechanicals_ _Death by Design_ _The Business of Tanks_ and _Great Tank Scandal_ makes for sad reading on the UK AFV effort.

Biggest downside on the Kestrel, was Roll Royce was spread too thin, and seems they weren't that willing to license designs out before the War.

How much power would a Lion detuned to run on pool petrol make?

As for RR being spread too thin and not willing to license anyone else to manufacture before the war forced them, yes definitely a problem. And IMHO, once the war started going with the Merlin derived Meteor was the right choice. One could quibble they could have started the project earlier (wikipedia mentions the Meteor project was only started in 1941).

 

[ThomasP]

The original early models of the T-34 had 2x fuel tanks (out of either 4 or 6 tanks total) in the crew compartment - this may have contributed to the vulnerability/fire problem. In the later models the 2x crew compartment fuel tanks were either moved to the engine compartment, or removed from the tank entirely.

One problem with diesel fuel, at least in colder climates, is that it can be problematic as far as starting and fuel 'gelling' - ie the fuel becomes too thick to flow well enough to reach the engine reliably. The Soviet Army figured out ways of dealing with the gelling problem - in the T-34 it was primarily through cutting the fuel in the engine feed tank (under normal circumstances the engine was always fed from the RH forward engine compartment tank) with a mixture of petrol and diesel, and/or running the engine periodically to keep the engine compartment fuel tanks warm. (The previous is from my translation from an original T-34 manual, so if I am off a bit on the details I apologize).

The British/Commonwealth used diesel engines in the Valentine tank (except some of the early-production) until the end of production. I think they also received most of the diesel powered M3A3 Lee/Grant and M4A2 Sherman tanks. As far as I have read they did not seem to have any particular problems with them in Europe. If anyone has any information about diesel engine related problems in the ETO I would be interested.

The USMC also used some diesel powered M4A2 Sherman tanks (I am not sure what models of the M3 Lee), as they did not have the problem of access to diesel fuel that the Army had (many of the landing craft and ship's boats used diesel engines) or gelling in the warm climates they fought in.

The Soviets received the lion's share of the Canadian made diesel powered Valentines and - aside from the small gun - quite liked them. I am not sure what models of the M3 Lee the Soviets received, but I know the diesel powered M4A2 was the majority of the Shermans they received.

Incidentally, the gelling problem is still a problem today, though not as much as in WWII for military applications (primarily due to having learned from past experience, but also helped by modern additives).

 

[bf109xxl]

The original early models of the T-34 had 2x fuel tanks (out of either 4 or 6 tanks total) in the crew compartment - this may have contributed to the vulnerability/fire problem. In the later models the 2x crew compartment fuel tanks were either moved to the engine compartment, or removed from the tank entirely.

AFAIK, it was not made during the war, and even post-war T-34-85 had the same design of the fuel system. The problem of fire safety has been thoroughly studied experimentally using different types of anti-tank projectiles, unfortunately nothing was made to improve the situation. The Soviets stated already in 1942 (in an official report) that there was no difference between the Soviet and German tanks by fire safety.

The Soviets received the lion's share of the Canadian made diesel powered Valentines and - aside from the small gun - quite liked them.

Moreover, after the war, the Valentine was recognized as the best tank in the Soviet army for peacetime employment.

 

[z42]

Incidentally, the gelling problem is still a problem today, though not as much as in WWII for military applications (primarily due to having learned from past experience, but also helped by modern additives).

Most cold places switch the diesel pumps at the gas stations to "winter diesel" when it gets cold. Winter diesel has a slightly different distillation profile which lowers the gelling point. If winter diesel isn't available it used to be common to blend in kerosene or petrol into summer diesel in order to make "DIY" winter diesel. I'm not sure if modern diesels with electronically controlled high pressure injection systems are pickier and this trick no longer works.

 

[ThomasP]

Hey bf109xxl,

re "AFAIK, it was not made during the war, an even post-war T-34-85 had the same design of the fuel system."

I do not understand quite what you mean. Can you explain which part is incorrect?

My understanding is that the total internal fuel load for was 460 L for the majority of the T-34-76 production, but that the early production had 2x of the fuel tanks in the crew compartment which were later moved to the engine compartment.

My understanding is that later production - ie T-34-85 - had 556 L with 8x fuel tanks total, 2x in the crew compartment and 6 in the engine compartment.

 

[bf109xxl]

My understanding is that the total internal fuel load for was 460 L for the majority of the T-34-76 production, but that the early production had 2x of the fuel tanks in the crew compartment which were later moved to the engine compartment.

No fuel tanks were moved or removed from the crew compartment.

My understanding is that later production - ie T-34-85 - had 556 L with 8x fuel tanks total, 2x in the crew compartment and 4 in the engine compartment.

The fuel system of the T-34-85 was identical to that of the T-34-76 according to the manual of 1944 for both models.

 

[ThomasP]

Interesting, thank you for posting the above image.

This is the image I have for the T-34-76 from a Soviet publication "Альбом фотографий и характеристика танка Т-34" that translates as 'Album of photographs and characteristics of the T-34 tank" dated 1940, plus the Soviet publication "Руководство по эксплуатации танка Т-34" that translates as 'Operating manual for the T-34 tank' dated 1942 had the same image.

As I said above though, I may have something wrong in the translation.

I am wondering if they were counting 2 of the tanks as one, or vice-versa. So instead of 4 tanks with 460 L total, maybe it was 6 tanks with 460 L total. And 556 L or 610 L with 8 tanks?

Does the 1944 manual list the total volume of internal fuel?

 

[bf109xxl]

This is the image I have for the T-34-76 from a Soviet publication "Альбом фотографий и характеристика танка Т-34" that translates as 'Album of photographs and characteristics of the T-34 tank" dated 1940, plus the Soviet publication "Руководство по эксплуатации танка Т-34" that translates as 'Operating manual for the T-34 tank' dated 1942 had the same image.

Absolutely the same image in the manual from 1949.

Does the 1944 manual list the total volume of internal fuel?

Yes, it does. The total volume of internal fuel tanks is 570...580 l

The 1949 manual specifies a somewhat smaller volume of internal fuel tanks:

Drawings of fuel tanks in the crew compartment from the same source:

 

[ThomasP]

Interesting again

re "Absolutely the same image in the manual from 1949."

Which image are you referring to? The Image from the 1940/42 manuals only have 4x fuel tanks total, while the image from the 1944 manual has 6x fuel tanks.

also

The fuel tanks from the 1949 manual (image Phc.77) are a different shape than the ones from the 1940/42/44 manuals.

 

[bf109xxl]

Interesting again

re "Absolutely the same image in the manual from 1949."

Ok, "the same number of fuel tanks in the crew compartment" is more correct. The difference is the additional tanks in the engine compartment.

Which image are you referring to? The Image from the 1940/42 manuals only have 4x fuel tanks total, while the image from the 1944 manual has 6x fuel tanks.

The latter one. The number of fuel tanks in the crew compartment remained the same until the end of production.

The fuel tanks from the 1949 manual (image Phc.77) are a different shape than the ones from the 1940/42/44 manuals.

Minor technological differences.

 

[ThomasP]

Thank you

 

[WARSPITER]

Aside from the fuel system, was the engine the best of the war though ?

 

[marathag]

I found this POOL PETROL (STANDARD) (Hansard, 13 November 1950) from 1950 where the UK house of commons rejected increasing the octane of road fuel to 80 octane, as increased TEL content would have caused problems for engines, and also it would have resulted in a reduction of volume. I would suspect the same argument would have held before or during the war; increased volume was considered more valuable than higher octane.

It mentions that before the war there were three grades of gasoline, 68, 75, and 80 octane ("very few vehicles used 80 octane"). I'm not certain, but I believe the "pool petrol" that was the mainstay of WWII auto petrol was the 68 octane variety.

I guess increased octane only became viable once refineries started adding some of the modern gasoline production reactors such as isomerization, alkylation, catalytic cracking etc.



How much power would a Lion detuned to run on pool petrol make?

As for RR being spread too thin and not willing to license anyone else to manufacture before the war forced them, yes definitely a problem. And IMHO, once the war started going with the Merlin derived Meteor was the right choice. One could quibble they could have started the project earlier (wikipedia mentions the Meteor project was only started in 1941).

"Mechanised Force" by Fletcher page 125
In 1937 Lt. General Martel had located a surplus stock of such engines belonging to the RAF: the 12 cylinder Napier Lion type X1A which had its cylinders arranged in three banks of four. Tests by MEE indicated an output of 465 bhp at 2,500 RPM, although it would not run well on service type Grade III petrol (65 Octane gasoline) without modification; in any case it was turned down by the Army as a possible waste of money.

Liberty(400hp)
Displacement: 1,649.3 in³ (27.03 L)
Compression Ratio 5.4:1
Length: 67.375 in (1,711 mm)
Width: 27 in (685.80 mm)
Height: 41.5 in (1,054.10 mm)
Dry weight: 845 lb (383.3 kg)
Lion(450hp)
Displacement: 1,461.6 in³ (23.9 L)
Compression Ratio 5.5:1
Length: 57.5 in (1460 mm)
Width: 42.0 in (1067 mm)
Height: 43.5 in (1105 mm)
Dry weight: 960 lb (435 kg)

To me, cheapest 'fix' is use thicker head gaskets on the Lion to lower compression to 5.1:1 or so, and should still get 400ish HP, which is better than the later detuned Liberty at 350HP

Doing 1910-20s style distillation, You get from 10-25% Gasoline per barrel of Crude, depending on how sweet or sour the base Oil is. Octane rating typically under 60.

Thermal cracking (Dubbs Process) became widespread in 1931 after patent disputes were settled and shared between US Oil Companies. Earlier Thermal cracking methods were expensive and dangerous, but gave 70 Octane

Dubbs Process gave about 40% Gasoline per unit, even with sour grades, but Octane ratings were in the 70-80 range.

Economical catalytic cracking by the Houdry Process started in 1938 in the USA with Sun Oil Company , giving about twice the gasoline output than the earlier thermal cracking, improved by the new moving-bed catalyst process in 1943, replacing the batch process for refilling the reactor.

The catalytic cracking process was used to process around 100,000 barrels a day by 1940, and more each year, to 500,000 by Wars end

It gave up to 60% Gasoline per unit of Crude, at 10-15 Octane points higher, even with heavier Crude stocks.

72 octane is the highest grade of gasoline that can be manufactured without additives like TEL

80/87 has 0.14grams TEL [tetraethyl lead] per Liter

current 100LL is 0.56 grams, while Wartime 100/130 was 1.12 grams, that this level would effect engines not set for this amount of lead.

the amount of TEL in 80/87 really shouldn't have been much of an issue on unmodified engines