Best tank engines of WWII

PStickney said:

Yes - the T23 turret was basically a drop-in replacement for the original Sherman turret. It must be noted that even before the original Shermans were deployed to North Africa, fitting the 3" High Velocity Gun (The same as the M10 Tank destroyer) was already well under way. The problem was, that while they could wedge it in, Armored Force concluded that, while teh gun performance was fine, there was no way to effectively us it in that turret.

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The US M5 3" gun was similar in size and weight to the US 90mm or British 17 Pounder. the 76mm M1 was made to duplicate the 3" performance in a lighter weapon. The US trialed the 76mm in the original M4 turret, and found it too cramped.

But there was a way. Israel picked up Shermans after 1948 from a vareity of sources, and began upgrade programs, that was easy, given the modular construction.

leftover from the 1973 war, the M50. Note original image has been flipped, here is proper orientation


This was an early M4 direct vision hull, upgraded with the E8 suspension and Wright Radial replaced with a Cummins Diesel

The turret was an original 'low bustle' but had a loader hatch added, a counterweight welded to the backside to balance the new heavier main gun, the French GIAT CN-50 L/61 75mm, a gun built to match the German KwK42 in performance.

Much more powerful than the original M3 75mm gun, a box was welded to the original mount opening, allowing the gun to be moved forward outside of the turret ring, a heresy that the US Armored Force abhorred from the balancing issues it caused

This was an improvement on what the British had done for similar reasons with the Firefly's 17 Pounder

by welding a box at the rear for recoil travel and retaining the Radio Gear in the Turret, per British practice

marathag said:

This was an improvement on what the British had done for similar reasons with the Firefly's 17 Pounder
View attachment 762736
by welding a box at the rear for recoil travel and retaining the Radio Gear in the Turret, per British practice

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Your description of the layout of the Firefly is a bit misleading.

The recoil of the 17pdr was contained within the limits of the original turret ring. A hole was then cut in the rear of the turret and an armoured box fitted to contain the radio, the weight of which helped balance the turret. Some vehicles, as in the artwork above, then had a light metal storage box attached to the rear of the radio box. That storage box was a common feature of ordinary Shermans in Commonwealth service, attached to the rear of the turret bustle.

Because the larger 17pdr breech obstructed the loader's exit route via the commander's hatch, a new rectangular hatch was cut above his position on the left hand side of the turret roof, on those earlier production base vehicles that did not already have the oval loader's hatch in that location.

Photos of Firefly turrets here (none with the storage box):-

And with the storage box:-

WARSPITER said:

The Liberty engine is somewhat maligned but that is due mostly to the tanks it went in which were not exactly
state of the art.

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The British decision to use the Liberty as a standard tank engine was bizarre to say the least. It was made in 1936. At this point the Liberty was long obsolete, a very primitive engine by that date. The Kestrel had been in production since 1927 and was a well established design. It may have weighed slightly more than the Liberty but this was irrelevant in a tank. It was actually more compact, being similar in width and length but much lower. The height of the Liberty was as serious problem which required rearranging its accessories causing no end of problems. I fail to understand why Nuffield was allowed to put it into production at such a later date when far superior engines were available.

Reluctant Poster said:

The British decision to use the Liberty as a standard tank engine was bizarre to say the least. It was made in 1936. At this point the Liberty was long obsolete, a very primitive engine by that date. The Kestrel had been in production since 1927 and was a well established design. It may have weighed slightly more than the Liberty but this was irrelevant in a tank. It was actually more compact, being similar in width and length but much lower. The height of the Liberty was as serious problem which required rearranging its accessories causing no end of problems. I fail to understand why Nuffield was allowed to put it into production at such a later date when far superior engines were available.

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I recall reading somewhere that RR was fully occupied manufacturing aero engines and weren't interested in tank engines, nor in licensing the Kestrel for someone else to produce a tank engine version of. Eventually it took the war to give the government a strong enough hand to force the issue, and of course by that time it made sense to start from the Merlin rather than the Kestrel. And even then there was some kind deal, IIRC in return for handing the Meteor over to Rover, RR took over Rover's turbine R&D project?

But apart from such organizational issues it does indeed seem that the Kestrel could have made a perfectly good WWII tank engine for the UK.

The US M4 Sherman was equipped with engines who's design dated back several years.
The R-975 radial was first developed in 1929 and the D-200 diesel radial (based on the R-1820 of 1931).

In 1939 Rolls Royce stopped making cars to concentrate on aircraft engines. The car division were then at a loose end
so they were put to work on a tank engine to replace or at least compete with the Liberty.

The Kestrel was the first engine considered as it had 525hp compared to the Liberty with 340hp. The new specification
for a thirty ton tank came with a requirement for a 600hp engine to maintain 20hp per ton. The Kestrel was then bypassed
in favour of what became the Meteor.

Leyland got involved and then decided to drop the Meteor as they thought it would not be able to be cooled properly. They
went back to the Liberty for the Centaur tank. Lord Beaverbrook stepped in as he believed the Meteor to be worthy of mass
production.

Enter the Birmingham Railway Carriage and Wagon Company with experience in aspects of tank manufacture. Roy Robotham
who had done the initial work on the Meteor met with the Birmingham company and it was the start of what would become the
Cromwell tank. This meeting took place near the end of 1941.

Rolls Royce had been given one million pounds to produce the meteor engine but this became very difficult to achieve due to the
need for the Merlin. Rover was having difficulty with the Whittle jet engine so there was a trade. Rolls took over the jet development
and Rover started manufacture of the Meteor.

WARSPITER said:

That was an unfortunate case in many countries. In Britain the cavalry still held sway in the thirties even after exercises
involving tanks clearly showed the ascendancy of the vehicle over the horse. British armour suffered for this in the war.

The US situation was not as drastic as what happened in Britain, thankfully.

Germany was able to grab a lead in tank and aircraft use as they were rebuilding from scratch.

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Actually the US hung on to its horses much longer than the British.



The British Army was the first to start replacing the horse in cavalry units and by the start of WWII the only cavalry units left were overseas.

EwenS said:

I would hardly say that the Ford GAA engined M4 became the "standard petrol engine" version.

After Ford's production run in 1942/43, production elsewhere restarted in Feb 1944 and ran to June 1945 with just over 10,000 built, of which some 3,000 were the support tank 105mm gunned version.

Meanwhile Wright radial engined M4/M4A1 production rolled through to July 1945, with over 5,000 of tge later versions built 1944/45 (1,600 105mm gunned versions) most of which were for the US Army. Diesel engined M4A2 production mostly for the USSR rolled through from Nov 1943 to May 1945 with over 3,900 built of the later 47 degree hulled versions.

Right through to the end of WW2, US Army units were using a mix of M4/M4A1/M4A3 often in the same units. Only Post war was the US Army able to standardise on the M4A3 powered by the Ford engine.

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The Ford GAA was determined to be the preferred engine as long ago as April 1942.

GrauGeist said:

The R-975 radial was first developed in 19

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True, but it was rated at 300hp at 2000rpm in 1929-30. They had done a lot of work to get it to be a 400hp engine at 2400rpm in the Sherman. The Aircraft R-975s were rated at up to 450hp at 2250rpm in 1940-41, but that was with 91 octane fuel.

WARSPITER said:

The new specification
for a thirty ton tank came with a requirement for a 600hp engine to maintain 20hp per ton.

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The British were looking forward, unfortunately a bit too forward as the suspension/track parts could not deal with 40mph speeds and most of the Cromwell's were re-geared to limit them to about 32mph to reduce breakdowns and injury to the crews.

British had a very good basis for future tanks in the A-13 Cruiser IV and then threw it away with the Covenanter, not just the engine.
The whole turret was an abomination in the eyes of the tank gods.
And the tank gods did smite the British and continue to smite them until they recanted their ways and built the A-34 Comet.

Reluctant Poster said:

At this point the Liberty was long obsolete, a very primitive engine by that date.

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Liberty was obsolete in the early 1920s.
It was a good effort at putting out a 400HP aircraft engine in 1917 when designed quickly in Five Days by Hall-Scott and Packard, but many were made, far more that what the combat aircraft of the day needed, and with the sudden end of the Great War, warehouses were filled with the 20,000+ engines made by Buick , Cadillac, Ford, Lincoln, Marmon and Packard in great hurry and cost..
NOS engines, still in the original shipping crates, were being sold for scrap metal price in the late '20s.

The reason I believe Nuffield went with these over the equally cheap(almost as old, but more advanced than the Liberty and even more compact than the Kestrel) Napier Lion, was that the Liberty could run on lower octane Army 'Pool' Gasoline since the originals used Automotive Delco points distributors rather than Magnetos-- that couldn't be easily changed for the spark timing and advance curves to run on poor fuel, unlike the Delco equipped Liberty.

That and the original engines were almost free, shipping them across the Atlantics was a far greater cost.

The idiocy really comes in, rather than using them as a stopgap, new tooling for a production run of the Liberty was restarted, with a continual set of revisions trying to adjust the engine to making reliable 340HP in a Tank, but never really was able to overcome the inherent torsional vibration of the 45degree V-12. The last user of the Liberty in US Service, the Navy found that they were 75 hour TBO engines.

Rather than build literally any other engine, Lions or Kestrels, whatever else, that would have been an improvement on the Liberty

Reluctant Poster said:

The British decision to use the Liberty as a standard tank engine was bizarre to say the least. It was made in 1936. At this point the Liberty was long obsolete, a very primitive engine by that date. The Kestrel had been in production since 1927 and was a well established design.

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Quite right. Who in their right mind in 1936 would buy a reproduction of a 1917 car over a 1927 car let alone a 1934-36 car.
And a 1917 car with very well known problems.
But that is what the British did. Ignored almost 20 years of progress in internal combustion engines out of the 40 (ish) year history.

Shortround6 said:

Quite right. Who in their right mind in 1936 would buy a reproduction of a 1917 car over a 1927 car let alone a 1934-36 car.
And a 1917 car with very well known problems.
But that is what the British did. Ignored almost 20 years of progress in internal combustion engines out of the 40 (ish) year history.

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The first British Cruiser Tank to use the Liberty engine was the Mk.III. Its origins lay in the US T3 Medium tank with its Christie suspension & Liberty engine.


So maybe we should blame the USA for using such an out of date engine. Note the similarities between that and the A13 in the wheel layout (see below).



Nuffield acquired one such vehicle in 1936 and the patent to allow it to develop it for the War Office. In doing so they improved the Christie suspension, took the turret from the Vickers designed A9 and kept the Liberty engine to produce the A13. Only the early Liberty engines were imported from the USA and they were modified by Nuffield with new carburettor systems. As that was before Lend Lease they would have had to have been paid for in full (whatever pricebthat was). Nuffield also acquired a licence to manufacture the Liberty engines used in its tanks at least from the Crusader onwards. That involved a redesign to reduce its height by relocating certain ancilleries and then changing the cooling system as well as a power increase.

(The preceding Cruiser Mk.I & II tanks, the A9 & A10 designed by Vickers used a 150hp AEC petrol engine and weighed 13 & 14 tons respectively.)

The A13 Cruiser Mk.III weighed only 14 tons. 65 built in 1939. Then the weight grew. A13 Mk.II/IIA Cruiser IV/IVA 14.75 tons. 272 built late 1939 to early 1941.

A13 Mk.III Cruiser Mk.V Covenanter 18 tons broke the mould, keeping the Christie suspension but using a 340bhp Meadows DAV flat 12 engine. Hull designed by LMS (a company with no previous tank design experience) & turret by Nuffield. Nuffield own designs had been rejected and cost played a part. It proved completely inadequate for a whole variety of reasons and was used only for training in the UK. 1,771 produced from 1940 to mid-1942.

Nuffield didn't want to build Covenanter so developed the A15 Cruiser Mk.VI Crusader, continuing to use the Liberty engine. Weight now 19 tons. 5,300 produced late 1940 to 1943.

Then the designations and development get complicated with the "Cromwell" tank. 3 versions all of which look outwardly similar but in reality weren't internally.

Cromwell I - A24 Cruiser Mk.VII later renamed Cavalier powered by a 410hp Liberty development. 27 tons. Built by Nuffield who didn't want to use the Meteor. 500 produced in 1942. Training use only.
Cromwell II - A27L Cruiser Mk.VIII later renamed Centaur powered by Liberty engine.
Cromwell III - A27M Cruiser Mk.VIII later renamed Cromwell with the Meteor engine.

The Tank Board worked with Leyland from Oct 1940 to look at installing what became the Meteor engine in a tank (a Crusader hull being used initially for engine trials). BRC&W were brought in alongside Leyland due to a lack of design capacity at Leyland. In 1941 Leyland began to have doubts about cooling the Meteor and the fall back was an improved Liberty engine. So in 1941 there was a reorganisation.

A27L with a developed Liberty engine under Leyland design leadership effectively as a fall back in case Meteor didn't work out.
A27M with Meteor under BRC&W design leadership. Sorting the cooling took some time.

It was early 1944 before a "Final Specification" Cromwell IV (nothing to do with the I/II/III designations noted above) was ready with sorted engine cooling, suspension, gearbox & 75mm gun. They were issued to 7th Armoured Div and the armoured Recce regiments in the Guards, 11th & Polish armoured divisions ahead of D-Day. Some Centaurs did make it into service in NWE in 1944/45 mostly in secondary roles.

The twists and turns with the development of the Centaur / Cromwell line are well set out in the Wiki article which draws on the best of sources. Be warned! It is not an easy story to follow!

Edit:- note the British Infantry tanks (Matilda, Valentine & Churchill) used a variety of other petrol & diesel engines and not the Liberty.

EwenS said:

So maybe we should blame the USA for using such an out of date engine. Note the similarities between that and the A13 in the wheel layout (see below).

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We may have to separate the USA from Christie. Christie wanted as much power as he could get for the 60-70mph road speed running on the wheels. Christie was an inventor without a large factory and working with limited funds. He had to take what he could get (cheaply) for an engine, perhaps not what he wanted.

I can even forgive the several hundred A-13s built with the Liberty engine. The British were in a hurry. It is the Covenanter that deserves the scorn, contempt and curses.


swapped the Liberty for one of the worst engines (certainly the worst ever built in such large numbers) put in a tank.
Building a bespoke flat 12 16 liter engine when they had the Kestrel (21 liters) sitting on the shelf takes a bit of explaining.
Then they took the infant 3 man turret and beat it into a misshaped lump with worse outward vision, worse ergonomics, worse turret hatch arrangement and limited the potential for a larger turret ring and set British tank development back 3-4 years.

marathag said:

Liberty was obsolete in the early 1920s.
It was a good effort at putting out a 400HP aircraft engine in 1917 when designed quickly in Five Days by Hall-Scott and Packard, but many were made, far more that what the combat aircraft of the day needed, and with the sudden end of the Great War, warehouses were filled with the 20,000+ engines made by Buick , Cadillac, Ford, Lincoln, Marmon and Packard in great hurry and cost..
NOS engines, still in the original shipping crates, were being sold for scrap metal price in the late '20s.

The reason I believe Nuffield went with these over the equally cheap(almost as old, but more advanced than the Liberty and even more compact than the Kestrel) Napier Lion, was that the Liberty could run on lower octane Army 'Pool' Gasoline since the originals used Automotive Delco points distributors rather than Magnetos-- that couldn't be easily changed for the spark timing and advance curves to run on poor fuel, unlike the Delco equipped Liberty.

That and the original engines were almost free, shipping them across the Atlantics was a far greater cost.

The idiocy really comes in, rather than using them as a stopgap, new tooling for a production run of the Liberty was restarted, with a continual set of revisions trying to adjust the engine to making reliable 340HP in a Tank, but never really was able to overcome the inherent torsional vibration of the 45degree V-12. The last user of the Liberty in US Service, the Navy found that they were 75 hour TBO engines.

Rather than build literally any other engine, Lions or Kestrels, whatever else, that would have been an improvement on the Liberty

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I wonder if the W configuration of the Lion posed installation problems? Also I am curious as to what happened the the Armstrong Siddeley air cooled V-8 and V-12s. I have not been able to find out much about them. Considering the success of the Tatra and Continental air cooled V-12s this line of development could have been a success.

The Kestrel was out of production before the end of 1939. Possibly in favour of the Merlin.

Fortunately the Covenanter was a seperate project to other designs which resulted in the Churchill and Cromwell.

The British military refused to consider combat use as the Covenanter had too many design faults to be reliable
in battle conditions. Germany did not have the luxury of developing competing designs for next generation tanks
so eventually the Panther appeared with it's many design faults and unreliability issues.

Reluctant Poster said:

I wonder if the W configuration of the Lion posed installation problems? Also I am curious as to what happened the the Armstrong Siddeley air cooled V-8 and V-12s. I have not been able to find out much about them. Considering the success of the Tatra and Continental air cooled V-12s this line of development could have been a success.

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Napier still had the Se Lion in production for light Naval boats.

Liberty
Displacement: 1,649.3 in³ (27.03 L)
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)
CR 5.4:1 Army 5.1:Navy
In its Crusader habitat

Lion
Displacement: 1,461.6 in³ (23.9 L)
Length: 57.5 in (1460 mm)
Width: 42.0 in (1067 mm)
Height: 43.5 in (1105 mm)
Dry weight: 960 lb (435 kg)

heavier( not excessively so) very Wide(Meteor was 31" or so and Ford GAA 33"), otherwise shorter. Still not an issue, considering that the Crusader had a 55" Turret ring race
Similar for the Meteor here in the Cromwell


Fuel tanks would need to be changed

Slightly more power than Liberty or Ford GAA, despite lower displacement.

Air cooled, high power engines had real issues in the interwar era, and Siddeley did not have much luck with any of their engine families., aircooled inlines as well.

Reluctant Poster said:

I wonder if the W configuration of the Lion posed installation problems?

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It's going to be wide, for sure, as mentioned. In general, I suspect you might have trouble with routing the manifolds such that you avoid one of the exhaust manifolds being just beside an intake manifold and thus heating the incoming air?

And then you probably need master-slave conrods, with associated issues with difference in stroke length etc.?

Bleh. Just make a V-12 and call it a day instead of inventing exotic layouts?

Also I am curious as to what happened the the Armstrong Siddeley air cooled V-8 and V-12s. I have not been able to find out much about them. Considering the success of the Tatra and Continental air cooled V-12s this line of development could have been a success.

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There are certainly damage tolerance and simplicity advantages that make those attractive, but they are also going to be large and heavy and a non trivial fraction of the power output goes to driving the cooling fans.

WARSPITER said:

The Kestrel was out of production before the end of 1939. Possibly in favour of the Merlin.

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Surely if the UK had decided to standardize on the Kestrel as their tank engine the production line would have kept going. Of course the Meteor project could just as well have gotten going a lot sooner had RR shown interest.

Wiki also mentions that the Peregrine, an improved Kestrel, was canceled in 1943. No idea when the last Peregrine rolled off the production line, could have been a lot earlier for all I know.

Lion had potential for bits and pieces. Use two banks of cylinders for a 16 liter V-8 of just over 300hp. Germans powered a lot of tanks with 12 liter V-12s.
The narrower V-8 gives more room for working on the engine, compared to the W-12, a rather neglected feature in many early tanks.
Remember that the Ford GAA engine was 18 liters. A Napier V-8 has potential.

The Peregrine was a beefed up Kestrel.
Main problem was getting RR to license the engine. Due to the complete and utter mess (trying to be polite) that the British made of licensed aero engines in the first world war, somebody at RR had said they would rather go to jail than license a RR engine. He had a point, the amount of money and labor and machine time that was flushed down the crapper and number of pilots/crew killed by woefully substandard engines (and in WW I that is saying something) is astonishing. He considered it his patriotic duty to resist any such schemes.
The thing with the Kestrel/Peregrine is you have the plans for a perfectly good V-12 (well over 4000 made) and you have a very good idea of what you are going to get running without supercharger and using different compression ratios/different grades of gas. Most of the development work is already done. The problem is productionizing it (seeing what you can make cheaper/faster) for tank use without jeopardizing reliability. If it gains weight who cares, you are shoving it in a 20-30 ton tank, not a 2-3 ton airplane.

Merlin can be kept on the back burner for when tanks get heavier (Comet went 39 short tons).

Kestrel would do for any cruiser tank until the Cromwell at least.

The 'TankLion' should do the job just as well or better - it was an unusually reliable engine by the late-1930s having reached near AS Cheetah leval TBOs.

The SeaLion was used for several land speed records in the 1930s, so I think it would do the job of tank engine (I am pretty sure it would fit OK in any tank that was designed to use it). The basic cube of the 450/500 BHP Lion was 50"L x 42"W x 36"H without reduction gearing, propeller shaft-shaft housing, or exhaust manifolds. The actual cube of the engine as installed in a tank would depend on where you mounted the accessories and such. In tests at McCook Field the Lion II of the early-1920s managed the 450 BHP output at 1900 rpm using ~65 octane with a CR of 5.53:1. By the early-1930s they were getting 500 BHP at 2200 rpm with the same fuel and CR. The Merlin in its early Meteor incarnation used a CR of 5.5:1 and 2500 rpm using WWII 'pool' petrol so I do not think there would be a detonation problem with a properly designed 'TankLion' using 'pool' petrol.