Sherman with Rover Meteor engine

[Foo Fighter]

Packard begin producing Merlin engines in 1940 as a preparation to supplying european nations. As a paper exercise they decide to fit the engine to an M4 type tank. Lower hull and more power earlier, what would the result be and could it be ready with a better armour and gun for D-Day?

 

[riggerrob]

May I suggest the Allison V-1710 engine instead? Its 12, liquid-cooled cylinders were arranged in two banks spread 60 degrees apart. With 28 liters of displacement producing 800 to 1200 horsepower it competed directly with the 27 liter Rolls-Royce Merlin that birthed the Meteor tank engine.

It was in large-scale production when the USA entered World War 2 and was reliable. V-1710 was widely used in American fighter planes: A-26 Apache dive bomber, P-38 Lightning, P-39 Airacobra, P-40 Warhawk, P-51A Mustang, etc. By mid-war, P-51A was the fastest WALLIED photo-recon airplane at low altitudes. Allison provided plenty of high-altitude performance when mated with exhaust-driven turbo-superchargers in P-38 Lightnings, but turbo-chargers proved too bulky for single-seat fighters ... limiting high-altitude performance.

V-1710 was even trialed in the T-29 Super Heavy Tank. T-29 was too late to serve in WW2, but at 141,000 pounds, it made Tiger II look dainty and delicate and petite. Mind you that weight would have broken most bridges in Europe! Hah! Hah!
In practice, aircraft V-12 engines proved a nightmare for tank crews when they wanted to replace spark plugs, etc.

Both V-12 engines would have provided lower drive shafts - way down on the hull floor - to match the lower silhouette of Hellcat tank destroyer.

 

[Apophenia]

Packard begin producing Merlin engines in 1940 ...

By 1940, the Americans already had a modern V-12 engine with exactly the same displacement as the Meteor but built to US standards - the Ford GAA. Putting more work into adapting that V-1650 engine for tank use would seem like a simpler solution.

The beauty of the Meteor was that is made use of components that failed to make the grade for use in high-performance aircraft engines. As Riggerrob suggested, you could so the same with the Allison V-1710 without changing the timeline.

Unlike combat aircraft, tanks didn't need supercharging or especially high-compression. I suppose, that is why the otherwise-obsolete Liberty V-12 was built by Nuffields for tanks. Prior to choosing the Meteor, a tank engine based on the Kestrel was also considered. So, why not use older engines which already fit the bill?

If your object is a relatively modern US-built V-12 in the Sherman by 1940, what about the Curtiss V-1570 Conqueror? That engine had become an industrial 'orphan' after the Curtiss-Wright merger. For a what-if scenario, have the Conqueror tooling moved to one of the US auto-makers prior to WW2. No need to change the aero-engine timeline.

 

[Foo Fighter]

Thanks folks, lateral and diverse. I must learn to be less limiting in this respect. Sounds very good and I wonder why these paths were those not taken.

 

[Elan Vital]

Producing the Meteor in the US might have been valuable...for the British, since it would increase the supply for Cruiser tanks while remaining compatible with British-produced engines.

One limitation for Sherman is that the transmission is only good for 550hp. Accounting for losses to accessories and cooling, this means that any engine beyond 650-700 hp will not be useable in this tank. Both the GAC and V-1710 could probably be downrated to that setting however. For the M6 Heavy tank and T2X series though, either of these engines would have been fine at a higher power setting.

The Curtiss D-12 was actually used in the T3E2 Christie tank, so the V-1570 might be suitable although it was not used anywhere near as long as the R-975 so didn't have the advantage of still being in service. The 1800 cu successor designed in the 30s could also have worked, and both were very narrow engines which might be interesting if you want to fit accessories or fuel tanks on either side of the engine.

Radials were selected because they were air-cooled and somewhat light for the power they had, but the Army missed their inherent problems with width and height, the driveshaft, the torque and the oil and fuel consumption. V-1570 probably would have been better in the long run.

 

[Elan Vital]

Packard begin producing Merlin engines in 1940 as a preparation to supplying european nations. As a paper exercise they decide to fit the engine to an M4 type tank. Lower hull and more power earlier, what would the result be and could it be ready with a better armour and gun for D-Day?

After a conversation with British historian Ed Francis who just got a lot of archives, it turns out that Packard DID want to produce Meteors.
Ford also deliberately tried to sabotage British Meteor production by asking that machining parts for this engine be made low priority.

 

[riggerrob]

During World War 2, tank designers struggled to solve a variety of technical and tactical problems.
It was only after they solved problems with cross-country performance and reliability that they started to worry about how profile affected survivability. Soviets were early adopters of Christie's sloped armor, but it was 1943 before Germans introduced a sloped glacis plate on their Panzer 5 "Panther". American tank destroyers paid lip service to sloped armor, but since most of their designs were based around the tall Sherman hull, they made little progress until the "clean-sheet" M18 Hellcat tank destroyer with a completely new hull wrapped around a modified (radial-engined) Sherman drive train.
British tank designers only introduced a sloped glacis in the final months of the war: Centurion.

 

[Foo Fighter]

The Meteor in the Cromwell had an output of 550bhp so would be at the upper end of the transmission ability to manage but might have been possible.

 

[jstar]

During World War 2, tank designers struggled to solve a variety of technical and tactical problems.
It was only after they solved problems with cross-country performance and reliability that they started to worry about how profile affected survivability. Soviets were early adopters of Christie's sloped armor, but it was 1943 before Germans introduced a sloped glacis plate on their Panzer 5 "Panther". American tank destroyers paid lip service to sloped armor, but since most of their designs were based around the tall Sherman hull, they made little progress until the "clean-sheet" M10 Hellcat tank destroyer with a completely new hull wrapped around a modified (radial-engined) Sherman drive train.
British tank designers only introduced a sloped glacis in the final months of the war: Centurion.

Hellcat was M18. M10 had GM 6406 twin diesel engine.

 

[Elan Vital]

The Meteor in the Cromwell had an output of 550bhp so would be at the upper end of the transmission ability to manage but might have been possible.

What the transmission cares about is net hp at the transmission inlet. Any engine loses a couple dozen hp to cooling and other accessories, so you could even push to the 620hp of early Centurion with no issues. In practice you'd use the Cromwell version during the war.