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M5 Stuart Light Tank

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That is a sweet looking installation buddy!    Loving this!   Following along!



I am sure that Mike will answer your question better than me, but here goes.

Obviously a tank needs a light, powerful and reliable engine. I think most tanks designed before the war used engines designed for them, In most cases the tank was under powered and not too reliable. The Germans and, I think, the Japanese and Russians continued with this practice. The British and, initially, the Americans turned to the aero-engine. Most American aero-engines were air cooled (OK, the big Allison engines were not) which probably gave installation problems. This, the need for engines for aircraft and spare capacity in the car industry led to them using large multi-banked car engines as on the Sherman. The British used the RR Meteor engine, an un-supercharged version of the Merlin. In 1942 Rolls-Royce swapped their Meteor manufacturing plant near Nottingham for Rover's jet engine factories in Lancashire.

I may not have got everything correct since it is a quick reply.


much better view of the air path.. that plate wasn't swiss cheesed in the early photos..
as for use of an radial air-cooled engine, the weight to HP ratio is great,, no need for a complex liquid filled cooling system,, Sherman tanks produced in great numbers operated in northern Russia to North Africa (from one extreme to another that would test a liquid cooled vehicle)  watch some of the hedgehog sherman vids,, they had great performance.. the main drawback was the high profile of the vehicle making it an larger target,  Gasoline was also a risk compared to diesel, but one good hit didn't really matter what kind of fuel was used..

The choice of engines powerful enough to propel a tank, at the required speed over a variety of terrain conditions, was limited by availability rather than an esoteric choice between radial or inline engine.

The power requirement for an effective armored tank is between 15 to 20 HP per ton. The choice of big powerful engines was limited. Suitable aircraft engine were available but even the biggest truck engine was nowhere near powerful enough. Big watercooled in-line engines were eventually developed, but it took time

A Light tank like the M3 or M5 Stuart needed a 220HP engine. Initialy a Continental W670 (220HP) radial was installed. Later, two Cadillac V8's (210hp) were needed to replace the the radial engines when supplies ran short.

A Medium Tank is much more heavily armored and needs a significantly more powerful engine. The M3 Lee/Grant and the M4 Sherman all started life fitted with the 400 to 450 HP Continental R975 radial engine. These big radials were eventually replaced with watercooled  in-line V engines, but only after engines of this enormous power had been designed and put into mass production.

By comparison the V12 RR Meteor tank engine was a  non supercharged derivative of the famous RR Merlin aircraft engine. It produced around 600HP from it's 27 litre engine and went on to power the more heavily armored and heavier tanks of later years.

Aircraft engines were therefore an obvious first choice. The US aviation industry in the 1930's favored the air cooled radial over the water cooled in line engine. In UK the industry were evenly split between the two. Bristol's lead the way with powerful air-cooled radials, while Rolls Royce produced equally good water cooled V12 in-lines.

The air cooled radial engine was light and compact but had the disadvantage of a larger diameter. The larger diameter engine forced their tanks to be much taller than desirable and therefore presented much bigger targets for the enemy to fire at.

Well that's my understanding



--- Quote from: tghs on January 16, 2021, 03:06:47 PM --- the main drawback was the high profile of the vehicle making it an larger target,  Gasoline was also a risk compared to diesel, but one good hit didn't really matter what kind of fuel was used..

--- End quote ---

Gasoline was always the fuel of choice, everything, including the cookhouse stoves ran on it. It was a question of logistics, one fuel ran all. Supplying more than one type of fuel to the forward troops was out of the question.

As to the vulnerability of gasoline v Diesel. It did not matter much. One good hit would usually set off a ton of high explosive ammunition first.



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