1930-1945: alternative engines for military purposes (3 Viewers)

[ThomasP]

For the UK a tankerized Cheetah might have worked, at least for early war tanks if they were designed for the size of the radial.

In 1935, the unsupercharged Cheetah V with a CR of 5.2 it was rated at 270 BHP at 2100 rpm on 73 grade fuel. Dimensions were Ø48" x ~36" thick not counting the prop shaft, and weight was about 600 lbs. If they could retain the reliability of the aircraft engine at ~1000 hrs between overhauls? (The supercharged Cheetah X was rated at 1200 between overhauls in 1941.)

 

[tomo pauk]

Germans seem to be in their own world. A 12 liter V-12 of 265-300hp and using 6-10 gears maybe an elegant solution, but tanks are not elegant, they are brute force. Using larger engines but fewer gears may have given the same result and been cheaper. May depend on a nations gear cutting ability? I wonder how much swarf (Chips)
you get from 10 speed transmissions? And you have to use very good steel. Which turned out in Germany's case, to be in shorter supply than they thought.

Their 'small' V12s were compact and reliable engines, but there the benefits really stop. Something that is V6 sibling of a 30-35L V12* would've gotten them compactness and reliability, too, but also lower price and time to make the engines and gearboxes, easier maintenance in the field, and will require the shorter engine bay.

* Germans were thinking about the heavy tanks much before they gotten into that in reality, that a big V12 should be powering.

There certainly is more time and more room for better engines.
Problem with the French is that they were going in several different directions at once.
They weren't really trying to find the 'best' tank and them build a crap load of 2-3 models. They were trying to find usable tanks and provide employment to different factories and build up the manufacturing capabilities of some factories. A lot of politics involved which led to most factories wanting to use their own engine/s and not a standardized engine.
But even a 500-1000 tank order was not enough for a bespoke engine and they tried to use something either in stock or something they can pull other pieces for.

The French were designing and making heavy tanks in the 1920s and 30s. Them opting for V12s for these tanks, with en eye for V8 and/or V6 versions for the smaller tanks might've been both economicaly and military prudent.
Also - their heavy tanks were big and boxy. A good radial engine would not be too much for the hull to house these.

An engine from a Char B1. Very much in the fashion of a split WW I V-12 aircraft engine. They seem to have added to both bore and stroke over the years but the sperate cylinders does show the dated design (Liberty was no better).

An inline 6 would've been an ideal engine if the tank has the 'Merkava' layout - engine sits besides the driver, front sprocket driving the tracks. While not common on tanks of the day, it was not unheard of - Vickers light tanks had that, so did a lot of Soviet light tanks, and so did the Elefant (but with the electric 'transmission'). Frees a hefty % of the hull length and volume, and the tank can be repurposed into a SP chassis in an elegant fashion.

Another way of making the engine+transmission bay a good deal shorter was to have the engine being installed in the transversal position. That 'trick' was done on the T-43 tank, making the tank much roomier. An inline 6 installed in such a fashion would've netted even greater benefits vs. the longitudinal installation.

 

[tomo pauk]

For the UK a tankerized Cheetah might have worked, at least for early war tanks if they were designed for the size of the radial.

In 1935, the unsupercharged Cheetah V with a CR of 5.2 it was rated at 270 BHP at 2100 rpm on 73 grade fuel. Dimensions were Ø48" x ~36" thick not counting the prop shaft, and weight was about 600 lbs. If they could retain the reliability of the aircraft engine at ~1000 hrs between overhauls? (The supercharged Cheetah X was rated at 1200 between overhauls in 1941.)

The twinned bus engine on the Matilda II was 57in long - so a good half a metre longer - and ~2650 lbs (1200kg). Also 58in tall.

 

[z42]

Were there other users of engines with similar requirements as tank engines, to get decent production volumes without having to make a lot of tanks? Beyond aircraft of course. I'd guess most civilian uses in the same size would prefer robustness and ease of maintenance over maximum power per volume. Maybe torpedo boats?

 

[Elan Vital]

The French were designing and making heavy tanks in the 1920s and 30s. Them opting for V12s for these tanks, with en eye for V8 and/or V6 versions for the smaller tanks might've been both economicaly and military prudent.
Also - their heavy tanks were big and boxy. A good radial engine would not be too much for the hull to house these.

This is correct, the French concluded that V or W layouts were best for their battle and heavy tanks. The idea of using half of the battle tank engine in I or V form for the light tanks didn't happen until 1939, largely because the 1933 program light tanks were too light and small to make use of such an engine and the evolution towards 15-20 tonnes happened in 1939.

The G1 and heavy tanks all used V or W engines bar the transverse I6 in G1R, but it isn't until 1939 that a V engine was designed for B1 Ter, largely because it was originally expected to use a modified B1 Bis' engine at a lower combat weight.

 

[tomo pauk]

Sometimes, the engines land in one's lap. Like the case with Germany getting many hundreds of enignes when they annexed Czechoslovakia, hundreds of radials and W engines when they conquered Poland, and thousands more when they conquered France.
Apart from the HS 12Y-45, 49 and -51, the other HS 12Y will not be suitable for 1st line aircraft come 1941, but they might warrant a try in a tank or in a transport aircraft. The CR of 5.5 will allow for the fuel of the low octane rating to be used, with a bit of down-rating if/when required. Low weight is another boon, up to 500 kg vs. 950-1000 kg of the HL 210/230 series. Sizable displacement will bring good torque.
The smaller 12M and X might've been also interesting, and also being shorter than the big bore siblings 12N and Y; both the M and N will probably need to go lower compression.

The HS 12 engines would've been a very intersting choice for the French heavier tanks, too, at least teh yesterday's models so the price is not over the top.