British Universal Tank Jan 1941

[NothingNow]

The thing is, a diesel doesn't make that much in the way of horsepower, but the level of torque it makes more than compensates for that, especially since most tanks spend a lot of time starting and stopping.

This is true, but the entire military at the time was already using petrol, so it makes more sense to stick with that.

The V2 engine has a superior power curve to the Napier Lion (max power available at 1800 vs. 2200 rpm) which makes it more responsive as an AFV engine.

"Reduction Gears! How do they work?"

Also, you're comparing a square engine with an undersquare one. Guess which is less efficient, and places more stress on engine components.

The marine version of the Lion likely requires a great deal of cooling.

As an inline engine it doesn't. You've got the radiators to deal with and that's it. And the Lion's well designed to handle that.

Also:
Larger displacement doesn't actually mean the engine is larger.

You're kinda right. Displacement is simply bore x stroke. The physical size of the engine is determined by a hell of a lot of other things. The Lion is large only because of it's square, w-12 layout. Which makes the thing pretty easy to do routine maintenance on, and easy to cool.

But weight is more closely related to displacement. The V-2 weighs a hell of a lot more than the Lion's 435kg, and you can't co-locate things in the same space the engine is in, like a fuel pump.

 

[AdA]

I'd like to know where you got your stats. Also, I didn't say the engine was larger, but with a bigger bore and a longer stroke (and noting that that the cylinders were asymmetrical, one side had a stroke of 180mm, the other of 186mm) means a greater surface area for the cylinders, which means a greater weight for the same reserve strength.

As for cooling, the Lion was an in-line engine so it relied on radiators anyway. Oh, and higher revolutions aren't an issue if you put in this little device we call a 'gear-box'.

Matt, have you ever driven a heavyweight vehicle with a diesel engine?
There is a reason why even in the USA, where gas is cheap, heavy duty pick up trucks have diesel engines.
High revving engines coupled to gearboxes with lots of ratios are great fun on motorcycles. I have driven Unimog trucks with both gasoline and diesel engines and for logging heavy loads cross country give me a diesel any day. That's why they don't make gasoline powered unimogs anymore...

 

[NothingNow]

Matt, have you ever driven a heavyweight vehicle with a diesel engine?
There is a reason why even in the USA, where gas is cheap, heavy duty pick up trucks have diesel engines.
High revving engines coupled to gearboxes with lots of ratios are great fun on motorcycles. I have driven Unimog trucks with both gasoline and diesel engines and for logging heavy loads cross country give me a diesel any day. That's why they don't make gasoline powered unimogs anymore...

The Lion isn't a high revving engine by any means. Peak power is @ 2200rpm. The little VW 2.0l TDI puts out peak torque at right about that same level, as do most diesel engines.
The M180/M130 straight-sixes they put in Unimogs were oversquare pieces of shit and we both know it.

 

[AdA]

The Lion isn't a high revving engine by any means. Peak power is @ 2200rpm. The little VW 2.0l TDI puts out peak torque at right about that same level, as do most diesel engines.
The M180/M130 straight-sixes they put in Unimogs were oversquare pieces of shit and we both know it.

I used to have a lot of those gasoline powered Unimogs in my company back in my company commander days. They broke down all the time (to be fair, they were pretty old and worn by that time). When we moved to the more modern diesel ones it was a revelation
There are engines and engines, but even with late 30s tech it should be clear that diesel was the way to go for military vehicles. The Japanese, of all people, bet on that trend. The Italians too, but failed to make big enough diesels for the late war tanks. The Russians were spot on.
There were good diesel engine makers in the UK. The Matador and the Scamell Pioneer had excellent engines. They used good if small engines on the Valentine. Like I said before, there is no reason why Gardner shouldn't have built a good 500HP tank engine if asked to.

 

[MattII]

Okay, diesels are better, but petrol gets you by well enough, and is probably the common fuel, and as with everything else in the military:
good enough and universal > great but specialised.

 

[phx1138]

Thinking of cooling & diesels & such has me wondering...

Couldn't Britain have bought/used/licenced the Guiberson diesel radial?

And why didn't it occur to anybody (since it appears not to have) to mount the Guiberson &/or R975 horizontally? It would have reduced hull height...

 

[Hoist40]

And why didn't it occur to anybody (since it appears not to have) to mount the Guiberson &/or R975 horizontally? It would have reduced hull height...

You could get a lower hull height using a radial without turning it horizontal.

The M-18 Hellcat tank destroyer had a R-975 engine and its hull was lower then a Sherman. The difference was that the M-18 had an additional gearbox near the engine which dropped the height of the drive shaft down to the bottom of the vehicle, the Sherman and the Stuart did not and so it was the high drive shaft which then forced the turret up higher which meant there needed to be a higher hull.

http://en.wikipedia.org/wiki/M18_Hellcat

Prior to WW2 the US Army wanted to introduce such a gear box on their radial engine tanks but they were so short of money they could not afford it, and when the war came they were in such a hurry to mass produce that they did not want to wait until such a gear box could be developed and tested.

 

[phx1138]

You could get a lower hull height using a radial without turning it horizontal.

The M-18 Hellcat tank destroyer had a R-975 engine and its hull was lower then a Sherman. The difference was that the M-18 had an additional gearbox near the engine which dropped the height of the drive shaft down to the bottom of the vehicle, the Sherman and the Stuart did not and so it was the high drive shaft which then forced the turret up higher which meant there needed to be a higher hull.

That works. I was thinking of a rear-mounted transmission, & needing the height to cope with the engine diameter. (A 45" {114cm} minimum engine deck height...)

 

[Hoist40]

That works. I was thinking of a rear-mounted transmission, & needing the height to cope with the engine diameter. (A 45" {114cm} minimum engine deck height...)

Agreed, a rear mounted transmission would get you an even lower hull height.

Even with the rear mounted transmission you might just do a bump up on the rear engine deck to accommodate the radial. It would be a little more vulnerable but it would also be protected by the turret from shots coming from the front. Many modern tanks have the rear higher then the front to accommodate the engine