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- #21
Radial engines favored for powering the tanks & AFVs, 1935-45 (3 Viewers)
- Thread starter tomo pauk
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A version of the Australian Sentinel tank, the AC III Scorpion, was to have a radial engine. The Scorpion was a standard AC I, but modified to mount the desired Pratt and Whitney Wasp radial engine. For tank use the Wasp was to be down rated to 400 horsepower and re-designated 'Scorpion' with tanks using the engine carrying the same name. However, experimental testing with the Scorpion engine revealed undesirable traits, such as poor torque output at low RPM and a high RPM ceiling required to reach maximum power output.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
BMW made blinkers?Some interesting tidbits wrt. the BMW-engined Panther: link
I'm not sure whether BMW was also supplying the blinkers...
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- #24
I was surprised as you are.
Shortround6
Major General
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- #26
Looking a bit on the Char B, it looks like about 55% of the hull length was devoted to the engine+trasmision section (cutaway1, cut2). Lenght of the inline six engine certainly was not a good feature to have there, since any lengthening of a tank means that weight goes up badly. A radial engine - being much shorter - would've netted the benefits there.
Elan Vital
Airman
- 41
- Aug 24, 2024
Or a Vee engine with only 3 or 4 cylinder lengths or smaller bore. However, it is mainly with the transmission that they saved length, first 222mm on B1 Ter (unchanged engine compartment length to use the space for other purposes), then another 200mm on B40 (to enlarge the fighting compartment).
Shortround6
Major General
But if you use a radial engine that fits across the tank you can't have a nice passage way down the side of the engine giving you access to the engine, the floor emergency exit, the rear upper hatch and access to a fair amount of the 75mm ammo. Your loader is going to get fat without getting in his hundreds (thousands?) of exercise steps lugging the ammo from the bins in the engine compartment up to the gun.
The drawings do answer the question the Chieftain had in his video about where the ammo was supposed to stored. Apparently much of it was not in the 'fighting' compartment
Again tanks are a conflicting bunch of compromises. French (and British) were obsessed with trench crossing some tanks and then totally forget about it with other tanks. Char B was supposed to cross WW I style trenches. You need a long hull, track run.
Meanwhile the accompanying light tanks, The Renault R35 tanks were lucky they could cross a medium sized pot hole. It typical French fashion they tried to solve this on the cheap.
Didn't do a lot for entering a trench.
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- #29
But if you use a radial engine that fits across the tank you can't have a nice passage way down the side of the engine giving you access to the engine, the floor emergency exit, the rear upper hatch and access to a fair amount of the 75mm ammo. Your loader is going to get fat without getting in his hundreds (thousands?) of exercise steps lugging the ammo from the bins in the engine compartment up to the gun.
The drawings do answer the question the Chieftain had in his video about where the ammo was supposed to stored. Apparently much of it was not in the 'fighting' compartment
Keeping the tank length constant gives you a longer fighting compartment in case the (much) shorter engine is used. The floor emergency exit can still easily be done.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
While not a radial engine, the Lycoming O-435 aircraft engine was used in the U.S. M22 Locust ligjt tank.
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- #31
From the German PoV, making a radial engine for the tanks instead the V12s might've improved the production rate and price point of their tanks?
It could also reduce the weight a bit, even without accounting for the possible save in tank length vs. the 12 cyl engine.
It could also reduce the weight a bit, even without accounting for the possible save in tank length vs. the 12 cyl engine.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Tomo, didn't the Germans toy with the idea of a BMW132 radial in the PzKfw Mk.II at one point?
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- #33
Or lean into it for plenty of HP for that space.
Hispano-Suiza 18Sbr W-18
detuned for ground use.
More realistically, use a two inline fours, one on each side of the gearbox, coupled together to drive the upper steering shaft.
Radiator in front the engines with air handlers routed to the top of the hull, not on the side
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
I was aware of the Panther, but I seem to recall that a prototype was tested before the war with either a PzKfw Mk.II or Mk.III tank.For the Panther
I've posted the link upthread.
Considering those two types were much lighter than the Panther, it may have been a much better performer.
Would it? Seems German WWII aero engine prices were all over the map. The BMW 132 was fairly cheap, but the BMW 801 was very expensive, with the liquid cooled V-12's somewhere in between. If you look at price per hp, they get a lot closer.
Further, a bespoke tank engine doesn't need to care that much about weight, and can thus use cheaper and more available cast iron construction rather than lighter weight but more expensive, and in war time harder to come by, aluminum or magnesium. Unless you're suggesting a radial designed for land usage rather than a derivative of an existing aero engine?
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- #37
I'd certainly not make suggestions that the BMW 801 is turned into a tank engine
Part of BMW 801 high price tag was that it used the Konnadogeraet, and part of the high price was the fuel injection. Being a two row radial is too much a luxury, too.The 9 cyl radials should've sufficed, and even 7 cyl radials for that matter. Germans can use the Czech and Polish factories to make these, both countries were making the radials of Bristol lineage in the 1930s.
Saving some 500 kg on a 500 HP engine (even without the cooling system is taken into account) means that armor protection can be thicker by as much as 500 kg of steel can offer. Engine being shorter allows for an even greater weight saving, this time via making the armored 'citadel' of the hull shorter.
People can start out with the 'normal' radial engine in the 1930s, and move to the steel crankcase version as a next step. Aluminum was very popular on the tank engines of the day, even during ww2.
Seeing it here, two 100x50x5cm steel plates will weight under 400 kg.
Shortround6
Major General
The Continental R-670 used in the M3 Stuart was 42.5in (1080m) in diameter. Since it is air cooled you have to leave a few inches at the top and bottom for air ducts.
It short lengthwise. Short hightwise is subject to question. Now flip the engine backwards and put the transmission/steering gear in the back. Maybe you can lower the tank due the drive shaft no longer under the turret, but the rear of the tank gets bit longer.
Everything is tradeoffs.
It short lengthwise. Short hightwise is subject to question. Now flip the engine backwards and put the transmission/steering gear in the back. Maybe you can lower the tank due the drive shaft no longer under the turret, but the rear of the tank gets bit longer.
Everything is tradeoffs.
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- #39
The power/weight ratio better than 1 (in HP/kg) is amazing, and it was not done on any kind of hi-octane fuel. No compressor, no fuel injection. Even 65 oct will do.
Germans were lucky to be getting 0.6 in their V12s years after the R-670 was making unity.
We can take a look at the Valentine tank. The engine bay was long enough for the 6-cyl diesel to fit, that went at 79 in long? The R-670 was under 35 in of lenght. Let's be conservative and have the radial engine of good power being 40 inches shorter - a full meter. In the time when tanks were 5+- meter long, that is a major thing. Even saving of 50cm leaves a lot of weight allowance to be used on other stuff.
I'd certainly not make suggestions that the BMW 801 is turned into a tank engine
Me neither. Just pointing out that engines, even from the same manufacturer, had wildly varying costs. So I don't think in general you can make the argument that a radial would be cheaper than a liquid-cooled inline, all else being equal.
I don't think you can attribute that 500kg (rough difference between BMW 132 and Maybach HL 230, if we're going by wikipedia numbers?) solely to cast iron vs aluminum. Or radial vs inline, for that matter.
Maybe? But maybe you instead lose by needing a higher hull, which adds weight by itself as well as being an easier target. If you look at the volume of the powerplant instead of focusing on any one particular dimension, I'm not sure the radial wins by that much, if at all, anymore. Also keep in mind the radial will need a large fan with assorted ducting for cooling, which will increase the length somewhat (of course the liquid cooled engine will need radiators and fans as well, but has a little more flexibility how these are placed). With a long and narrow engine like a V-12, maybe you can compensate with a lower hull, and by putting things like fuel tanks beside the engine bay?
Yes, but since we're playing with the retrospectoscope here in this thread, we don't need to repeat every mistake of the past.
