Radial engines favored for powering the tanks & AFVs, 1935-45

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For the actual gearheads: how workable a thing might've been a 'cropped radial' - something with the genes from the Jupiter/Pegasus/Bramo 323 engine, but without the lower 4 cylinders? Sorta 5 cyl W engine?
Jupiter was making more than 500 HP on '73-77' octane fuel; shaving 4 cylinders = about 300 HP remaining. Having 300 HP from a 5 cyl engine of under 400 kg is not too shabby. Height of the engine drops down by 1/3rd? (from 1.4m to under 1m), and the prop shaft is now as low as it gets. Yes, a new crankshaft will be needed (doh).
 
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There were some pre WWI 3 cylinder fan engines (Anzani) and there were a few experimantal engines using more(?). One French inventor Robert Esnault-Pelterie even built engines with multiple banks, like 3 cylinders in one bank and 4 in the other for a 7 cylinder engine.

A major problem with large displacement, high powered engines with a small number of cylinders is the vibration. Companies, like Bristol, offered them, like the 8 liter 3 cylinder Lucifer.
They were light weight and cheap, but they may have been unpleasant to fly behind.
The 'fan' engines needed more counterweighting than the 3 cylinder "Y" engine and were heavier for the same power.

What 'worked' in early aviation (just getting the plane to fly for more than a few minutes) was not what was wanted in the late 20s or early 30s, aside from homebuilders or companies looking for small, cheap engines.

50hp engine, Company offered 5 cylinder and 7 cylinder versions.

The US went for air cooled radial engines in tanks because they had them, in quantity. The US also had large truck, marine, industrial gasoline/diesel engines that were rugged and long lived. They were also heavy. The US didn't want to spend the money to develop a special tank engine when they were only ordering small numbers of tanks in the late 30s.

It took the US around 3 years to build over 300 of these plus the M1 combat cars. Spending hundreds of thousands of dollars on a "special" tank engine meant fewer tanks purchased when you are ordering under 200 tanks per year.

There are all kinds of things you can do from an engineering perspective. Wither they should be done is subject to question.
 
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French and Germans and Soviets were making hundreds of tanks a year from 1935-ish, Soviets even more, and the British and Italians were also catching up (granted, the best part of the Italian production were not real tanks).
The reasons of why were stated several times in this thread. Just cutting the tank's length due to having a shorter engine is a major boon. Or, having more volume under armor for the same external dimensions and weight.
 
tomo pauk said:
The reasons of why were stated several times in this thread. Just cutting the tank's length due to having a shorter engine is a major boon. Or, having more volume under armor for the same external dimensions and weight.
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Those are the advantages. Now balance them with some of the negatives. Brand new engine..........trouble free or troublesome?
Air cooled engines in a steel box with a fan? Please note that the British failed in rather spectacular fashion to figure out how to use a fan (or fans) to cool a liquid cooled engine, twice. People had been using fans on liquid cooled engines in cars and trucks for over 30 years. Granted on the Crusader it was the 'details' like the fan drive system failing/breaking in under 1000 miles (miles not hours) as much the more common "leaks" but still. They had changed the fan/fan drive on the Crusader from the system used on the older Cruiser tanks to use two small fans vs one large one. Maybe they got enough airflow, I don't know. But using an open to the air chain drive (with oil) around sprockets in a tank operating in the dessert turned out to be a bad idea.
Note that often the radiators/ducts and fan/s took up more space than the engine did.
Oddball cylinder layouts are not a guaranteed failure, but they increase the odds.
Many 1930s and early 40s tanks did NOT pay attention to servicing the engine in place.
Do you know why that 3 cylinder engine in the aircraft was located with the single cylinder up the other two splayed out to the sides instead of the other way around(single straight down)? It is because a single cylinder pointed straight down has a bigger chance of oil fouling the spark plug/s.
Granted cutting off the bottom cylinders of a radial solves that problem

If you need more room to work on an engine than a 'proper' 6 cylinder or V-8 (most everything should have been arranged (often wasn't) to be reached from the top with a W or multi bank engine some of the space saving disappears.
Airplane engines don't usually have flywheels. They depend on better balancing, low rpm, vibration dampers, layout and yes, the propeller, acting as a flywheel to average out the power pulses and smooth out the engine. In the 1930s cars and trucks also used heavy construction to help dampen out vibration, or at least help survive it.
A lot of what we know now was unknown in the 1920s and 30s. In the 1950s and 60s nobody was making a 4 cylinder car over 2.2-2.4 liters. The engine vibrated too much to be comfortable. Mitsubishi refined the idea of the balance shaft from Frederick W. Lanchester of 1909 in 1975 (using computers) to make a smooth engine in the 2.4 liter range.
Worrying about crew comfort in a 1930s tank seems a little silly at first. But how well do you want the crew to fight after a 6-8hr road march? or even trying to tend to end of the day maintenance? For a less human perspective, and engine with less vibration doesn't vibrate things loose or crack/break things on the engine or tank.
This is one reason for using 6 cylinder engines in light tanks even though it might be possible to use a large 4. V-6s don't balance as well as inline 6s.
In the 1950s and 60s they knew a lot more about vibration. How to design better rubber mounts, how to design certain parts of the engine, how to balance moving parts better and so on. What they could do in the 1950/60s may be different from what would have been a good design in the 1930s.
 
JuniorJarhead09 said:
can you lay the radial engine flat? move oil pump as needed etc.
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I thought of that too, including using a liquid-cooled radial so to omit the need for direct air flow. But most multibank radial engines are as long as they are wide. And then we'd need some complicated differential and drivetrain routing from the top centre of the radial to the transmission and drive wheels.
 
couldn't you split the radials near the bottom of the tank laying it flat, give each a seperate coolant requirements as need along with sharing the same drive shaft. it'll be laid uhm Phallus like. with reducer gear to power tracks on both sides,
 
JuniorJarhead09 said:
couldn't you split the radials near the bottom of the tank laying it flat, give each a seperate coolant requirements as need along with sharing the same drive shaft. it'll be laid uhm Phallus like. with reducer gear to power tracks on both sides,
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We're getting complicated now. What advantages does your idea offer compared to a liquid-cooled inline, V-12, or horizontally opposed engine?
 
JuniorJarhead09 said:
just spit balling man.
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All good, me too. I wonder if that's how the German Panzers and much of their vehicles, aircraft, ships and weapons became so overly complicated. Who else would design a complicated, foul-prone interleaved road wheel suspension system (Schachtellaufwerk) on their tanks when the intended terrain is the brutally cold winters and seasonal mud (rasputitsa) of the Russian steppe? Just keep it simple Siegfried (kiss) and make a German T-34. And then there's the Heinkel He 177 Greif, being overengineered with coupled engines, leading to engine fires and mechanical failures - just make it with four proven and reliable engines. Even on the small stuff the Germans preferred complicated engineering over common sense, such as the FG 42 automatic rifle which was too complex and expensive for widespread use, with delicate internals and high production costs - the Germans loved to use precision machined parts where stamped parts would suffice for the Allies.

Given their love for needless complexity, I would not have been surprised had the Germans tried to stick a BMW 801 radial on its end, driveshaft pointing downward into a tank. The bevel or worm shaft gearing to get the power from the vertical output to the transmission and drive wheels would have been amazing to see.
 
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Late in the war, Caterpillar contemplated development of twin-row radials that were cut in half (so about 3-5 cylinders per row spread over a <180° angle). The company was in no position to undertake the project on its own however. Presumably this was seen as a compromise between the short (in length) but tall radials and conventional Vee engines, instead leaning closer to a sort of W or fan engine.
 
have the radials up higher, one row on each side, providing protection to the crew with scoop inlets thats just made of armour, remember air is armour after initial contact in some degree... too many wonder weapon projects, more of, make weapons of "convientiality/conventional", perfect the ghewer 43 and every solider in the Wehrmacht is instantously more dangerous..... every solider has a has g43style or similar, even the grenadiers and panzerfoust team, each nine man squad with a 3*/4* scope marksmen, everyone can pretty much use it, more scopes add to more more men in each squad.... hindsight's 20/20, i'm over here saying no capital ships, 20,000 schnell boats,
 
JuniorJarhead09 said:
have the radials up higher, one row on each side, providing protection to the crew
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That could work on the Russia Tsar Tank. Though calling this trackless beast a tank is being generous.



Or, imagine a radial engine on either side of the big wheel, like on this 1922 Megola motorcycle below. Though that's a fixed-crank rotary engine rather than a true radial.

 
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JuniorJarhead09 said:
couldn't you split the radials near the bottom of the tank laying it flat,
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Here's some ideas for air cooled radials laying flat. If we can pull this off we could get a very low profile tank.



And some info on how to route the driveshaft.

Cars with radial engines

Douglas Self, Cars with radial engines
www.douglas-self.com

 
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JuniorJarhead09 said:
can you lay the radial engine flat? move oil pump as needed etc.
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These engines were often used in dirigibles and sea planes An engine of this type besides lending itself conveniently to installation affords better visibility and diminishes head resistance The propeller drive was through bevel gears which usually reduced the speed in the ratio of 9 to 5
B-9
The Model B-9 was a nine cylinder water cooled horizontal radial type rated 140 hp at 1250 rpm The bore was 120 mm 4.72 in the stroke 150 mm 5.91 in and the total displacement 930.69 cu in
D-9
A larger nine cylinder horizontal radial type known as Model D-9 was rated 300 hp at 1200 rpm The bore was 150 mm 5.91 in the stroke 210 mm 8.27 in and the total displacement 1945.62 cu in The weight was reported to be 990 lbs or 3.3 lbs per rated hp 2D-9
An eighteen cylinder engine a double form of D-9 model and with 3891.24 cu in total displacement was rated 600 hp at 1200 rpm The weight was said to be 2460 lbs or 4.1 lbs per rated hp

Airplane Engine Encyclopedia

Much larger


29,556 cu in (484.3 L)
 
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