V16 Aircraft Engine

[davebender]

Auto Union racing car - Wikipedia, the free encyclopedia
The Germans made a serious effort to develop V24 aircraft engines. Why not a V16 aircraft engine? That would build on extensive experience with V16 engines which powered Auto Union race cars.

 

[red admiral]

Auto Union racing car - Wikipedia, the free encyclopedia
The Germans made a serious effort to develop V24 aircraft engines. Why not a V16 aircraft engine? That would build on extensive experience with V16 engines which powered Auto Union race cars.

DB 609; big, heavy; too late.

 

[Shortround6]

The V-16 had some problems that ment it was less than ideal for an aircraft engine.

Racing car engines had very different desgn considerations than aircraft engines.
Most racing car engines are built to definte displacement limit. getting the most power from that displacement is the most important thing. evryting else, including power to weight of the engine is secondary.

The aircraft engine designer on the other hand can use what ever displacement he wants, providing the resulting engine is reliable enough and light enough to fit (balance) in the aircraft. A large displacement, slow turning but light for it's size (compared to a car engine) might show better reliability and fuel economy than a smaller displacement, high revving, heavy engine. Stress on bearings and some reciprocating parts goes up with the square of the speed (rpm) of the crankshaft.

 

[river]

Hi,

Didn't the Americans have a V16 Liberty engine? Not sure if it was ever used, but IIRC the Liberty program was to have a common design that could be used from 2 to 24 cylinders.

river

 

[Shortround6]

Hi,

Didn't the Americans have a V16 Liberty engine? Not sure if it was ever used, but IIRC the Liberty program was to have a common design that could be used from 2 to 24 cylinders.

river

It may have been planned but I am not sure it was ever built. At least one of the Versions that were built (the 6 and eight) had such severe vibration problems that production stopped in single digits. Vibration problems were not well understood at that time and lead to more than one engine being dismal failures.

 

[vikingBerserker]

I think there was an experimental V-16 that was put into a P-47 very late or after the war. It's in one of my Jug books. I honestly cannot remember if it was a Liberty or not.

 

[Shortround6]

I think there was an experimental V-16 that was put into a P-47 very late or after the war. It's in one of my Jug books. I honestly cannot remember if it was a Liberty or not.

No, it was a completly new design: Chrysler IV-2220 - Wikipedia, the free encyclopedia

Please note that the propellor drive was taken from the middle of the engine which from a crankshaft stress and vibration standpoint sort of made the engine act like two V-8s.

 

[PWR4360-59B]

Allison, I think everyone miscatorgorizes it, I say it is a W-16 as it was 2 side by side allison V-12 engines that formed a W configuration.

 

[PJay]

2 V12's equal one W-24 I would have thought.

 

[Vincenzo]

in early '30s there were some french engine w12 (hispano suiza and lorraine detrich i know)

 

[Shortround6]

The British Napier Lion was a W-12.
There may have been a few others.

Advantage of the W-12 was that it is short and stiff compared to a V-12 and so the weight of the crankcase and crankshaft can be less than an equivelent V-12.

Disadvantage is that it is a lot wider.

Issota-Fraschini made some W18s as did the Russians.

 

[MikeGazdik]

The V-12 engine is the optimum design for an internal combustion V engine. I little above my head, but it has to do with balancing because of the 6 crank throws and 12 pistons, working with 4-stroke firing, which results in an engine that doesn't need any counter balancing or balance weights on the crank. Once you begin to remove cylinders ( V8, V6, I6 etc.) you need "crutches" to rebalance the engine. Weights or sometimes counter shafts.

I am not certain, but I would believe that it also is the same if you add cylinders to the V-12. So a V-16 or more would need added crank weights or counter balancers. All which add reciprocating mass, and overall engine weight.

 

[Lucky13]

Would a V14 work? Was there a 14 cylinder inline engine, thinking that there were 14 cylinder radials?

 

[Shortround6]

I think there is a bit more to it than that.

V-12s might be able to get away with less or no crankshaft counter weights only to a certain point. A low powered or slow revving (or both) V-12 might be able to get away with no counter weights but the high powered ones certainly used counter weights. In some cases the engine used small counter weights that did not fully balance the crankshaft but did reduce the bearing loads and loads/stress on the crankcase to an acceptable level.

Late model Allisons used a fully counter weighted crankshaft that added 27lb to the engine. But it allowed an easy 3200rpm instead of the 3000rpm limit of the lighter crankshaft and lowered th bearing loads and stresses. This is the crankshaft that was used in most of the hydroplane race boats and in most of the Alison powered unlimited race planes regardless of what engine block they used.

The pictures of Formula 1 race engine V-12s (parts laid out, oilpan/crankcase cover off, cut away drawings)that I have seen also show counter weights on the crankshafts.

 

[Shortround6]

Would a V14 work? Was there a 14 cylinder inline engine, thinking that there were 14 cylinder radials?

maybe, but what would be the point?

Airplane engines, in order to be as light as possiable, have to be built to minimize vibration and stress.

Torsional vibration in a crankshaft occurs as the power is applied and released on one end of the crankshaft while the load at the other end resists turning.
You have the propeller on one end which is both the load and acting as a heavy flywheel resisiting changes in rotaional speed. you have a piston trying to twist the crankshaft but only for 180 degrees or less of every 720 degrees of crankshaft rotation. ANd the amount of force acting on the crankshaft varies in those 180 degrees. so the crankshaft is being twisted and then relaxed, twisted and relaxed over and over. this sets up vibration patterns in the crankshaft.
The more cylinders acting on the crankshaft the more often the twisting forceis applied and smoother things are. A twelve cylinder engine (V-12) gives a blow to the crankshaft every 60 degrees of rotation. A V-14 would have to have a 51.43 degree angle between the banks in order to have an even firing order. It is doable but more complicated. an uneven firing order makes the vibration worse because 2 cylinders fire closer together and then there is a longer pause before another cylinder fires.
A V-14 will probably have a longer crankshaft than a V-12. The longer crankshaft gives the rear cylinders more "leverage" when acting on the crankshaft to twist it. So the V-14 will probably have to have a longer, heavier crankshaft than an equivilant V-12.

 

[chip haehnel]

check out the Lycoming Hyper Engine in Wikipedia.CH

 

[Shortround6]

The Lycoming was a flat 12 that proved to be too small. in an attempt to salvage something from the work one engine was placed on top of another to create a horizontal "H" engine of 24 cylinders.
Two 12 cylinder crankshafts geared together.

 

[Lucky13]

Would be possible to make a V-14 the same size as the V-12, smaller cylinders?

 

[Shortround6]

Would be possible to make a V-14 the same size as the V-12, smaller cylinders?[/QUOTE}

It would be possiable but what is the point?

The V-14 would be more expensive to manufacture (more parts even if they are smaller) more expensive to service, spark plug changes and valve adjsutment.
Depending on the exact bore and stroke it is likely to have more internal friction (approximately 80% of the friction in an engine comes from piston scrubbing in the cylinders) meaning poorer fuel economy.

On the plus side you might get better breathing with the smaller cylinders and you might better cooling. A larger cylinder wall to cylinder volume ratio. So you are trading better peak HP for worse fuel consumption at all speeds.

Throw that in with the odd ball firing order and/or strange V angle and crankshaft journal spacing and it just seems to offer a lot more headaches than advantages.