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> I think is that cast vs billet crankshafts are almost a pointless argument outside of classic car enthusiast communities, or race communities. It is an aviat
by rdtsc 8y ago
> I think is that cast vs billet crankshafts are almost a pointless argument outside of classic car enthusiast communities, or race communities.
It is an aviation community in this case as well. They are re-purposing a car engine. It seems the loads on the crankshaft if it is directly attached to the propeller will be quite different that what the would be in a car. With a propeller there would be a bending component (propeller acting a gyroscope) besides the twisting component, especially when say doing aerobatics, while in a car the it will be mostly a twisting component.
So perhaps then cast vs billet becomes more important as one can withstand bending forces better than the other generally.
- jcims 8y agoDon't most props drive off a gearbox? Wouldn't that soak up most of the bending forces?
- sokoloff 8y agoMost (probably 99+% of them) piston airplanes are direct drive, meaning the prop hub is directly bolted to the crankshaft flange as can be seen in the last photo in the linked article. Cessna 421 is one of the common geared engine aircraft. Twin Bonanza, Navion, late Widgeons, R985s, and others also have geared engines, but they’re the vanishingly small minority of piston aircraft. Common types (Cessna 172/182/210, Beechcraft Bonanza/Baron/Skipper, Piper Cub/Warrior/Arrow/Seminole/Seneca/Apache) are all direct drive.
- jcims 8y agoCool! I had always thought they were direct drive, it makes sense to go that route. But then I started noticing gearboxes in various videos to the point where i switched my thinking.
- WalterBright 8y agoGearboxes are another source of failures in aircraft engines, so running direct drive is more reliable.
- jabl 8y ago> With a propeller there would be a bending component (propeller acting a gyroscope) besides the twisting component, especially when say doing aerobatics, while in a car the it will be mostly a twisting component. Is this a significant component? From what I've heard, a big thing with using automotive engines in aircraft is that aircraft engines spend most of their time at close to full throttle. In a car, however, average power output is probably 20% or even less of full power.