Contra-rotating engine revisited

Steve Foley writes:

No, there is not.

Unless the engine is weightless and frictionless, it will exert torque
on the airframe whenever it is turning, even if there are no props.

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In article ,
Mxsmanic wrote:

Steve Foley writes:

No, there is not.

Unless the engine is weightless and frictionless, it will exert torque
on the airframe whenever it is turning, even if there are no props.

No, that's not true. If there is no prop, the engine will only exert
torque on the airframe when its rotational speed is changing.

My mom used to have a 1960-something Buick with a big-ass V8 and a mushy
suspension. You could set the thing rocking just by revving the engine in
neutral.

Roy Smith writes:

No, that's not true. If there is no prop, the engine will only exert
torque on the airframe when its rotational speed is changing.

The forces that compel the engine to rotate in one direction engender
equal and opposite forces that tend to rotate the airframe in the
opposite direction.

My mom used to have a 1960-something Buick with a big-ass V8 and a mushy
suspension. You could set the thing rocking just by revving the engine in
neutral.

That's because the amount of torque changes with the rotational speed
of the engine. However, as long as it is turning, it is exerting
torque on the rest of the car.

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Please do not feed the trolls!

Sorry, but you are wrong here. As long as there is no load external to
the engine, it's own friction torque will have no external
manifestation. There will be an external torque, momentarily while the
engine is accelerated or de-accelerated.

tom


Mxsmanic wrote:
Steve Foley writes:

No, there is not.

Unless the engine is weightless and frictionless, it will exert torque
on the airframe whenever it is turning, even if there are no props.

--
Transpose mxsmanic and gmail to reach me by e-mail.

tom writes:

Sorry, but you are wrong here. As long as there is no load external to
the engine, it's own friction torque will have no external
manifestation. There will be an external torque, momentarily while the
engine is accelerated or de-accelerated.

If you run the engine in zero gravity, does the crankshaft spin while
the engine remains still, or does the engine spin while the crankshaft
remains still, and why?

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