Contra-rotating engine revisited

The previous post on this topic got me wondering. Just how different
would the two engines need to be? I'm no expert, but it seems to me
cam shaft(s), magnetos, and prop are the parts that would be different
from one side to the other. I almost forgot, reverse the polarity on
the starter motor. What am I missing?


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"Chris W" wrote in message
...
The previous post on this topic got me wondering. Just how different
would the two engines need to be? I'm no expert, but it seems to me cam
shaft(s), magnetos, and prop are the parts that would be different from
one side to the other. I almost forgot, reverse the polarity on the
starter motor. What am I missing?

How about an engine with the crankshaft running out the front and back, so
you could mount a prop on the either end? That way you could have
counter-rotating props using the same engine.

Steve Foley writes:

How about an engine with the crankshaft running out the front and back, so
you could mount a prop on the either end? That way you could have
counter-rotating props using the same engine.

There's still some asymmetrical engine torque, since the engine itself
turns in only one direction.

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Mxsmanic wrote:
Steve Foley writes:

How about an engine with the crankshaft running out the front and back, so
you could mount a prop on the either end? That way you could have
counter-rotating props using the same engine.

There's still some asymmetrical engine torque, since the engine itself
turns in only one direction.


I think he meant you could mount the engine backwards, then it would be
spinning the other way. With the crank going out both ends you could
mount the prop on it, no mater which way it was in the plane. Seems to
be more work than what some twins do now if you ask me. Mounting the
engine in backwards, would not a simple matter.

--
Chris W
KE5GIX

"Protect your digital freedom and privacy, eliminate DRM,
learn more at http://www.defectivebydesign.org/what_is_drm"

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"Mxsmanic" wrote in message
...
Steve Foley writes:

There's still some asymmetrical engine torque,

No, there is not.

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.

Vacuum pumps are different (although these are accesories)
"Chris W" wrote in message
...
The previous post on this topic got me wondering. Just how different
would the two engines need to be? I'm no expert, but it seems to me
cam shaft(s), magnetos, and prop are the parts that would be different
from one side to the other. I almost forgot, reverse the polarity on
the starter motor. What am I missing?


--
Chris W
KE5GIX

"Protect your digital freedom and privacy, eliminate DRM,
learn more at http://www.defectivebydesign.org/what_is_drm"

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com

This is annoying. "COUNTER-rotating" is the term you want.
"CONTRA-rotating" is when you have two different blades on the same
shaft spinning in different directions. About 50% of the time one of
these terms gets used, they get them mixed up.

http://en.wikipedia.org/wiki/Contra-rotating_propellers
http://en.wikipedia.org/wiki/Counter...ing_propellers

Chris W wrote:
The previous post on this topic got me wondering. Just how different
would the two engines need to be? I'm no expert, but it seems to me
cam shaft(s), magnetos, and prop are the parts that would be different
from one side to the other. I almost forgot, reverse the polarity on
the starter motor. What am I missing?

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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