Re: Torque on twin engine planes?
- From: "Doug McLaren" <dougmc+usenet-20060911@xxxxxxxxxxx>
- Date: Mon, 11 Sep 2006 23:19:27 GMT
In article <nuadnYBU67nJQJjYnZ2dnUVZ_o-dnZ2d@xxxxxxxxxxx>,
Jennifer Smith <jennifer@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
| I know that the common way to counteract torque in twin prop (i.e. the
| banana heli config) HELICOPTERS is to just counterrotate the blades.
Well, short of a tail rotor, that's the only way to counteract the
torque :)
| On my own planes I've never bothered, since I never consciously
| thought about it.
Torque issues are *huge* in a helicopter (and I guess in a plane like
the Osprey.) In a plane, they're much smaller and can be safely
ignored in many cases.
| Google searches showed that counterrotating seems to be the common way
| to fight it... but why even bother?
Why bother? Because it makes for a slightly better (in most cases)
flying plane. For most planes the torque, prop wash, P-factor and
gyroscopic precession aren't usually a big deal except possibly at
takeoff, but if you can minimize them simply by having one engine run
the other way, that's a good thing.
Why not bother? Logistics. If your engines go opposite directions,
you probably can't just swap engines back and forth, and something
will have to be different about each engine to make it turn in a
different way. And you'll also need a `pusher' (reversed) prop for
that side.
Talking about models, for a glow engine I think you generally swap out
the crankshaft to get an engine that rotates the other way. Of
course, this special crankshaft may not even be available ...
For brushed electric motors, all you do is swap the wires, and that's
fine if the timing is neutral, but if it's not, you also need to
adjust the timing. (And it shouldn't be neutral unless you just don't
care about performance or motor life, which is often the case with
cheap can motors.)
For brushless motors, you can generally reverse a motor just by
swapping two of three three leads -- no sweat. (If it's a sensored
brushless motor, then you also have to worry about timing again, but
sensored brushless motors are rare nowadays.) The ESC takes care of
the timing.
--
Doug McLaren, dougmc@xxxxxxxxxxx
It's always darkest right before it goes pitch black.
.
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