[ODE] Torquing the joint

[Henri Hakl]

When I apply the torque it makes the body behave like a propeller, turning
through the center of mass - but instead imagine that you have a body
attached to a string and you spin the body in a far arc. The center of
rotation is not at my hand that holds the string. Clearly these aren't the
same.

Another example: apply torque to your lower arm by twisting it manually in
the middle with your other hand, and due to the nature of your body this
torque is propagated to your upper arm. This is fun, for sure, but what I'm
looking for is the "torque" that needs to be applied to just let the arm
pivot at the elbow (imagine you're lifting dumbells) - and the upper arm
stays motionless.

I think it is true that the overall angular momentum on the body(part) may
be the same, but here I'm looking for a more complex interplay of forces.
Any ideas?


----- Original Message -----
From: "Nate W" <coding@natew.com>
To: <ode@q12.org>
Sent: Wednesday, December 04, 2002 11:16 PM
Subject: Re: [ODE] Torquing the joint


> On Wed, 4 Dec 2002, Henri Hakl wrote:
>
> > I've put together a little articulated system and now wish to apply
> > torque forces to various parts of it. But I'd like the torque forces
> > to act at the joints/pivots, rather then through the center of mass of
> > each object. Any suggestions on how this can be accomplished?
>
> It's my understanding that the effect is the same either way.  Don't
> worry about it. :-)
>
> --
>
> Nate Waddoups
> Redmond WA USA
> http://www.natew.com
>
>
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