[ODE] Torquing the joint

[Henri Hakl]

Thanks guys...

I'll go and mess with it some more.

hmmm...

OH yea - anybody else around here excited about the soon-to-be-released
Master of Orion 3???

----- Original Message -----
From: <jnilson_99@yahoo.com>
To: <ode@q12.org>
Sent: Thursday, December 05, 2002 12:08 PM
Subject: Re: [ODE] Torquing the joint


> > 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.
>
>
> I know exactly what you're talking about. The classic
> example of what you want is best exemplified by the
> difference between a propellar and a pendulum.
>
> A propeller spins about it's center by applying ONLY a
> torque.
>
> Whereas a pendulum is just like a propellar except it
> has an additional linear acceleration applied to it at
> the center of mass, gravity in the case of a pendulum.
> The torque is applied by the joint holding the
> pendulum to a fixed object.
>
>
> To get the motion you want you need to apply both
> torque and linear acceleration. I think angular joint
> motors do this implicitely for you.
>
>
> john
>
> --- Henri Hakl <henri@cs.sun.ac.za> wrote:
> > 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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