[NSRCA-discussion] Rudder pull-pull

[Bob Richards]

As a lot of people do, I have my own opinion about pull-pull and using wheels/arms on servos.

Using pulleys on both the servo and the control ends would make the system truely linear, even if the pulleys are not the same size. Running differnt size pulleys would not be a problem, if it were there would not be different size pulleys on your auto engine. All you really have to be careful about is that the center of the pulley on the control surface is located exactly on the axis of the hinges.

Using a pulley on the servo, and regular arms on the control, would result in built-in expo. The control surface would move an increasing amount for a given servo movement as the surface moves away from center. To me, this would be desireable for pattern since, for a given max deflection, you would have more precision and holding torque at neutral. Any problems that someone might preach about using this setup can be minimized to a non-issue amount with careful location of the horns on the control surface.

I agree to disagree with some people that the servo arms and control horns have to be the same length to work properly. In my opinion, careful location of the control horns will minimize any problems. It may not make the problem go away completely, but it will be small enough to be a non-issue. If one side goes *just a little slack* when fully deflected, that is ok with me. FWIW, the further apart the servo and control surfaces are from each other, the less of a problem you will have with geometry.

Just my humble opinion.

Bob R

--- On Fri, 5/9/08, chris moon <cjm767driver at hotmail.com> wrote:

> From: chris moon <cjm767driver at hotmail.com>
> Subject: [NSRCA-discussion] Rudder pull-pull
> To: nsrca-discussion at lists.nsrca.org
> Date: Friday, May 9, 2008, 10:13 AM
> Can someone explain the benefits (real or otherwise) of the
> pull-pull 
> wheel type rudder servo arm vs. a regular servo arm?  Is
> there some real 
> benefit, or is it bling?
> Thanks
> 
> Chris
> 
> 
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