[NSRCA-discussion] Rudder pull-pull

[J N Hiller]

Ops I blew it this morning when I stated that using wheels of different
diameters would result in slackening or tightening of the cables, WRONG.
Thanks Bob for putting me straight and my apologies to all. It may just be
that round wheels of unequal diameter may be the best, amplifying torque and
reducing angular deflection without using bell cranks, while maintaining
cable tension. I must try this.
Oh Matt, flying was good this afternoon / evening. I went out about 3:00 PM,
after some painting and yard work and a little CAD time on a 55 size Option
this morning waiting for the temperature to come up a bit.
Boy dose my flying suck.
Jim Hiller

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Bob Richards
Sent: Friday, May 09, 2008 1:27 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Rudder pull-pull

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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