Pull-Pull servos

[Troy A. Newman]

Jim,

Better geometry on the linkages doesn't end at the pivot point over the
hinge line.

I use longer rudder control horns. I just measured mine on both Supreme's
and the Pinnacle. My clevis connection point is 1.5"  from the center of the
hinge. I see lots of guys making this linkage very short...This causes
problem when the rudder is deflected 30+ degs

I use the MK offset medium control horns  (part# MKD0815)These horns put the
pivot forward over the hinge line and they are very light and strong. Also a
big bonus is they are super easy to install. Yes they cost more than a 6-32
bolt but I think the easy way they install and the weight is lighter than
the  6-32 bolt gives a reason to buy them...Not to mention the offset angle
that puts it over the hinge line.


Also you are not giving the mechanical advantage to your servo. All servos
will have some slop or gear lash...Having a longer control arm on the
surface will reduce the effect this gear lash has on the surface...

Also this will have the effect of being better on you servo.

I have been using longer control horns on the rudder since About 2001 and it
makes a difference. I tried shorter horns this year and the rudder felt
spongy to me.
Another thing is my cables are very very tight....As in Banjo tight. I have
not had any problems running 8411SA or 8611's on this setup.

I don't believe in elevator on cables but the rudder is a good candidate for
cables.

Troy
----- Original Message ----- 
From: "Jim Ivey" <jivey61 at bellsouth.net>
To: <discussion at nsrca.org>
Sent: Tuesday, November 30, 2004 4:44 PM
Subject: Pull-Pull servos


> Guys
>  Another discussion about pull-pull systems. I use pull-pull on the rudder
and compared to the elevator servo the rudder servo gets worn and loose at
the top bearing much quicker than the elevator servo.The cables are not too
tight and are setup correctly so far as ackerman is concerned.The rudder
being much bigger than the elevators may cause some of this problem. More
momentum...
>  I have used the JR top post brace before, but it can't be used with the
8411's without some mods.
>  Any input or solutions?
>
> TIA
>
> Jim Ivey
>
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