[SPAM] Re: Re: Pull-Pull servos

[Jim Ivey]

Troy
I measured my rudder horns on 2 planes One was 3/4 in to the hinge line and the other is 1 in. to the hinge line. I agree with you about the mech. advantage of longer horn distance. They need to be longer.However I don't think that has a direct effect on the wear of the top of the servo. I am thinking the continous pull of the cable tension is what is wearing my servos on the output arm for-aft.I am leaning toward what Bob P. said about which is worn the bearing or the case. My tension is not as much as you describe on yours. I am thinking your top end may be worn also. When you get time disconnect the cables and check the output shaft for play in the for-aft direction.
 My next plane will have longer horn connections and a longer servo arm to match.
> Thanks Troy
 Jim Ivey

> From: "Troy A. Newman" <troy_newman at msn.com>
> Date: 2004/11/30 Tue PM 07:53:22 EST
> To: <discussion at nsrca.org>
> Subject: Re: Pull-Pull servos
> 
> 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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