[NSRCA-discussion] Pull-pull setups

[J N Hiller]

I make them from ‘G-10’ fiberglass sheet available from FTE.   http://www.franktiano.com <http://www.franktiano.com/>  I laminate 3 .03” thick for to get .09” thick. I pivot them on 1/8 shaft using brass tube bearing through a 3/8” dowel hub for secure gluing and to prevent flexing of a long shaft. Here is a photo showing the entire sub-assembly, which I build and set-up before installation in the fuselage.
Jim
 
-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of CHV69 at aol.com
Sent: Wednesday, January 23, 2008 5:09 PM
To: nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] Pull-pull setups
 
In a message dated 1/23/2008 8:06:14 P.M. Eastern Standard Time, jnhiller at earthlink.net writes:
John, I can’t comment on Kevlar. I have only used steel (.021” Sig control line cable). I also use internal bell cranks to eliminate cable tension load on the servo mount rubber grommets and shaft. This way I can run the cables quite snug. Short ball link connectors connect the bell cranks to the servo.  By using different holes in the servo wheel or bell crank I can use the full servo travel, and reduce the control surface travel without resorting to non-parallel linkage or transmitter endpoint and accompanying resolution reduction.
I haven’t been totally happy using dual elevator servos so I cable them as well, connecting all 4 cables to a single bell crank. It is quite easy to balance the travel, center and end-points by adjusting the threaded control horn and cable length. When I started doing this it yielded the tightest system I ever used.
For what it is worth.
I like that idea for the elevator setup.
What type of bell crank is it that you use?
 
Carl



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