Elevator control: Pull-pull vs push rod

[ronlock]

I use pull-pull with vinyl coated kevlar cord it for rudder, 
and have never had a failure. But somehow, I can't bring 
myself to trust pull-pull linkage for an elevator.

I don't like bellcrank systems- I prefer to avoid the weight
and additional linkage points.

Bushed at the rear push rods work OK, some setups require 
a bushing or vibration dampener in the center.

Another possibility Ive used with good success a few times -
Sullivan  Precision Rod.   It's a golden rod type system but 
the inner rod is carbon fiber reinforced.   It comes in
2-56 and 4-40 sizes.   Using the 4-40 size for pattern birds, 
I set up one outer/inner pushrod sytem from the servo to a 
point about midway between servo at stab.   Then transition 
to two outer/inner pushrods, one to each stab half.   This set up
requires mounting braces every 12 inches or so.   Where
you put the one rod to two transition isn't critical, other than
placing it where you can reach it to work on.   Getting the 
mounting braces into ther rear of a fuse shell may be a 
difficult reach.    Once installed, it never vibrates or needs
maintenance.

Later
Ron Lockhart
  ----- Original Message ----- 
  From: Keith Black 
  To: discussion at nsrca.org 
  Sent: Saturday, December 07, 2002 2:38 PM
  Subject: Elevator control: Pull-pull vs push rod


  I'm in the process of building a new Aries and am trying to decide whether to use pull-pull or a push-rod on the elevator. I'd like to hear some opinions on which is the best way to go. I plan to go with pull-pull on the rudder, but I'm undecided on the elevator.

  The Aries requires no formers so there would be no problem with space in installing a pull-pull system for the elevator, however I know there are different theories as to which is the best approach. If you have an opinion please explain why you feel the way you do (weight, control accuracy, reliability, etc.).

  For those push-rod proponents I'd be very interested in hearing your opinion on the best approach to installing a push rod system. For example using a "Y" push rod with bushings, using an bell crank, etc. 

  I look forward to hearing everyone's opinion.

  Thanks,
  Keith Black
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