Please use good strong pushrods and other linkage parts.
A sample of the assembly that we
used is shown in the picture below. Notice we use carbon fiber pushrods and Dubro HD horns.
The servo connection is done with Sullivan 4-40 or Dubro clevises, or with HD 4-40 ball links.
Avoid using ball-links with plastic servo arms, they generate a twisting force on the servo arms
that will fatigue and fail.
Making pushrods that will withstand the forces involved in a large plane of this type is very
simple once you see how it is done. If you have your own design, feel free to use it, but here’s
one that is cheap and strong.
You will need a length of 3/16” carbon fiber or fiberglass tubing, a length of 4-40 all-thread
rod, and some 4-40 nuts. All this hardware is included in our optional hardware kit.
First, set up your linkage using the clevises and the 4-40 all thread cut to the proper length. You
can make all your pushrods at once, so get all those rods set to the right length. If you use a
metal clevis, be sure the pushrod goes all the way into the threaded section, plus a little to allow
a range of adjustment. With plastic clevises like Dubro or Rocket City, the rod should screw
into the clevis about 1/2 inch to be sure there is sufficient strength.
Measure each pushrod, and cut a piece of carbon-fiber tube that is 1 1/2” shorter than the rod.
Slip the tube over the rod and tighten down a nut from each end so that you leave an equal
amount of thread at each end to mount the clevis. Tighten the nuts slightly so they don’t come
loose and so there is a little tension on the rod inside the tube.
You’re done. Install the pushrods.
