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Old 04-11-2003 | 05:02 AM
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Giant Scale
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From: Baltimore, MD
Default Rudder/Elevator Pull Pull Systems

Pull-Pull sytems are really quite simple to use. They offer several benefits over pushrods, they are lighter,reduce flutter and are less prone to slop. There have been may threads on this forum that overly complicate the setup but in reality they are easy to install. The system consists of a set of control horns on either side of the surface to be controlled, 2 nylon coated braided wires and servo with a horn. To set up the system you will need some clevises and some swages to crimp onto the wire. Dubro sell a kit that has all the parts you need. Start by installing your control horns on the surface. Some people line up the holes in the control horn with the hinge line. From my experience this can cause binding of the cable.I usually offset the control horn from the hinge line a small amount, maybe an 1/8". This causes a positive ackermann in the system, what this does is to cause one of the cable to go slack as the surface is moved to the extreme and both lines to remain tight at the neutral position. Do a search on ackermann to learn more about this. Mount your servo into the plane, install the servo arm and center it. If you bought the dubro kit it will show you how to attach the wires onto the clevises which will attach to the servo arm. Once attached run the wires to the control surface. Some people use a small piece of pushrod tube at the exit hole or you can cut a slot so the wire exits the rear of the fuselage. Now come the critical part, turn on the radio and center the stick and trims. Center the control surface and tape it or put a small clamp on it to hold it neutral. Pull the wires tight and install the clevises. Adjust the wires so they are taught when the surface is at neutral. Release the clamp and the surface should be at neutral. When you move the control stick away from center you will see that one line it tight and the other line goes slack. Push on the control surface and you will see that there is almost no slop. Thats all there is too it.