How to replace plastic pushrods
07-22-2007 | 03:59 PM
#1
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From: Frisco,
TX
How to replace plastic pushrods
I am a newbie and building is not one of my strong points. About a month ago, I build a SIG Kadet LT-40 trainer plane. I've been flying it for about a month. Yesterday I was flying with my instructor and it felt like the plane was flying sideways. At first we thought it was the wind, however my instructor landed the plane and realized that the rudder was sticking. It sticks in the last position it was in at take-off...if the rudder wasn't straight on take-off, then it wasn't straight during the flight. We took off the wings and noticed that the servo is working fine. It responds to the transmitter just fine and it is moving well, however the movement of the servo is not causing the same movement of the rudder. My instructor thinks there is a problem with one of the plastic pushrods and has recommended that I replace both pushrods (for the rudder and elevator).
Like I said, building/repairing is not my strong suite. The pushrods were installed at the factory and ripping them out and replacing them scares the hell out of me. I'm afraid I'll either tear things up really bad getting them out or that I won't be able to get the new rods back in!
Anyone have any good tips on how to perform this "surgery"?
Like I said, building/repairing is not my strong suite. The pushrods were installed at the factory and ripping them out and replacing them scares the hell out of me. I'm afraid I'll either tear things up really bad getting them out or that I won't be able to get the new rods back in!
Anyone have any good tips on how to perform this "surgery"?
07-22-2007 | 04:08 PM
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RE: How to replace plastic pushrods
well remove them, them buy some sullivan gold'n'rods and put them in there (they are nylon rods running through plastic tubes), just cut the length you need, screw the little clevises on, slide them donw the fuselage and out the opening at the end, connect them up and jobs done (i replaced all of my stock metal linkages with sullivan rods and they are great
07-22-2007 | 05:09 PM
#3
RE: How to replace plastic pushrods
if the nylon rods are not suported or installed in a 's' type pattern they will flex.use 1/4 dowel with a piece of 1/16" wire at the servo end with a z bend then a threaded rod at the other end you may have to make a few bends to exit the fuselage if you do only make 45 degree bends do not make 90 degree bends as they will flex too.I would check the nose gear linkage first to see if it is binding then check the servo for stripped gears as there really is no load on the rudder while in flight.
07-22-2007 | 06:16 PM
#4
RE: How to replace plastic pushrods
aerowoof - he said that the servo was moving but the rudder was not, even on the ground from the impression I got. Before I tore ANYTHING out, I'd be tempted to find where the problem is. It may not be the pushrod at all but a binding rudder itself. Find the problem BEFORE you cure it. Disconnect the pushrod at the rudder and see if the pushrod end moves freely with the servo. Then see if there is any binding in the rudder itself.
07-22-2007 | 06:41 PM
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From: Riverhead, NY
RE: How to replace plastic pushrods
ORIGINAL: dwilt72
I am a newbie and building is not one of my strong points. About a month ago, I build a SIG Kadet LT-40 trainer plane. I've been flying it for about a month. Yesterday I was flying with my instructor and it felt like the plane was flying sideways. At first we thought it was the wind, however my instructor landed the plane and realized that the rudder was sticking. It sticks in the last position it was in at take-off...if the rudder wasn't straight on take-off, then it wasn't straight during the flight. We took off the wings and noticed that the servo is working fine. It responds to the transmitter just fine and it is moving well, however the movement of the servo is not causing the same movement of the rudder. My instructor thinks there is a problem with one of the plastic pushrods and has recommended that I replace both pushrods (for the rudder and elevator).
Like I said, building/repairing is not my strong suite. The pushrods were installed at the factory and ripping them out and replacing them scares the hell out of me. I'm afraid I'll either tear things up really bad getting them out or that I won't be able to get the new rods back in!
Anyone have any good tips on how to perform this "surgery"?
I am a newbie and building is not one of my strong points. About a month ago, I build a SIG Kadet LT-40 trainer plane. I've been flying it for about a month. Yesterday I was flying with my instructor and it felt like the plane was flying sideways. At first we thought it was the wind, however my instructor landed the plane and realized that the rudder was sticking. It sticks in the last position it was in at take-off...if the rudder wasn't straight on take-off, then it wasn't straight during the flight. We took off the wings and noticed that the servo is working fine. It responds to the transmitter just fine and it is moving well, however the movement of the servo is not causing the same movement of the rudder. My instructor thinks there is a problem with one of the plastic pushrods and has recommended that I replace both pushrods (for the rudder and elevator).
Like I said, building/repairing is not my strong suite. The pushrods were installed at the factory and ripping them out and replacing them scares the hell out of me. I'm afraid I'll either tear things up really bad getting them out or that I won't be able to get the new rods back in!
Anyone have any good tips on how to perform this "surgery"?
Edit: Oops! I was writing this while Bruce posted his similar reply above. Jeez, you guys are quick.
07-22-2007 | 06:57 PM
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RE: How to replace plastic pushrods
Most definitely. Those that say to "just rip 'em out" are giving bad advice. Too many people will make the mistake of starting to just replace parts instead of diagnosing the problem and fixing it correctly. For instance, your instructor recommending replacing BOTH the rudder and elevator pushrods when you are only having problems with the rudder. That definitely falls under that category of "If it ain't broke DON'T fix it". Follow the advice of Bruce and Ptmac3 and figure out what is causing the rudder to not bind. I've build the LT-40 as well as have instructor a lot of people using that plane and there is nothing wrong with the setup Sig has for the pushrods.
Ken
Ken
