Not sure my linkages are up to the job

[Adrian Smith 1]

All the 50-60cc aircraft I have bought over the last couple of years include the nylon ball joint couplers for use with metal push rods. An example is here:-

**LINK**

I am beginning to doubt whether they are up to the job on bigger scale aircraft when you consider a metal and nylons threads are mixed. On flying one of my 60cc leccys recently I noticed the rudder cables had sagged somewhat ( I can understand it in hot weather if cables relax a bit, not in cold.) The couplers here are of the nylon/metal variety and I suspect the metal coupler thread is "pulling out" marginally from the nylon horn. The same effect was noted on the starboard aileron. I duly adjusted both surfaces and painted the exposed coupler thread to see if this is the case in subsequent flights. I Know Secraft produce an all metal coupler to solve the rudder issue, but I am thinking I may need to go back to using more heavy duty metal clevises with say a M4 pushrod & nut. What do you guys use?

 

Edited By Adrian Smith 1 on 07/01/2019 14:21:43

[john stones 1 - Moderator]

I have both on various models Adrian, I've found myself tightening up closed loop on my Cap, that has metal clevises, I put it down to the wire stretching slightly, couldn't find any other obvious reason for it. The nylon links are so good a fit and tough to thread on, I've had no problems with em.

[Adrian Smith 1]

Thanks for that, John. I just thought may be I was missing a trick here. Your observations about the challenge of threading nylon links I agree with. I just notice after few adjustments the link's thread seem to loosen in some cases. In not all I hasten to add.

[john stones 1 - Moderator]

If you feel threads wearing, change them Adrian, you wouldn't forgive yourself if it let go. Check for any burr on the threaded link as well.

[Ronaldo]

Hi Adrian. On my 50cc o 100cc petrol I have been using the plastic ball links that take both the 3mm threaded push rod, and 3mm threaded closed loop connectors. All been ok so far. As for rudder wires, mine sometimes slack off in warm weather, so I put that down heat expansion. Have you checked that the crimped brass ferrule isn't slipping, causing the wire to slacken off ? I had that problem years back when I first started with closed loop, I fixed it by double looping the wire through the ferrule, sometimes replacing the kit provided brass ferrule with my own home made ferrules from bigger bore brass tubing to take the extra loop of wire if needed. Then crimped in 2 places and a dab of thin CA to finish off.

 

PS ..... as John mentions about checking for burr. Sometimes I've come across  sharp burrs in the closed loop connector's hole where you thread the wire through, chafing the plastic covering of the wire. This can be cleaned up easily by twisting a larger diameter drill bit with the fingers over the hole to slightly chamfer the hole's edge. Also I agree with John, if in doubt, and not happy with them ... best change them

 

 

 

Edited By Ronaldo on 07/01/2019 16:21:40

Edited By Ronaldo on 07/01/2019 16:36:40

[Adrian Smith 1]

Thanks, gents. All good advice I will be following