Seeking advise on adhesive to use

[sublynx]

What is the best adhesive to use for plastic on plastic? It will need to hold strong as it is a fix for a tail rotor gear that is belt driven.

a little more info that might not make any sense to you:
the gear and the little cylinder shaped part that drives the belt are attached on the same shaft, if a crash involves the tail rotor in any way the plastic connecting the gear to the little cylinder thing will strip causing the tail rotor to not spin at all (the gear will turn, but since the plastic notch that is supposed to turn the part that the belt is attached to is stripped it just spins freely). I am going to attempt to glue these pieces together, and hope that it holds stronger then the little plastic notch that held it together originally.

[Pinecone]

What heli?

In general cyanoacrylate glue would probably be best. Sold at hobby shops as instant glue, you want one of the thin versions to wick deep into the joint.

[brettlw]

My guess would be that it's made out of nylon. Nylon won't hold glue. It's to slippery.

[ghtracey]

I agree with Brett. You need to know what its made of, and find a glue designed for that. CA, in my experience won't hold tortional loads in plastic. What you want is a glue that will "weld" the plastic pieces together, the type you put on both sides and wait a bit before putting them together. Again, you need to know what you are gluing though. The type made for plastic modelling (its a solvent type of glue) may work. If its nylon, you may have more of a problem.

[EricW]

All of the above is true,
If you can order a replacement part than that would be the best solution.
Plastics are nice to work with, but very hard to repair.
If the part ript unevenly and has a large glueing area than it maybe hold with CA or a 2 component glue.
Another option could be to machine the plastic part out of another material like aluminium and attach the gear to that (if possible).

[ghtracey]

I re-read your post and maybe there is something you can do to prevent the problem. It sounds like you are saying that you have the rear pulley on the tail belt that turns a gear in the tail system. These two should be connected together, but in a crash they shear apart?

If this is correct, you could maybe try "pinning". This is a solution that modellers use to strengthen joints. Using a pin-vise (small drill you turn with your fingers) and a bit the size of a paper clip (it needs to be a fairly tight fit), drill 2 holes into the part 180 degrees apart, through the location where the part usually shears. Slide a straight piece of paperclip into the hole, mark it for length remove and cut it and then glue it in using slow CA. Try and get these as close to 180 degrees apart as you can to keep the pulley in balance.

Don't do this on a high-powered heli, but if its just a small plaything, it may help avoid the replacements. Of course all of this assumes there is enough room on the pulley to be able to drill through.

If I'm wrong in how the part is setup and where it's breaking, a pic or two may result in some other advice.

Graham