Cottered crank and pin problem (question for gurus)


I have a very old unicycle. There is no indication of brand name, and it doesn’t look similar to anything I’ve seen on or elsewhere. I need to post a picture sometime, but anyway… the point of the post.

It has cottered cranks, and the right-hand side likes to eat cotter pins. I’ll put a new one in, and after about two weeks, the crank arm starts to have some “play” to it. About a month after that and it’s barely rideable. In the past I have just been buying pins from local stores, but they are carrying them less and less.

What happens to the dead cotter pins is they are twisted. It looks like somebody cuts them in half and glues them together slightly twisted.

I want to know if anybody has seen this and where the problem lies. Is it the axle? The crank arm? What are some possible solutions?

One thing I noticed about the axle is that on the left side, it sticks out from the bearing 2-3cm, while on the right side it sticks out 3-4cm.

I hope to get a new 20" eventually, but even then I’d like to keep this one… and in good condition; it has served me very well.

Thanks for any help…

i had an old uni too that i learned on and had the same problem with the cotter pins. what does it is probably that they werent made to handle trials or off roading and the pins just get mangled. i solved the problem by getting a united trials uni and now the lasco cranks are flopping so i need to get new cranks. i guess thatll be a problem till i get profiles hehehe

Kyle Grasso
aim- KyleBMX4fun