A couple weeks ago, one crank started to get loose. I tried tightening the
cotter and ended up breaking it. I went to the local bike shop, bought a new
cotter for $1.50, and they put it in using a weird gadget that squeezed it in.
They also tightened the other one. Anyway, the moral of the story is that if
your crank starts getting loose, take it to a bike shop, and they’ll probably
tighten it for free, and you’ll save $1.50… 
Now, back to unicycling…
Greg