My cranks always seem to be loose, and I just made a crank press from two pieces
of 8/4 maple, two pieces of 3/4 inch allthread and several 3/4 inch washers and
nuts. It worked, it took the wobble out of my cranks even after they were
already worn.
I cut the 8/4 maple to 1 7/8 by 3 1/2 by 12 inches and drilled a 3/4 inch hole
two inches from each end centered on the narrow side and passing all the way
through. I cut the allthread to sixteen inches long, and pushed one piece
through each of the holes in one piece of the maple. I put a washer and nut on
both sides of this piece and tightened as much as I could.
I then placed the unicycle so that the wheel was hanging half over the edge of
the bench, carefully placed the block underneath the wheel so that the allthread
poked up through the spokes with the block centered on the end of the crank and
hub, and slid the other block of maple down over the allthread so that I had a
hub sandwich. I put washers and nuts over the ends of the allthread, tightened
securely, and tapped the blocks with a hammer to farther seat the cranks. It was
possible to retighten somewhat after tapping.
When I removed the press, I was able to tighten the crank nuts about a quarter
turn, enough to eliminate the wobble. I torque to forty foot pounds at Tom
Miller’s recommendation, and have never stripped any threads.
The cranks left severe indentations in the maple so I have glued some washers to
the blocks where they seat on the cranks, but I have not had the oppertunity to
try this arrangement as the glue is not dry yet.
Good Luck, Joe Stoltzfus