I have put together a Level wind mechanism that uses a 1" steel bar 40" long with a helix cut into the bar in opposite directions. At each end of the bar the counterclockwise helix joins up with the clockwise helix. I am using a 'key' that fits into the helix to travel along the shaft when the shaft is rotated. The travel speed is about 12 inches per second, and I am carrying about a 15 pound load on the key mechanism.
I am finding that the key (presently made of brass) wears down very quickly (about 1000 cycles) and suspect that it may be due to two reasons:1) The rapid change in direction hammers the key on the end of the spline 2) The key is not positively, centered in the spline when it reverses direction, and during travel along the bar.
This causes the key to wear prematurely. I am tempted to build a steel key, but fear that then the double helix bar will wear or fail, and it is fairly expensive.
Has anyone had any experience that they would like to share on projects of similar nature?
Thanks in advance,