Hub Failure

When riding the uni.5 on Monday 25 February 2002, one of the planet shafts galled and seized. This caused me to rapidly meet the pavement. I skinned up my right knee pretty badly and bruised it as well as my left hand. I was 15 miles into the initial test riding of the unicycle with the geared hub.

When I took the hub apart I found this (see photo below). The 440 stainless steel planet shaft is clearly marred up. So is the inside of the planet gear but it is difficult to see in this photo. The shaft had spun in its press fit into the planet cage flange. I decided to redesign using a completely encased planet cage, bronze bushings in the planet gears, hardened steel dowel pins as the planet shafts, and bronze thrust washers. The gear teeth survived with no indication of damage so I decided to reuse them.

Photo by Greg Harper