Tuesday, June 2, 2009

Holy Oversized Sprockets Batman!

In order to maximize acceleration, I needed the biggest rear sprocket that would fit. I measured the clearance avialable on the swingarm and a 71 tooth sprocket would just barely fit. So to give myself a little extra room, I decided to go with a 68 tooth unit. Combined with a 12 tooth in front, the gear ratio of 5.66 is a little high, and will sacrifice top speed, but I'm not too interested in going on the freeway. If I decide freeway speed is needed later, I can always put in a 14 or 15 tooth front sprocket.

The front sprocket and chain arrived from Grainger a few days ago, but the rear sprocket from Sprocket Specialist was taking it's sweet time. After finally arriving, I nearly choked at how big the sprocket was. Had I made an error calcualting the sprocket size? I estimated the 68 tooth sprocket at 13.75" diameter, but it looked like 16" to me. You know that saying "measure twice, cut once"? Well I'm famous for cutting twice, and sometimes more.

A tape measure told the truth: 13.875" (whew!). Still looks pretty big to me.

After putting together the hub and sprocket, I threw the rear wheel in place and cut the chain to length. Sprocket has a least 1/4" clearance from the swingarm, the chain fits and lines up just fine. Even the mislocated bolt pattern for the motor is not going to be a problem.

At this point, I'm feeling a little lucky and may go buy a few lottery tickets.

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