Sunday, January 25, 2009

Driveshaft Disassembly

Today I finished stripping my Crosstown 7 in order to replace the broken frame. That involved removing the driveshaft assembly, cleaning it out, and re-greasing it. The bottom bracket came out by loosening the three screws on the left-hand side. Here's what the inside looks like. Somehow, dirt managed to get in there, but I don't think that had any consequence on performance, since the whole front crank case is sealed.

Here's what the front crank-case assembly looks like fresh from the bottom bracket.

Loosening the three screws on the other side allowed me to open the case and remove the gears for cleaning. Initially, the inside of the crank-case was full of grease, which I removed with clean rags.

I noticed that the gear ratio was 11:27. Because 27 and 11 are both prime, each tooth on the shaft eventually interacts with each tooth on the bevel gear, and no wear pattern develops. After cleaning everything up, I closed it up again and shot it full of fresh Teflon grease.

Here's what the rear end of the drive shaft looks like. This is where the 7-speed internal hub connects. The hub is similar to the chain driven version except for the bevel gear in place of the chain cog.
The next step is to receive the new frame and reassemble. I'm expecting the frame on Wednesday, so I'll post photos of the reassembly process then.


Jared said...

Interesting drivetrain! How often do you need to add grease to the crank case?

Tim said...

I usually put in a shot of grease every 100-200 miles. At my pace it was about every second or third week.