Monday, April 13, 2009

Axlus Interruptus

I felt something funny as I rode my bike to work on Friday morning, but I couldn't quite figure it out. On the way home that afternoon, the symptoms steadily got worse and became more identifiable. I heard a loud clunking sound now and then, which was very similar to the sound made by my industrial padlock banging on the frame. I removed the padlock from its hanger, but the banging continued. As I pedaled, I also felt a very fast buffetting sensation, as if the wind was blowing me forward and backwards, reversing direction about eight times per second. It was very windy on Friday afternoon, but I didn't think wind could change direction so fast.

About the third time I stopped to check things out, I realized that my rear wheel was free to wobble side-to-side about an inch at the rim, even though the axle nuts were tight to the frame. Uh oh, not good. When I got home and took it apart, I discovered that the axle was broken in two pieces.

I expect the clunking sound was from the wheel flopping from one side to the other. And the buffeting feeling was probably related to the ball bearings being forced around unnaturally, several times per second.

A little bit of internet research at the Parke Tool and Sheldon Brown websites confirmed this old bike has what is called a 'freewheel' hub. And some general googling found opinions on their shortcomings:

Broken axles used to be fairly common with freewheel hubs since the drive side bearings were well inboard and the unsupported axle under the freewheel was quite long.

Yep, my drive side bearings are about 1.5 inch inbound, and my axle was broken right at the inboard bearings. I guess my break is due to old age, excessive pothole shocks, carrying too much weight, letting the bearing cones get loose, letting the grease dry out, or all of the above.

A quick visit to a local shop provided a replacement axle, cones, and bearings. Everything was replaced except the bearing cups in the wheel. Everything reassembled quickly. Adjustment was a little tricky with only two hands, until I figured out some secrets. We'll see how well I adjusted it after riding a few miles, and whether the bearing cups were damaged or not...

No comments: