Treebeard's Homepage : Stumpers

Treebeard's Stumper
27 April 2001

Kinky Chains

While tuning up my bike for the Dunn Middle School Refugio Ridge Ride on Friday, my chain slipped off the rear sprocket and ended up tangled in the peculiar kinked loop shown below. Bike chains are stiff, so you can't just turn a loop over, and pulling on it only makes it worse. Since I didn't actually remove any link to get into this fix, I know it must be possible to get my chain unkinked. The stumper is to clearly visualize step by step how to create kinky chain loops and how to undo them. Can you find similar patterns that can't be made or undone without removing a link?

Here's a photo of the kinks in my bike chain, and an illustration that shows the overs and unders. To really appreciate this stumper, you should play with a real bike chain and try to make and undo the knots. (Wear rubber gloves unless the chain is new!) The circle on the left represents the front chainwheel which traps the chain. It's interesting that when I finally untangled my chain, I didn't know how I did it! The stumper is to visualize the process step by step.

Answer


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Copyright © 2001 by Marc Kummel / mkummel@rain.org