Tour Easy: Terracycle Chain Idler Bushing

It turns out that under rare conditions, triggered by fumbling a front derailleur shift, the upper chain section (out of the picture on the top) can whip vertically enough to jam between the Terracycle Idler’s mounting bolt and its longer chain retaining pin:

Tour Easy - Terracycle idler
Tour Easy – Terracycle idler

Whereupon the chain falls off the chainring, jams firmly between the spider and the crank, and brings the proceedings to a halt.

Having finally figured out the cause, I made a simple bushing to fit around the mounting bolt, reduce the gap, and (I hope) eliminate the problem:

Tour Easy - Terracycle idler bushing
Tour Easy – Terracycle idler bushing

Given its rarity, I will need a few more years to verify the solution.

Might get around to cleaning the chain one of these days, too …