Archive for September 23rd, 2013

BOB Yak Trailer Flag Ferrule Reaming

The BOB Yak trailer I tote behind the ‘bent has a flag with a two-part pole which generally stays together; I pull the entire affair out of the frame socket when I hang the trailer up after a trip. The ferrule between the two pole sections recently worked loose and I took it to the Basement Workshop for repair.

The assembled nickel-plated brass (?) ferrule came off both pole sections all too easily, which was a Bad Sign: those little punch marks originally clamped the tubes to the pole. You can’t overestimate the Bad Effects of prolonged vibration on bike parts.

Separating the two ferrule sections required running several pin punches down the bore and tapping gently, all accompanied by considerable muttering; the joint was no longer a slip fit. Eventually I produced this tableau:

BOB Yak trailer flag ferrule

BOB Yak trailer flag ferrule

The small hole gauge to the far left showed that the inside of the larger section (on the bottom) had entirely enough clearance for the smaller section, but the rolled ring at its end had somehow shrunk to a tight interference fit.

I’d actually chucked up a piece of rod in the lathe, with the intent of making a mandrel to expand the ring, when I came to my senses. The smaller part was 0.253 inch diameter, so I deployed the letter drills:

  • an E drill (0.250 inch) just kissed the inside of the ring
  • an F drill (0.257 inch) opened the ring to a nice sliding fit and still fit easily inside the tube

A few whacks with a center punch reclamped the dimples firmly in place on the dents in the poles.

That was easy…