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Another Circumferential Seat-Frame Clamp

This is another step along the way to getting our daughter’s radio firmly mounted to her Tour Easy, not tucked into one of the panniers. The general idea is to use a water bottle holder for the radio, with a seat wedge pack from an upright bike cushioning the radio. The secret ingredient is a circumferential clamp that mounts the holder to the lower rail of the bike’s seat frame.

This clamp is basically the same as the ones on our bikes, but I doodled up a sketch with some illegible dimensions that almost matches the actual clamp; we may both find it useful the next time.

Clamp layout sketch

Clamp layout sketch

Machining the clamp is straightforward: bandsaw a block of about the right size, square it up in the mill, helix-mill the clamp hole …

Helix-milling the clamp hole

Helix-milling the clamp hole

Drill the clearance and tapping holes for the screw, bandsaw it in half, clean up the cut edges …

Finished clamp parts

Finished clamp parts

Obviously, I didn’t put those nice bevels on the front side.

Both previous water bottle holders required a spreader plate between the clamp screws and the holder’s screws, but this time the holder had a nice aluminum plate all by itself. It just fit on the Sherline and a bit of manual CNC center-drilled the curved plate and poked a jobber-length drill through the holes …

Drilling holder for clamp screws

Drilling holder for clamp screws

And then it fit perfectly on the bike …

Mounted holder

Mounted holder

A side view …

Mounted holder - side view

Mounted holder - side view

Now, to find a wedge pack big enough for the HT and small enough to fit in the holder!

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  1. #1 by John Rehwinkel on 2010-06-13 - 10:05

    Now, to find a wedge pack big enough for the HT and small enough to fit in the holder!

    No problem, you can machine foam on the Sherline, right?

    • #2 by Ed on 2010-06-13 - 10:51

      Nah, I’d be forced to build a six-axis CNC hot-wire gantry cutter: XYZ UVW. With closed-loop temperature control, of course.

      The weird sex-toy seats for upright bikes have really put a dent in the under-seat-pack supply. I looked around at the LBS and didn’t see anything particularly useful: the old two-rail seat with a big cavity under the leather shell is a thing of the past.

      Now, my ladies are pretty good with the sewing machines, so perhaps *they* can crank out a custom pack without too much difficulty…

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