The Clamping System

Upper Clamps

This was the system I hoped I could use (but didn't at first; rev 1.0 used a clamp at each end, but the wood kept splitting).

I suspected This approach would be too weak. Nope!

Those are two 7/8" hardwood dowels with threaded inserts, screws, locknuts and knobs. The dowels insert 1/16" into the cage rings, and glue holds it all together (along with a single finishing nail at each end).

Lower Clamps

It's not that easy to see, but these work the same way as the upper clamps, save that the side of the rocker box replaces one of the dowels (you can see the knob at left center).

I don't know why this works so well and so easily, but perhaps the torque on the clamps makes them tighten more quickly. Surprisingly little effort is required.

Possibly bicycle quick-releases would be more elegant, but these are so easy and fast, I'm not sure I care enough to try it.

One of the biggest problems was getting the clamp holes just the right size. The tubes are theoretically 2-1/4" in diameter, but no 2-1/4" bit I tried gave the right hole size. I eventually solved this by putting a 2-1/4" hole saw in the drill press and grinding it down with a sharpening stone until the diameter was just right.

No, I didn't get it right the first time. I had to go back and buy another hole saw...

I used a JSL from Crazy Ed. It's a great focuser, but heavy. Anyone with serious weight considerations should probably use the JMI, which is very good and a bit lighter.