The Worm [photo credit: Paul Horowitz - 640x480 version]

The Worm

Machining the worm shown to the right was a fun exercise. It was made from a single 20"-long piece of stainless steel (2" diameter), and is used as part of the cable-drive system to move the roof of the all-sky optical SETI observatory. The 4/inch helical groove is 3/16" deep, with a semicircular crosssection, so that a steel rope of the same size nicely winds it. ("What tool did he use to machine that, you ask!") The ends are each turned down to 1" (-0.0005") so that they sit nicely in the bearings of a yoke. The worm is turned (and the roof moves as the cable -- attached to either end of the roof -- translates) by attachment of a motor to the far end, via a keyway (barely visible). The 3/4" hex pattern on the near end is fodder for a big socket (and a lot of muscle) to close the roof in case of power failure.

To see what I'm really talking about, check out pictures of the worm in action!