Astro Drive Bits & Pieces

I had been thinking about a astro drive for a while. But just couldn't accept the prices for factory stuff.

So I started scrounging again. :)

I found a 4", 120 tooth, 32 pitch worm gear on an astro site. It had a .750" hole for the shaft.

I drilled and tapped a shaft collar to act as a hub. I used a .750" rod to keep it centered while drilling. Next I installed a 32 pitch worm on a .1875 shaft. I pulled a couple of .1875" bearings from a printer to use on the worm shaft. I then built the worm carriage from some .500" Corian that was laying around. I made sure to have the stepper motor mount as part of the carriage, to prevent misalignment.

The main housing is also made from .500" Corian. I drilled and tapped the pieces for 8-32 machine screws, and washers. I machined notches to set the carriage in. I made them a little deep, to allow for shimming the carriage/worm for perfect meshing.

I used two .750", 2 bolt flange bearings for the .750" aluminum shaft. The shaft has .125" walls, giving a .500" sighting tube. I'll install crosshairs after everything else is done.

The stepper motor is from a large Epson dot matrix printer. It has 1.8 degree steps, and is unipolar. I made the motor to worm shaft coupler from a piece of .625" aluminum rod.

The hub that the ballhead mounts to, was made from a aluminum pulley. I cut the center from a 4" pulley, that had a .750" bore. I then mounted a 4.5" X .125" disc to make a turn table. I then made a long setscrew to attach it to the shaft. This way I can reset the ballhead without unmeshing the gears, or having to run the motor in reverse.