|
Gday - I built an Elgin machine a few years ago (well about 10 or 15 to be honest) and it happily sits outside now as the ugliest garden gnome you have ever seen (gotta dump that thing).
This does not detract from its performance - it was fatastic. I even polished to spherical with it and then hand figured on a drum.
I had two windscreen wiper motors driving both the blank and the mirror on top. Rotation speed of the tool was controlled with a little pulse width modulation unit I built which allowed varying the speed to avoid patterns. The rocking arm that moved the mirror was connect to a disk on the drive motor with a series of holes that allowed variation of stroke depending on mirror size.
I never did a mirror above 12 incjes but. W/W motors have a mile of torque but so I dont think weight would be a problem.
Anyway - it was cheap to build and very efficient and would be worth considering.
Mark
|