Building a declination gear brake/clutch

Started by Bryan J R, 03/28/2007 04:26AM
Posted 03/28/2007 04:26AM Opening Post
I'm fixing up an old Starliner GEM.

It came with a 5 1/4 " worm gear on the shaft, but no external clutch/brake attachments(just a pair of threaded holes on the top and bottom hubs of the gear itself).

I'm thinking of anchoring 1/2 of a 2 piece shaft collar to the hub of the worm gear with a bolt or set screw.

I could then clamp the worm gear with fewer, more accessible set screws or shoulder screws with plastic knobs attached.

Q1: I was thinking of drilling the pilot hole in the collar 1st, then using that as a guide to drill pilot hole in the gear hub itself, with both collar and gear clamped to end of the dec shaft. Sound like a plan?
Q2: Do I need(and how) to shim the "fixed" half of the collar so there will be clearance to rotate freely when disengaged?
Q3: Obviously, I'm not an experienced machinist, is this plan feasible?

Thanks
Posted 03/28/2007 06:04AM #1
Not a good plan. The gear needs to be clutched on its faces. Attaching it to a smaller hub will only make it difficult to get the "grab" you will need. Also, you do NOT want to mess with the gear or any hub you would attach unless you've got it well centered on a lathe.