Re: ATM Building a clutch

["Scott Ewart" <scott.e@quicksurfer.com>]

|
| Teflon clutches work great as long as the required torque isn't too high.
If
| you try to up the torque by using more force the teflon just cold flows
and
| you don't get much of an increase.
|
This is why I need to get the diameter right.  Too big and it'll have too
much surface area.  It won't slip enough while slewing manually (roller
rotates 22X faster than the scope) and the ring will skid on the roller,
eventually causing a groove to wear in the roller.  Too small and you have
to crank up spring pressure so high you get the cold flow effect above.
    Too much taper and the roller will try to slide off the shaft against
the spring by the weight of the scope.  This would also partially disengage
the clutch.  I could simply use a stiff spring, but I still worry about
stability and then you have to think about the added friction of the spring
pressure on the end of the roller (not where I want it).  Too little taper
and it could just jam together and may have too much minimum torque leaving
little adjustability.
    Or course if I take my best guess and torque comes up short, I could try
other sheet materials.  Delrin won't flow, but friction is 5X higher.
There's also milk jug.  Tough and cheap!  Maybe worth a try.

Scott