Hello everyone

Capstans - have had a project in mind to make a capstan for some time
now. Anyone any experience or ideas on capstans?

Last summer, rescued a worm-drive gearbox from a machine being
scrapped - had a 15HP electric motor attached - big beast. Gives 50:1
reduction.

Overall idea is that if had small petrol/gasoline (or diesel) engine
attached, would be useful tool.

Anyone have ideas about how to make the capstan barrel with its waist
in the middle?

Bearing arrangement for capstan?

Any ideas how to size the capstan barrel and what shape it should be -
are there "rules" or "rules of thumb" about capstan proportions?

My idea is to take some steel pipe and slice "eye" shaped slits out of
it longways evenly around the circumference then collapse the tube in
the middle until the edges of the "eye" slits touch, then weld up.


Another line of enquiry:

Calculations suggest that if you chose the right size of motor, you
could come near to but not exceed the breaking strength of your rope
by reason that the motor would stall first - for any revs / inhaul
speed. Would make this machine very easy to use if that were the case
- wouldn't need any gauges or whatever.

Here is how I calculate this

Work done = force x distance
Therefore
Power = force x velocity
(where velocity means in this case the inhaul speed)

The faster the motor is turning and the more power it is making, the
faster the inhaul rate so it's doing more work - so engine
throttle-opening is self-cancelling and with power approximately
proportional to revs, you end up with a capstan which will always pull
the rope to the same maximum force at any revs be it slow or fast???

This is theoretical - and real experience say how these machines
really behave?

By these calculations, where the capstan is about 125mm (5inch) dia at
the waist, would I be about right in my estimation that a 6.5HP motor
should never be able to break a 12mm (1/2inch) polypropylene rope
which is in good condition?

Thanks in advance

Richard Smith