[ Phil Dayson wrote in 220227 MMD ]

> I have not been able to figure out what size motor I should aim for;
> can somebody help me?

Take the maximum force you put on the handle (5 pounds?), multiply by
the handle radius in feet(= 7 inches / 12 inches per foot?) times Pi
(3.14) to get the distance traveled, then multiply by the rate of
rotation (60 rpm?) and you have the energy requirement in foot-pounds
per minute (175 ft-lb/min).

1 foot pound per minute (ft-lb/min) equals 0.000030 horsepower (hp).
Assuming 100% efficiency, you need 0.016 hp, if my math is correct.

But then, your motor might be only 50% efficient, and your belt system
only 25% efficient, so you need about 0.10 hp, which would have been my
rough guess. Deciding on actual dimensions and converting to metric
units is up to you.

Wallace Venable

 [ A healthy human can produce about 1.2 hp (0.89 kW) briefly
 [ and sustain about 0.1 hp (0.075 kW) indefinitely ...
 [ Ref. https://en.wikipedia.org/wiki/Horsepower -- Robbie