> > is not enough. Ideally it would have 50 Nm. The idle speed is not 
> > critical and may be lower, so a similar power motor with a 
> different gearing should be ok.
> > 
> > The other problem is that this particular motor has a plastic gear 
> > that is designed as a "mechanical fuse" to prevent burning 
> out of the 
> > motor. The connection between that gear and the output 
> shaft sometimes 
> > strips off, probably when there's a mechanical backlash on 
> the output shaft.
>
> 
> My current thought is to use a normal 12VDC ~60W motor and 
> drive a threaded bolt, making a custom linear actuator. The 
> linear actuators I found that work this way are usually too 
> slow. I'll see whether there's a reason for that... I need at 
> least 10 cm/s, ideal would be 20 cm/s.
> 
> Another possibility would be to continue using my gear motor 
> and drive a belt. That would also get me more force on the 
> cable than I have now.
> 
> Gerhard


Another reason plastic gears are used is that they are quieter than metal
ones, not really an issue in a low RPM application.

Threaded rod isn't all that efficient, but there's different grades.
Ballswcrews work the best, but are expensive by comparison.

Another method to get linear movement is to have the cable in a loop, with
one end wound around the threaded rod, the other around a pulley.  Cable is
tensioned by a spring.  Rod turns, cable winds 'on' one end, and 'off' the
other.  Old timers would say "just like old radio tuners!" but I've seen the
same setup in photocopiers.

Tony

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