[chbot] Cheap Rack and pinion servos?

[Geoff]

The towerpro mg996r is a cheap metal geared servo ($5 from aliexpress). The
ones I had use a m3 bolt to hold the horn on the output shaft. This should
make it easy to drive a threaded-rod/bolt assembly (or anything really).
If you open it up, use a pair of side cutters to remove the mechanical
turning end-stop, and mount the potentiometer elsewhere (presumably with a
crank to measure the extension), you can turn it into a linear actuator. It
revolves rather slowly though, about 1 turn per second (on m3 -->
~1mm/sec), so perhaps you should instead mount a pinion with a 3mm shaft
diameter....

I did a similar servo->linear actuator on a micro servo recently: taking it
out of its case, soldering a bolt directly to the brass pinion on the
motor, and mounting the potentiometer via a crank. Didn't have the force I
wanted though.

What force/speeds are you looking for?

Geoff
On 21/04/2015 9:17 PM, "Brahm Boelee" <brahmboelee84 at hotmail.co.uk> wrote:

> That linearmotion site is super interesting
>
> > On 21/04/2015, at 8:41 pm, Helmut Walle <helmut.walle at gmail.com> wrote:
> >
> >> On 21/04/15 19:42, Brahm Boelee wrote:
> >> I really want an extension of 40cm.
> > [...]
> >
> > How much force do you need? I remember these linear actuators from my
> days in the mobility industry:
> >
> > http://www.linak.com/medline-careline/?id3=2334
> >
> > They surely aren't cheap, though.
> >
> > Also, this local supplier might have answers:
> >
> > http://www.linearmotion.co.nz/
> >
> > Kind regards,
> >
> > Helmut.
> >
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