[chbot] Cheap Rack and pinion servos?

[Michael Field]

How about https://www.pololu.com/product/2268, much the same but with 
with the 38cm threaded rod, for US$50...

But if you detach the pot from a standard servo you can make it rotate 
continuously. With no feedback the PWM position signal then becomes a 
direction/speed control and if you make the appropriate external 
connections you can hijack the servo positioning loop to do your bidding 
(but this could be pretty imprecise).

See 
https://learn.adafruit.com/modifying-servos-for-continuous-rotation/overview 
or 
http://shop.ninjablocks.com/blogs/how-to/7540682-convert-your-servo-motor-into-a-continuous-rotation-motor 
for examples.

On 21/04/2015 8:20 p.m., Brahm Boelee wrote:
> That's good but I need a longer extension than 10cms and pardon my 
> pickiness but it's a bit pricy. Multi-turn servos sound good but it's 
> just finding the pinion on the drive shaft to match the teeth.
>
> Is this a multi-turn servo:
> http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=22528&aff=757677
>
> ?
>
> > Date: Tue, 21 Apr 2015 19:47:20 +1200
> > From: hamster at snap.net.nz
> > To: chchrobotics at lists.linuxnut.co.nz
> > Subject: Re: [chbot] Cheap Rack and pinion servos?
> >
> > 
> https://nicegear.co.nz/robotics/stepper-motor-29-ozin-200-stepsrev-threaded-shaft/
> >
> >
> > Maybe?
> >
> > Brahm Boelee <brahmboelee84 at hotmail.co.uk> wrote:
> >
> > >I really want an extension of 40cm.
> > >
> > >On 21/04/2015, at 7:33 pm, Mark Beckett <m.beckett at amuri.net> wrote:
> > >>
> > >> Brahm might have been after one of these.
> > >> 
> https://www.google.co.nz/search?q=central+locking+actuator&tbm=isch&tbo=u&source=univ&sa=X&ei=Jf01VcbDH8jFmQXj7IHAAQ&ved=0CBwQsAQ&biw=1680&bih=913
> > >>
> > >>
> > >> Andrew Errington wrote:
> > >>> Does such a thing even exist? You might have to make your own. 
> Maybe using a multi-turn servo such as a sail winder with a pinion on 
> the driveshaft.
> > >>>
> > >>> Presumably you are looking for linear motion. Have you 
> considered a threaded rod?
> > >>>
> > >>> Best wishes,
> > >>>
> > >>> Andrew
> > >>>
> > >>> On 21 April 2015 at 16:17, Brahm Boelee 
> <brahmboelee84 at hotmail.co.uk <mailto:brahmboelee84 at hotmail.co.uk>> wrote:
> > >>>
> > >>> Hi.
> > >>> Does anyone know where to get cheap rack and pinion servos?
> > >>> Preferably with a longer rack.
> > >>> Thanks for your help
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