I am completely new to robotics and engineering and it looks as though I have stumbled at the first hurdle when building a prototype.

I am trying to build a curved track upon which a motorised carriage can run. I know that I need a stepper motor and a cog, however for the tracks I can't find anything similar to the picture below:

Curved track

The youtube video is as follows: Lumia 640XL mach3 step motor curve motion

There is a slight difference in that I need straight sections and 90-degree bends for the tracks, rather than a circle.

Does anyone know what these sections are called, as "tracks" and "runners" doesn't yield anything.

  • $\begingroup$ google rack and pinion $\endgroup$
    – jsotola
    Aug 18, 2020 at 15:37
  • $\begingroup$ hi @jsotola I did that, along with curved rack pinion, but absolutely nothing that resembles this. $\endgroup$ Aug 18, 2020 at 15:43
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    $\begingroup$ does it have to be transparent? ... you could use a toothed belt that is attached to the side of the track $\endgroup$
    – jsotola
    Aug 18, 2020 at 15:52

1 Answer 1


This particular part is called a ring gear, but you're probably not going to find one because the item in your picture is almost certainly custom-made.

The particular article I linked is for engine starter motors, so it has external teeth, but there are internally-toothed ring gears, too.

What you're describing, beyond the picture, does sound like a kind of modular track system, but I'm unaware of any off-the-shelf solutions. You might have luck with timing belts (or toothed belts), but it would probably be easier to get parts custom-fabricated to your exact specification than to try to cobble something together from miscellaneous parts.

There seems to be a good number of off-the-shelf small-scale timing belts like this intended for 3D printers, though. Not affiliated with or recommending the Amazon link, just wanted to give an example.

  • $\begingroup$ thanks for that Chuck! Looks like I'll have to go down the custom route for this project, as you suggested. $\endgroup$ Aug 18, 2020 at 21:11
  • $\begingroup$ @luke_mclachlan yeah, hate to say it. Looks like the ring gear in your picture is made out of polycarbonate or acrylic sheet. Fortunately, if that's good enough for you strength-wise, then it shouldn't be super expensive to have machined. If there's a maker space near you then you might be able to go cut the parts yourself with a laser cutter! $\endgroup$
    – Chuck
    Aug 19, 2020 at 13:21
  • $\begingroup$ Well Chuck it's amazing you mention it because I found a maker hub by chance today, smack bang in the middle of stockholm. For prototyping it's perfect. $\endgroup$ Aug 20, 2020 at 20:48

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