Wallace Y Rack & Pinion Drive

by Komb, published

Wallace Y Rack & Pinion Drive by Komb Dec 14, 2012
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I didn't like the belt layout under the bed, and after building finding the once tight belt was now slack, I did something about it.

I borrowed parts from theodleif's Prusa R&P design. The Y motor mount from Domonoky's casted Wallace and the standard 6mm bed mounts for the Wallace.

You can see it working here: http://www.youtube.com/watch?v=LibplYh-9XI

y_motor_holder_rack.scad is a scalable motor mount for those looking for the smaller wallace version. I would like to atribute the kind person who sent it to me, but can't seem to find the e-mails...


  1. Print parts. You might want to change the fill direction for the Rack or full plate to 0.

1.5 Buy 6mm threded rod 28cm, 280mm long. (For my bed anyway...)

  1. Re-mount Y motor using Y motor mount. Use only 2 screws. The Rack travels over the other holes. Leave loose on rods.

  2. Assemble Rack and bed mounts.

  3. Impotrant: Be sure the Pinion and Rack are facing the same way.
    Pinion colar should be at top of shaft. Use either press-on or screw mount pinion.
    Pinion should be flush with top of motor rod.

  4. Mount Rack to bed with holes for belt screws.
    Test fit to ensure Rack and Pinion line-up verticly.

  5. Slide belt ideler with plastic pullies removed, Just the berrings on the screws, to sit behind smooth side of Rack. They don't actually touch, unless someone makes rings for them, but are close enough the Rack has nowhere to go.

  6. Assemble bed.

  7. Snug Y motor up to Rack. Be sure Pinion and Rack are fully engaged. Do Not put pressure on Rack. Slide Ideler block till it meets Y motor. Tighten into place.

  8. Manualy slide bed and watch R&P to verify working condition.

  9. Motion Tests. Adjust Y steps in Firmware. (Mine is at 77.4790)


You will never have to adjust the belts under the bed. :)

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Is the rod used with the herringbone 6mm by default, I saw that the radius in the scad file is 3.1mm so i would assume so, but you mentioned that your Wallace was 8mm.

If you mean the Rack, then Yes. I do mention buying 6mm rod for the Rack in the instructions.

Hi, I was wondering if you had the code for the small gear. It doesn't seem to be present in the scad file. Cheers

Unfortunatly, The files for the Rack didn't come with any. (see http://www.thingiverse.com/thing:22475 )

I hacked the .stl file to make the collared pinion.

Rack and Pinion for Prusa - Beltless

As stated 'The Y motor mount from Domonoky's casted Wallace'. The holes are as Domonoky left them.
I've only worked with the 8mm Nema17 Wallace designs.
I will be releasing a compleate R&P 8mm Wallace desing this month, with the scad files.
I'll upload an scad made by someone else (Wish I could find there name...) who also wanted the smaller mount.

Could you attach the scad file for the motor mount? I think your design uses the nema17 motor? The wallace uses a nema14 for the y mount. Or maybe you could suggest a scale I can reprint the mount with?

are the print results better or worse?? can you post some pictures of prints??


First pic is the two prints I did for this test. The sides show the belt accuracy of the X carriage.

The second pic close-up shows the accuracy of the Y carriage.

My first attempt was scrapped as the X belt had gone slack and I had to re-tighten it.

Now there IS a small bit of layer smash. these lines go all the way around, but not in a spiral and not in sync with the threaded rods.

I'd say the results are comparable to a properly tensioned belt. I just don't have to worry about a Y belt anymore. :)