Ball-Chain Pulley for Polargraph

by JohnA, published

Ball-Chain Pulley for Polargraph by JohnA Oct 10, 2011
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Ball-Chain Pulley for Polargraph by JohnA is licensed under the GNU - GPL license.

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This is a ball-chain pulley for 3.5mm ball chain, intended for use as part of a Polargraph:


Regular metal ball-chain was easier to locate versus the type that Sandy had used on his Polargraph.

I use a slightly modified version of Ed's stepper motor mounts as well:


The ball-chain I'm using came from here: http://www.kitkraft.biz/product.php?productid=8353&cat=&page=2

Update: The gondola I printed for mine is here: http://www.thingiverse.com/thing:12557 - and it works!


Pulley is sized for a 5mm shaft, and has a 3mm bolt / nut setup for tensioning on the shaft. If this doesn't match your stepper, edit the .scad file and change it up.

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Comments deleted.

It does not compile with the current version of Open SCAD it stops around 2/3 into the process. Am I the only one?

I had the same experience (it stopped at step 730 out of 1000), but it turned out it was just thinking really hard. I came back 10-20 minutes later and it had finished generating and rendering the final product. Does anyone know if there's an easy way to reduce the "resolution" OpenSCAD compiles to for faster prototyping?

the link to the ball chain you posted was 4mm and not 3.5mm. Is the number in your description a mistake or does the link go to a different chain than you used?

Is making the sprocket smaller and messing with the programming possible for higher resolution, or just getting .9 resolution with a 1.8 degree motor?

Even like this, it'll do impossibly small resolution. You need to start getting .02mm pens, etc....

is the ball chain better or worse than monofilament spool for this application?

2 days ago - Modified 2 days ago
BrainSlugs83 - in reply to rrhb

Better. -- I would avoid using a "spool", of anything for this -- instead use a counter weighted chain or belt of some kind -- with a matching gear -- because with a spool the diameter is variable instead of constant, and your steps per mm will also likewise be variable instead of constant.

I'm not sure? I was trying to keep it like the original, so I went this route. You could probably use anything and be fine.

Hi there! Question : which motors are you using? I coudn
´t find any motor matching the specs (0.9 degree resolution, 0.6A ) Please help!

I'm using this one: https://www.adafruit.com/products/324https://www.adafruit.com/produ... - just took some small modifications to the code. The ones that Sandy used don't seem to be widely available in the US.

Would you mind sharing the code modifications?