How to model a GT2 pulley profile, please?

[i-make-robots]

I don't have engineering textbooks, youtube doesn't appear to have a useful example, and my most clever googling hasn't born fruit.  Please!  Show me the magic.  I have the straight belt profile:

and I don't know how to convert that to work around a circle.  If you would be so kind, I would really love to know the secret.  Ideally in a way that I can generate other round-tooth profiles for other metric belts, too!

Thank you,

[mavigogun]

The actual shape of the sprocket teeth is an engineering question.   Sketching those teeth I might  start with Circles at the bottom and top of the tooth extents, then Lines radiating out form the center point defining the degree arc of half a tooth profile; Mirror that profile, then Circle Pattern the combined product.

[etfrench]

In this thread @davebYYPCU shows how to draw a GT2 pulley.  I still use Gearotic to generate the pulleys.

[webweave]

Here's the best one I could find. 

https://youtu.be/qV_C6Xu-WKY

[MichaelT_123]

Hi Mr. I-Make-Robots,

There are a few solutions which come to mind:

1. An experimental one – real pulley imprint in a thermally settable patty.
2. Numerical approach. Perhaps if you are reasonably math/programming skilful the modification of Mr. Ekins script as proposed in (https://forums.autodesk.com/t5/fusion-360-design-validate/spur-gear-design-script-problem/m-p/880924... could arrive in a long-lasting more or less sophisticated solution. 
3. The semi-empirical solution (which can be done entirely in F360) can be devised by modification of the example given in https://forums.autodesk.com/t5/fusion-360-design-validate/need-rollers-that-conform-to-cable/m-p/871...

 Regards

MichaelT

[b.sattmann]

I know this thread is old, but I gave it a try and I think i managed to recreate a sketch from your textbook.

I used 3 circles and connected them via bent lines (drag with the line tool; L key). I cheated a bit using dummy lines for the bent lines to hold onto. Then I gave everything the right dimensions using the D key and connected everything using the "Tangent-Constraint". Finally i trimmed the unnecessary lines using the T key for less clutter.

Maybe that helps a few people that find this thread somehow.

[Anonymous]

Take the SCAD file from this thik in thigiverse 

https://www.thingiverse.com/thing:16627/files

edit the file to get the pulley you want (beter with OpenScad)

open the SCAD file with Freecad

export to STEP file

now open With Fussion

[etfrench]

I would not rely on a Thingiverse model to be accurate 😀  In this screenshot, orange is the Thingiverse model for GT2-3mm-13 tooth pulley, while the blue is from Gearotic.

Which would you rather use?

[vewoci6695]

Not spending $120 sounds wonderful. 😀

Found this thread while asking the same question. Given that I'm going to be using a (cheaper) 3D printer and it will not be hugely critical the part is 100% accurate I don't think a little error is going to matter. I'll take the free version over spending quite a bit of money.

[etfrench]

3d printed timing pulleys work really well. I've been using them on my rose engine for several years now.  I just added linear glass scales and found the error over 10" was less than 0.0005".  The timing pulleys are GT2-3mm with a 5:1 reduction.  Leadscrew is TR8-2mm. 

Follow @davebYYPCU 's instructions and you shouldn't have any problems.

This image was taken before adding the glass scales:

[vewoci6695]

Cool!

I'm going to be using GT2 3mm pitch as well. My printer is on the cheap side so I doubt I can get them too terribly accurate. I'm more worried about the 6mm wide belt handling the load. It may be fine but we'll see. I seem to be having issues finding good availability for belts (and pulleys) with all the supply issues people are having.

[etfrench]

What size pulleys do you need? 

I've had good luck with Royal Supply for belts.  They do have a minimum order amount.