Calculating timing belt lengths

[Jonathan]

Here's a spreadsheet to help when working out timing belt lengths. There are plenty of these calculators online, but I made this as I find it makes it easier to compare options when you can list them.
I've put 5mm in the belt pitch to use it with 5M HTD pulleys, which are often recommended here for driving ballscrews, but if you want to use it for a different belt series just enter the pitch. So for instance to use it with XL timing belts, put 5.08mm.

Attachment 8374

As for buying the belts and pulleys, Bearing Station tend to be the cheapest, but sometimes a bit slow to deliver. There's also Belting online who offer a service to bore and tap the pulleys, however they are more expensive.

[Ross77]

Thanks Jonathan, I was trying to find pulley sets that had the same centre distance so I could make my motor mount future proof and be able to change the ball screw ratios by just using different pulleys.

Hope you don't mind but used yours as a base to do a comparison tab? I've attached my addition in case it helps anyone else but please feel free to remove it there's a problem.

CheersBelt centre distance calulator3.xlsBelt centre distance calulator3.xls

[Jonathan]

I'm glad you found it useful. I tend to make motor mounts with about 20mm of center distance adjustment, as that's generally enough to allow changing the ratio whilst only changing one pulley. That might cost you less than buying (or making) 4 or more pulleys per axis.

[birchy]

How about this online version? SDP/SI

[Ross77]

How about this online version? SDP/SI

Yeah found that but you cant quickly and easily compare different pulley combos and belt lengths.

I tend to make motor mounts with about 20mm of center distance adjustment, as that's generally enough to allow changing the ratio whilst only changing one pulley. That might cost you less than buying (or making) 4 or more pulleys per axis.

good point but I was thinking along the lines of a quick change system with the pulleys all fixed permanently and just move the belt over like on lathes or mill spindles. anyway going a bit off topic.

[Robin Hewitt]

I tried a bunch of pulley separation calculators a couple of years ago then checked the result by drawing and listing and found they were all a bit naff.

Then I tried writing my own and found the maths was quite beyond my poor old brain.

Have they improved? I get the separation by drawing, measuring, redrawing, measuring... etc., until I get my tolerance.