Rotating Ballnut - design ideas

[jcb121]

I'm just wondering, that timing pulley you used? was it around 26 teeth 5mm pitch?

[Jonathan]

I'm just wondering, that timing pulley you used? was it around 26 teeth 5mm pitch?

For the one in post #61 I used a 30T HTD 5m pulley. Clearly it depends on the ratio you require, but if you can keep the pulleys small that helps a lot with reducing the moment of inertia of the rotating assembly.

[jcb121]

yeh, i was thinking of using a 24 tooth one as that would give me a lot of factors to change the gearing.

but it has the same amount of factors as 30 so either will be good in my design :)

[Jonathan]

But factors aren't the only factor...
Ideally you don't want to be using less than a 15T pulley as that bends the belt a lot and gets lower tooth engagement, so if you need a 1:2 ratio then you've got to go with at least 30T. However if you're happy with ratios from 15:24 and you can fit the ballscrew shaft through the 24T, then use it as it's inertia will be about 60% less than the 30T pulley. That will help get high acceleration, although you need to consider the system as a whole not just the pulley.