idea for linear belt drive

[dickieto]

slow down a bit irving!! it will take me all night to take all that info in!!!:confused:
only joking, thanks for the calculations.
does this mean i could fit the 10 toothed pulley directly onto stepper motor with out reduction?or am i missing something,i would like to go for bigger motor just incase i was going to do some alloy or do you think this would just be overkill??
i was also thinking of making my own v bearings with twin bearings inside round bar turned down to suit angle iron or do you think this would be to much friction??
sorry for all the questions but its your own fault for being so knowledgable!!:naughty:
thanks again Tom

[Ross77]

my plan is to build router that can take 8x4 sheets so the belts would run full length of table crossing over gantry to other side,both being driven by toothed gear reduced down from stepper motor then the back of the belts would go round idler then down the other side of router. Hope that kind of makes sense:confused:
I wish i could just draw a bit faster and better but am just learning autocad

Understood perfectly. Have you priced it up tho? as Irving said belts arnt that cheap espesially as you'll need them 12' or more in one run as it also goes thro the Y axis.

I think that once you get to 8'x4' belts arnt a cheap option, just cheaper than ball screws

I wouldnt have thought belt sagg would be to much of a problem as they will be on their side, and if you use collar less pulleys you could put a small ledge for the belt to sit on.

If you make our own Vee bearing will you save that much? Have a word with vic66, hes using vee bearings and angle, look at his thread and theres a link to the mechmate stuff which sounds simillar to what you want.

[irving2008]

slow down a bit irving!! it will take me all night to take all that info in!!!:confused:
only joking, thanks for the calculations.
does this mean i could fit the 10 toothed pulley directly onto stepper motor with out reduction?or am i missing something,i would like to go for bigger motor just incase i was going to do some alloy or do you think this would just be overkill??
i was also thinking of making my own v bearings with twin bearings inside round bar turned down to suit angle iron or do you think this would be to much friction??
sorry for all the questions but its your own fault for being so knowledgable!!:naughty:
thanks again Tom

dont take these as gospel, its a frst cut. I may have missed something, or my approach to estimating how forces giving rise to motion of the gantry translates to torque might be wrong. I dont want to diss your idea, but can't help but think if it was that easy why hasn't someone done it before? I do think the limiting factor might be belt width/torque handling and availability in the lengths you need. One or two suppliers do continuous belts larger than 3.7m which could be cut open, but these tend to be in the 8mm not 5mm HTD and the pricing is >£50 per belt. With 8mmHTD a 10t pulley is 25mm dia so the torque needed at 200rpm is 0.3Nm, and the resolution at 1/4step is 0.1mm. 8mm belts come standard at 30 and 50mm widths

I was working on the assumption that the steppers drive the pulleys directly, but in practice you can't because the shaft length is too short. You will need the two drive pulleys mounted on a shaft in bearings which is driven by the motor via a coupling.

Before embarking on the big build, I would trial a small version of the X say 200 or 300mm square using 5mmHTD and cheap drawer slides from B&Q to measure the loads/forces/etc. operating load could be added by a bit of string running over a pulley to a pan that can be filled with sand or other stuff to see how it performs under load.

[BillTodd]

However open-ended belting is only available in 100m rolls, so this might not be as cheap as you might think!

A grovelling appeall to the afore mentioned Mike Everman might be worth a try :)