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Variator for small lathe

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BillTodd:
Actually, I used a scooter variator on a milldrill conversion, a while ago ( is it really 15 years ?) .

Most automotive variatirs will only have about a 3 and a bit to 1 range (it is all that's required for most engines) 

But , yes they work well 8⁠-⁠)

Well only 14 years :

https://www.cnczone.com/forums/uncategorised-metalworking-machines/89480-cvt-continuously-variable-drive-rf30-type-drill.html

vtsteam:
I'd like to see one built, naturally. Far more interesting than installing a manufactured unit. Whether it has problems in development or construction is irrelevant to a good project thread. It's what is tried and learned that is so valuable to read about and follow. I understand if it's just easier to go with an existing unit, and I've done that many times myself. But I do hope for something truly inventive to liven up these MadModder pages.  :coffee:

vtsteam:
I think the biggest obstacle in the disk design is that the driving area of contact is very small by comparison with a belt drive. You can't widen the rollers to increase the contact area since that will cause increased skidding. The two edges of the rollers will apply against different areas of the driving disks. Rubber might make up for a small differential there, but not a large one. Also the wider the roller the smaller the reduction ratio range.

All of this will be a matter of degree -- whether it is practical for a small lathe vs a vehicle is the question.

Factors that would be helpful with the relatively low torque capacity of the disk drive are, a relatively high rpm motor, and a reduction after the variator.

A disk variator like the above can apply more pressure to the driven surfaces than a pulley and belt drive can because a belt is tensioned along its length and isn't actually trapped between the sheaves as a roller between disks is.

Sea.dog:
A conical roller surely would be best? The rolling radius of the inner and outer would automatically be compensated for.

BillTodd:
The trouble with conical wheels is that it they can only really be used with one conical disc and then one or both have to be able to move laterally .

Vtstream :

The contact patch limits the available traction. Increasing wheel size increases torque for a given traction (and slightly increases contact) so bigger wheels are better.  The wheels in this design are set by the depth of the extrusion, as are the disc diameter. The disc diameter determines range , from minimum contact diameter to the edge if the disc.

I could couple two sections of extrusion to make a bigger box for larger wheels, but then it starts to get quite big

As to making it, I don't want to upset Phil and his the kind generosity , but I may still make it just for kicks.

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