Backlash free rotary table

[Zoidberg]

Made a little animation of the 81:1 gearing!

[Zoidberg]

I did just figure out how to draw the lobes correctly

With a little bit more drawing i realised that was wrong! The correct way (i hope) is in the PDF. It looks good anyway

Edit: It should be: Y/4 = Eccentricity

[Zoidberg]

Yet another variant :P A single stage cycloidal traction drive with -59:1 ratio.
I used an oldham style output.

A little video.

I REALLY need to get my mill working soon

[NEATman]

Zoidberg-
Ingenious use of an oldham coupling! Very cool.
You could have the output stage of the oldham clamp directly to the shaft you are driving, and eliminate the need for a traditional coupling. It would reduce the length, and remove the bearing on the output shaft.

Keith

[Zoidberg]

Yeah that would be cool! But then you probably would need 2 bearings on the input axle to support the radial load!

[NEATman]

If you kept the bearing inside the output cup there wouldn't be any radial load on the output clamp. I suppose that that it could cause angular alignment problems when it comes to mounting it, but to be real clever, you could have a slightly spherical section on the end of the eccentric shaft that would fit into the ID of the bearing mounted in the output cup that would minimize slight angular misalignment.

[Zoidberg]

What about something like this? Then it's balanced for higher speeds also

[NEATman]

I like that as well. Counteracting forces almost cancel out. How about a adjustable paralell type wedge that would preload one up and the other down - against each other, instead of against the cone angles on the setscrew? That way, it would ensure that there was equal and opposite forces acting on the contact points.
Alternately, you could hollow out the input shaft on the left and put a setscrew in from that side as well and balance the loads at assembly.

[aystarik]

Here is some math and CNC info about gear profile... In short, it can't be described by two arcs
http://gears.ru/transmis/zaprogramata/2.139.pdf

[aystarik]

Some more oldham coupling -- with rollers.

http://www.spinea.sk/page.php?id=1

[Zoidberg]

Ah, cool! I have to write a rhinoscript or something

[Mike Everman]

Hey Zoid, I like that last reducer. Only comment is the (radial force) balls need separate setscrews, or better still, no thread in the main shaft, and a nifty way for one ball to push against the other, so radial load equalizes.

BTW, I've got a bucket of Santotrac grease when you get down to it. It was a minimum order thing. The stuff is like ear wax, if you've never seen it. ha