[Zoidberg]

But if your determined to make it all yourself, I like the duel servo idea. But are you going to make the servo's?

I have been thinking of building a BL AC motor/servo for fun But thats another story!

Good points about the problems with the wormgear solution! I'm thinking of perhaps using something like in the globalspec link! Drawing will follow!

[Zoidberg]

This is what i came up with, it has 60:1 gearing. I think it would cost about the same because now you can skip the angular contact bearings and just use bushings!

[BillTodd]

This is what i came up with, it has 60:1 gearing. I think it would cost about the same because now you can skip the angular contact bearings and just use bushings!

That's clever; I like the use of a single spring to preload two gear sets (two reduction stages)

BTW I think I've spotted another problem with the spring loaded worms:

Effectively one worm moves the gear in one direction and the other worm moves it in the opposite direction.

In one direction, when the main-shaft worm is driving, the friction on the spring loaded worm will act with the spring (in effect the spring will be dragging the worm around against the worm-gear friction).

In the other direction the spring loaded worm is driving, the friction will be acting with the spring, so as the spring is turned it is pushing the worm against the worm-gear friction increasing the load on the worm and thus the friction. If the initial friction is high enough (i.e. if the load on the main gear is high) and there is sufficient backlash to allow it to build, there is a danger that the friction will increase until it locks. The main gear will then stop until the back-lash has been taken up by the main-shaft worm.

It may be better to use a axial spring to pre-load the worms (rather than a rely on twisting the worm to generate the axial force).