Linear Actuators

[Jared]

Originally Posted by JamesTerm

I almost understand this and see the benefit of doing it this way... how exactly does the sprocket interact with the nut though? I know the vex #25 sprocket has a nice 1/2 inch Hex ID... does a sprocket like this mate with the driven nut in what you were saying?

http://www.mcmaster.com/#fast-travel-acme-nuts/=syswre

We used nuts identical to the ones at the top of that page. All the half inch multi start lead screws and their nuts can be purchased from amazon.com for a lot less. IIRC, they were from nook industries. To connect the nut to the sprocket, used a 14 tooth sprocket from McMaster, removed the hub and put a clearance hole for the lead screw.

To transfer the torque, we cut a small (0.1 thick?) groove about .25" deep on the diameter of the nut. We left behind part of the sprocket's hub, and it fit into this groove. There were also 2 4-40's that went into holes we tapped in the nut.

McMaster also sells flanges that can be screwed onto the end of the nuts too. You could also make your own if you have the ability to cut the threads. The 1/2" screw nuts have 15/16-16 threads on the outside.

If you aren't carrying a ton of weight, you could probably get away with using a few 8-32's to transfer the torque. You can buy "machinable" nuts that have room to add larger tapped holes to the end.