Elevator: Screw Drive, or Not?

Elevator with Screw Drive

Proof of concept of using a screw-driven elevator. It works, but it may not be the right solution.

The first garage door opener we had at this house had a long threaded rod that turned when the door opener was activated. The door was hooked to the threads and as the rod turned, it moved the door up or down by pulling the connector down the threads. I thought for the elevator I'm working on that I should borrow from that idea. I attached a threaded rod to the shaft of the motor, and glued some nuts to the elevator car. My hope is that using a screw drive will help me avoid something more complicated, like using pulleys and counterweights or some other complex system. And as a bonus, all the parts are easily found at the local hardware store.

I bought some 1/4" rod with 20 threads per inch, and a half-dozen nuts. I put the nuts on the rod first, then glued them to a small piece of wood. I glued a few more nuts to help square up the wood as it moved on the rod - otherwise, it might have twisted sideways and not run smoothly.

The good news is that it works; the motor runs, turns the rod, and the test "car" moves up or down depending on the direction of the motor.

The bad news? Just as the garage door opener produced a horrible amount of vibration when it ran, this setup also produces quite a bit of vibration. Without anchoring the end of the rod to something, it vibrates plenty, which is not good for the motor. And if the rod doesn't line up pretty well with the motor's shaft, it makes the motor work too hard.

I might be able to solve the vibration problem by using a rod with fewer threads per inch. This would allow the motor to run more slowly, and would reduce the vibrations. It's not easy to find threaded rods with (say) 16 TPI at the hardware store, so I might have to see if I can make one. I think I'll have to make the rod's diameter bigger, though, to get that low number of TPI. I have a few dies that have 10 or 12 TPI, but they're 7/16" or 1/2" diameter.

As much as I'd like to go with the screw drive, I am starting to think it's not going to be a practical approach, and I'm going to spend some time looking into pulleys and chain systems.

Speaking of pulleys and chains, this place is fun to look at. They have a huge catalog which also shows how to calculate various setups for chains, pulleys, etc. You can download the catalog as a PDF, but it's pretty big.

Made In Brooklyn
I like these videos by Dustin Cohen about people who make things (jewelry, violins, and watches) in Brooklyn, NY. There are only three right now, but I hope there will be more soon.