trapdoor elevator question

[lighttech11]

So, we've just brought our trap door elevator back to life for a big musical that we're doing in a month or so. It's been in our theater for a long time and hasn't been used for quite a while either. And the people who built it aren't around any more, so we can't ask them how they used it back in the day.

But it's a pretty simple counterweight elevator, just using counterweight bricks from a fly system.
It's pretty obvious how it works, and we've got it working pretty well and safe now. But preferably, we'd like to run it with a motor of some kind.
We happen to have an old "Automatic Curtain Control" device (probably about as old as the trap, 10 or 15 years) that we were thinking about using to attach the cabling to, but it lacks an actual motor.

So my main question is, what kind of electric motor would be appropriate to drive this elevator trap? With the trap counter-weighted correctly of course.
What horse power should we be looking for? What would it take to raise and lower a weighted elevator trap that would have a total of 200-250lbs of weight on the platform (so 400-500lbs total for both platform and counterweight?)

Any suggestions or ideas anyone has would be great.

Thanks!

[hsaunier]

I think that the answer that you are going to get is one of "not in this forum". We typically will tell you to find a certified rigger to come to your house and do the rigging. Anyone who answers this question is opening themselves up to tons (pun intended) of liability.

[icewolf08]

hsaunier is right, this is a question that you really need to talk to a local professional about. There are too many engineering considerations that have to be accounted for when trying to set up a vertical lifting system, especially if you are lifting people. The best thing to do is to contact a rigging company like JR Clancy or Sapsis Rigging, or contact an automation company like Creative Conners Inc. They will either be able to help you or send you to someone who can.

[Footer]

A dead counterweight elevator is not a safe elevator. This is the cheap and unsafe way to do it. To do it right, either a sciscor lift style lift or something on those lines should but use. Mixing motors and counterweights together works, but only when properly engineered. What sort of fail safes do you have in place? Do you have stops every 6"? Is the lift enclosed at all times? Odds are you do not, therefore I would suggest not going along with this. I have seen this lifts in use, its not a pretty thing to watch. You are lifting a person, and odds are you are lifting them at least 6'. There are plenty of things that can go wrong here. This effect can be done safetly, you need to get the right people in there to make this happen. This goes beyond what a rigger can do, you need a TD with a strong engineering background.

[lighttech11]

Thank you for the safe suggestions. Looks like we're taking a motor out of our equation. It does make things easier as well, not having to worry about a motor driven rig.
Thanks again!

[cdub260]

Thank you for the safe suggestions. Looks like we're taking a motor out of our equation. It does make things easier as well, not having to worry about a motor driven rig.
Thanks again!

It sounds to me like you missed the entire point of hsaunier's, icewolf08's and Footer's answers.

The point was not whether or not you should add a motor to this system. the point was that you should not be using this system at all until it has been inspected, evaluated and certified as safe by a qualified engineer.

You need to get a qualified individual to do this before someone gets killed or seriously injured.

This is not something you should be messing around with unless you are qualified to do so. The safe assumption for you to make here is that you are not qualified.