Retracting power wiring ?

[mdatkins]

My team is building a fork-lift-like tower, with a motor near the top to control an arm. What is a good (non-entangling) way to run power wiring to that motor ? The wire must extend from about 4' long to 12' long. I am considering a spring-retracting reel of flexible cable, like a trouble light, or maybe a motor-driven reel of cable, that parallels the cable that lifts our fork tower. Any hints on this problem would be appreciated.

--Mark Atkins, novice, team 1529

[Jaine Perotti]

Good question, I have been wondering about this also.

To add to the question,

Our team is planning on having a turreting mechanism. What would you recommend for wiring an arm that has to spin, as well as move up and down?
I have heard of connectors that rotate (I don't know the actual name), but I have a limited knowledge of them and have never seen one. Are they the best way to accomplish this task? Why or why not? What would you recommend?

Thanks,
Jaine

[pakrat]

you can run cable through your frame, and make sure it doesn't get caught in the sliding places where peices of aluminum meet.

[rswsmay]

You could use the surgical tubing on the outside of the arm to constrain the wiring, but still be flexible enough to move with the tubing.

[dhitchco]

Jaine & Mark,

1) You can limit your motion (less than 360 degrees) such that you leave enough cable slack (with maybe a spring to keep it neatly retracted). Or, you can go to the expense of building or buying (if allowed) a 360 degree turntable assembly. Do a search on turntable displays for trade shows which have a wiper inside to carry power to the rotating turntable. Someone here even has a 30' Christmas tree that rotates via such a turntable device!

2) There is also "curly-cable" which is multiple conductor coil cord that could be used (again, if it's a legal part). Just ask at an industrial electrical place. Or get some coiled air hose and run your wires up the middle of that.

3) A poor-man's wire retractor might be the cord retractor from an old vacuum cleaner too.

[Al Skierkiewicz]

Hello all,
The name you are searching for is "slip rings" and they are available from many sources like McMaster and other vendors. They are not cheap but do provide constant electrical contact while spinning a full 360 degrees. They only became legal devices last year so double check through the Q&A and parts usage flowchart before using.
As to feeding the motor on a lift... There are a few ways to do this depending on the operating design of the lift. If it is a simple elevator (i.e. sliding parts going straight up and down) then wiring can be attached on the side with surgical tubing used to keep it out of the way during operation and to manage it when the elevator is retracted. A cable reel can also be used but it adds weight. A simple drum can be used that is attached to part of the lift. You measure how much wire you are going to need and add a few feet. Then you fold the wire in half and attach the fold to a rotating drum that contains a spring return. Then wind both ends of the wire onto the drum in parallel and attach to speed controller and motor. As the lift rises (and the drum with it) wire is payed out in both directions. When the lift falls, the spring rewinds the drum and the wire. It adds some weight but not as much as the cable reel. Again check the appropriate sources to make sure the reel is legal.