Quote:
Originally Posted by Jared
It may just be simpler to use a transmission which cannot backdrive, like a worm gear. They provide large amounts of reduction in a small amount of space, and do reasonably well with large amount of torque. We plan on using a 10:1 worm reduction in our elevator for exactly these reasons.
If you'd like more details on the worm drive we're using, let me know and I can send you some specifics.
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We are also using a worm gear drive - AndyMark RAW. Many right angle drives are worm gears and can hold position without requiring the motor to be energized. Bevel gears are also right angle, but don't exhibit the anti-backdrive feature. Other legal worm drive motors include the window motors and the tailgate motor.
Just a warning that the window motor also has a pin that engages when not energized that causes issues with speed controllers - there are CD threads on how to remove the pin.
Also keep in mind that the ratcheted gearboxes from last year can not drive in both directions - by design. Depending on how you unload your elevator, you may need to drive the motor backwards.
We chose the RAW drive due to its simplicity to control. The PID loop does not have to do anything special (like engage a break) and can drive to a desired position in either direction. Given the relatively large load of up to 60lb, we were concerned with the holding current for traditional gearboxes.
AndyMark shows the RAW box as out of stock, and has removed the estimated restock time of Jan 26th. We did not want to wait till Jan 26th and ordered the individual part to build our own - which turn out to be more difficult than imagined. They do seem to have restocked the "worm box" and perhaps it is sturdy enough for your elevator. Other wise, your best bet may be the tailgate motor if you want a worm drive.
Having the ability, opportunity, and inclination to do manual labor makes you a better engineer. - MrForbes [more] 
23-01-2015, 08:30
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