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Electric motor to turn large, non-centered load? Answered

I would like to get a solar-powered motor to turn a compost tumbler at very low speed, and would like some advice at what the cheapest motor I can get that would do the trick. My idea is to have a ratchet system so it only needs to turn one click at a time every hour (having the compost bin make a full rotation every 1-7 days; I'll experiment with what works best).

I've never done a project like this, so the more basic the advice, the better.

Thanks!

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user
steveastrouk (author)2014-09-17

How about using cords with weights wrapped on the drum, and a ratchet released by a timer, just like a pendulum clock ?

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sangretoro (author)steveastrouk2014-09-18

I like the idea but could use some help picturing it (Googling brought up a bunch of clocks). How could the cord be wound?

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steveastrouk (author)sangretoro2014-09-18

You'd need a smaller drum than the composter, fastened at one end, with enough turns lifting a heavy weight that you could store several days on it.

Then you need an "escapement" like these

http://en.wikipedia.org/wiki/Anchor_escapement

My idea would be that the moving arm was driven by a little solenoid, powered by a timer. Every few minutes, the solenoid would jerk the arm back, and the drum would turn one notch.

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rickharris (author)sangretoro2014-09-18

The mechanism you looking for is an escape mechanism - yes like they use in clocks.

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rickharris (author)sangretoro2014-09-18

The mechanism you looking for is an escape mechanism - yes like they use in clocks.

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rickharris (author)2014-09-17

Gonna to be hard to get a solar motor to produce a lot of torque even well geared down. you might be better off with wind power.

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sangretoro (author)rickharris2014-09-18

Sorry, thought I had posted a follow-up question yesterday:

Do I still need a lot of torque if all I want to do is move
the barrel 1-2 inches at a time (to ratchet it 1 click)?

If I were to go with wind power, do you have any
recommendations of wind power projects you’ve seen that might do the job of
moving the barrel at very low, relatively predictable speed?

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rickharris (author)sangretoro2014-09-18

No matter how far you move the drum it will have the same inertia. This is what you need to over come. Yes if you massively gear down the motor you amplify the torque available at the cost of speed BUT this would be a serious gear box.

A worm drive with a large drive gear would probably be the best option but hard to find or manufacture.

Wind power - again a wind mill with a large gear step down to turn the drum very slowly.

http://www.bbc.co.uk/learningzone/clips/how-does-a...

NOTE the mill sails are very big to turn a relativly small diameter mill wheel.

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