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The budget: Tiny. Want to try to do this with salvage if possible, with cheap off the shelf components otherwise.

The drum: Recycled 100 liter drum, roughly 16" x 3 feet. Could step up to a 215 liter drum, but they are harder to handle.

Portions of the drum are replaced with screen. On some drums 1/2" screen, On some drums 1/8 x 1/2 screen. On some drums 1/8" holes. The idea is that the operator can be filling one drum with a mix of seeds and stuff (cones, pods, stems...) while the separation operation is running.

In some cases we will want to run it, see how many more seeds fall out of the cones, let the cones dry more, and repeat.

The key here is that we want to keep drum mods as simple as possible.

Options:

  • Some form of capstan drive using 1/8 braided cord on a small very small diameter pulley. The drum itself is the large pulley. A 1/2" drive spool compared to on a 16" drum gives a 30:1 reduction. 1800 rpm = 60 rps. Divide by 32, still 2 rps. Still too fast.

  • This combined with a slower speed motor. 1800 (ok, 1725) rpm motors are common and cheap. The only common slow speed (more than 4 pole) motor I can think of are ceiling fans.

  • Some form of gear reduction. 1800 rpm to 3 rpm is a reduction of 600 to 1. Pretty big range.

  • Ok 4" wheels on a small driven axle would themselves do a 4:1 reduction. So now I need a way to to reduce 1800 rpm to 12 rpm

Another approach is to find a small 3 phase motor, and a matching VFD. I love the degree of control this gives for speed. Running a motor a lot slower than it's design speed can have big heating problems. And this is a several hundred dollar solution.

So now I'm looking for consumer devices that run at slow speed.

  • treadmill at it's slowest is about 1 foot per second. Surface speed of 1 fps on a 16 drum is about 12-13 rpm
  • barbecue rotisserie is certainly slow enough. Don't know if it would handle the torque. Typical load would be no worse than 10 kg, and material typically rolls or slides at under 45 degrees. Still this would correspond to a badly balanced turkey on a spit.
  • Clothes dryers are a only a bit too fast. How do they gear it down? Hmm. My try modding a clothes dryer.
  • something that uses a worm drive might be adaptable. Garage door opener?
Sherwood Botsford
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2 Answers2

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Source a car wiper motor, then fit a pulley and drive the drum with belt.

For power either car battery or 12V power supply (from old computer possible).

The car wiper motor will often give the advantage of 2 speeds...

Solar Mike
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This sounds like the sort of thing where instead of pivoting the barrel on an axle through its own axis, it would be better to have it resting on a pair of long rollers that you turn with your motor.

And the term that you're looking for is "gearhead motor", of which a windshield wiper motor is just one example. They are available in a wide range of output speeds and power levels, and if you look in surplus markets, for quite reasonable prices.

Dave Tweed
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