HI everyone,

 

Here is a fun task for the afternoon. I am drawing a blank here and could use some inspiration.

 

I am trying to think of an inexpensive solution for a rotary motor that is adjustable from around 100 RPM at the low end to about 800 RPM at the high end. Only needs to be in the 100 watt range, but has to give reasonable torque at the low end.  I'm looking for some way to do this quickly and cheaply using parts that I can get anywhere. Pretty much any appliance motor I can think of spins way too fast. And DC motors are either too small or way too expensive.  Also being able to vary the speed is a problem.

 

I wanted to use a hand drill, but it doesn't offer enough torque at the low end, and would require some kind of gear assembly to run it at higher speed. Since I need this working quick, I can't really order parts, and Thai Watsadu has limited supplies.  Something like a microwave motor is geared and would provide enough torque at the low end, but is too small and can't reach the speeds that I need.

 

The only solution I can think of is to build an inverter and tweak the frequency. I've got some MOSFETs lying around and a few Arduino boards that I might be able to coax into doing the job, but that would be a lot of work, and honestly I'm not sure how far below 50Hz I could go and still have everything work reasonably well. Anybody have experience with slowing down AC motors?

 

The setup is 2 parallel, horizontal PVC pipes mounted on bearings with a tumbler drum sitting on top of them. One of the pipes is free spinning. The other one I need to turn in order to spin the drum. The whole apparatus is only about 50 cm long, and the drum weighs around 10kg.

 

Any thoughts on how I could get this working this afternoon? Doesn't have to be pretty.

 

Thanks for any advice.

 

A scrapped washing machine motor?

29 minutes ago, bankruatsteve said:

A scrapped washing machine motor?

Interesting. Probably available from Amorn.

 

What RPM does a washing machine motor spin at? And is there any way to adjust the speed?

 

46 minutes ago, Monomial said:

Interesting. Probably available from Amorn.

 

What RPM does a washing machine motor spin at? And is there any way to adjust the speed?

 

Our old washer would spin to 1000 rpm, I think, but definitely had slower speeds.  Probably with gears somewhere.  Our local fixit guy must have 10 old washers sitting around and the motor is most likely still good in most of them.  Maybe find a guy like that and see what he thinks.

Where are you?

 

What is the length of the drum?

 

Edited March 12, 20206 yr by DekDaeng

Just use an old spin dryer for the whole thing.

Cheap (mains) electric drill, big lamp dimmer.

 

An old bike, preferably with gears.

Put the engine/motor at the pedal side with coupling after removing the pedals.

The wheel could function as a flywheel and with some modification you are then able to use the drive.

 

(weld another gear to the wheel, or use one of the gears for driving an axis. So 2 chains.)

Any car starter motor might work.  They run on 12Volts, but draw a fair amount of current so you may have to drag in and use a car battery for convenience just to get things going quickly. They provide a lot of torque and depending on the gearing can give you all the RPM you need.  Maybe a motorbike starter would be more of the size and RPM and torque you need? 

Edited March 12, 20206 yr by gk10002000

Why?

Add my vote to the electric drill.