What's the right electric motor for me?

Question

I have been tasked with building something called a yarn "carder" http://www.strauchfiber.com/dc_madBattr.php I am a reasonably skilled woodworker, but do not have much experience with electronics assembly.
I need something that can handle fairly significant torque as the drum will be stretching and pulling at fibers. I also need it to be variable speed, say, between around 15-90 rpm.
My understanding is that is should probably be DC and maybe have a worm drive gearbox for torque.
Also I need a DC converter so it can be plugged into a regular outlet.
What do you think? Are these requirements unreasonable? Links to example products would help.
Thanks!

Answer 1

It would help to know how many foot pounds (or inch pounds) of torque the drum itself will require to accomplish its task. After that it's fairly easy. And I'd not recommend a DC motor.



Here's what you need to have going on: Torque at the drum, RPM at the drum, RPM (motor) and an associated gear box or belt & pulley drive to lower the RPM of the motor. I'd recommend an AC motor that spins around 3600 RPM.



Now: Suppose you want to turn the drum at a modest 24 RPM (that's 1 rev per 2.5 sec). Sounds modest enough for me. You need to gear 3600 RPM down to 24 RPM, so you need a gear ratio of 150 to 1 (150:1). That's a significant step down. Worm gears will probably get you there faster. Just finding them will be difficult enough. Then put them into a frame. LOTS of work.



But whatever you come up with, the ratio downspeeding the mechanism will result in (in theory) the same torque increase. So if you have a small motor capable of 6 inch pounds of torque (0.5 ft lb), you'll be applying 75 foot pounds torque to your project. That's not a TON of force but that is rather significant. You'll have to build to withstand 75 ft lbs. force.



Finding a lower speed motor will help. Just do the math and calculate out your desired RPM at the drum and what gear ratio you can reasonably acquire then get the appropriate motor.



There IS an alternative, but you'll need to be savvy with electronics: If you can find an old tread mill - they have variable speed motors of significant power. The good thing about that is you can reduce the force and reduce the need for a large transmission. But to use it you'll have to figure out how to build your speed regulator. Quite likely a simple potentiometer will work, but it will need to be the right size otherwise your controllability will be drastically limited.



Hope this helps.



'av'a g'day mate.



'')

Answer 2

There are several options to use an electric motor to drive the assembly. A box fan with a speed control might supply the motor and speed you want and a gear reduction or belt drive should give enough torque for the system. Strip the fan blades from the box fan and use the motor and a belt drive should allow a good speed control. Maybe $50 for the box fan and the speed control parts.

Answer 3

I suggest exploring an industrial supply house like Grainger or McMaster Carr. they will have all kinds of motors and gear reduction units to choose from. Or perhaps you could use a rotisserie motor or maybe an inexpensive winch for a geared down power unit.

Answer 4

I'm with Tony here, I don't think Jim's fan motor is designed to give torque, all a fan does is move air which is a very small load.

Answer 5

there are several web sites that will help you get started and provide good information ====http://video.search.yahoo.com/search/video?p=how+to+make+an+electric+yarn+carder === and you can use the search web line to open&scroll === how to make an electric yarn carder ==== try it ..