# Question on Torque, RPM, and Control for a Stepper motor.

Hi Yall,

I'm working on a project that will require a stepper motor. It needs to be able to run at *75rpm or *150rpm, and rotate a load of about 100-150lbs. The load is on a chain and many sprockets, as such ( I figure) much of the weight will be carried on the shafts. Shafts and sprockets weight about 75lbs. So we're looking at around 200lbs I figure?

I'd rather use a stepper as I think it'll be easier and provide better control.

1. How do I calculate/figure out the force needs for my project?
2. Is a stepper better for this?
3. What steppers could work? *75rpm & *150rpm.
4. What is a good control board for this?
5. If not viable, what are some other options I should look into?

::Edit:: It is important I can tell where the motor is at all times, as other parts need to sync with the motor. ::Edit:: *::Edit:: Did my math wrong orginally::Edit::

Do you know how to calculate torque from force times distance?

A stepper is useful if you need to move a defined distance or angle, stop and reverse. If you only want to control speed of a continuously-rotating device then a brushed motor will be much better.

It's not clear from your description if the motor needs to lift all 200lbs of if this is the mass of rotating machinery that needs to be accelerated and braked. What acceleration do you need? How quickly does it need to come up to speed?

I do not know how to calculate torque.

It will be continuous motion. With gradual speed increase and decrease. Around 10 seconds to full speed/stop would be nice, but start up/stop speed is not super important.

It does not need to lift all 200lbs, I believe. The wight will be evenly distributed over many sprockets. In other words I know it's not dead lifting 200lbs. But all the moving parts will weight around 200lbs. I hope that helps.

It is important that I can tell where the motor is at all times. The rotation needs to be synced with other things.

BTW, sry about the major change in RPM. I used numbers from an old design that I forgot I made major changes to. (It's happens when you've been working on a project for over 2 years)

puzzlerf: It does not need to lift all 200lbs, I believe. The wight will be evenly distributed over many sprockets. In other words I know it's not dead lifting 200lbs. But all the moving parts will weight around 200lbs. I hope that helps.

Make a sketch drawing of the machine and post a photo of it. Or, if the machine already exists, post a photo of it.

If the moving parts are in balance and the bearings have low friction you may not need much torque to keep it moving. However because the parts are heavy it will require considerable force to get it moving - or to stop it.

There is a simple system for estimating torque in Stepper Motor Basics - but it depends on having something to measure.

...R