How to Find out Max Torque

How do I calculate the maximum torque of a Stepper motor when running it at a constant speed? Do I have to make a pulley and put weights on it to see how much max weight it can lift up or is there any better way?

Ericgibbs posted this recently.
https://www.linengineering.com/site/resources/onlinecalculator.htm

Problem is that I have around 5 motors with exactly the same rating but In practical they all seem to have different torques or the amount of weight they can lift up.. so i was wondering a practical way of measuring the exact torque?

A 2” diameter pulley / spool ( 1” radius) that can wind up a string with fishing sinkers on it will give you inch ounces of torque. If you need Newton meters or stones per square cubit, you can find conversion charts.

ClydeCrashKop said:

A 2” diameter pulley / spool ( 1” radius) that can wind up a string with fishing sinkers on it will give you inch ounces of torque. If you need Newton meters or stones per square cubit, you can find conversion charts.

Click to expand...

Someone building a pyramid?

I don't understand... Can anyone elaborate?

Stones per square cubit was my retaliation for companies, tech support and service manuals that use obscure units of measure with no cross reference chart. It started with testing Yanmar diesel fuel injectors. Our tester showed PSI and KPa. Their specs were in kgf/cm2 and some other “damn fool furrin” (foreign) unit of measure with no cross reference. I ran into the same thing researching piezo benders. I took it as camouflage because they didn’t want you to know little force they actually exert . Stepper motors are in oz-in and M&Ms when I want FOOT POUNDS and HORSE POWER.
The strongest stepper motor in the Digikey catalog will hold 122 M&Ms. They don’t even say how many M&Ms it will pick up because it is a whole lot less. If you were buying a truck, would you base your decision on how well the brakes hold?
End rant.

Sorry baberjaved.
However much weight it will pick up on that string with a 1 inch radius spool is the actual inch ounces of torque.

OKays I got it now... I just need to Multiply the Radius of the Pulley attached to the motor and multiply it by the maximum weight it can lift with that pulley in order to find out the maximum torque
Thanks a lot guys!

You can also "torque step" your motors by energizing two coils per step...

Ok I checked out the torque and using a 1inch diameter pulley I was able to pull up a weight of around 5 kg but the motor was unable to pull up a 10Kg weight... Is this Ok or is something wrong with my circuit (L297/L298)? I am using a 2-phase bipolar 1.6amps stepper motor... When pulling the weight the current of the motor doesn;t even exceed 1A although the motor is rated 1.6A.. Why so?

To get maximum torque and speed from a stepper you need to feed it from a far higher current limited voltage - like 48V for a 12V motor.

Units

ClydeCrashKop said:

obscure units of measure

Click to expand...

With "standards" happens more or less the same: everybody recognize HIS as the real standard for everyone. And very seldom it is!

And yes, the lack of table of equivalents is the worst.