I was looking up the motor parameters for some stepper motor where they listed the torque of the motor at different current/voltage but the torque they listed was in kg/cm.
How is kg/cm even a remotely acceptable unit for torque?
How do I calculate the torque in Nm from kg/cm?
Clarity note: Its not kgcm which represents [0.098 kilogram force = 1 Nm.]
Website where this happens.
It is most likely kgf-cm, as kg/cm is not a valid unit for torque.
Apparently writing kg/cm when kgf-cm is meant is a common mistake made on datasheets.
According to this conversion of kgf-cm to Nm, 28 kgf-cm of torque is 2.7 Nm, and 150 kgf-cm of torque is 14.7 Nm.
Y[Nm]=X[kg-cm]*9.81[m/s^2]/100[cm]
1kg multiplyed with gravitational constant will give you 10N and normalizing the cm to m by multiplying it with 0.01.
Basically, unit in their table is wrong. It is not kg/cm but rather kg-cm. Kg/cm would mean normalized linear pressure, which makes no sense for torque.
Also, what you have mentioned that 0.02 Nm is small torque. It is but not for 0.1A and 0.4V. If you take a look at torque for 1.5A, it is 0.18Nm for 9W of power.
The motor they listed apparently has 1.548 kg·cm of torque at 4.8 V. (As Ian pointed out, on this website -- like too many other websites -- "kg·cm" is often misspelled as "Kg/cm").
It is apparently a NEMA 17 motor. From the photo, it looks about half as long as a typical NEMA 17 motor, so I'm not surprised it has about half the torque of a typical NEMA 17 motor.
A torque of 1.548 kg·cm is more than adequate for many robots -- 1.4 kg·cm of torque is adequate for axis motors on a RepRap.
They use this unit only for the stepper motors and not for the DC motors
Huh? Every motor Several motors listed on that site, both stepper and DC motor ( a b ), are rated using the "Kg/cm" unit, which in every case is a misspelling of "kg·cm".
0.222 ... its absurdly low again.Most DC motors on the website
The "0.222 kg·cm" applies when driven at 0.4 V. That's a small fraction of its rated voltage, which is 6 V where the motor gives 1.869 kg·cm.
As far as I can tell, all the DC motors on that website include a gear box, which multiplies the torque.
It is unfair to compare motors by comparing only the torque at the output of a torque-multiplying gear box of one motor driven at its full rated voltage, to the torque of some other motor without a gearbox and when driven at a small fraction of its rated voltage.
On the other hand, I have to laugh when this website calls this a "High torque" motor when it is almost the lowest-torque NEMA 17 motor I've ever seen. It reminds me of the "Schnell-Bahn" (literally "fast train"), which are the slowest trains still operating in Germany.
EDIT: I shouldn't have said "every motor"; most of the motors are rated in "Kg-cm" or "kg-cm", which is close enough to "kg·cm".
