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Why is are some motor torques listed in Kg*cm instead of a force*distance?

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cbc02009:
Hello,

I'm trying to size a motor for a project I'm working on, and I'm really confused. I have a flat square panel that I'm rotating, with the length and width parallel to the ground. The center of rotation is through the center of the panel, and perpendicular to the ground.

 I've calculated the angular acceleration I need in radians/(s^2), and the moment of inertia of the panel in Kg*cm^2. So the torque I calculated has the correct unit of Newton meters.

But most of the motors I've found for sale list their rated torque in Kg*cm, which is not the same units as Newton meters. Do they actually mean kgf*cm? Or am I missing something?

Any help would be greatly appreciated.

these are my numbers in case they're helpful:

These are the dimensions of the panel:
H = 3.5cm
W = 62cm
L = 66.5cm
mass = 10.2kg

I got a moment of inertia of 7.033 Kg*cm^2 using I = (1/12)*mass*(L^2+W^2)

The acceleration I want is .314 radians/sec^2

The torque I calculated was therefore .11 Newton meters

Rerouter:
1kg*cm would mean able to lift a 1kg mass on a spindle with a 1cm radii. So for all intents it is N*m (i know 9.81... not 10 for acceleration)

langwadt:

--- Quote from: Rerouter on September 18, 2018, 10:56:06 pm ---1kg*cm would mean able to lift a 1kg mass on a spindle with a 1cm radii. So for all intents it is N*m (i know 9.81... not 10 for acceleration)

--- End quote ---

~0.1 N*m  ;)

CatalinaWOW:

--- Quote from: Rerouter on September 18, 2018, 10:56:06 pm ---1kg*cm would mean able to lift a 1kg mass on a spindle with a 1cm radii. So for all intents it is N*m (i know 9.81... not 10 for acceleration)

--- End quote ---

I'll give you your 2 percent rounding error from 9.81 to 10, but you can't have the factor of 10 error in converting cm to meters.

A newton is a kilogram-meter/second squared.   In earths gravity you get close to 10 meters/second squared.  So a kilogram weight on earth produces 10 newtons of force.  At one centimeter (0.01 meter) you get 0.1 Newton-meter.

There are two advantages to the metric system.  One is the decimal relationships, which is nice but not compelling.  The other is complete self consistency.  No need to differentiate between pounds force and pounds mass or other dodges like poundals or slugs.  This is the real advantage of the metric system, and is compelling.  When people use bastard units like kg-cm they are throwing away the real fundamental benefit of metric.

Rerouter:
Yep sorry, got my head flipped between centi and deci, I've seen that on motor specs before.

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