http://electronics.stackexchange.com/questions/27931/torque-kgcm-what-is-kgcm
Anyway, 1kgcm is 0.09807Nm----butofcourse right? so then my 5 kgcm motor has five time .09807nm...so then... .45 roughly Nm q100h has about 40 Nm so then now I need 100 or so of these to equail that....hum...
Torque kgcm (what is kgcm)?
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I know what torque is but I find difficult to understand what Torque: 3kgcm means ?
I am not sure, how much weight that motor can carry, and I want to know how I can calculate that.
Please give me some hints
motor torque
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asked Mar 12 '12 at 23:24
Splendid
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kilogram-centimeters? – The Photon Mar 12 '12 at 23:58
Yeap I got that, but is mining of that that that this motor can in theory carry max 3kg ? – Splendid Mar 13 '12 at 0:05
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More likely the maximum torque it can produce is (the force exerted on a 1 kg mass in a 1 g gravitational field) x (1 cm). Why they didn't use proper units is unclear, but many many people mix up mass with weight. – The Photon Mar 13 '12 at 1:55
kg.cm should really be written as kgF.cm (kilograms-force . centimetres). kg is a measure of mass, kgF is a measure of force. – Li-aung Yip Oct 23 '13 at 14:52
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4 Answers
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Torque is a measure of "twisting force".
Power is a measure of twisting force x speed.
Torque is usually expressed as a Force x a distance So for the same Torque if you double the distance you halve the force to get the same answer.
So kg.cm is kg force x centimetre distance.
In fact kg are a mass and not a force BUT kg are sloppily used as a force in many cases.
Other torque units include foot-pound, Newton-metre, dyne-centimeter (!) ...
In your case 3 kg.cm means that a "force" of 3 kg acting at a radius of 1 cm would produce the same amount of torque as your motor.
Equally that could be 0.1 kg x 30 cm, or 10 kg x 0.3 cm or ...
FWIW - kg is a unit of mass and Newton the corresponding unit of force. Where the "weight" of 1 kg = g Newton where g = 9.8 m/s/s. Close enough g = 10 here so 1 kg weighs 10 Newton.
BUT pound IS in fact a unit of force. The corresponding unit of mass is the Slug where
1 Slug weighs ~32 pounds force.
You will not find people selling vegetables by the slug, or by the Newton
.
A Newton glass of beer is about 4 ounces.
A useful approximation
•Power in Watts ~= kg.m torgue x RPM
This is just happenstance as various constants cancel almost exactly but it is extremely useful. Accurate to about 1%.
So in your case 3 kg.cm = 0.03 kg.m
So the power that your motor makes at a given RPM at this torque is
Power = 0.03 x RPM Watts.
ie about 30 Watts at 1000 RPM at 3 kg.cm torque.
I have spent many long hours playing with dynamometers while developing alternator brakes and controllers to act as loads for exercise equipment. The Watts = kg.m.RPM was a useful approximation to remember.
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edited Feb 6 at 1:57
answered Mar 13 '12 at 1:53
Russell McMahon
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It may be helpful to note that while the units for torque and work may appear similar, the force and distance vectors related to torque are always perpendicular, while those for work are always parallel. Torque is the cross product of the force and a distance vector between the applied force and the pivot point, and is thus a vector; work is the dot product of the force on an object and a distance vector representing its motion; it is thus a directionless quantity. – supercat May 30 '13 at 17:40
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kgcm would be kilogram-centimeters, the motor is very old or the manufacturer does not like SI units. Anyway, 1kgcm is 0.09807Nm.
The weight that your motor will be able to lift will depend on how big the pulley is. If the pulley is 2cm diameter (1cm radius) the motor will be able to lift 3kg. If the pulley is 20cm, the motor will be able to lift ~300g.
If you want to lift more than that, you need a gearbox that reduces the speed, but increases the torque.
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answered Mar 13 '12 at 0:23
Pentium100
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Thanks, I understand better now, now I need to calculate stuff for my wheels
– Splendid Mar 13 '12 at 1:57
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Huh. I thought kgcm was the way the world was going now. I keep seeing it pop up everywhere these days. I used to see more Nm, but that seems to be fading away. – Brian Knoblauch May 30 '13 at 12:36
@BrianKnoblauch - well, with SI insisting that 1024 bytes must be called a kibbidibibidibibibyte, I feel I must insist on newton-meters. =) – JustJeff May 31 '13 at 1:36
Nothing against NM, I prefer it. It just seems to be fading away from what I've seen. – Brian Knoblauch May 31 '13 at 12:26
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A motor with 1 kg.cm torque is capable of holding a 1 kg weight at a radial distance of 1 cm.
Here is a diagram to explain.
enter image description here
Torque is the cross-product of force and distance: F=τ×d . So the same weight, at twice the radial distance, will require double the torque.
enter image description here
Note that the measurement 'kgcm' is 'kilograms-force × centimetres' and would be clearer if written as kg F .cm , which avoids confusion between kg (mass) and kg F (force.)
The kg F unit is not used for engineering work any more because 1kg F is defined as the force on a 1 kg weight in 'standard Earth sea-level gravity', but no-one can agree on a precise value for 'standard Earth sea-level gravity'. Plus, it's not a very intuitive unit when you aren't on Earth.
The SI unit of N.m, which doesn't depend on the exact value of Earth gravity, is preferred instead.
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edited Feb 6 at 3:13
answered Feb 6 at 2:44
Li-aung Yip
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Torque is a measure of force times distance. Think of turning a nut with a wrench: the further out the wrench you pull, the easier it is to turn the nut. This is because the same force, further out the handle, gives higher torque, because it has to apply that same force over a longer movement distance to do the work. A gearbox also uses the same principle, it's a way to exchange distance from center for distance of movement to step up the torque.
US units are dumb, because they use the same unit ("pound") for both force and mass, even though they are different. SI units are better, because they use one unit (kilograms) for mass, and another unit (Newtons) for force. A kilogram of mass will typically exert 9.81 Newtons towards the center of the Earth under normalized gravity (varying depending on where you are.)
I've seen a lot of motors with torque expressed in kgcm, and I don't quite understand why that is. Perhaps someone translated pound-inches (or the 12 times stronger foot-pounds) and used the wrong destination unit at some point, and the convention stuck. In countries that use real SI units, you want torque in Newton-meters, and if you have small stepper motors or whatnot, you may get Newton-centimeters.
So, can your motor hold 3 kg? Yes, if the distance between the center of the axle, and the center of mass it's holding, projected along the axis of gravity to the plane of the axle, is 1 cm or less. If the distance between center of driveshaft and center of mass is longer, then you need a gearbox, or a lighter load, or a stronger motor.
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answered Mar 13 '12 at 1:01
Jon Watte
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torque actually the cross product, work is the scalar product – russ_hensel Mar 13 '12 at 12:56
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