# Want to find out the mass movement capability of my motor

1. Feb 1, 2012

### SOA

am not sure if i am asking it right, it appears to be very easy, but am un able to solve it...
any help is highly appreciated..:)

Ques: ihave a motor wuth these specs

torque = 5 Nm
no of revolution = 90 rpm
radius of wheel mounted on motor shaft = 0.05 m

i need to calculate the mass which this motor can drive????

2. Feb 1, 2012

### Simon Bridge

A constant torque of 5N turns the wheel at a constant 90rpm means there is friction in the system balancing it out. No net torque.
But if you put a Newtonmeter on the rim and figure the force to stop it, then you also have the maximum weight it can hold.

3. Feb 1, 2012

### sophiecentaur

Does this motor have a gear box in it? 90rpm seems very slow for an off-load speed. What sort of motor is it?

4. Feb 2, 2012

### SOA

yea i will mount it on some wheel definitely but before that i want to get the idea of its capability...

5. Feb 2, 2012

### SOA

yea it is worm geared motor... mostly used in car windows.

6. Feb 2, 2012

### Simon Bridge

iirc there are important real-life restrictions - don't rl electric motors draw more current under load or something? I remember something about motors burning out.

But doing stuff with motors is usually more about power than work.
So you need to settle on something for a benchmark.

Manufacturer usually has a clue or three too.

A naive calculation would suggest to expect it to hold 10kg against gravity with the specs shown. I wouldn't bet on it though. The RPM given, if stamped on the motor, may be that under normal load (eg - lifting a window). Have you run it without yet?

7. Feb 2, 2012

### sophiecentaur

From the data, it looks as though the motor will produce a force of 100N at the periphery of the 0.05m wheel. That suggests it should lift 10kg if you use it as a winch, for instance.

Torque = Force times radius
so Force = Torque/ radius

There is another important parameter and that is the useful Power output.
The power out will be Torque times angular speed (in radians)
That's 5 * 90*2π/60 = 47W
If the motor is 50% efficient, that means a current draw of about 8A, when running on full spec load. Doesn't sound too far wrong for a chunky bit of car electrics.

The motor should lift this 10kg at about 0.5m/s.

Someone else might like to check these shirt cuff sums.

[edit - well, at least Simon agrees with my 10kg figure. Ain't sums wonderful?

and the bit about being careful not to overload is relevant too.]