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• # Torque and power calculation of motor

Discussion in 'Calculations' started by Rutujab, Mar 15, 2013.

1. ### RutujabMember

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Hello,

I have one question.
I have to design a motorized trolley which will travel on a vertical wall.
How to take effect of gravity in consideration while calculating torque and power
requirement of motor.

2.
3. ### PierArgWell-Known Member

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Hi Rutujab,
could you post a sketch?

The action of the gravity depends as the trolley is bonded.

4. ### RutujabMember

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Hello PierArg,
I tried to attach sketch with my post starting this thread. But, I am unable to find it how to.
I will try to explain configuration.
It will travel on a vertical wall in vertical, up-down direction. Front Wheels will be driven by one motor
and Rear Wheels will be driven by second motor. I cant give drive from one pair of wheels to another due to design constraint.
Is it sufficient data?

5. ### GarethWChief ClickerStaff Member

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There's a button for "insert image" when you make a post. You have to host your image remotely (e.g. photobucket) and insert the URL.

6. ### mhjones12Well-Known Member

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I believe, just to overcome gravity (not including friction or other efficiency losses)

Power = mass*gravity*speed_of_trolley

All in SI units

Last edited: Mar 16, 2013
7. ### PierArgWell-Known Member

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Hi Matthew, I agree with you!

I was just waiting for the sketch!

@Rutujab: why do you want to use two motors?

8. ### RutujabMember

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Hello PierArg & Matthew,

I have attached a schematic sketch of trolley. I think you can see the design constraint. I will have to use magnetic wheels as trolley has to travel across a metallic wall.

Last edited: Mar 19, 2013
9. ### RutujabMember

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Thank you Matthew.

10. ### PierArgWell-Known Member

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Hi Rutujab,
i'm so sorry but i can't see the attached picture!

11. ### harry29041993New Member

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For the motor, you need to consider the friction that you need to keep your wheels rolling on the wall. Also, in addition to the torque being equal to mass*gravitational acceleration*radius of the wheel, you should consider internal friction of the motor and the gear box if you need a gear box. In most cases, motors rotate at pretty high RPMs and you may or may not want such high rpm (high rpm = high speed). So you may need a gearbox to "gear it down" so that you can achieve the correct rpm.

Torque (N-m) = Force * radius = m*g*r

For power, you need to know what your rotational speed of your wheel is. Say, if your wheel is 0.1 m in radius and it rotates one cycle per second, then your rotational speed is 1 rev per sec (1 rps) which is equal to 1 rev per min. To stay in the SI units, you should look at the rotational speed in terms of rad/s which is (rpm*2pi/60).

Power (Watts) = Torque(N-m) * rotation speed(rad/s)

It is definitely important for you to consider the right motor. Which is why here are a few things you should think about for later, I guess.
1. Is the motor just one directional or will your cart be going up and down. If it goes up a certain distance then comes down then goes back up and so on, then you might want to consider a 3-phase motor or a stepper motor.

Hope this helps