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.

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?

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.

I believe, just to overcome gravity (not including friction or other efficiency losses) Torque = mass*gravity*radius_of_wheel Power = mass*gravity*speed_of_trolley All in SI units

Hi Matthew, I agree with you! I was just waiting for the sketch! @Rutujab: why do you want to use two motors?

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.

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