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I know it might be a naive question but am not really an electrical or a mechanical engineer, but am in a situation here and I need some help. I work in motorized rolling doors and I need to know how to chose the right motor for the door I have. Basically I want to calculate how much a motor can lift, maybe a general rule of thumb on how does it work.

So the information I have is Torque (Nm), hollow Shaft diameter (mm), voltage (V) output speed (RPM), and motor output (kW).

And as an example of this is that i have an industral motor with

  • Torque = 450 Nm,
  • Hollow Shaft = 40 mm,
  • Voltage = 230/400 V,
  • Output Speed = 14 RMP
  • Motor output = 1,5 kW

marked as duplicate by winny, Bimpelrekkie, Harry Svensson, Marcus Müller, Elliot Alderson Jan 17 at 12:35

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Torque and Radius of the shaft are the necessary specs that you need for a first approach of the calculation.

The force at the radius of the hollow shaft can by calculated as

F = M / r = 450 Nm / 0,02 m = 22,5 kN

Depending on which planet you want to use the device, you can calculate the mass that you can lift against gravitational force. For earth it can be calculated as follows:

m = F / g = 22,5 kN / 9,81 m/s^2 = 2293,58 kg.


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