# how to find the motor specification

I need a motor for my project. My aim is to move a 10 kg mass using a belt pulley system, with a velocity of 15km/hr to a distance of 3.6m. The maximum time for moving the same is 1.5 sec. Can somebody please help me with the calculation and finding out the right motor, that is the max power and max rpm of the motor required?

• Find the power first, multiply it by safety factor, dived it by gearing efficiency, the result is the power you need. Probably you can't find the right motor, so you have to choose the one with slightly higher power, then repeat all the procedure again and again to find what you want. – Sam Farjamirad Mar 22 '19 at 7:44
• can you please help me with the calculation? I am not from a mechanical background – Nate Mar 22 '19 at 8:12

## 1 Answer

There are two masses here to accelerate, the target $$10$$ kg and the mass of the belt which is yet unknown(usually it is given as weight per meter), the total mass is $$M$$. I make some assumptions here:

1- There is no relative motion between the belt and the mass.

2- There is no air resistance.

3- The mechanical losses are also negligible (This is very rough assumption).

4- Constant acceleration from the beginning to the terminal speed.

The effective pull force (on the belt) can be calculated as:

$$F = \mu_sMg$$

Here $$\mu_s$$ is the static coefficient of friction, you can find it by looking at the brochure, $$g$$ is about $$9,81$$ $$\frac{m}{s^2}$$.

Multiplying the force $$F$$ by safety factor $$s$$ and of course not to forget the gearing effect $$\eta$$:

$$\Phi = \frac{sF}{\eta}$$

Now the required power is:

$$p = v\Phi$$

You need at least one another parameter, the diameter of the conveyor disc $$d$$ to calculate the speed of the motor:

$$\omega = \frac{v}{d/2}$$.

Now you have the power and the speed.

But, there remain some design consideration here, for example, you have to specify the dimensions of the machine, before calculating the speed of the motor, and countless other small things, but here i tried to demonstrate the very basic steps. I hope the other engineers here, also contribute.

• Thank you so much for helping. I dont think i need to consider the gears. My plan is to mount a 15cm pully on the motor and connect it to another pulley on the other end. and does the time have any effect on the design? – user19805 Mar 22 '19 at 13:32