# Torque Calculation for Sweeper machine Broom

1. Feb 24, 2015

### Tejas Patel

Can any body tell me how to calculate torque for rotating sweeper machine broom?

Broom Dia is - 0.6 m
Length - 2 m
Weight - 150 Kg
Rotating RPM - 150

2. Feb 24, 2015

To start rotating any object, there has to be an unbalanced torque. Let the torque required be $\tau$.
What is the change in angular momentum when rod starts rotating with the required RPM starting from rest?

3. Feb 24, 2015

### Tejas Patel

I dont know about angular momentum, But i know time. In 10 sec shaft pick its max speed 150 RPM.

4. Feb 24, 2015

Are you familiar with this equation: $\tau=\Delta I\omega$

edit:$\tau = \Delta (I\omega)/\Delta t$

Last edited: Feb 24, 2015
5. Feb 24, 2015

### Tejas Patel

Yes in this i have calculated w, angular speed come is 15.7 rad/s. But i have confusion regarding I

6. Feb 24, 2015

Assuming its a rod rotating about one end, I=(1/3)ML^2

7. Feb 24, 2015

### Tejas Patel

In this what is M and L?

8. Feb 24, 2015

I is the moment of inertia which is analogous to mass in rotational mechanics. M is the mass and L is length of rod.

9. Feb 24, 2015

### Tejas Patel

than I value is 2594.75 N-M2

10. Feb 24, 2015

So you can find the torque using the equation in post 4

11. Feb 24, 2015

### Tejas Patel

Than Unit come in N-m2/s ? bcz w unit is rad/s and I N-m2 so bit confuse in this

12. Feb 24, 2015

Oops... I am very sorry.
its $\tau=I\alpha=I\frac{d\omega}{dt}$

13. Feb 24, 2015

### Tejas Patel

Ok thank you so much.

14. Feb 24, 2015

What I am trying to say is the change in angular momentum is $\Delta(I\omega)$.
Now you can find alpha is angular acceleration. Its is like acceleration.
$\alpha=\Delta\omega /\Delta t$

15. Feb 25, 2015

### Baluncore

I assume that you want to know the torque needed to keep it turning once it has reached speed and is being used. The operating torque will depend on the contact pattern with the swept area, the velocity of travel and the friction between the brush and the swept surface.

The size of the bristles on the brush will have a significant effect. Use the biggest bristles that will do the job.

Review the marketing information from manufacturers of sweeping machines. Make a list of published motor HP and brush RPM. From that you can calculate torque since power is torque multiplied by RPM.

16. Feb 25, 2015

### Tejas Patel

Hello,

i am using it to clean solar panel, and my selected bristles dia is 0.3 mm also coefficient of sliding friction between solar panel and brush is 0.1 as per supplier data.
any specify calculation formula for same? Bcz i try as per post 12 but its value come too high.

17. Feb 25, 2015

### Baluncore

Broom Dia is - 0.6 m. Weight - 150 Kg.

A quick estimate begins with 150kg * 9.8 = 1470. N
Coefficient of friction is 0.1 so force needed is 1470 * 0.1 = 147N

Diameter is 600mm therefore radius is 300mm = 0.3m.
Torque needed is 147.N * 0.3m = 44.1 newton.metre

18. Feb 25, 2015

### Tejas Patel

May be this start up torque, So can i need more torque to rotate it constant ?

19. Feb 25, 2015

### Baluncore

44.1 Nm is an estimate of the continuous operating torque while being used. You may need more torque to start the rotation, but that will only be if you need to accelerate it quickly, or if it is started while it is in contact with a panel.