# Thread: Torque required to open & close the gate.

1. ## Torque required to open & close the gate.

Hello ,
I need to find the torque which i should be applying at the shaft to close and open the gate.

2. Using D'Alemberts principle, you need to know a number of desired variables. I would use the "Electric Motor Sizing Design Formulas and Calculator" to determine the torque needed to open and close your door.[/FONT]

Then decide the electric motor you want to use and then determine the reduced/multiplier gear box (if required).

https://www.engineersedge.com/gears/torque_in_gear_drives_formulas_15662.htm

3. I did some calculation but the number I got is reasonable low....I don't see an option to attach a snip of my calc while writing this reply.

4. I have a gate opener on my property (Mighty Mule) for convenience . Manually opening and closing that 12' gate can be done with a single finger push - so yes the force needed are low.

5. The start time should be less than 1 second, ~ 0.5 sec and I would suggest the velocity at around 1 rpm or less.

6. I calculated the torque which I need to apply at the hinge point( through some shaft) for gate which is 105 in long and 200 Lb in weight and number I got is 5 lb- in .
I used Torque = I ( mass moment of inertia of rectangle) * Alpha
Alpha = w/t = .1 (rad/ s) / 20 s
I = Ml^2 / 3 , M is mass in Kg which is 91 kg and L = 105 in
TORQUE I GOT = 0.56 Nm or 5 lb - in
Which seems low as i need to apply the torque at hinge point. What do you think?

7. Originally Posted by sharma18aug
Which seems low as i need to apply the torque at hinge point. What do you think?
No, that torque does not seem low. However, you will actually need to design for more as that torque is in equilibrium with the forces needed.

Usually you'll need to size motors and gearsets approximately 2X or even more to achieve a robust system.

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