# How to calculate torque required to move a heavy object on wheels

## Main Question or Discussion Point

I would like to work out the torque required to move an Airbus A380 along the runway to taxi it back to the gate after touch down. I want to look at using electric motors on the wheels to do this

Say the weight of the plane is 400,000kg, the speed required is to be around 10 m/s and the diameter of a single wheel is around 1.4 m

How would I calculate the torque or power required to move it? Sorry I just can't remember much about mechanics as an EE

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Danger
Gold Member
I would like to work out the torque required to move an Airbus A380
Planning to steal one? :D
I don't know all of what's involved, and definitely not any math regarding it, but some things that you have to look at are rolling resistance of the wheels, axle friction, force deflection do to suspension dipping (probably not applicable, but I wouldn't rule it out), even wind force for something that big... If I think of anything else, I'll get back to you.

edit: Oh, yeah... if you're asking about the required torque of the engine, you also have to factor in all of the aforementioned, along with drivetrain losses, for the tow vehicle itself.

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I'm doing a regenerative braking on aircraft project and I basically wanted to know what type of motor will be better for using on the planes landing gear to taxi it along the runway.

I know DC motors have better speed control but since the plane is so heavy I'm not sure if even a few DC motors would be able to move the plane. There is a company that has got this electric motor taxiing to work but they won't tell me what type of motor they're using

Danger
Gold Member
I see. I'd be seriously tempted to look into hydraulic motors, which become pumps when driven from the shaft. There'd need to be some serious gearing on hand if you want it to be able to apply braking pressure at touchdown speeds, but simple taxiing should be an ideal situation for it. Don't go on my word, though; I'm not educated in the subject.

So the force required to move the aeroplane would be equal to:

Total force = (2 x Static frictional coefficient x Normal force) + (mass of the aeroplane x acceleration)
The above is under the assumption that front wheels are free to roll and thus no friction developed. The normal force will be equal to the mass of the plane divided by 4 so N = (mass x gravity)/4

The acceleration can be found by using SUVAT equations with the time/distance to the end point being arbitrary values, so you can use v^2 = u^2 +2as with u^2 = 0

Once you find that out, you can find the torque which is Torque = Force * Radius

Then you find the Power by first finding the RPM.

You find the power which is P = Torque x RPM (in rad/s) ----> Note that the power is constant.

Once you have the value of the torque that is required, you devide it by the gear train of the machine. So say gear 1 is 2.3 and gear 2 is 0.2. Then you just divide the torque value by (2.3*0.2) to get the torque value at the motor.

However, losses such as the transmission efficiency and so on have to be catered for as well as a safety factor. So it's better to divide your initial value of torque by the safety factors and losses to get the actual required value of torque.

This is how I would do, Hope I helped :)

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