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• # Torque and power calculation of motor

Discussion in 'Calculations' started by Rutujab, Mar 15, 2013.

1. ### Alfred PutterMember

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Have you considered a winch to lift & lower using a steel rope.

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3. ### RutujabMember

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Thank You Harry.

4. ### RutujabMember

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Hello Alfred,
I do not get your question. Can you please explain. I may be missing on something which is important.

5. ### Boothby171Member

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You've got a few loads that you've got to consider in your calculations:

Force = Weight of Vehicle + Acceleration force on vehicle + Rolling resistance of magnetic wheels

Torque = Force * Wheel Radius

That's the torque needed AT the wheels. The torque needed at the motor will need to be increased to overcome inefficiencies in the (assumed) gearbox, though reduced (of course) by the gear reduction

Tmotor =Twheels / (n * eff)

Speed of the motor, and power of the motor is fairly straightforward. Assume that the motor will need to run at top speed while accelerating up the wall.

I think the trickiest part (basically because I don't know how to calculate it yet) is to figure out what the magnetic wheel system will add as what would otherwise be considered rolling friction. Hmm....actually, I'm picturing you flinging the vehicle laterally across the wall (pointed left to right, instead of up/down). It would pretty much skitter right across the wall, wouldn't it, without much in the way of loss?! Add 5% frictional loss, then, just to cover your bases.

6. ### doneyNew Member

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Nov 2011
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Maybe use a counter balance

Hi Rutujab,

Would it be possible to use a counter balance to bring the trolley back down the wall. The size of the counter
balance (measured bu trial) would also give you an idea of the friction/magnetc forces at play.
Also, must the wheels be magnetic? can there be a magnetic plate on the trolley or make it out of magnetic material. Maybe then some standard low friction casters could be used on guide rails.
Just some points to add as you have pretty much got your main question answered here with some great feedback.
Regards,
D

7. ### Jitesh NairMember

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I believe by your arrangement you will be spending much more energy than required. First you need enough magnetism to balance gravitational pull so that the trolley does not fall. Then you have to force your motors to push against the magnetism and gravitational pull. The winch mechanism similar to the one used in elevators will be more energy efficient.

8. ### joninstjohnMember

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Bear in mind that the offset CofG of the trolley will create a turning moment that will tend to pull the upper wheels away from the wall. The magnetic wheels will need to counteract this.

Also assuming metal wheels on a metal surface will mean that the torque will need to be applied gradually to guard against wheel slip.

9. ### SekocanMember

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Jan 2014
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Hi there,

You may be missing something big.

If you are using magnetic wheels, it means you will be creating Eddy currents while turning the wheels. This will also drain some energy from your cart. (Actually this is also why most of the "infinite energy" machines won't work).

Think about this. If you roll an aluminium cylinder on a steel table, it will roll easily but if you try to roll a cylinder magnet on a steel table, the magnet will stop after some short time.

I don't know the calculations of Eddy currents but you can get help from an electrical engineer.

10. ### dprideMember

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If you wish to make an untethered unit, discard the idea of magnetic wheels. Neodymium magnets placed in the body of the cart will hold it against a vertical surface with a SMALL STANDOFF to allow using wheels (tires) that have sufficient grip to move the cart.

The original drawing shows a block in the center which could be viewed as a magnet, it is the simplistic approach I would take to make a prototype.

The calculations for motor torque will depend on your finished weight.

Last edited: Mar 15, 2014

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