# Motor Recommendations

I'm looking to buy a dc motor that is capable of lifting between 0.5-0.7Kg at any one time and also travel at an rpm of between 100-400. I will need to run 4 of these motors simultaneously from one Arduino board. I am very inexperienced in this field so any recommendations would be greatly appreciated.

fazzen:
I'm looking to buy a dc motor that is capable of lifting between 0.5-0.7Kg at any one time and also travel at an rpm of between 100-400

You do not say how the motor will be connected to the load it is going to lift. If, for example, it will be using winding a string onto a drum then the diameter of the drum and the gear-ratio between the drum and the motor will be critical.

How fast, in cm/sec do you want to lift the load? That will give you the minimum number of watts that you require. You also need to allow for friction.

...R

Thanks for the reply, to give you some background information; I am creating a shaking table by using cams below a sheet of plywood to create an oscillating motion. The motors will connect to the cams and each cam will have have to lift up to 0.75 kg at any one time. I understand that the lifting force of the cam (when its pushing the plywood upwards) will be greater than the force going back down, this could create problems when keeping the shaking motion constant. So I would need a motor that does not create this problem. In terms of getting this motion into cm/s, I have no idea how to make that conversion. Thank you, anymore help would be greatly appreciated.

fazzen:
In terms of getting this motion into cm/s, I have no idea how to make that conversion.

How far does the table move from the bottom of the cam to the top of the cam. What is the shortest time in which that must happen?

With cams add a ginormous amount for friction unless you are using roller bearings at the rubbing face. Or maybe the cams will be running in an oil bath?

...R

fazzen:
Thanks for the reply, to give you some background information; I am creating a shaking table by using cams below a sheet of plywood to create an oscillating motion. The motors will connect to the cams and each cam will have have to lift up to 0.75 kg at any one time. I understand that the lifting force of the cam (when its pushing the plywood upwards) will be greater than the force going back down, this could create problems when keeping the shaking motion constant. So I would need a motor that does not create this problem. In terms of getting this motion into cm/s, I have no idea how to make that conversion. Thank you, anymore help would be greatly appreciated.

Until you figure out the geometry of the linkages there is no way to calculate anything.

I think we need more information on the mechanical set up. Cams are quite unusual too, you'll need
some sort of encoder by the sound of it.

BTW for oscillations of fixed size the forces go up as the square of the frequency,
you may be surprized at the levels of power needed for this sort of application. So
its vital to know the true hard minimum requirements, not just a "would be nice if"
set of values.

You may get less friction using bearings and a crank rather than a cam...

like a windscreen wiper motor.

regards

Allan

fazzen:
I understand that the lifting force of the cam (when its pushing the plywood upwards) will be greater than the force going back down, this could create problems when keeping the shaking motion constant.

No, the acceleration forces may be dominant over the weight.

For instance a 400rpm (6.67Hz) oscillation of 0.75kg with amplitude of 2cm is a max
velocity of 0.84m/s and peak acceleration of 35m/s/s, ie 26N peak force (compared to
a weight of ~ 7N)

We need more details.