Optimizing Plate Surface for a Weighted DC Motor

[Molochlp]

Hey guys,

I have a DC motor and i want to glue to it's rotor a round plate (make a hole through it and stick the rotor in that hole :) )(consider the plate weightless) and on this plate i will glue a weight, doesn't matter what the weight is...just know that it's constant.

My question is this: how does the surface of the plate (on which the wight stands on) be so that the motor can, more easily, turn the weight. If i use a smaller plate (2cm diameter) instead of a bigger one (7cm diameter) will this make it easier for the motor or harder? How does the surface of the plate influence the force of the motor?

Hope i explained it right, if you don't understand something..do tell and i'll explain it again :)

(I know it might seem like an electrical engineering problem, but i don't think it is)

 

[Mech_Engineer]

You're right that it's a mechanical engineering problem, not an electrical engineering problem. If you're picky, you could consider it an electro-mechanical engineering problem.

The answers you seek should all be contained here:

http://en.wikipedia.org/wiki/Rotational_inertia

The moment of inertia of an object about a given axis describes how difficult it is to change its angular motion about that axis. Therefore, it encompasses not just how much mass the object has overall, but how far each bit of mass is from the axis. The farther out the object's mass is, the more rotational inertia the object has, and the more force is required to change its rotation rate. For example, consider two hoops, A and B, made of the same material and of equal mass. Hoop A is larger in diameter but thinner than B. It requires more effort to accelerate hoop A (change its angular velocity) because its mass is distributed farther from its axis of rotation: mass that is farther out from that axis must, for a given angular velocity, move more quickly than mass closer in. So in this case, hoop A has a larger moment of inertia than hoop B.