Motor Brushes Question!

[dreamer_1uk]

Hi,

Whats the purpose of having brushes on your Motors and whats the difference in all the different kind of brushes what you can buy along with springs?

This is something ive never known about before so i need some help please!

Thanks in advance,

[Crazy Canuck]

Purpose of brushes:

THe brushes transfer power from the endbell of the motor to the armature. The armature hass 3 segments, so, during the rotation cycle, one is charged positive, one is charged negative, and one is not charged. This, combined with the repulsion/attraction of the magnets in the motor can, causes the motor to spin. The "comm" is a small section at the top of the armature that recieves the power from the brushes to energize an armature segment.

Brushes:

The ones with higher silver content will transfer power to the comm faster, but wear more quickly. The "harder" brushes, with less silver, will wear less quickly, leave less deposits on the comm, but they will not be quite as fast.

Springs:

A harded motor spring will push the brush against the comm harder, giving the motor more torque, because there is a better contact patch, but it will have less RPM, because there is more friction. Softer springs work exactly the opposite, a softer spring means higher RPM and less torque. Aditionally, a harder spring will cause more wear on the brushes and the comm. A general rule is to stick with the manufacturers springs, unless you have a specific reason for changing them, such as a need for more torque.