Extending the Life of Lamb 5.7 inch Vacuum Motors: A Guide to Changing Brushes

Brushed vacuum motors have driven blower, fan, grinder, and vacuum designs for more than 100 years. They remain more relevant than ever as their core strengths — simplicity in control, cost-effectiveness, reliability, and high peak torque outputs — are continually complemented by innovations that extend useful life and applicability.

Consider Lamb universal motors from Bison, which can be mass-customized for use in an array of consumer and commercial-grade appliances.

These are universal drive motors — brushed motors — with field winding and armature in series.

Such motors deliver high starting torque, a characteristic useful particularly for grinding and mixing machines. The magnetic path through the motor includes lamination stacks that minimize eddy currents that arise upon power input.

Speeds range from a thousand or so rpm to many times higher, also useful in designs that might run as much as 30,000 rpm at their fastest.

Of course, one mechanical wear point occurs at the rotor’s commutator interface with the brushes. But brushes are one of the few motor subcomponents that you can easily change yourself.


How to Change the Brushes

1. Follow the steps below to change the brushes on a 5.7-in. vacuum motor.

2. Remove power from the motor.

3. With a flat-blade screwdriver, bend back the metal safety clips so they’re no longer over the plastic cap.

4. Use a screwdriver to pry up on the plastic cap — to pop the cap loose. (Once the cap has been removed the brush mechs are exposed.)

5. Use the flat blade screwdriver and locate the brush clip, and using the screwdriver press down firmly and push the clip towards the center of the motor. (The clip should slide out from under the black nylon of the brush mechanism.)

6. When the clip is free from the brush, remove the two screws holding the brush clamp in place.

7. Lift the clamp and remove the brush.

8. Now install the new brush and start the brush clip into the nylon.

9. Use the top bracket of the motor to press the clip into place.

10. Secure the brush clamp back in place using the two screws. Repeat this for the second brush.

11. Press the black plastic cap back into place until both sides click. Then bend the metal safety clips back so that they help hold the plastic cap in place.

One caveat is that brushes can’t be changed an infinite number of times because the commutator upon which they ride is also a wear item. The general rule of thumb is that brushes can be changed two or three times before the commutator on the rotor reaches the end of its useful life — and renders the motor itself unserviceable.