Yes the motor is very good it just need new brushes.i have tryed but it started crackling noise.i think i need a white chalk stone to clean what brushes go round on.

This is for a Dyson dc o7

Dave, April 2013

The bit that rotates is called an armature - the piece on the armature that the brushes bear against is called the commutator.

I have been messing with motors on and off for over 50 years and had not heard of the stone you mention until now.

Research shows me it's called a commutator stone and its purpose is to clean up the commutator. In the past I have only ever used fine grade abrasive paper and Scotchbrite scourers to do this job.

Carbon dust can clog up the insulated gaps in the commutator - an old toothbrush and a fine screwdriver can be a useful cleaning aids.

If the motor runs with lots of sparks then you need to pay it some attention - a few tiny sparks are normal.

http://weldingweb.com/archive/index.php/t-80281.html

http://www.sportsmith.net/faq.aspx?ID=164a8165-e847-41db-b83c-36c983b6fa18

I bed brushes in by just running the motor - the important thing for me is to have a clean commutator.

Peccavi, April 2013