Tip & How-To about Stairmaster Exercise & Fitness

How to Use A Commutator Stone

A commutator stone is used to remove carbon build up from the commutator of a motor or alternator, which is created from worn brushes. The commutator is the internal part of the motor or alternator that spins and makes contact with the motor or alternator brush.
BE ADVISED: The dust created from cleaning the commutator is a carbon dust. Use caution when removing dust so as not to inhale.
If servicing the motor or alternator without removing from the unit, be sure to disconnect power from the machine.
To remove the carbon build up from the commutator, first remove the brush from the motor or alternator. Insert the commutator stone into the brushes place in the motor or alternator. Apply slight pressure against the commutator stone and by hand, slowly turn the motor or alternator shaft. As you are turning the shaft of the motor or alternator, the commutator stone cleans away the carbon that has built up on the commutator.
Use a vacuum hose to suck out the dust debris or tip the motor/alternator over and allow the carbon dust to fall out.


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stairmaster pedal resistance electrical problem


How To Clean Commutator Using Commutator Stone
Did you use a commutator stone when installing the new brushes? A commutator stone is used to remove carbon build up from the commutator of a motor or alternator, which is created from worn brushes. The commutator is the internal part of the motor or alternator that spins and makes contact with the motor or alternator brush.
BE ADVISED: The dust created from cleaning the commutator is a carbon dust. Use caution when removing dust so as not to inhale.
If servicing the motor or alternator without removing from the unit, be sure to disconnect power from the machine.
To remove the carbon build up from the commutator, first remove the brush from the motor or alternator. Insert the commutator stone into the brushes place in the motor or alternator. Apply slight pressure against the commutator stone and by hand, slowly turn the motor or alternator shaft. As you are turning the shaft of the motor or alternator, the commutator stone cleans away the carbon that has built up on the commutator.
Use a vacuum hose to suck out the dust debris or tip the motor/alternator over and allow the carbon dust to fall out.

I am also attaching a video on how to install the brushes just for an extra reference.
Stairmaster Alternator Brush Replacement Video

Jan 20, 2014 | Stairmaster Exercise & Fitness

1 Answer

intermittently trips mains fuse when kicking into fast spin


Hi from retired Englishman in SW France,
(Sorry but this does go on a bit!)
It does sound as if it is the motor causing the tripping especially if the washer is not very young.
It is not uncommon to find that the brushes are worn sufficiently for them to not make perfect contact with the commutator at the higher speeds asked of it in spinning- bouncing and sparking.
The carbon dust from the worn brushes can also cause 'shorting', in some cases cured by removing the motor and carefully cleaning/blowing off the carbon dust - which is well worth trying. If that does not cure the tripping it's possibly a new motor.
It might be suggested that just the brushes on the motor want changing; experience (of others) suggests that they may only last months rather than many years UNLESS the motor itself is refurbished. Refurbishment includes skimming the commutator on which the brushes run. Without skimming the brushes do not sit cleanly on the commutator (like the worn ones!), often causing excessive sparking and excessive wear on BOTH. Alternately a new motor! I changed the motor on our 19+ year-old Bosch at a cost of GBP250 ;-0(
The choice of course is entirely up to you- but do not forget that it is not an uncommon fault, especially if the washer is not exactly new. Others I have given this advice to have chosen new brushes and I don't blame them!
Good luck,
John C

Mar 30, 2011 | Hotpoint Washing Machines

1 Answer

my stairmaster 4400 is "slipping" during workouts. This has happened several times before and it was always the resistor needed repacement. any help where I can get part and/or repairman. I am in montana..40 minutes south of missoula. Thamks, Tom Martin


It sounds like the alternator brushes may be worn and causing the slippage.
You con this part from Nation Gym Supply call the @ 800-496-7278 and order part # SM001 cost $10.50 plus s/h Also order commutator stone part # MCT035.1 cost $3.90 Here the procedure of replacing the alternator brush:
Pull the side panels off locate the alternator where the wire connections are you will see a brown wire with a diode attached to it connected to a spade connector. This is where the brush is located remove the diode and the 2 screws pull the brush out. Now push the foot pedal and insert commutator stone and clean the 2 section of the commutator. Then Be careful when inserting the brush have both sections go in simultaneous as you pulled out the old brush. Insert screws and connect the diode then test unit this should take of problem.

May 30, 2010 | Stairmaster 4400 PT Stair Stepper

1 Answer

How to change carbon brushes


You need to know that very seldom will new carbon brushes alone `FIX`a motor in todays vacuums as they are higher RPM than those of 30 years ago.
On a salvageable motor a good rebuild procedure will generally include repacking bearings, cleaning suction fans and reseating new brushes with an abrasive seating stone at low speed with a motor run in device with variable voltage

That said, I have not done a HENRY in years but it likely will contain a generic AMTEK Lamb type motor as it is sold as more durable vac.
On a traditional vac motor, carbon brushes are removed by releasing a clamp over the brush. The brush holder will have either a flag terminal on it where the wiring will disconnect from the side, or a flat flag terminal which slides into a pocket on the carbon brush housing.
. If you are going to the trouble of replacing the brushes, remove and inspect the old ones for wear and chipping. Also inspect the commutator surface on the motor where the brushes contact. If there are any curved gaps between segments, or if the com is worn like an apple core , you need a motor complete.
If the motor has simply worn to the point where a brush has stuck or worn to nothing, you may be bale to reseat the new brushes, however any evidednce of BLUE sparks or noise is not a good sign . Best of luck. Post back if you need more help

Nov 01, 2009 | Henry Numatic "" Canister Vacuum

1 Answer

bosch wfr2460


hi Many universal motor malfunctions are caused by wearing down of the carbon brushes, the soft blocks of carbon that complete the electrical contact to the motor's commutator. When these brushes become worn, the motor will spark, and electrical contact may be incomplete.try this
Step 1: To sight-check the carbon brushes, remove the screws that hold the brushes and brush springs into the brush holders at the sides of the commutator. The screws will pop out of the screw holes; turn the motor over to tap out the brushes. The ends of the brushes should be curved to fit the commutator; if they're worn down, new brushes are needed.
Step 2: To check carbon brushes with a continuity tester, remove the motor lead wires from the circuit. Tag the wires as you disconnect them so that you'll be able to reconnect them properly. Hook the tester clip to one motor lead and touch the probe to the other lead; the tester should light or buzz. Slowly rotate the motor shaft, keeping the tester in position. If the tester doesn't light or buzz, or if it flickers or stutters when you turn the motor shaft, the brushes should be replaced. If the springs behind the brushes are damaged, they should be replaced as well.

Step 3: Replace worn carbon brushes and damaged springs with new ones made specifically for the motor. The model information (number and make) is stamped on a metal plate fastened to the motor, or embossed on the metal housing of the motor. If you can't find the model information, take the worn brushes and springs with you to an appliance-parts store to make sure you get the right kind. Insert the new springs and brushes in the brush holders, replace the brush assemblies, and secure the new brushes with the mounting screws that held the old brushes.

Sep 13, 2008 | Bosch Axxis+ WFR 2460 Front Load Washer

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