Commutator Polishing

After a strip down and rebuild of a chassis it is nice to give a cleaned commutator a polish. I find this enhances the conductivity from the brushes to the commutator and makes for better running. Admittedly it’s not something I have time to do on every locomotive, but it’s a nice added touch, part of the “full works” if you like. The process is outlined below;

For this you will require a cocktail stick, modelling knife, cutting board and chassis complete with newly cleaned commutator. It is also handy to have a rolling road and some IPA, as I shall explain later.

First, chop the end of the cocktail stick off, as illustrated below:

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You will be using the long section of the cocktail stick. The short section can be discarded.

Next, connect your locomotive chassis, with the body off, to a track power supply (normal 12V DC) so that the motor rotates. This is where a rolling road comes in handy. You need the chassis to remain stationary whilst you polish the commutator, so it either needs to be mounted on a rolling road, or have the bogies removed so that it does not move. Either way is fine.

Next, with the motor rotating, take the portion of the cocktail stick that you kept. Place the flat end up against the moving commutator, gently at first, and let it “polish” the commutator surface. This is shown in the illustration below. Apply pressure as necessary, but not too much. It is important that you use the FLAT end of the stick and not the “tooth pick” end, since you do not wish for it to lodge between the commutator segments. Additionally the flat end provides a good surface area across which the commutator can be polished.

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Position the flat end up against the commutator so that it is not rising against the direction of the commutator. For example, if on the side you are polishing the commutator is rotating in the direction from bottom to top, place the flat head of the stick towards the upper portion of the commutator. Placing it at the bottom would be going against the direction of the rotating commutator. This is easily apparent when you carry out the polishing.

Be sure that the cocktail stick is cut cleanly, and that there are no fibres at the cut end that could lodge between commutator segments. Work on a clean commutator, since a dirty one might have deposits which could scratch the commutator surface. Never use anything other than a cocktail stick and don’t be tempted to clean your commutator with any metal surfaces – you will scratch it and thus provide crevices into which carbon can lodge, thus reducing the efficiency of the commutator. For added effect you can soak the end of the cocktail stick in IPA.

This process should always be carried out with caution, since you are making contact with a revolving part. I would only suggest this method to those who are comfortable with working on their locomotives. The cocktail stick will not scratch the commutator, providing both are clean.

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