Eggerbahn motor brushes

[danny]

I have an old Egger 0-4-0T. The motor heats up more than it used to, probably because the brushes are wearing out. Does anyone know if and where I could get new brushes? The loco is a 1980s Joueff made Egger number 5.

[MickT]

Danny,

Could it be that the armature is either dirty or has oil on it? Try gently turning the motor and rubbing a cotton bud across the copper segments. If the cotton bud collects a black oily mark, then this may be the cause of the heating and bad conductivity through the brushes.

Similar maintenance with the underside of the phophor bronze pickup strips where they make contact with the wheel rims will also help with reducing electrical resistance and therefore heating.

All worth trying to see if things improve before you try to obtain and replace brushes or even change the motor.

Mick

[B.Meldon]

Hi Danny

Just to confirm we are all talking about the same chassis I assume that it looks like this:



This chassis has a Mabuchi skew wound five pole motor.

Have you removed the motor brushes and had a look at them yet?

What can happen with these is the spring tension on the brushes can get increasingly weaker. It is a vicious circle as the spring gets weaker it generates more heat that in turn can make the spring weaker!

Another problem can be oil on the commentator. This can make its way down from the top bearing. This will cause a build up of carbon in the gaps on the commentator and make the brush to commentator connection poor causing it to heat up.

I have also known the plastic motor cradle to distort with time causing the worm to be tight on the axle spur gear.

But the first thing I would do is have a look at the brushes and re-tention the brush springs.

Brian Meldon

[Tigger]

While we're at it, and I think this is an appropriate platform for my comments, many thanks again to you Brian for the second instalment of the Eggerbahn story.  You've now got me pulling bodies off chassis to see exactly what I've got!!

That said, again an excellent and very informative article.  Well done.

David.

[B.Meldon]

Thanks David.

I think at 2

[petersmith1942]

Dont worry about the length Brian, it will in due course make an excellent collection of pieces about Egger . I am looking forward to future articles
Peter Smith

[tedp]

...Another problem can be oil on the commentator. This can make its way down from the top bearing. This will cause a build up of carbon in the gaps on the commentator and make the brush to commentator connection poor causing it to heat up.
....

I'm afraid the main cause of a motor to heat up (apart from a faulty winding) is arcing between the commutator segments, not brush to commutator contact. The build-up of carbon and oil between the segments you describe will produce a low resistance bridge that will heat up so much it will start glowing. This will quickly destroy your motor. An open frame motor will show glowing trails on the commutator when running. The remedy is to use a seamstresses pin or a fine toothpick, and scratch out the gaps. Then clean the commutator 'dry' using a tiny swab. Be careful not to damage the solder points and windings.

Cleaning the brushes using a piece of tissue to remove any loose carbon and oil deposit will prevent quick fouling of the commutator.

[B.Meldon]

As always you explain it better then me Ted, but that was what I was getting at.

In extreme cases in the past I have cleaned motors by soaking then in meths for a while then using as soft brush dislodge all the accumulated dirt, before rinsing it off again with the meths.

Obviously it has to be completely dry before you try the motor again, but this does not take long.

In mild cases it may be beneficial to run the motor without load (in this case with the rear wheels out of the chassis) at

[Sven]

What is the "commutator"?

I like to thank Brian as well for the excellent Egger-Bahn articles. They are not too long at all, I can't wait to read more!

[Isle of Stoner]

Another thanks, Brian. Interesting stuff. Keep it up.

Cheers

John W

[Hugh Norwood]

What is the "commutator"?

If I recall correctly, it's the bit at the end against which the brushes rest.

[tedp]

I think you are Dutch, Sven. The Dutch word for commutator is 'collector'.

[B.Meldon]

What is the "commutator"?

If I recall correctly, it's the bit at the end against which the brushes rest.

Yes indeed. It is the brass bit on the rotating part of the motor that the brushes rub against.

http://www.ereplacementparts.com/images/armature_commutator.gif

Brian Meldon

[petersmith1942]

Some of us showing our age. I the 1950s/1960s and a bit longer maybe it was impossible to find a mag that didnt include a reference to motor, commutator and cleaning thereof. Now pick up any mag and doubt you will find the word or the need for brush cleaning. Any reference to motor will simply be a description of type with the assumption it will perform flawlessly forever
Peter Smith

[Graeme Dunbar]

I'm not sure about other languages but in English there is a distinction made between "commutator" as found on DC motors and "slip rings" as found on AC machines. I believe commutation means "exchange", i.e. it is the commutator that switches power between the windings whereas slip rings simply carry the power to a rotating shaft. On some DC motors there are no brushes (the windings are stationary) but they have electronic commutation (e.g. PC fan motors). However it is done the magnetic field has to move around or the motor would simply stop with the North and South poles lined up.