Mashima 24mm x 13mm brush failure

[Fordyce]

Unidentified Mashima can motor, measured at 24mm x 13mm wide with a Branchlines gear box, has failed. Cause is the brush not making contact with the fixing screw which is screwed down as far as it'll go. There is no brush spring (and, no, one didn't escape when I dismantled it). Should this motor have had springs? 

 

What's the best way to fix: pencil lead to provide a miniscule bit of extra length and hope-for-best fixing screw adjustment, or a light spring (which I haven't got!) pushing on a cut-down brush?

 

Edited April 23, 2021 by Fordyce

[DCB]

Pictures would be useful.   I can't believe it didn't have brush springs,  they were probably the powder which fell out of the brush holders when you disasssembled it.   Brush springs disintegrating is a common issue with tired or undersize motors.   Anchoridge are my nemisis.  I am trying to sort the springs on one  of those myself.  You may be able to find some springs on line depending on size but bigger ones are easier to find than smaller ones. .  I make new brushes from old car alternator brushes, jammed in a 3 jaw black ad decker chuck I make them round using a file and carefully work down to around 1mm dia. then trim to length.  Success rate is about 33%    I never had any luck with pencil lead as brushes.   If you can't obtain internal coil springs then drilling the end caps and poking stiff wire through to bear on the brush and using an external spring a bit like the Hornby Dubo Ring Field might work.

[hayfield]

I recently lost a spring from one of my Mashima's, I cut down a spare spring from a buffer set I had

[Fordyce]

Thanks for the responses. Further investigation showed there was a spring in the bottom brush holder. But further testing has showed that even when there is an electical path through the motor, it's not turning. I don't know why not. Total motor replacement might be the only option.

[Gordon A]

A build up of muck on the commutator?

I have recently taken a Bachman can motor apart because it stopped running which involved removing the plastic end.

This brought to light that the commutator was black. Gentle cleaning with IPA followed by a final polish with a soft fibreglass brush resulted in a smooth running motor when reassembled.

 

Gordon A

[Fordyce]

Problem found (I hope) was a disintegrated brush: on second dismantling (to try the IPA suggestion), the bottom carbon brush was all but disintegrated to dust. How it had held together- even with (gentle) handling - on first dismantling to make it look as though it was whole, defeats me. Testing with a simple brass rod in place of the dusty brush showed the motor does still work, even with the springless brush (which will be 'sprung' with two very old Kean Maygib loco buffer springs - the smallest springs I've ever seen. Thanks for the suggestions - we've got there!