Starter motor brushes

[Roland Alcock]

My 1927 Chummy has records showing a few refurbs of its bacon slicer starter motor. It can’t have done that many miles to have the overhaul repeated. 

When I took ownership of the car, the starter would turn, but as if the battery was no longer serviceable. A fresh battery was no improvement. The switch contacts were clean and not burnt. The commutator was thick with carbon. Carburettor cleaner sprayed and the commutator cleaned and the brushes exercised. The starter now works with enthusiasm. 

Is it possible that there the starter motor brushes are too soft a material?

If so, who supplies appropriate brushes?

I have heard of others who have experienced similar issues. 

Roly

[Ian McGowan]

Roly,
A7 Components, David Cochrane, supplies the brushes. In fact, he supplies two different sets of brushes to suit either the CAV Bacon slicer starter 1923-26 part No. BG53b or, the Lucas model 1926 -29 bacon slicer part No. BG953b. Currently, both types appear to be in stock with him.
http://www.a7c.co.uk/spares.php#electrical

David's training being in electrical/electronic engineering I would expect any brushes supplied by him to be appropriate for the application.

[Bob Culver]

Presumably not carbon dust. Have owners attempted to lubricate and overdone? With the enamelled wire I woud be wary of poweful cleaners unless restricted to just the comm.

[john williams]

When you sat the commutator was "thick with carbon" , have carbon dynamo brushes been been used instead of copper starter brushes?

[Ian McGowan]

At some point in the car's past, when correct replacement brushes possibly weren't available, a previous owner probably fashioned brushes from what he deemed to be acceptable, available material, albeit incorrect for the application. It happened all the time with all sorts of things in the '50s. The 6 years of WW2 had left a strongly ingrained culture of "make-do and mend".

[Roland Alcock]

I have been told today that starter motor brushes needed a much higher copper content, to,take into account the high current passed. So maybe I have a set of modified dynamo brushes installed.

A new set of correct brushes are clearly needed.

Thank you for your responses.

Roly

[Nick Turley]

Roly,
A7 Components, David Cochrane, supplies the brushes. In fact, he supplies two different sets of brushes to suit either the CAV Bacon slicer starter 1923-26 part No. BG53b or, the Lucas model 1926 -29 bacon slicer part No. BG953b. Currently, both types appear to be in stock with him.
http://www.a7c.co.uk/spares.php#electrical

David's training being in electrical/electronic engineering I would expect any brushes supplied by him to be appropriate for the application.

I can confirm that I have used these brushes from David in several starter motors without problem.