3-speed starter motor

[Tony Press]

After studying the differences between a 3 speed and 4 speed brush end covers the brush end cover was turned through 90 degrees and it now runs the correct way.

Not sure what this means - I would have thought some connections would have to be reversed not just a 90 degree turn - but I am not good with electrics. 

I assume the left endplate indicates anticlockwise rotation and the right clockwise - the brushes could possibly be inverted and refitted on the opposite pins to change the rotation settings.

I will go now 

[Dave Mann]

Basically by rotating the brushes another portion of the armature is energized and the resultant armature magnetic field reacts with the fixed field magnetic field causing it to turn in the desired direction. With this motor I knew it had the correct bendix because it didn't engage the flywheel when it went the wrong way so all I had to do was reverse the direction of rotation. If you dismantle (never disassemble) a 3 speed and 4 speed starter you will also find the armatures are wound differently but in our case someone inadvertently fitted 4 brush end plate to a 3 speed motor or as an act of devilment to give another owner a problem.

[Dave Mann]

Here's a photo of the modification     

[Dave Mann]

Somebody else has come across the problem of the late 3 speed starter motor rotating the wrong way. After various phone calls it appears that the 3 speed CAV and Lucas starter motors have their field coils wound the opposite way and consequently you must not swap the brush end shields over or the motors will rotate the wrong way. Trust Joe Lucas to complicate things.

[john williams]

As an apprentice, I was told you never undercut the starter armature as the stater brushes are harder than the commutator insulators, therefore undercutting is unnecessary, whereas carbon dynamo brushes are softer than the comm' insulators, so undercutting is required.

[Tony Press]

I knew you weren't supposed to undercut starter motor segments and was just advised by a Club member with electrical knowledge that if you undercut a starter commutator, segment edges will cut bits from of the copper brushes that will later cause shorting between segments. 

Sounds reasonable 

[Dave Mann]

I knew that starter commutators should not be undercut but never why until I was given a starter to repair which had a seriously undercut commutator which a light skim didn't remove. On test the commutator and brush gear was like a Catherine wheel just a mass of arcing. I had no choice but to skim the commutator to remove all traces of undercutting which stopped the Catherine wheel effect. I now know why you don't undercut a starter commutator.
Does anybody have a photo of a CAV starter brush end shield?