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Anybody know how or what is involved to get a electric starter motor to run in its opposite direction ?

R.E.A.R.

It's been a while since my electrical engineering classes but...
It depends on the type of motor. Early (old) motors use commutators and brushes to energize the rotor
(think of it as a crankshaft) to get it to spin one way or the other.
If that is what you have, you could simply reverse the wires going to the motor leads.
I suspect Mr. Kneisel is more knowledgeable in the this topic and he may have more to share.

My starter for my Macs uses a Ford flat head starter motor. I think I read somewhere that if you clock the brush holder differently, that'll reverse the rotation. I'm looking for documentation for that...

I can't imagine it applies to starter motors, but I accidentally learned how to reverse a GM power window motor recently. I took the motor apart to clean the commutator and brushes. When I put it back together, I accidentally installed the motor "can" (containing its permanent magnets) 180°, rotation-wise, from its original position. No wiring was changed. The switch then ran the window down instead of up, and up instead of down. Rotated the can to it's correct position, and it ran correctly. I am not completely sure how to explain it, but I'm pretty sure that it's a timing issue, with regard to the orientation of the magnets vis-a-vis the brushes, affecting which direction the armature is pulled when power is applied.

I'm fascinated. I'll share info if I find it, unless, of course, an electrical engineer weighs in with some real science, lol.

Kurt

So... I have found some consensus in various corners of the internet (LOL!) regarding these statements:

1) If the motor uses permanent magnets, you can reverse the rotation by reversing the polarity of the power source.

2) If the motor uses field coils, you need to reverse the polarity to the brushes or the field coils, but not both.

3) On my antique Ford flathead/model-A/tractor starter, rumor has it that you can rotate the brush holder 90° to reverse the rotation.

4) Durability of the brushes & commutator might be compromised if they are not perpendicular to the commutator, and are mounted at an offset, due to the designed direction of rotation.

Of course, there may be other concerns and compromises to be considered. It'll be interesting to hear how others have succeeded or failed in similar endeavors.

Kurt

I remember from my slot car days that reversing the wires which is the same as what Kurt mentioned above, would make a motor run in a reverse rotation but as the armature 'timing' which is the commentators relation to the lamination was advanced for more performance the motor would run better in one direction then the other.

I have a late style starter motor also which has the solenoid built into it as opposed to the old Ford style with a remote solenoid.

R.E.A.R.

I just happened upon some more musings on this topic here:

http://vkakarting.com/phpbb/viewtopic.p ... 603&p=8736

Kurt,

Thanks for the heads up. Went another direction.

Think before you move on this. The Coleman type starters have a one way bearing in them that will only allow the shaft to engage going one direction., reverse the rotation and it spin the starter motor but not the shaft.

R.E.A.R.