# Modifying non reversible DC motor



## major (Apr 4, 2008)

Do you even know if it is series or compound wound? Let's assume it is series wound (good chance it is). The 4 field coils are most likely wound with copper ribbon, say about 7 or 8 turns/coil each of .400 x .090 inch cross section. These 4 coils are connected in a series or parallel circuit having the copper ribbon brazed or welded. One end of that circuit goes to the electrical terminal input. The other end of the field circuit goes to the brush holders, 2 at 180° from each other. The other 2 brush holders are connected to the other input terminal.

You need to break the connection from the field coil circuit to the brush holders. Then bring out the field connection for the other _S_ terminal so you have 2 field terminals, S1 & S2. Then you need to make an external connection to the 2 brush holders which were just disconnected. Then you have 2 _A_ terminals, A1 & A2.

Then determine if there was a factory brush advance and reset it if necessary by rotation of the brush gear.

Simple as that


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## Randeb56 (Apr 6, 2015)

Thank you Major. Makes perfect sense to me. Got the motor apart and cut a couple of leads off. Drilled for the studs. Need a bit of wire, studs and some insulators but it looks good.


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## Randeb56 (Apr 6, 2015)

A great big public thank you to Major for providing me with excellent info on how to convert my 2 pole series motor into a 4 pole. I have reverse now!! Have the tranny coupler welded up now, bell housing finished and painted. Cleaned n painted the drive frame and the tranny while I was at it. Put it all together and it looks and works nice.


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## jwiger (Oct 18, 2014)

One shot, one kill. Major is a tech support sniper.


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## jameswang (May 1, 2015)

I would say not. It could ruin your car.


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## Randeb56 (Apr 6, 2015)

Got it done and it's working perfectly. A tad scary cutting those large wires inside the motor, especially since I have no experience with this sort of thing, but Major's explanation sounded good to me.


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