wire gages and rewinding motors

[Bill Goddard]

I have been researching wire diameters for rewinding 6v to 12v. There have been many posts on this and they all seem to be saying we should use twice the turns and half the wire DIAMETER. A write up in Wikipedia says we should be using half the CIRCULAR AREA of the wire if we want to half the current capacity. Does anyone have an opinion on this?

[Bruce of MN]

I vote for area!

[CWPASADENA]

I think you want to wind up with twice the resistance so that would be twice as many turns of the original dia. wire or the same number of turns of wire half the aera

My thoughts on the subject

Chris W

[Simonpie]

The number of windings gives the "oomf" to the motor. The area controls the resistance of the whole length of wire. The challenge is, can all the windings needed fit in the space available? The geometry isn't quite as simple as "what diameter gives me the same area" because of how the wires can nest into each other. Also, some people successfully run a 6V starter or coil on 12V (for a while) so there's got to be a bit of wiggle room to overdrive the thing a bit, either on diameter or windings. Another, smaller, factor is that if the wire gets thicker, each winding layer is farther away from the iron core. This distance reduces effect, like magnets losing force when further apart.
A lot of it depends on whether you're smart enough to stop cranking after 10 seconds and turn your gas on, or of you just crank away for a full minute.

This is all just theory for me. I'm no motor winder. If you get advice backed by experience, take it.

[holdover]

http://www.mafca.com/tqa_electrical.html

look here and scroll down to horn, worked for me..

[Mike V. Florida]

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Information for the field coils of the horn:

6 Volt

(1) The 2 field coils are wound in opposite directions.
(2) Original field coil wire is 20 gauge.
(3) a. 45 turns using coated wire.
b. 6 to 7 turns per layer, not perfect is OK
(4) After completing, spray with varnish or epoxy insulating enamel.

12 Volt

(1) Same as above.
(2) Use 24 gauge coated wire.
(3) a. 100 turns
b. 6-7 turns per layer, not perfect is OK
(4) Same as above.

[Bill Goddard]

I have done some more research and it turns out wire diameters 3 ga nos apart are 2:1 areas. That is , 20 ga wire at .518mm2 is 2x the dia of 23 ga wire at .258mm2, but the dias in inches are not 2:1, so I used the area approach to rewind my windshield wiper. The result was a wiper with somewhat higher speed than I expected but compared the the highest speed setting on my modern car not so bad. I didn't rewind the armature because it looks like a formidable job.
This brings me to a debate here at home. I'm told I should not be running 12v through a 6v armature. I don't think I should either but it works. Does anyone have and opinion on this? Thanks Bill G

[Tom Wesenberg]

I would have used a resistor in the power wire, and left the motor original.

Since the armature isn't rewound, then I'd go with what Mike just posted.

[MAG]

Post #6 is correct. Done a few that way with good success.

[Kahuna]

I have done this twice:
Once on a Ahooga horn & another was done for me by the late & Great George Pounden on a coil (6-12 volt for an early V8) before they were reproduced many years ago. The coil still resides in my hi-performance 290 cube flathead powered 32 and runs great.
I used the twice the winding using half the wire size & both worked out just fine.
Jim

[Tom Endy]

A friend and I just finished rewinding the two field windings of two 6-volt ahooguh horns to make them 12-volt. We stripped off what appears to be 20 gauge wire that was a nominal 10' long on each field. We replaced it with 20' of 24 gauge wire on each field and they both ahooguhed just fine on 12-volts.

I think the length of the wire is the controlling factor not the gauge. The gauge is reduced so that it can be physically wound in place in a restricted area.

Tom Endy

[grj]

Saw some "A" horns in Hershey years ago labeled 12v. Asked why 12v? Said they did not sound good on 6v.

[Mike V. Florida]

Originally Posted by Tom Endy

I think the length of the wire is the controlling factor not the gauge. The gauge is reduced so that it can be physically wound in place in a restricted area.

Tom Endy

Without getting into theory Wire size does make a difference. There is a trade-off of gauge and room to wind the wire that goes into motor design.