Rewiring a Model T starter to run safely on 12 volts

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Model T Ford Forum: Forum 2013: Rewiring a Model T starter to run safely on 12 volts
Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach & Big Bear on Wednesday, July 10, 2013 - 01:41 pm:

I understand the a Model T Starter has two sets of coil windings hooked up in parallel and that it works perfectly on six volts. I also understand that the wires can be changed so that the two coils are hooked up in series so that they can run safely on a more easily obtained 12 volt battery. I am interested in rewiring a Model T starter for 12 volts but don't want to hook it up wrong so that it runs backwards or even worse, catches on fire due to a short through my incorrect modifications.

It appears to be a simple action but I would like a quick sketch to follow so That I can hook the two coils in series. A photograph with step by step instructions would also be very helpful. I believe that a lot of Model T folks would enjoy these instruction too. I would like to know which wires to switch and how much insulation to use.

I have seen all sorts of modifications which add resistance to the circuit, but understand that the full battery power is there for the initial jolt and that the resistance has to slowly build as the starter begins to do its job. Some folks run a long battery cable while other's add resistance items such as Bendix Springs into the circuit.

Any suggestions would be welcome. I need to use some 12 volt equipment in out Model T and I don't need a lecture about properly using a six volt system with good connections, thank you, Frank


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth from NC on Wednesday, July 10, 2013 - 02:00 pm:

LOL Frank if you rule out all of the people who want to tell you how to better tackle your problem (or redefine your problem and then answer that!) without actually answering your question, you won't get many responses!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, July 10, 2013 - 02:25 pm:

I converted mine years ago. It was straightforward, but it's mounted in the car, so can't take pix, sorry.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Bright on Wednesday, July 10, 2013 - 02:29 pm:

I have NOT tried this out. I just saved it in my email account when we talked about it last. http://www.mtfca.com/discus/messages/257047/293280.html?1338519126 Again... does it work? I have no idea.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Wednesday, July 10, 2013 - 03:05 pm:

The link posted by Nathan is correct. The field coils are changed from a parallel wave to a series wave. It's mandatory that the coils be wired as shown. It won't work otherwise.

Below is a simplified drawing of the circuit. Normally, I wouldn't provide this since I charge for the conversion. It's also mandatory that the cross-over wire be a minimum of 8ga and insulated. You can use cable or flat wire. (1/4" flattened copper tubing works well.)

Original Circuit



Modified Circuit


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Robison on Wednesday, July 10, 2013 - 03:12 pm:

http://www.spokanemodeltclub.com/12-volt-starter.php

Another way


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Wednesday, July 10, 2013 - 03:13 pm:

Here's a message with a schematic showing the change Frank, but there are no accompanying instructions. Also in the message is LD Beckers contact info to buy a 12 volt Model T starter.

http://www.mtfca.com/discus/messages/257047/293280.html

Another option previously mentioned on the Forum is adding a second 6 volt battery in series with an existing 6 volt battery and run the starter from the bottom half - two 6 volt Optimas may do it.

Regards,
Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Wednesday, July 10, 2013 - 03:16 pm:

Forgot to mention:
The conversion is simple but not necessarily easy. You must insure the connections are soldered well and you're working with some heavy wire. No to mention reforming the original coil connection loops. Be sure to anneal them before re-forming. I might also mention that the post connection to the first coil should be doubled to maintain the strength of the connection and prevent the post from turning.

Good luck!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Bright on Wednesday, July 10, 2013 - 03:17 pm:

just for the record, i tour with several 12v cars with 6v starters. they have logged thousands of miles and have never had a problem. I plan to run mine unmodified. When your T is running properly, it only takes a second to crank it up on 12v with a 6v starter.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Wednesday, July 10, 2013 - 03:29 pm:

Miles don't mean anything. It's the number of starts. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Woods, Katy, Texas on Wednesday, July 10, 2013 - 04:48 pm:

check with Ron Patterson. He has done this and posted about it several years ago.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach & Big Bear on Wednesday, July 10, 2013 - 05:55 pm:

Back in the day . . . I love that saying, back in the day the cars such as Cadillac and Packard had hot start issues and so a six - twelve volt battery was constructed to solve the problem. They used a 12 volt battery that had external straps. The strap in the center was cut and bent up at a 90 degree angle. Holes were drilled and tapped and a switch was installed so that it could be used as a 12 volt battery or two six volt batteries. The car was started on the twelve volt battery and as so as the engine started a switch attached to the battery changed it over to two (2) six volt batteries wired in parallel so that all accessories would work correctly. When sealed batteries with internal connections came about, they stopped making the battery conversion.

It should be noted that Charles F Kettering used such a system on the first self starter car, the 1912 Cadillac.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, July 10, 2013 - 06:05 pm:

You could just get a real 12 volt starter from L. D. Becker for $ 145 plus shipping.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, July 10, 2013 - 06:11 pm:

Ken is right on the mark, this conversion is a tedious job.
Clearances inside the assembled starter brush end cap are very tight and finding the real estate needed to make the inter-connections with insulated #7 wire is tricky. I have done this conversion in a slightly different (though not necessarily better than Ken's method) manner while maintaining the full series winding. I used a short piece of insulated field buss bar to make a shorter connection and you will need an one additional field winding from another field to do it this way and it is still tight spacing.
Here is a photo of the pattern modified field (right ) next to an original unmodified field (left) I use (certainly not the quality of workmanship when installed!)
1
You get the idea if the new wiring.
I swore off doing this modification a long time ago as it is just too time consuming.
Have fun.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach & Big Bear on Wednesday, July 10, 2013 - 06:50 pm:

I have been running our Speedster on 12 volts for 16 years and finally had an issue. The Bendix spring did not break, it was simply the rear screw that bent and for some reason the head was half way ground off and polished to a fine luster. It appears that the tab washer failed, the screw backed out, and the head made contact until it finally back out and quit. The pointed end of the screw was bent like a cork screw.


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike_black on Wednesday, July 10, 2013 - 06:56 pm:

I put a 12V battery and bulbs in my TT when I first completed the running gear in 1978. I've never got around to changing it back! I've only broken one bendix spring, but, several years ago it slung the winding out of the generator armature. I removed the generator gear and put it back on. I keep the battery charged and don't drive it at night. MORAL IS: put in the 12V battery, change the bulbs, but, do the gen wiring correctly, or put an alternator, and leave the starter alone.


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