One-Wire Generator
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209813
Printed Date: 21 Mar 2026 at 6:13pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: One-Wire Generator
Posted By: Les Kerf
Subject: One-Wire Generator
Date Posted: 21 Jan 2026 at 8:21pm
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No, that is not a typo, this gadget truly is a one-wire generator.  I have several old generators (thanks ORBill) that I am finally getting around to testing. This unit is a third-brush type and has no provisions whatsoever for controlling the field current; a quick google search for the part number 943U shows that it is for a 1931-34 Studebaker. Some further searching led me to a Studebaker forum where I found schematics that clearly show this generator having only one wire leading from the armature to the cutout relay. The amazing thing is that it actually works! I realize that I am probably the last person on earth to learn that this was at one time state of the art technology, but I have always been a bit slow on the uptake   8 Volts at ~8 amps   My high tech generator test bench
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Replies:
Posted By: steve(ill)
Date Posted: 21 Jan 2026 at 9:16pm
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never heard of one wire gen ... ------------- Like them all, but love the "B"s. |
Posted By: Les Kerf
Date Posted: 21 Jan 2026 at 10:01pm
Reckon I ain't never heerd'a sech neither  But thar 'tis, right at the bottom of the diagram. The third brush picks off the field current from the armature, and the circuit is completed inside the generator by being grounded through the thermostat gizmo. Whereas our familiar Allis-Chalmers charging systems give us the choice of manually selecting a high charge of ~10 Amps or a low charge rate of ~3 Amps, this unit simply provides a fixed charging rate of ~8 Amps depending on where the third brush is adjusted. The only other control is the thermostat which I presume to break the field circuit if it gets too hot.  |
steve(ill) wrote:Posted By: Riprock
Date Posted: 21 Jan 2026 at 11:39pm
| Some of the early 9N's used a one wire 3 brush generator. |
Posted By: Riprock
Date Posted: 21 Jan 2026 at 11:48pm
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Posted By: Jim.ME
Date Posted: 22 Jan 2026 at 6:09am
| I believe it does have a method of controlling field current (regulation). That method is the position of the third brush in relation to the main brushes. The third brush mount should be adjustable to allow some movement of the brush location on the commutator which can increase or decrease the charge rate. |
Posted By: SteveM C/IL
Date Posted: 22 Jan 2026 at 11:07am
| Jim is right. 3rd brush position changes output. |
Posted By: Les Kerf
Date Posted: 24 Jan 2026 at 10:19am
Did some more web surfing and found that Ford installed literally millions of one-wire generators in Model T's, etc. My Grandpa would be amused at my ignorance!  |
Posted By: Les Kerf
Date Posted: 28 Jan 2026 at 8:23pm
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When you are working on vintage machinery, it adds to the fun when you have vintage test equipment with which to do the testing. This SUN VAT-60 automotive meter was in my late Father-in-law's shop when it was purchased from the long-time proprietor, Chas. Wallace of Careywood, Idaho. The ammeter was non-functional but the voltmeter still worked fine. I opened it up and and found the ammeter switch was bad which turned out to be an easy fix. A bit of google searching revealed some newer versions of the VAT-60 but they have more modern digital readouts rather than the old analog units on this one. Just for grins I decided to test the SUN meter against my Fluke 88, so I set it up checking the one-wire generator output with the Allis-Chalmers meter, the SUN meter, and the Fluke meter all in series so as to compare the readings simultaneously. The Allis-Chalmers meter was a bit optimistic at ~7 Amps, The SUN meter read ~4.5 Amps, and the Fluke reads right at 4.15 Amps. Not bad for test equipment that hasn't been used for more than 60 years.   .
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Posted By: steve(ill)
Date Posted: 28 Jan 2026 at 8:31pm
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interesting... got any idea of the DATE of the SUN ?
I worked at a Power Plant that was built in 1947 and lots of meters looked similar to that.. ------------- Like them all, but love the "B"s. |
Posted By: Les Kerf
Date Posted: 29 Jan 2026 at 8:51am
Best I can do is make a guess, but probably 1940's. When I was an avionics tech in the Marines back in the 1970's I worked on some old DC3 (the Marines called them C-117's) Com-Nav black boxes, the test equipment for these units dated from the 1940's and also had meters of this same general type. My minimal web searching didn't reveal any meaningful clues about my SUN meter.
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