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We're doing something a bit different this month, namely, introducing readers to the Sparks & Arcs bulletin board.

The Sparks & Arcs conversational board can be found on the internet at, and it's one of several bulletin boards on EnginAds, where you'll also find the SmokStak bulletin board.

Unlike SmokStak, which deals mostly with general engine questions and issues, the Sparks & Arcs board is specifically for antique gasoline generator and home light plant collectors, a place for these collectors to discuss and share their restoration and collecting experiences. So without further ado, we present this discussion from the Sparks & Arcs bulletin board.

Do any of you guys have a schematic, or maybe a manual, for a Universal Model D 3KW generator, circa 1918? Also, who can do a good job of re-varnishing and baking the windings? This unit appears to be in good condition, but the wrapping is dried out and cracked and I don't want to risk damaging anything when I run the engine. It hasn't been run since the 1920s. I'm assuming the original wire was covered with either cotton wrap or varnish, shellac, etc., and that the insulation is still intact. The coils are covered with what appears to be cloth tape and I haven't removed any of the covering. Should the complete coil assembly be soaked and baked as is, or is it best to rewind the coils with newer wire? - Harvey

Spray varnish may not be the way you want to go with this project. Originally, the machine was soaked in a tank of varnish for several hours, drip dried and then baked for final drying. Motor rewind shops still do it that way. The varnish needs to penetrate the open spaces to be most effective and to adhere all the winding parts together. Spray varnish is intended for touchup purposes only. - Franz

Why varnish instead of shellac? - Harry

Harvey, since you say it appears to be in decent condition, physically, the simplest and best thing to do as a first step would be to meg it. That simple test should tell you if you have to rewind, or just varnish. My feeling is that I'd do everything possible to save the original windings before I'd consider rewinding. A machine originally wound with cotton covered wire would definitely have different characteristics when rewound with varnished wire.

Harry, I don't know why varnish instead of shellac, but I sure soaked enough of them in the tank back when I was a 17-year-old apprentice. If memory serves, there is good information on the subject in Audel's Technical Manuals, volume 9 or 10 in the set I have. There is epoxy technology using a single component epoxy that I'm told doesn't require the baking step, but I don't have a source for that product immediately available. Motor rewinding is becoming a lost art in my part of the country. - Franz

Harry, varnish is preferred because it is unaffected by most solvents and water after it dries. Shellac, on the other hand, is attacked by alcohol, water, gasoline, etc. It also softens at temperatures well below what modern magnet wire will tolerate. This softening allows motion in the windings when the motor heats and cools and can cause winding failure. - Sherm

Well, guys and gals, I have a 1,500-watt, air-cooled Delco-Light generator I bought in 1991. It had the field housing removed and the wires 'jerked' from the engine. The engine, with the armature still attached, had been sitting with the armature half buried in sand or dirt for I don't know how long. I brought it home in the fall and checked it out with an ohm meter, which showed it was shorted to the shaft. I set it in my shop, which was heated all winter, and the next spring I checked it with the ohm meter again, and by golly it showed open to the shaft.

My son said, 'that thing will never work.' The strips of fiber that were between the armature segments were completely gone on the half that had been buried. I took all of the remaining pieces out and wire brushed the rust from the armature core, then sprayed all the windings with electric motor and brake cleaner. I took an air hose and blew all the dirt and crud off of it. I had some Formica V32 lying around and I took it and made new pieces to slide in between the armature segments and put some NOS Super Glue on each one so they wouldn't slip out. I used a clear lacquer spray and sprayed all the windings with that, including the segmented core and Formica.

The field coil insulation was nearly all gone. I took them out of the housing and took all the old wrap off and replaced it with friction tape (still available in most electric departments). My HWI man says that gardeners still use it to wrap their hoe and shovel handles with. I just sprayed the field coils with the electric motor and brake cleaner after I had the old tape off and blew them dry with the air hose.

I have been taking this generator to shows and running it since 1992 and it is still working. I guess what I did isn't recommended by the experts, but it worked for me. However, I wouldn't recommend doing what I did if you were going to depend on it to supply your house with power. -Don

Don, Formica is very close to the 'fish paper' coil shims that are used to hold winding segments in place when motors and generators are wound or rewound. The way the old timers taught me, the shims were actually driven into place with a rawhide mallet, so the coil didn't move before the unit was dipped in the varnish tank. That was in the day of varnished wire, and I think I'd want to use a little less shimming if I were dealing with cotton wound magnet wire. The tape used is called varnished cambric, and it is still made and used in both motor work and electronics. There is also a sticky-faced paper tape that is used to hold individual coils before they are taken off the winding machine. -Franz

Your use of Formica as insulator strips reminds me of a friend's tour of a Formica manufacturing plant where he was told the name 'Formica' derived from one of the substance's original design uses: a replacement material for mica used as an insulator. - John

Gus Simm's circa 1915 Universal Manufacturing Co. generator engine. It is identical to the Model B Badger made by Badger Manufacturing Co., Oshkosh, Wis., which Universal bought out. It's thought to be an early production 'D' series.

Harvey, any competent motor shop can do the job, all you have to do is drop enough Jeffersons or Hamiltons - or maybe Grants - on the counter. Question is, does it need it? I'm in agreement with Don: if it ain't broke, don't fix it. Almost all of my 70-plus plants work. For the most part, the problems they have are quite easy to fix. I recently got an estimate to rewind my big Lister, '$800 or so' the guy told me. 'Correct the grounded winding, put it back together and see if it works, at the worst it will still need to be rewound.' I took his advice and have it all back together. It motors well, and I am going to start it as soon as I get my hands on a couple of replacement springs for the engine coupling. I have a Model D, s/n 1491 (see photo). It runs very well, I might add. - Gus

Good looking generator, Gus. Hey, maybe mine isn't a Model D after all. Mine has the same engine and dynamo, but the radiator is mounted above the starting crank end of the engine and the control panel is mounted above the dynamo. The radiator has a triangular-shaped top tank with a Model T radiator cap. The original guts for the control panel are missing, and I'm trying to figure out how to reconstruct a new panel.

Truth is, I bought this plant to drive a mechanical line shaft in my shop since there is a lovely little flat pulley outboard of the dynamo. But the whole thing is in such good shape that I just didn't have the heart to run it that way. The commutator is in mint condition, and there are no shorts in any of the windings. I really want to hear the engine run, but I don't want to lose the dynamo in my moment of passion. By the way, I manufacture a line of Teflon/fiberglass sheets and tapes that have exceptional dielectric properties -1,000 volts/mil or better - that were originally designed to replace the old varnished paper and cloth tape. It might be heresy to redo a vintage machine with this stuff, but GE Electromotive buys a lot of it. If any of you guys want to play with some of this stuff, let me know. - Harvey

This discussion can be found by visiting Sparks & Arcs on the Internet at, where the engine conversation bulletin boards have over 28,000 messages on file.

Spark & Arcs and SmokStak are part of the Old Engine series of Web sites that started in 1995 as Harry's Old Engine. Harry Matthews is a retired electronic engineer and gas engine collector from Oswego, N.Y., now residing in Sarasota, Fla.