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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,

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