Gas Engine Ignition

By Staff
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Courtesy of Ted Worrall, Loma, Montana
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Courtesy of Denis McCormack, 404 West Timonium Rd, Timonium, Bait. Co., Md.
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Courtesy of Gary D. Smith, 708 Lexington Ave., Zanesville, Ohio 43701
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Courtesy of Gary D. Smith, 708 Lexington Ave., Zanesville, Ohio 43701
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Courtesy of Donald Mc Vittie, Box 508, Alliston. Ontario, Canada
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Courtesy of Gary D. Smith, 708 Lexington Ave., Zanesville, Ohio 43701

Atkins, Iowa 52206

With the invention of the gas engine as such, came many
problems, one of the greatest being that of a dependable ignition

In the earliest gas engines, an electric spark was used to fire
the charge. Electricity then being comparatively little understood,
the troubles experienced with this mode of ignition led to its
being abandoned in favor of first the slide-valve method of
ignition, and later of the hot-tube method.

The slide-valve method consisted of a small reciprocating slide
valve which had a pocket that was put in communication alternately
with the fresh mixture and the cylinder. When this pocket was
filled with the fresh mixture, a further movement of the valve
brought it into contact with a small external flame which ignited
it. As the slide-valve continued its travel it was brought into
communication with the cylinder when the gas still burning in the
pocket ignited the compressed charge. Engines of this type were
known to be in existence as late as 1907 and possibly some may
still exist.

1917 model of a 12-25 Avery tractor and Avery 4 bottom plow
owned by Ted. Ted. is the Montana Director of Western Steam Fiends

The many obvious problems encountered with the slide-valve type
of ignition led to the development of the hot-tube method of
ignition. An iron, nickel or platinum tube having its outer end
closed was screwed into the combustion chamber, usually in the
cylinder head. The open end of this tube was inside the cylinder. A
gas burner kept this tube at a red heat. During the exhaust and
suction strokes the tube was filled with burned gases, but toward
the end of the compression stroke they were forced into the back of
the tube and the fresh mixture following was ignited upon striking
the incandescent portion of the tube.

Some hot-tube igniters made use of a ‘timing-valve’,
which opened a passageway between the cylinder and the incandescent
tube at the proper instant.

With hot-tube ignition, timing was a matter of trial and error.
It proved most satisfactory where the engine was under a constant
load, and in fact, this type of ignition held its own for many
years, even after electric ignition had made its re-entry into gas
engine ignition.

Hot-tube ignition principles were also applied to
‘oil-engines’. A tube or plug was heated red hot before
starting the engine, after which the heat of the explosions was
sufficient to keep the tube incandescent. Engines of this type were
built for many years.

In general, hot-tube ignition was destined to failure in favor
of electric ignite-century took the findings of their predecessors,
developed and refined them, and most important reduced their ideas
into practical inventions which paved the way for efficient, cheap
and reliable electric ignition.

Ironically, one of the main reasons for the demise of the
hot-tube system of ignition was not its lack of dependability, but
rather its cost of operation. Most hot-tube burners consumed from 4
to 5 cubic feet of gas per hour, and with a small engine this made
the operating cost high. Hot-tube ignition with a timing-valve had
some to be fairly reliable, although many inherent problems existed
which affected operation such as the air-gas ratio, cylinder
temperature, tube temperature and length and other

All this led to the development of electric ignition, and as
well all know, that’s when the headaches really started. More
on that issue later.

A pair of beautifully restored and running Evenrude engines-all
the way from Detroit for exhibition at the Florida Show in
February. The water cooling was nicely arranged as can be seen.

A Mc. D. model LA 3-5 Hp. S/NLAB6151, painted gray with red
flywheel. The trucks belong to an older model McD. engine.

Bruce Nicolson and Gary Smith, two city boys, learn what Iron
Men mean by a day’s work at H. Kenneth McDonald’s farm in
Dresden, Ohio. Picture taken in August of 1966. That’s the
32-54 New Huber Separator, manufactured in the late 1930’s.

H. Kenneth McDonald’s 40-62 Super Four. This is used every
year in driving his separator.

H. Kenneth McDonald’s John Deere 10-foot PTO binder, hitched
behind a 1939 Model L.C. Huber tractor. Both are used

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Gas Engine Magazine
Preserving the History of Internal Combustion Engines