Scientific American Supplement, No. 484, April 11, 1885 | Page 7

more quickly the explosive force is utilized,
the less will be the loss, and the greater the power produced from a
quantity of burning gas--it is evident that if any method can be
discovered to increase the pressure upon the piston without increasing
the temperature of the flame causing this pressure, then a great gain
will result, and the engine will convert more of the heat given to it into
work. This is exactly what is done by compression before ignition.
Suppose we take a mixture of gas and air of such proportions as to
cause when exploded, or rather ignited (because explosion is too strong
a term), a pressure of 45 lb. above atmosphere, or 60 lb. per square inch
absolute pressure. Then this mixture, if compressed to half volume
before igniting and kept at constant temperature, would give, when
ignited, a pressure of 120 lb. total, or 105 lb. above atmosphere, and
this without any increase of the temperature of the flame.
The effect of compression is to make a small piston do the work of a
large one, and convert more heat into work by lessening the loss of heat
through the walls of the cylinder. In addition to this advantage, greater
expansions are made possible, and therefore greatly increase economy.
The Otto engine must be so familiar in appearance to all of you, that I
need hardly trouble you with details of its external appearance. I shall
briefly describe its action. Its strong points and its weak points are alike
caused by its cycle. One cylinder and piston suffices to carry out its

whole action. Its cycle is: First outstroke, gas and air sucked into the
cylinder; first instroke, gas and air compressed into space; second
outstroke, impulse due to ignition; second instroke, discharge of
exhausted gases. When working at full power, it gets one impulse for
every two revolutions; this seems to be a retrograde movement, but,
notwithstanding, the advantages obtained are very great. The igniting
arrangement is in the main similar to that used on the rack and clutch
engine. The engine has been exceedingly successful, and is very
economical. The Otto compression engine consumes 21 cubic feet of
gas per I.H.P. per hour, and runs with great smoothness.
In 1876 I commenced my work upon gas engines, and very soon
concluded that the compression system was the true line to proceed
upon. It took me two years to produce a workable engine. My efforts
have always been directed toward producing an engine giving at least
one impulse every revolution and, if possible, to start without hand
labor, just as a steam engine does. My first gas engine was running in
1878, and patented and exhibited in 1879. It was first exhibited at the
Kilburn Royal Agricultural Society's show.
This engine was self-starting, gave an ignition at every revolution, and
ignited without external flame. It consisted of two cylinders, a motor,
and a compressing pump, with a small intermediate reservoir. Suitable
valves introduced the mixture of gas and air into the pump, and passed
it when compressed from the reservoir to the motor cylinder. The
igniting arrangement consisted of a platinum cage firmly fixed in a
valve port; this cage was heated in the first instance by a flame of gas
and air mixed; it became white hot in a few seconds, and then the
engine was started by opening a valve.
The platinum was kept hot by the heat derived from the successive
ignitions, and, the engine once started, no further external flame was
required. I have here one of these platinum cages which has been in use.
Finding this method not well suited for small engines, I produced the
engine which is at present in the market under my name.
The cycle is different, and is designed for greater simplicity and the
avoidance of back ignitions. It also consists of two cylinders, motor
cylinder and the displace or charging cylinder. There is no intermediate
reservoir. The displace crank leads the motor by a right angle, and takes
into it the mixed charge of gas and air, in some cases taking air alone

during the latter part of its stroke.
The motor on the outstroke crosses V-shaped parts about from
one-sixth to one-seventh from the out end, the displacer charge now
passing into the motor cylinder, displacing the exhaust gases by these
ports and filling the cylinder and the space at the end of it with the
explosive mixture. The introduction of some air in advance of the
charge serves the double purpose of cooling down the exhaust gases
and preventing direct contact of the inflammable mixture with flame
which may linger in the cylinder from the previous stroke. The instroke
of the motor compresses the charge into the conical space at the end of