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THE GASOLINE MOTOR

by

HAROLD WHITING SLAUSON, M. E.

Author of "The Motor Boat"







Outing Handbooks

New York
Outing Publishing Company
MCMXIII

Copyright, 1913, by
Outing Publishing Company

All rights reserved




CONTENTS


     I. TYPES OF MOTORS              9

    II. VALVES                      24

   III. BEARINGS                    43

    IV. THE IGNITION SYSTEM         62

     V. MAGNETOS                    83

    VI. CARBURETORS AND THEIR FUEL  90

   VII. LUBRICATION                112

  VIII. COOLING                    130

    IX. TWO CYCLE MOTORS           148




THE GASOLINE MOTOR




THE GASOLINE MOTOR

CHAPTER I

TYPES OF MOTORS


There are certain events that must happen in a gasoline motor before
the engine will run of its own accord. For instance, to obtain
successive power impulses, the charge must first be admitted to the
cylinder and compressed; it must then be ignited to form the explosion
that creates the force at the flywheel; and the burned gases resulting
from this explosion must be ejected in order to clear the cylinder
for the new charge. To accomplish this series of events, some motors
require four strokes, while others do the business in two. These are
popularly called four-cycle and two-cycle motors, respectively.

A cycle, of course, can be any round of events, such as a cycle of
years--at the end of which time the previous happenings are scheduled
to repeat themselves. But in gas engine parlance a cycle is taken to
mean the round of events from, say, the explosion of one charge to the
ignition of the next. Thus, it will be seen that the four-cycle motor
requires four strokes of the piston to accomplish its round of events,
and is, properly, a four-_stroke_ cycle motor. Likewise, the so-called
two-cycle motor requires two strokes to complete its cycle and should
therefore be termed a two-_stroke_ cycle motor.

If this longer terminology could be adhered to, there would be less
misunderstanding of the meanings of two- and four-cycle, for when taken
literally, these abbreviated forms signify absolutely nothing. Usage
seems to have made them acceptable, however, and if the reader will but
remember that four-cycle, for instance, means four _strokes per cycle_,
the term becomes almost as simple as does "four-cylinder."

It is evident that there are two strokes for each revolution of the
flywheel--one when the crank is forced down and the other when the
crank moves up. As the piston is attached to the crank through the
medium of the connecting rod, the strokes are measured by the motion
of the piston. Thus, since it requires four strokes of the piston to
complete the round of events in the four-cycle motor, the explosions
occur only at every second revolution of the flywheel. In this
connection it must be remembered that we are dealing with but one
cylinder at a time, for a four-cycle engine is practically a collection
of four single-cylinder units.

But even though the explosion in a four-cycle motor occurs only every
other revolution, the engine is by no means idle during the interval
between these power impulses, for each stroke has its own work to do.
The explosion exerts a force similar to a "hammer blow" of several tons
on the piston, and the latter is pushed down, thus forming the first
stroke of the cycle. The momentum of the flywheel carries the piston
back again to the top of its travel, and during this second stroke all
of the burned, or exhaust, gases are forced out and the cylinder is
cleaned, or "scavenged." The piston is then carried down on its third
stroke, which tends to create a partial vacuum and sucks in the charge
for the next explosion.

On the fourth, and final, stroke of the cycle the piston, still
actuated by the momentum of the flywheel, is pushed up against the
recently-admitted charge and compresses this to a point five or six
times greater than that of the atmosphere. At the extreme top of this
last stroke, the spark is formed, causing the next explosion, and the
events of this cycle are repeated.

Now, inasmuch as on one up-stroke of the piston the charge must be held
tightly in place in order that it may be compressed, and on the next
up-stroke a free passage must be offered so that the exhaust gases may
be forced out, it is evident that a valve must be used as a sent