To understand the operation of a gasoline vehicle it is necessary to
be somewhat familiar with the principle on which gasoline motors act.
Briefly stated, it is as follows: The gasoline is converted into a
vapor, and in this state is mixed with a sufficient amount of air to
cause it to ignite when heated to a proper temperature. This mixture
of air and vapor is admitted into a cylinder in which a piston moves
freely, this part being substantially the same as in a steam engine.
By means of an electric spark or a hot tube, the mixture is ignited,
burning so violently as to expand the products of the combustion with
such rapidity as virtually to become an explosion. The force of this
explosion pushes the piston to the further end of the cylinder, and by
means of a connecting rod and a crank this movement imparts a rotary
motion to a shaft.
[Illustration: FIG. 1. GASOLINE MOTOR.]
The entire operation is made perfectly clear by the aid of Fig. 1,
which is a simple diagram of a single cylinder motor. The chamber _R_
contains the gasoline. Air enters this chamber through tube _b_, as
indicated by the arrow, and passes out between the plate _c_ and the
surface of the gasoline. The float _d_ keeps the plate _c_ in the
proper position regardless of the amount of liquid in the reservoir.
The heated gases exhausted from the cylinder pass through the pipe
_r_, and thus heat the gasoline so that it vaporizes freely and the
air passing under _c_ becomes charged with the necessary proportion of
vapor. The mixed air and vapor enter a valve chamber _S_, from which
the flow into pipe _e_ is regulated by the movement of handle _a_.
In this chamber there is another valve, operated by an independent
handle, and by means of this more air can be admitted into the mixture
when desired. Through the pipe _e_ and the valve _f_ the vapor enters
chamber _Q_, which connects with the top of the cylinder. Suppose the
shaft _G_ is rotating, then the piston will be drawn down from the
position in which it is shown and thus a vacuum will tend to form in
chamber _Q_. This action will cause the valve _f_ to open and the
mixture of air and vapor will flow into _Q_ until the piston reaches
its lowest position and begins to ascend. At this instant the valve _f_
will close, and then the upward movement of the piston will compress
the mixture in the chamber _Q_. When the piston reaches the upper
position, after completing the down and up strokes, the lever _l_ and
the contact point _p_ will come together, and an electric current
developed in the induction coil _M_ will pass through the wires _j_
and _k_ and produce a spark at _i_ between the ends of the metallic
terminals passing through the plug of insulating material, which is
shown in dark shading. This spark will cause the mixed air and vapor
to ignite, producing an explosion that will force the piston down for
the second time. On the second upward movement of the piston the gases
produced by the combustion of the vapor will be forced out through the
valve _h_ into the chamber _T_ and the pipe _r_. The valve _h_ and the
lever _l_ are operated by cams mounted on the shaft _m_, and they are
so set that the spark at _i_ occurs when the chamber _Q_ is full of the
explosive mixture and the piston is at the top of the cylinder. The
valve opens when the piston begins to move upward after the explosion
has forced it to the bottom position.
As will be seen, the piston must move down to draw in a supply of the
explosive mixture; it then moves upward to compress it, and on the
second down stroke it is pushed by the force of the explosion. From
this action it can be clearly realized that the power developed by the
motor comes from the force exerted by explosions at every alternate
revolution of the shaft. On that account the cams that move the valve
_h_ and the lever _l_ are placed on a separate shaft, which is geared
to the main shaft in the ratio of two to one; that is, the wheel _K_ is
twice the diameter of the wheel _J_. As the force of the piston acts
on the shaft only once in every two revolutions it is necessary to
provide a heavy fly wheel _O_, which will store up enough momentum to
continue the rotation of the motor through the ineffective revolution.
Before the motor can put forth an effort it is necessary for the piston
to move downward so as to draw in a supply of explosive gases and then
to move up so as to compress them and produce an explosion; therefore,
the motor will not start of its own accord, but must be set in motion.
In the act of starting the wheel _O_ is turned by hand.
The combustion of the gasoline vapor within the chamber _Q_ and the
upper end of the cylinder develops a large amount of heat, and unless
means are provided for dissipating it the temperature will soon rise
to a point that will interfere with the proper action of the motor.
Two ways are employed to carry off the heat. One is by surrounding the
cylinder with a water jacket, as shown in the diagram at _NN_; and the
other is to provide the exterior of the cylinder with numerous thin
ribs so as to increase the surface exposed to the air and thus increase
the radiation.
[Illustration: FIG. 2. PETROLEUM SPIRIT MOTOR.]
The electric spark is a very effective igniter for the explosive
mixture, and, by properly setting cam _n_ the explosion can be made
to take place just at the position of the piston that may be found
the most desirable; but the points at _i_ are liable to get out of
order, and the battery that actuates the induction coil _M_ and the
coil itself can become a source of more or less trouble, and on that
account the igniting is effected in some motors by means of a hot tube.
When this is used the cam _n_, the lever _l_ and the electrical parts
of the apparatus are not required. In their stead a tube is placed
on the upper side of the chamber _Q_ and this tube is maintained at
a red heat by means of a flame impinging against its outer surface.
When the explosive mixture is compressed it rises in the interior of
the hot tube, and when it reaches the portion that is hot enough to
produce combustion an explosion takes place. By many engineers this
arrangement is regarded as superior to the electric spark on account of
its simplicity.
Gasoline motors are made with one, two or more cylinders, but in each
cylinder the action that takes place is that described above. The
actual construction of a motor is not so simple as might be assumed
from the appearance of Fig. 1; many details are required which are
not here shown. A more perfect idea of the actual construction of a
gasoline motor can be had from Fig. 2, which is a working drawing of a
recent European invention. In this design it will be noticed that the
cylinder is cooled by radiation into the surrounding air, the exterior
surface being increased by numerous circular ribs and also by extending
a hollow trunk from the upper side of the piston, so as not only to
increase the radiating surface, but also to allow the hot air to escape
from the chamber _T_ in which the crank discs revolve. In this drawing
_E_ is the explosion chamber, corresponding to _Q_ in Fig. 1, and the
valve _s_ is the counterpart of _f_, while _s’_ corresponds to the
valve _h_. The upper pipe _t_ is the pipe _e_ of Fig. 1 and the lower
pipe _t’_ is the pipe _r_ of the same figure. Although the crank discs,
connecting rods and other details are different in shape, it will
readily be seen that their relation to each other is the same.
[Illustration: FIG. 3. REVERSING MECHANISM.]
Since a gasoline motor cannot start of its own accord, it is necessary
in vehicles in which they are used so to arrange the driving gear that
the motor may be kept in motion all the time and always in the same
direction, hence, to reverse the direction of the carriage, reversing
mechanism, independent of the motor, must be provided. The most simple
mechanism for a gasoline vehicle employing spur gearing exclusively is
shown in diagrammatic form in Fig. 3. In this figure _A_ represents
the cylinder of the motor, _B_ the crank disc chamber and _M_ the
vaporizing receptacle, which is generally called the carburator. The
pinion _C_, on the end of the motor shaft, meshes into a gear _D_
which is mounted upon a sleeve _E_ which revolves freely round shaft
_G_. This sleeve has its ends formed so as to engage with the gears
mounted upon shaft _G_, and by means of a lever, which is not shown,
but which works in groove _a_, the clutch either _s_ or _ss_ can be
thrown into engagement with its corresponding gear. If _s_ is thrown
into gear, as shown in the drawing, the wheel _F_ will turn _H_ and the
pinion _I_ will rotate the gear _J_ which is mounted upon the axle of
the carriage. If the clutch _ss_ is thrown into engagement, the gear
_G_ will turn _K_ and this wheel will turn _l_; but, as can be clearly
seen, the direction in which _l_ will revolve will be opposite to its
motion when driven through _F_ and _H_, therefore, if when _F_ drives
the carriage runs forward, when _G_ drives it will run backward, and
when _E_ is moved to the central position, so that neither _s_ nor _ss_
engages with their respective gears, the vehicle will stand still, but
the motor will continue to revolve.
[Illustration: FIG. 4. PLAN AND ELEVATION OF UNDERBERG MOTOR
VOITURETTE.]
This diagrammatic arrangement is more simple than the gearing actually
used and is not as complete in action as many of the devices, as it
only provides means whereby the direction of rotation of the axle may
be changed, while in many carriages the gearing also varies the ratio
between the speed of the motor and the driving wheels. It is also quite
common to combine in the train of gearing spur gears and sprocket
wheels, and in some instances even belts. Fig. 4 illustrates a French
gasoline automobile made by Underberg, of Nantes. The first figure is a
side view, and the second is a plan of the truck and driving mechanism.
[Illustration: FIG. 5. CHERRIER TWO-SPEED GEAR.]
The motor, which is of the single cylinder type, cooled by radiation
into the air, is located at _N_. The pinion on the end of the motor
shaft engages with the wheel on the end of shaft _A_. This shaft
carries four gears, which can be moved by means of lever _C_, so as
to engage with corresponding gears on shaft _B_, thus providing four
different speeds. The motion of _B_ is transmitted to the rear axle
by means of a belt that runs over the pulleys _p_ and _P_, the latter
being carried by a differential gear, so as to run the two driving
wheels at proper velocities. The circular ribs surrounding the motor
cylinder are well shown in the figure, in which the carburator of _C_
is also seen. The housing for the motor is open at the sides so as to
give air currents free access. In Fig. 4 the speed changing gears are
shown, the reversing train being omitted; but if it were also drawn in,
the diagram would be far more elaborate than Fig. 3.
Another form of variable speed gear is shown in Fig. 5. This provides
for two speeds. The large wheel _E_ is on the carriage axle, and it is
driven either by a pinion _F_, or by _J_. Upon the shaft _O_ there are
two friction clutches _C D_, and when _C_ acts the pinion _F_ drives
_E_, and when _D_ acts the pinion _G_ drives _H_, which in turn drives
_I_, and this wheel is mounted on the same shaft as _J_.
Some of the best-known makers of gasoline vehicles do not employ
variable gears and depend for changes in the speed wholly upon
variation in the velocity of the motor. The De Dion carriages are made
in this way, the gearing being substantially as illustrated in Fig. 3.
[Illustration: FIG. 6. PANHARD & LEVASSOR VEHICLE.]
[Illustration: FIG. 7. MOTOR OF VEHICLE.]
Fig. 6 shows a gasoline vehicle made by Panhard & Levassor, who are
perhaps the best known French manufacturers of automobiles, as their
vehicles have been the winners in all the notable races held within the
past few years. The motor they use is shown in Fig. 7, and, as can be
readily seen, is of the two-cylinder type, cooled by a water jacket,
just as in Fig. 1. The explosion is produced by means of a hot tube,
as explained in connection with the last-named figure. This motor is
placed under the body of the vehicle, and is connected with the rear
axle by means of a train of gearing which terminates in sprocket wheels
and chains that connect with driving wheels, each one being operated
by a separate chain. In Fig. 6 the sprocket wheel and chain are well
defined, and forward of these can be seen the outline of the casing
enclosing the gearing.
[Illustration: FIG. 8. GENERAL VIEW OF RENAULT VOITURETTE.]
[Illustration: FIG. 9. PLAN OF THE TRUCK.]
[Illustration: FIG. 10. VARIABLE SPEED GEAR.]
Fig. 8 shows another European design, in which a variable-speed gear
is used. The plan of the truck, showing the general arrangement
of the mechanism, is presented in Fig. 9, and the details of the
variable-speed gear are shown in Fig. 10. The motor is located at _A_,
and through a friction clutch _B_, and the variable speed gear _C_, it
rotates the shaft _H_, which runs lengthwise of the vehicle. Motion is
imparted to the hind axle by means of bevel gears contained within the
casing _D_. The large bevel gear on the axle is of the differential
type, so as to drive the wheels _R R_ at the proper velocities.
When a high speed is desired, the variable speed gear, Fig. 10, is set
so that shaft _M_ drives _N_ direct, the clutch at _E_ being moved
so as to interlock. _N_ is the end of shaft _H_, so that with this
connection the bevel pinion, which meshes into the axle gear at _D_,
revolves at the same velocity as the motor shaft. By moving the handle
_V_, Fig. 9, to the right, an intermediate speed is obtained, and by
moving it to the left, the carriage is run at the lowest velocity. When
the handle _V_ is turned to the right, the ends _M_ and _N_, which form
the clutch _E_, Fig. 10, are separated, and at the same time the lower
shaft _H_ is moved toward _M_, so as to cause gear 1 to mesh into gear
2, and also 3 into 7. By this means the end _N_ of the axle-driving
shaft is rotated through the train of gears 1, 2, 3 and 7. If the
handle _V_ is turned to the left, the shaft _I_ is moved toward _M_, so
as to cause gear 1 to mesh into gear 4, and gear 6 into 8, the latter
being secured to end _N_ of the axle-driving shaft. The speeds obtained
by these changes are in the ratio of nearly 1, 2 and 4.
[Illustration: FIG. 11. PLAN OF THE TÜRGAN-FOY VOITURETTE.]
Fig. 11 shows the plan of a light French carriage, which is equipped
with a double cylinder motor, set in a horizontal position above the
front axle, and arranged to impart motion to the hind axle by means
of belts. The motor, which is located at _A_, turns a vertical shaft,
and this, through spur gears, rotates a horizontal fly wheel, _B_. Two
pulleys are mounted upon the motor shaft, and from these belts run
to tight and loose pulleys on a countershaft, _S_. From the latter
the rear axle is driven through two sets of spur gearing, which give
two different speeds. By means of the belts, two other speeds are
obtained, thus giving, in all, four different velocities. To stop and
start, the belts are shifted from the tight to the loose pulleys by a
belt-shifter, _f_. At _h_, a muffling chamber is located, into which
the motor exhausts, so as to reduce the noise.
The elevation and plan of one of the celebrated French racing-machines,
the Vallée car, is shown in Fig. 12. The motor of this machine is of
sixteen horse-power capacity, has four cylinders, and is connected so
as to impart motion to the hind axle by means of a single wide belt,
which is marked _G_ in both the line drawings. The driving-pulley on
the motor shaft is located at _H_, and the axle pulley at _H’_. Within
the latter there is a train of gears for reversing the direction
of rotation of the axle, and also for obtaining the differential
velocities of the two driving wheels. There is no mechanism for
variable speed, this being obtained wholly by changes in the velocity
of the motor. The motor speed can be made to vary through a wide
range by using four cylinders, with which it is possible to reduce
the velocity so low that it would be likely to bring the machine to a
standstill if provided with one, or even two, cylinders. The change
in the motor velocity is obtained in part by the action of a governor
located in a chamber at _A_, and in part by the action of the electric
ignition device which is arranged so that the time when the spark is
produced can be varied. The rear axle is so held that it can be moved
through a short distance, horizontally, by manipulating the lever _D_,
and in this way the belt _G_ can be made tight or loose, thus affording
another means for varying the speed. A brake is provided which presses
against the inner side of the axle pulley, _H_. This brake is used
ordinarily, but in the case of an emergency another brake can be
operated which presses against the outside of the wheel in the space
between the two sides of the belt. It is claimed for this vehicle that
by the elimination of mechanical speed-changing devices, a great deal
of weight is saved, and that this is more than enough to compensate for
the extra weight of the motor, arising from the use of four cylinders.
In most gasoline carriages it is necessary to provide a slow-speed gear
for hill-climbing, as the motor cannot put forth a sufficient effort to
ascend a steep grade at the normal velocity. With this racing-machine
such a gear is not required owing to the enormous power of the motor.
[Illustration: FIG. 12. ELEVATION AND PLAN OF VALLEE CAR.]
There are quite a number of gasoline automobiles manufactured in this
country, and, as in the case of the steam and the electric carriages,
they compare most favorably with the best European products, in so
far as the artistic effect is concerned. That such is the case can
be realized at once by an examination of Figs. 13 and 14. We regret
our inability to illustrate the mechanism of these vehicles, but
the truth is, that the manufacturers appear to be unwilling to make
public the details of their designs. In the phaeton shown in Fig. 13,
a single-cylinder motor is used, and it is so arranged that it can
run at different velocities, so that no variable speed mechanism is
required, except a single train of gears, which is thrown into action
when running uphill. The motor itself can be run at any velocity from
200 to 800 revolutions per minute, thus giving a speed variation of
four to one. A carriage of this make competed in the last international
automobile race from Paris to Lyons, France, and although it failed
to come in first, it made a remarkable showing, which might have
been considerably improved if it had not been for an accident which
compelled it to retire from the contest.
[Illustration: FIG. 13. WINTON PHAETON.]
[Illustration: FIG. 14. OAKMAN VEHICLE.]
The vehicle shown in Fig. 14 is of small size and light construction,
although amply strong for the purpose for which it is intended. The
power of the motor, which is located under the seat, is transmitted
through friction wheels. In looking at the illustration it will be
noticed that the hind wheels have a circular rim attached to the inner
side, and of a diameter somewhat smaller than the wheel itself. Two
small friction wheels are placed so that either one may be pressed
against the inner surface of this rim. The shape of the rim, as well
as that of the small wheels, is such that they hug each other firmly,
so that the rim is carried around in a direction which corresponds
with the direction of rotation of the friction wheel. In operating the
carriage the motor is set in motion, and then one or the other of the
two friction wheels is pressed against the rim on the driving wheel,
according to whether it is desired to run forward or backward. While
this arrangement might not operate with entire success if applied to a
heavy vehicle, it appears to be all that could be desired for a light
carriage.
Three-wheel vehicles have been used, but there is a difference of
opinion as to their value, as the construction has disadvantages as
well as advantages. It is evident that such a vehicle can be steered
with greater ease than one running on four wheels, but on country
roads, where the wagon wheels roll down a smooth surface, and leave
the space between in a rough condition, it is equally evident that
the third wheel, in passing over this uneven surface, would jolt the
vehicle to a considerable extent. On a smooth pavement the three-wheel
vehicle will run fully as well as the four-wheel; but, on the other
hand, on such a pavement the latter can be steered with as little
effort as the former, so that the question of superiority of design is
one that probably depends upon individual taste.
From the descriptions of automobiles given in this and the two
preceding articles, it will be seen that although many of them
are used, especially in France, they are not entirely free from
objectionable features. The electrical vehicles are provided with the
most simple and durable machinery, and, being noiseless, odorless and
free from smoke, are all that could be desired in so far as their
operation is concerned; but they are heavy and can only be used in
places where the batteries can be recharged. The steam vehicles are
light, have simple mechanism and can run anywhere; but they exhaust
steam into the air, which is clearly visible in cold or wet weather,
and the heat from the engine and boiler is an objection, at least in
summer time. The gasoline vehicles run well, but are noisy, and the
odor of the gasoline is disagreeable as well.