AUTOMOBILE ACCESSORIES
Self-starting devices are the latest permanent addition to a perfect
car equipment. Two general types are being made, one purely mechanical
in its character, and the other operated by the engine itself.
The mechanical devices usually have some connection with the
forwardly-projecting end of the crank shaft, where the present cranking
shaft is located, and some of the inventions in this respect have an
arrangement whereby the driver is able manually to operate the starter
from his seat.
The actual work of turning the shaft is now performed by compressed air
which actuates mechanism that gives from one to two turns to the shaft,
sufficient to ignite the fuel in several of the cylinders.
SIMPLE TYPE OF STARTER.--The simplest type of starter is that which
utilizes the cylinders themselves to give the initial turns. To
illustrate the matter we have given some sketches of the engine cycle,
in Fig. 95. The four positions of the piston in a four-cylinder
engine are so placed that the spark cannot ignite the charge in either
cylinder.
Cylinders 1 and 2 are descending, and 3 and 4 are ascending. The charge
in 4 is partially compressed, but it must reach the position indicated
by the dotted lines A before it can be ignited.
[Illustration: Fig. 95. Starting Mechanism.]
The sparking mechanism was cut off before the cylinder 1 reached its
highest point, at the previous stopping of the car, so that it still
has an unexploded charge; and piston 3 is now discharging the gas from
that cylinder.
As the engine is now at rest, the problem is to supply a charge to
cylinder 1, or a pressure of sufficient strength to turn the engine
shaft so that the piston in 1 will be brought up to the explosion line
A. It is accomplished in the following manner:
One or more of the engine cylinders is connected up by a small pipe
with a storage tank, located at any convenient point, so that at each
explosion a portion of the charge in the cylinders goes into the tank,
where it is held by a check valve.
THE DISTRIBUTER.--This tank is connected with a distributer, which
controls the pressure flow to the different cylinders. In Fig. 91 the
distributer would send this pressure to cylinder No. 1. The opening of
a valve readily accomplishes this, and if the charge in No. 4 should
not explode, the next in order to get the compressed gas from the tank,
would be cylinder 4, which would bring cylinder 3 into position for
firing.
As soon as ignition takes place, the driver merely shuts off the valve,
and no further attention is required to operate it.
LIGHTING.--Most cars depend for illumination on the use of compressed
gas usually, some form of acetylene, which makes a brilliant light, and
is not expensive.
The best cars, however, are also equipped with electricity, some
depending on storage batteries, and others on current generated on the
car itself. There is nothing in either system that requires any special
explanation, nor are they difficult to care for and operate.
SIGNALING.--It has been the custom for drivers, in approaching corners,
or street intersections, to hold out the right hand as a sign that a
turn is to be made to the right, or the left hand for a turn in the
other direction.
CAR SIGNALS.--Numerous devices are now on the market designed to be
located both in front and in rear of the vehicle, which are intended to
indicate direction, as well as to impart other information.
These signals are under control of the driver, and have signs on them
which indicate “_stop_,” “_right_,” “_left_,” or other words which
conspicuously display the intention of the driver.
All machines have signaling horns of some character, operated, usually,
by some mechanical arrangement connected with the gearing or by
compressed air, and others are connected up with the engine exhaust.
Chime whistles are so operated.
SPEED SIGNALS.--Other inventions are designed to indicate, by automatic
mechanism, the speed of the car, in which color displays the relative
speed. Thus, a car going at the normal speed, say 10 miles per hour,
would show a white light; from 10 to 15 miles, blue; from 15 to 20
miles, green; and above that speed, red.
The foregoing colors and speeds are arbitrarily selected, merely to
show the ideas involved. The device in question has nothing whatever
to do with the regular speed registering mechanism of the car, but is
designed to show pedestrians and police officials the actual running
speed at a glance.
MUFFLERS.--There is really no excuse for noisy automobiles. Mufflers
are now made which absolutely eliminate all noise from the exhaust.
The great difficulty in the past has been to make them sufficiently
large for the engine. If too small they do not take care of the exhaust
properly, and they also serve to check the flow of the exhaust gases
from the engine, and thus greatly decrease the power of the engine.
EXHAUST.--All racing engines are made without exhausts, so there will
be nothing to retard the flow of the exhaust.
The function of the muffler is to receive the exhaust gas and permit
it to expand as nearly as possible down to atmospheric pressure before
delivering it to the air. Fig. 96 shows the simplest form in which it
can be made.
CONSTRUCTION OF MUFFLER.--The inner pipe A, from the engine exhaust,
passes axially through a cylinder B, the pipe, however, being closed at
its inner end where it is attached to the head C. Numerous small holes
D are formed through this pipe for the escape of the burnt gases.
Within the cylinder B is a smaller cylinder E, surrounding the inner
tube. This has one end attached to the head C, and its other end
is open so as to provide a passage way F from the interior of the
cylinder. The discharge ports are at G, through the head C.
[Illustration: Fig. 96. Muffler.]
Almost any design of muffler is serviceable, if it has sufficient area.
However large it may be it is always advisable to have a valve in the
pipe A from the engine manifold, so the muffler can be cut out going up
steep hills.
BALL AND ROLLER BEARINGS.--All running gears are provided with either
ball, or roller bearings. For heavy vehicles roller bearings are most
serviceable, but for light vehicles and for speed most manufacturers
prefer ball-bearings.
RACE WAYS.--The object in the use of balls, is to provide two, three,
or four points of contact, which should be so arranged as to have the
paths of the bearings of equal lengths, as nearly as possible, and thus
prevent the balls from wearing by creeping along the contact walls, and
also thereby wearing the paths on which they travel.
[Illustration: Fig. 97. 3-Point Roller Bearing.]
THE THREE-POINT CONTACT.--To understand the full importance of this,
examine Fig. 97, in which A is the roller, or shaft, and B the hub
having the raceway C designed to hold the balls D, and gives two points
of contact, the third point being the shaft A.
[Illustration: Fig. 98. Wrong Bearing.]
Compare the foregoing figure with the illustration given in Fig. 98,
where the contact points A, B, C, represent the three bearing circles,
which differ in their circumference, and it is obvious that a ball in
traveling around must slip somewhere on one or more of the paths A, B,
C.
[Illustration: Fig. 99. Improper Alinement.]
WRONG CONSTRUCTION.--Another sample of wrong construction is shown
in Fig. 99. In this diagram the three bearing points A, B, C, also
represent circles of different diameters, which are sure to wear
grooves in the three paths made by the balls.
[Illustration: Fig. 100. Correct Raceways.]
The most ideal form of bearing is shown in Fig. 100, which represents
the four-point contact, and this also provides against longitudinal
thrust of the shaft or axle.
ROLLER BEARINGS.--This type of bearing is ideal because of the large
surface which is available. The difficulty is to keep the rollers
parallel, with the shaft. Furthermore, they should not roll in contact
with each other. To obviate this the rollers are put into a cage.
[Illustration: Fig. 101. Cage for Roller Bearing.]
FORM OF ROLLER BEARING.--Fig. 101 shows a side and a cross section of
a set of rollers held within a cage formed of two end rings A A, each
roller B having at its end a reduced bearing C, and intermediate the
rollers are tie rods D, which keep the rings in proper relation to each
other, and also prevent them from alining themselves diagonally along
the shaft, or against the bearing within the boxing.
To provide means for utilizing roller bearings so they will take up end
thrust, taper rollers are employed, as shown in Fig. 102.
[Illustration: Fig. 102. Roller Bearing.]
The shaft, or axle, A, has two runways, B, C, which are
conically-formed, and inclined toward each other. The rollers D are
tapering, and have their small ends pointed towards each other so
that the outer ends of the bearing surfaces E of the hub are at a
considerable angle to the axis of the shaft.
These rollers are also mounted in cages which turn around the shaft.
This structure, in a modified form, is largely used in automobile
construction.