Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-09-08
NJ II. CLIFFORD RRoKAw.
AutomobiIe Technical Adviser.

One of the interesting diseoverie,
generally made some time in life is thai
it is easier to proceed along on the
level than 1t Is to climb q hill. While
it may require little effort to trip gayly
aieng down grade, when it comes to
climbing stairs considerable expendi-
ture of energy becomes necessary and
the steps are taken at Q slow rate OF
| speed.
In the automobile we demand a ma
chine that not only viii carry US rapidly
on the smooth level roads but will climb
the steepest hills and pull through the
deepest mud or sand without question
These extreme requirements could be
met by eQuipping our cars with very
high powered engines, but such motors
would be costly to build, their weight
would be 80 great that it would require
p heavily built car to carry them
around, and most. Of the time they
would be burning up gasoline in very
inefficient manner.
To provide all the speed it is practical
to use and all the driving power that is
necessary to carry the car over the
steepest hills without employing an en-
CINE that is too cumbersome, the motor
car is equipped with a transmission or
change of speed gear.
1.-THE transmission gears usually are
designed to give selection Of three diff
feFent ear speeds forward, with the en-
CINE running at constant speed, and
also provide for means of reversing the
car. A greater range of car speed may
be obtained by varying the speed of the
engine through the use Of the accelera-
tor pedal.
How Motor Performs
When a car is travelling along a
smooth level road in high gear with the
throttle Of the engine wide open, 1t is
proceeding at the maximum speed at
which the engine is capable Of driving
1t. II down grade is reached the car
speed viii increase, because the force of
gravity adds its power to the power of
the engine. If an UP grade is en-
countered, the force of gravity becomes
opposed to the power of the engine and
this added load causes the engine to
slow UP through overwork. When the
hill becomes steep enough the engine is
overpoWered and stops entirely unless
something Is done to relieve 1t.
This is where the transmission gears
GENE into use. The operator before the
engine has slowed too much. shifts the
gears from high to second. The engine
SpeeQS UP, DuL Tie car PI0ceeas At q
comparative slower rate. The power of
the engine is now being utilized for
pulling force rather than for speed.
The transmission gear case contains
two shafts, upon each of which several
gears are placed. On one of these shafts
the gears are all fixed rigidly and they
must all revolve with the shaft at the
same rate Of speed. The gears on the
other shaft must revolve with it, but
they may be slid back and forth along
its length. The shafts are placed
parallel; and through the aiding Of the
gears, which is done by means of the
gear shift lever, the operator may bring
different combinations Of sizes into
mesh as desired.
If q gear driven by the engine has
10 teeth and this is brought into mesh
with gear on the shaft that drives the
rear wheels which has 90 teeth, the
engine will make two revolutions while
the driving shaft Is making only one.
This cuts the driving speed in halt
and doubles the pulling power of the
car ever what it would be II no gears
were employed.
More power is required to start a car