Evening star. [volume] (Washington, D.C.) 1854-1972, 1927-07-10
MOTORING
"The long, road" long
that has equipped itself with good motor
BY WILLIAM ULLMAN.

an increasing extent, such establish
ments are adding equipment which
permits them to get away from the
inefficiency of testing the brakes by
hand to determine whether they are
properly adjusted and equalized
And, why not? Precision long has
been a justihable boast of the auto
mobile industry. Today the labora-
tories in which constantly better
motor cars are being made are cal
culating their measurements in thou
sandths of an inch and even less,
and the makers of precision instru-
mentS are kept busy producing de-
vices to determine the accuracy with
which finely machined parts fit to-
gether.
Precision has made the motor car
popular. Now, it seems well on the
way to making its brakes much safer
by giving the mechanic and car
owner accurate information regard
ing the cars declaration equipment.
This development, now reaching
fruition, has been on the way for
some time. Many arc surprised that
il was so long in reaching its des-
tination.
There has been no questioning the
lack of precision of methods of brake
testing that have prevailed in the
vast majority of repair establish
ments up TO the present time. The
usual method has been to jack up the
car and have some one apply the
brakes while the mechanic tried TO
turn the various wheels If all of
them turned with approximately the
same expense of energy on the me-
chanic's part, they were regarded as
properly adjusted and nicely equal
lied. But, were they? If the me-
chanic were sent to barrel of sugar
and told to measure out a pound by
feel" might he not have 20 ounces,
or II, as we'll as 16?
Gradually, however, this system of
brake testing is. being replaced. Va
rious types of decelerometers, which
measure with much greater accuracy.
are being added to the equipment of
hundreds of automotive repair estab-
lishments. And, as many know, po-
lice department are purchasing SINH
lar devices to be used to test the
brakes of cars that have figured in
accidents. In addition, metropolitan
police departments use their de-
celerometers from time to time in
campaigns designed to check up on
the brake equipment of cars chosen
NJ random on the streets of the city.
IL II
Brake-testing devices, so used. vary
In design. They are not always
called decelerometers by their max
ers. The term is a general classical
ton, however, and in this way all
OF them are described by it.
The most generally used device of
this kind is similar to the odometer
of the average car in that it is cali
brated to record the number of feet
1t takes to stop a car from a given
speed after the driver has been given
signal. While it is not true of all
devices of this character, some of
them have the weakness of not
showing the Inequalities between the
brakes on the various wheels of the
Car.
In addition. there is the question
of the drivers reaction time. 1t is
obvious that many motor car opera
tors have definite margin on others
in the matter of getting their brakes
into operation with minimum loss
of time. And the time lost in the
case of the slow driver is recorded
against the brakes. From this, it is
clear that some cars might have
good brakes that would be classed as
inefficient under some such deceler-
oneter tests.
In connection with the ordinary
decelerometer, there is the fact that
it does not show precisely why the
brakes are failing, whether it is due
to warped drums, low coefficient
of friction because of worn tire tread
or bad road conditions. With all
these defects. which easily could be
made to appear more important than
actually they are, this, the oldest OF
the mechanical brake-testing devices,
IS vastly superior to the touch" sys-
tenn employed in many repair shops.
Still better testers are being made.
however, involving new ideas that
eliminate the human element in
brake efficiency and many of the
other factors that confuse the situa-
ton.
These improved devices put the car
on rollers, or treads. for purposes of
testing its brakes. These treads are
so designed that their FRACTIONAL CO.
efficient with the tire virtually is
identical with that of a good con-
crete road. On some of these, the
engines power plant is utilized to get
both car and tread into motion. On
some Of the latest types, however,
even this is unnecessary.
Both, of course, represent an inn
provement over the conventional
road test, for the reason that condi-
tions may be kept equal under viz
tually all circumstances.
Great claims are made for the type
ct tester that uses an electric-motor-
driven transmission dynamometer.
This completely eliminates the driver
and the power plant of the car itself
It's operation is fairly simple. The
brakes of the car are set and the
wheels turned against their resis-
lance by means of the electric motor.
Some of the faults shown up by this
device that do not appear in other
tests are degrees of inequality of adj
justment so slight that they other
wise could not be detected, warped
and worn drums and points whcr.
the band is out OF concentric.
Win such equipment available to
tell him the whole story of his
brakes, and tell it accurately, the
average motoriSt is likelv "a LIZ