Newark leader. ([Newark, Ohio]) 1917-1946, 1924-06-13

! What shall we do with our brakes
All car owners and drivers should
test them frequently.
How shall they be tested?
Brakes can be tested very easily by
the following method: When the car
is running about 20 miles an hour,
apply brakes enough to lock wheels
and then examine the marks on the
pavement. If they are about equal,
you may be sure that your brakes
are efficient.
In case you fail to lock either rear
wheel, and fail repeatedly. your
| brakes have not their maximum eff
, cheney. Please observe that we say
maximum. We do not claim that they
are inefficient. In fact, it is possible
to have brakes that will not lock
| wheels just as efficient as those that
| will lock wheels, but this is like cal
! culating in advance the exact amount
of money required to make project
ed trip and have nothing in reserve.
It is really worse in case of brakes, as
you have no ready means of Judging
your efficiency unless you have the
maximum.
Of course, We do not advise locking
as it increases the tendency to skid
and also destroys tires. On wet pave
ments, if brakes are applied SO as to
| lock wheels, their application will de-
crease control, and we must realize
that it is much easier to lock wheels
on slippery pavement. Even with
| skid chains on the locking of the
wheels usually renders the chains use
less, as the locking necessarily occurs
while the tire rests on the pavement
| between two cross chains.
With all these objections to locking
wheels, why do we recommend it as
test?
Just because it's the maximum lin
it of efficiency. However, consider
ing the dangers of locking wheels in
traffic, brakes are most efficient i'm
mediately before locking.
The efficiency Of a brake depends
upon the factors, i. e., (1) the diane
ter of the brake drum, (2) the me-
chanical advantage between pedal and
drum or what is commonly called lev
erage, (3) the force applied to the
pedal, (4) the frictional efficiency of
lining on drum, (5) the proportion of
weight on rear wheels, CO. the char
acter of pavement, tire initiation, etc,
| CD brake equalization, (8) the aver
age clearance of lining and drum, and
| (9) the extent of wrapping which the
brake permits. In stating these fac
tors, we are assuming the ordinary
| type of service brake external on rear
wheels only.
1t is evident that but three of these
factors can be controlled-namely,
the clearance between lining and
drum, and equalization.
Let US take up these factors sepa-
rately. First the pressure which may
be applied to the pedal will vary with
the weight and strength of the driver,
and as most cars are not built to give
variations of mechanical advantage
for stronger or weaker drivers, ad-
justment must make this adaptation
as far as possible. 1t is important to
note in this connection that the eff
cheney of brakes may be more than
doubled by increasing the extent Of
contact of band and drum in applica-
ton, so as to take full advantage of
wrapping.
Wrapping is factor in brake eff
cheney which is almost mysterious to
the uninitiated. In wrapping, we
make use of some of the momentum
of the car to apply brakes. This can
not be realized on external bands un-
less the lining be brought in contact
with drum over almost all its circum-
ference. 1t is by this perfect round
ing of the band that we take advant-
age of the wrapping, more than
doubling it's efficiency and thereby
adapting brakes to weak drivers.
The clearance between lining and
drum will vary with the mechanical
advantage of the installation. The
clearance should be nearly equal all
about the drum and should be nowhere
less than .025 inches, as drum expan-
sion at 500 F. will increase the dame
ter of the drum from 40 to so thou
sandths. Too close clearance means
locked brakes. Mechanics will tell
you they "froze with the heat"
The service brake should be adjust
ed with such clearance that the Sc
verest application does not cause the
pedal to take position less than one
Or two inches from floor board. Long
continued severe application will in
crease this distance or make the ped
al seem to rise against the foot be-
cause of drum expansion.
Equalization is important because
it is necessary for full efficiency and
because unequal action increases
tendency to skid. Brakes should be
equalized by adjustment at three
points upon the band and not by
shortening or lengthening pull rods.