Los Angeles herald., 1910-07-10
ON CARS DRIVER
DEPENDS ITS LIFE
Designers Make Provision in the
Plans for Everything but
Care of Chauffeur
SLOW SPEED lessons RISKS
Succession of JoIts Often Causes
Fractures Which Show
Up at Later Date
SLOW SPEED lessons RISKS
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driver would give the machine decent
usage and care, but as soon as the car
leaves the factory the stresses to which
it is subjected and the results of these
strains are beyond calculation, yet
these stresses and the resulting strains
enter most markedly in the life of
the car.
THE REAR AxLEs
Take rear axle, for instance, one
might take lead hammer and strike
this axle hundred thousand blows of
a given strength without injuring 1t,
yet double the strength of this blow
and it might go to pieces before it had
been hit five hundred times. In actual
work one careful driver might give this
axle its hundred thousand blows by
dropping it easily into the holes and
over distractions, while the more reck-
less one could quickly destroy it by
striking these holes and distractions
at great speed.
Technically speaking, a stress is the
internal resistance which body offers
against any force tending to overcome
cohesion, while a. strain is any deform-
ity resulting from an excessive stress.
Any material like iron and steel will
stand any number of stresses if they
ing deformity, while perhaps a few
shocks. almost to the limit of its en-
durance, will do an injury which is ir
repairable. And a great number of
small sudden jars always does much
more harm than a steady force applied
almost to the limit.
AN EXPERIMENT
If a bar of steel should be suspended
so that it could swing freely and then
struck hundreds of thousands of light
blows a change will occur in its struc-
ture. Looked at with microscope, its
fibrous nature will tend to disappear,
and a certain form will be assumed
which shows an appearance of crys-
talline nature. This is not true crys
utilization, and l believe is still unde
termined in character but whatever it
is this new arrangement of the mole
cules decreases the ultimate strength
of the steel and causes 1t to fracture
much more easily than If it was still in
the original molecular construction.
The time required to produce this so
called crystalline structure does not
depend so much on the number of
blows to which the steel is subjected as
to the power of these blows, and in
driving over a given stretch of road
the force of these blows in any given
car increases about in proportion to the
square of the speed.
The Automobile of June 16, in speak
ing about the life of a car and using
a speed of five miles an hour as 100 per
cent, states that at ten miles an hour
its life would be about 25 per cent,
while at twenty miles an hour it would
be only 6A per cent. That is, if you
drive five miles an hour and wear out |
your car in 100000 miles, if you had |
driven twenty miles an hour it would |
have lasted for only $3.50 miles. Ac- |
pOr0inor n this estimate If OP bo
cars built today were driven never to |
exceed five miles an hour they would |
be still good at the end of few mill
lion miles, and I believe this is true.
THE BREAKS
The break in any part of your car
rarely occurs completely at the time
you discovered it, unless you subjected
1t to some special shock which would
be great enough to be appreciated in
stantly and cause you to expect trouble.
but it is generally the result of a COLI
siderable number of excessive stresses,
each one sufficient TO cause a strain.
Your spring or axle breaks. perhaps on
a perfectly smooth and level road, and
you wonder why. You have dropped
that axle thousand times into holes,
banged" it against humps" in the
road with force greater than it could
stand. Each shock was sufficient 10
overcome the cohesion between a few
molecules, until finally there was not
sufficient good material left to carry
the weight of the car. Sometimes a
great number of microscopical cracks
appear before the final fracture occurs
The man who wants to secure all the
mileage possible during the life of his
car first finds that the material of
winch IT is constructed is good He
next notices the provisions made for
preventing shocks. These consist of
The wheels, tires, frame and spring sus-
pension Large wheels and tires. with
a flexible frame and springs. greatly re-
duce the shocks transmitted to the
parls' ne aXles and differontial get the
greater blows because thev are ''cush-
Toned from the inequalities of the road
only by the pneumatic tires. but if the
frame and springs are TOO rigid the re