Arizona republican., 1917-04-02
TWO THIRDS LOSS
Of POWER CAUSED
TROUBLE IN TIRES

PHILADELPHIA, March 31-Two-
thirds of the power lost between your
engine and the rear wheels Of your
car is caused directly by the tires II
you run your car with the tires, in
flated to 30 lb. when they ought to
have so ID. in them. il takes IS per
cent more power to drive the car
along the roads.
So oct out your tire pump motorists
for Professor Z. NJ. Lockwood, head of
Sheffield Scientific School Of Yale
University is authority for these state
ments. Professor Lockwood gave
these somewhat startling figures III a
paper before the Pennsylvania section
of the Society OF Automobile Engin-
GERS. His subject was Power Losses
in rheumatic Tires
Another important point lie made
was that these losses remain practi-
cally the same regardless of whether
you drive 20, so or 40 m. u. h. And
still another was that all this eating
up OF power is due directly TO the
flexure of the tires themselves as they
roll over the humps and bumps in the
roads. He p. 5ved this by calculating
how much rise in Temperature the alb
sorption of this much power would
bring about which is about 81 de-
grees; ana then he ran one of tne tires
half an hour at 40 miles an hour and
measured the temperature with a Their
mometer. The test showed that the
tire was just 80 degrees hotter than
when the run was started.
Deductions
From this, Professor Lockwood de-
duces that what we really want is u
tire that will bend and straighten out
nc ,is, Nstif
heat than u steel spring does. "sor, ="
he said. 'if we can produce such a
tire. tire in which internal friction
has been eliminated. we shall then
have a tire that does not absorb any
power
The tests that Professor Lockwood
made required the use OF special APP
paratus,. the car being mounted on
rollers flush with the floor of the lab
oratory. The car was anchored and
the rollers driven by a celebrated cleo
trio motor. BY first determining the
amount of power required, to drive
the rollers with the car on them and
carrying its normal load and then
lacking the car up and determining
the power required to turn the rollers
alone, the difference gave the actual
power required to turn the wheels of
the c.
Some of the results are given in the
appended tables. the first of these
showing the figures from series of
runs made with light SiX-cylinder
chassis and with a heavier ix-cylin-
der chassis. Professor Lockwood takes
great pains to point out that the tests
were not originally intended to deter
mine the power Losses in the tires,
but that these figures Were obtained
and - now published because of
their interest.
It should be noted in the accom-
panying table that the pressure in the
cord tire was higher than that in the
fabric tire, and for this reason the test
is perhaps not quite as fair as it might
be. Subsequent tests, however. do
show that the rolling resistance of the
cord tire is considerably less than that
of the fabric tire. and furthermore that
the rolling resistance of the cord tire
does not increase nearly so rapidly
with a reduction in initiation pressure
&C is the case with the fabric tire.
This is well brought out by the set Of
curves given herewith.
From these, it will be seen that the
fabric tire inf ted to so Id. gave a
the initiation pressure was reduced TO
30 h., the pulling resistance iInmed-
lately mounted to As ban increase
OF SO per cent With the cord tire on
the other hand, the rolling resistance
remains constant for pressures from 80
ID. down to So To-. and from here down
to 30 ID. the rolling resistance in
creases only 2k ID.
Similarly the load carried by the
tire has an important effect on the
rolling resistance, for, the greater the
load. the greater will be the flexure of
the tire; and as Professor Lockwood
has rointed out. the more fleXure there
is, the greater the heat generated and
as it requires power to generate heat
this power is lost because the heat is
dissipated into the air.
Summing up. Professor Lockwood
saws. "Only a limited number of tests
of cord tires have been made under
conditions permitting accurate COM
parison with fabric tires. The charac-
teristics of the cord tire are: greatly
reduced resistance loss and ability to
run at low initiation without much in
crease of resistance. While these ex-
periments point TO the value OF cord
tires for reducing tire losses. more nu-
mero.'s and exhaustive tests are re-
quired covering a wider scope