Evening public ledger. [volume] (Philadelphia [Pa.]) 1914-1942, 1916-01-12
POWER OF WIND
RESISTANCE NOT
WIDELY KNOWN
Designers Realize Its Pow
er Far More Than
Driver of Car
THE BACKWARD P U L L

Wind resistance as a consumer OF the
power OF an automobile is not appreciated
by the average car owner anywhere near
as much as 1t is by the designer. It is
this attention TO the resistance due to
the pressure Of the wind on the projected
surface that has been one of the most Inn
portant factors in determining the shape
of the car exterior. Human nature is such
that refinement of detail generally leads
tho finished product to operate along the
lines of least resistance. and the stream
line automobile body Is only significant
illustration of this point
Looking at the forward end OF the car
for 1916 II will be noted that the entrance
lines, or that part OF the car which acts
as an entering wedge to split apart the
volume OF air in front, is narrower than
ever before. Strange TO say. however, the
lines of entrance into the wind are not
OF as much Importance as those at the
rear of the vehicle, which determine the
ease OF juncture OF the split-air currents.
II is a well-known fact that 1t is easier
to tow wedge through the water with
tho blunt end foremost and the apex at
the rear. The same rule applies to the
design of automobiles as applies TO boats
ana what is known as the inverted-wedge
principle is used with both.
THE APPLICATION.
Bringing this theory down TO actual
practice and applying it specifically to
the cars exhibited at the show. 1t will be
noted that the cars OF today do not termi-
nate at the rear OF the body lines in
the square high wall that was customary
IN earlier designs. As much attention has
been put on a nodded rear surface as has
N..l,t
lines OF the engine hood and the fiattenlng
OF the cowl piece.
This moldIng Of the fore-and aft lines
of the car does not only apply TO the
touring models. but also to the closed
ears. Limousines. coupes and sedans are
given as much attention al regards en-
trance and terminating lines as the tour
ing cars. A good example of the nodded
surface In closed cara Is to be seen in
the Pullman coupe. This car has the
rounded front and rear which are sug-
gsstiye OF the submarine In marine archl-
lecture and Zeppelin Of the air.
PULLING POWER.
To appreciate the actual backward pull
ing power OF the wind II may be men
toned that 1t increases practically as
the cube of the velocity. In cars travel
ing at fairly high rates OF speed 1t takes
more of the power Of the engine 10 over
come the wind resistance thAn " does 10
perform any other work about drtvin &
the ear. For each square foot OF pro-
Jeeted area. at a speed OF Is miles per
hour, the progress OF the car Is opposed
by a steady pressure Of three pounds.
At 45 miles per hour the resistance Is 10
pounds per square foot. AS the projected
area or an average touring car will be
around 10 square feet, there is steady
drag OF 100 pounds on the car At As miles
PEI hour. Up in the racing speed OF 100
f1zies per hour the drag Is 50 pounds per
squire foot, and Is. OF course. OF Inn
is}enas importance. To reduce the entrance
resistance and tho suction at the closing
lines Is one OF the most important tasks
OF the designer.