Page 9 - Combined_134_OCR
P. 9
FLYING CARS
Photo courtesy Wynn Oil Co.
Dragsters:
Force/Weight of Tires
?4 Estimated
Idealized- Streamlining Vs. Weight
2.0 IN TWO DECADES the dragster has evolved from a
Acceleration ~’g ' 1.6 cceleration----- production street auto to a specialized vehicle capable
Measured /
of %-mile runs under 7 seconds at speeds up to 220
1.2
mph. It has a power-to-weight ratio 3 to 4 times the
I I
.8
-------' Estimated -1—
Aerodynamic Drag best W. W. II piston engine fighter. The competition
dragster’s sole purpose is to gun it from a standing
.4 start a distance of 1,320 ft in minimum time.
The dragster has little analytic work back of it.
0 Aerodynamic principles applied to dragster design
0 80 160 240 320 400
have yet to be the rule. However, front axle airfoils
Velocity - Ft./Sec. exerting a downward force are often used to improve
Test results of an accelerating dragster used to traction and handling qualities at high speed. At
tempts have been made to reduce drag through stream
estimate order of magnitude of hp/wt ratio, tire lined bodies and break the “200 mph barrier” but
static friction/wt ratio, and tire viscous friction such attempts were guided by styling rather than
coefficient, v. fluid mechanics principles. Performance was poor
and many thereby rejected aerodynamics as a design
8.8 I-
factor.
AA/GD Dragster High power-to-weight ratio permits operation of
H = 1.4; P = 0005 dragster tires in the slip condition over most of tne
Time-Sec. 8.0 Sym. 5Cd ground and tire generates large amounts of heat,
course. But initial relative velocity between the
reducing tire surfaces to a plastic state, says Bernard
O 002
Elapsed A 004 Pershing, an engineer at Aerospace Corp, and a drag
ster authority. Increased hp gives lower ET (elapsed
time). Some of this hp goes into tire tractive force.
□ 008
7.2
Drag reduction on today’s high performance fuel
AA/FD Dragster
g ■ 1.8; v = .0005 dragsters can reduce ET enough to warrant con
sideration in current and future design. Drag re
duction must not be performed at minimum weight
6.4 ----------1----------1--------- 1--------- 1--------- 1--------- 1--------- 1----------1------
120 160 200 240 280 to prevent streamlining advantage being devoured by
reduced hp/wt ratio, adds Pershing. He cautions
Trap Speed - MPH
that care be used in any streamlining exercise to be
Aerodynamic drag influence on performance of sure that it truly reduces drag.
two class AA dragsters, one fuel driven (FD), and Pershing believes there may be only a small im
one gas driven (GD). SCD/W is area-drag/weight provement in elapsed time with aerodynamic air re
ratio. Drag reduction lowers ET moderately, but duction. A fuel dragster is more capable of carrying
has a strong effect on trap speed. the weight of a large body than the gas dragster.
And concludes Pershing: “With all the power today,
current dragsters might well benefit by a re-examina
tion of the streamlined body.” If anyone attempts
drag reduction with the body or modifications in
shape “it best be a drag reduction in reality rather
than a mere styling change,” he emphasizes.
Influence of various design parameters on per
formance shown for two nominal dragsters.
Elapsed times are seen to be most strongly af
fected by changes in tire tractive force. Aerody
namic drag has a moderate but not trivial in
Trap Speed - MPH fluence on elapsed time.
30 Machine Design
