Mass Properties & Advanced Automotive Design

Brian Paul Wiegand, PE
74TH SAWE International Conference on Mass Properties Engineering
Alexandria, VA, 18-22 May 2015

…USUALLY BEAR THE STAMP OF A GREAT
INDIVIDUAL:
 H ENRY ROYCE – QUALITY
 PAUL JARAY – AERODYNAMICS
 ENZO FERRARI – ENGINE
 POWEL CROSLEY – COST
 PRESTON TUCKER – SAFETY
 ALEC ISSIGONIS – SMALL SIZE
 COLIN CHAPMAN – MASS PROPERTIES
74th SAWE International Conference 2

THE LOTUS ENGINEERING COMPANY WAS
FOUNDED BY CHAPMAN ON 1 JANUARY 1952
WITH VIRUALLY NO CAPITAL. ENGINES,
GUAGES, TRANSMISSIONS, DIFFERENTIALS,
AND MOST OTHER COMPONENTS WERE
PURCHASED. THE ONLY WAY THAT LOTUS
VEHICLES COULD BE DIFFERENTIATTED
FROM OTHER VEHICLES AND GAIN A
COMPETITIVE EDGE WAS THROUGH MASS
PROPERTIES, AND IN PARTICULAR THE
RUTHLESS PURSUIT OF MINIMUM WEIGHT.

…IN LACK OF RELIABILITY AND IN INJURY
& DEATH. CHAPMAN OPTIMIZED MASS
PROPERTIES, BUT DID NOT DO SO IN THE
WAY A PROFESSIONAL MASS PROPERTIES
ENGINEER WOULD HAVE. HE WOULD
OVERRIDE THE JUDGEMENT OF HIS STRESS
ENGINEERS AND REDUCE THE WEIGHT OF
STRUCTURE AND SUSPENSION IN LOTUS
RACE CARS TO THE POINT THAT FAILURE
IN USE WAS INEVITABLE.

…AND RE-ENGINEERING EVERTHING
UPWARD FROM THOSE PRINCIPLES TO
ACHIEVE TOTALLY NEW AND SUPERIOR
DESIGNS. ACTUALLY, NOTHING COULD
HAVE BEEN FURTHER FROM THE
TRUTH…

“Colin was extremely sharp, clever and quick-
witted, and very charismatic, but not a really
great engineer or designer. He had a few
principles which he pursued to great effect,
such as light weight…but he never had a really
close grasp of fundamental principles. Perhaps
he might have had if he had more time to learn.
But in his hectic and unscrupulous life it was
quicker to rely on other people to whom he
gave minimum credit.”
Charles Bulmer

…WHAT WOULD BE THE RESULT
IF SOMEONE WERE TO RETURN
TO FIRST PRINCIPLES AND
DESIGN AN AUTOMOBILE
FROM A PROFESSIONAL MASS
PROPERTIES ENGINEER’S
VIEWPOINT ?!?

NEWTON’S SECOND LAW:
F = m a

…INCLUDE THE CONCEPT OF “EFFECTIVE
MASS”:
F = me a
74h SAWE International Conference 9

TEXT
Wt = Weight of the vehicle (lb).
g = Gravitational constant, “g” = 32.174 ft/s2.
I1 = Rotational inertia about front axle line (lb-ft2).
I2 = Rotational inertia about the crankshaft axis (lb-ft2).
I3 = Rotational inertia about transmission 3rd motion axis
(lb-ft2).
I4 = Rotational inertia about rear axle line (lb-ft2).
TR = Transmission gear ratio (dimensionless).
AR = Axle gear ratio (dimensionless).
RD = Dynamic rolling radius at drive wheels (ft).

A REDUCTION OF “I1” AND “I4”:
1) REDUCES WEIGHT MASS
2) REDUCES EFFECTIVE MASS
3) REDUCES UNSPRUNG MASS

ONE FOURTH THE WEIGHT:
Whalf / Wfull = ( π R2 t / 4) /  π R2 t = ¼
ONE SIXTEENTH THE ROTATIONAL INERTIA:
Ihalf / Ifull = ( π R4 t / 32) / ( π R4 t / 2) = 1/16

WEIGHT OF TIRES, WHEELS, ETC. IS NOW:
8W8 / 4W4 = (8 π R2 t / 4) / 4 π R2 t = 1/2
AND THE ROTATIONAL INERTIA IS NOW:
8I8 / 4I4 = (8 π R4 t / 32) / (4 π R4 t / 2) = 1/8

 REEVES OCTOAUTIO – 1911
 PANZERSPAHWAGEN – 1942
 PAT CLANCY SPECIAL – 1948
 AVS SHADOW – 1970
 ELF TYRRELL P34 – 1975
 MARCH 2-4-0 – 1976
 WILLIAMS FW08B – 1982
 COVINI C6W – 2004
 KEIO UNIVERSITY ELIICA - 2004

21
74h SAWE International Conference

22
74h SAWE International Conference

PERFORMANCE COMPARISON OF:
BASELINE VEHICLE – KNOWN ENTITY
WITH:
“ADVANCED CONCEPT” – DEVELOPED
FROM BASELINE

TRIED TO AVOID ANY CHANGES NOT ESSENTIAL TO
TRANSITION FROM 4 FULL SIZE TIRES TO 8 HALF
SIZE TIRES.
HOWEVER:
1) HAD TO REDUCE SPRING STIFFNESS BY HALF AND
RESIZE SUSPENSION, 1 INCH LOWER.
2) HAD TO KEEP FULL SIZE BRAKES AND INCREASED
NUMBER TO EIGHT & MOVED INBOARD.
3) HAD TO MAKE BOTH REAR AXLES DRIVE (“LIVE”)
AXLES.
4) HAD TO CHANGE ORIENTATION OF ENGINE
FROM LONGITUDINAL TO TRANSVERSE.

1) WEIGHT: -0.3% 2) EFFECTIVE WEIGHT: -1.5%
3) ROLL RESIST: -55.1% 4) LOAD CAP: -17.7%
5) TRACTION: +5.1%
6) AERO DRAG: -14.6% 7) AERO LIFT: +15.0%
8) HYDROPLANING: Vc : -14.5%, Ls: -51.6%
9) TIRE LIFE: -49.8% 10) STANDING WAVE: -9.4%
11) SSF (OVERTURN RESISTENCE): +13.9%
12) ROLL GAIN: -8.9% 13) LAT ACCEL: +44.1%
14) DIRECTIONAL STABILITY: Kus = 6.85 vs. 0.20 deg, Vchar
= 32.6 vs. 188.3 mph, SM = 0.09 vs. 0.02
15) TRANSIENT RESPONSE: DIY = 0.74 vs. 0.75, AYR/ω =
1.185 vs. 1.003 16) ROAD SHOCK: -49.3%
17) ROAD CONTACT: BUMP -6.0%, DIP +34.6%
20) GYROSCOPIC REACTIONS: -80.5% front, -64.0% rear
21) FUEL ECONOMY: HIGHWAY +6.3% / CITY +3.3%

1) PRODUCIBILITY
a) TIRE PROCUREMENT
2) MARKETIBILITY
a) STYLING

FIVE MINUTES ARE ALLOCATED FOR
ASKING QUESTIONS OF THE AUTHOR
Alexandria, VA, 18-22 May 2015 32

Lastly, it should be noted that the “advanced concept” as presented
herein does not represent the pinnacle of achievement, and would
seem even more compelling when subjected to further development.
The “distributed traction” characteristic of the “advanced concept”
lends itself naturally to take best advantage of the benefits of
“distributed drive” as proposed by Hao, Chen, and Wang in their
paper, and as demonstrated by Keio University with their Eliica. That
the automobile of the future will have complete electronic control over
braking, drive, roll, pitch, ride, and stability seems certain, and the
mass properties driven configuration of the “advanced concept”
represents a complementary means to physically employ that new
technology to greatest advantage. Many have gone a part of the way to
this goal, but at present it still remains a place “where none have gone
before.”
FURTHER DEVELOPMENT ?

“…friction would be off the chart when the thing turns......or tries to! And the weight of four more tires, wheels and related suspension and
steering bits would so negatively impact fuel economy that it would more than offset the reduction in rolling resistance. "Rolling resistance"
is just one small variable in the overall “…friction would be off the chart when the thing
turns......or tries to! And the weight of four more tires, wheels and related
suspension and steering bits would so negatively impact fuel economy that it
would more than offset the reduction in rolling resistance. "Rolling resistance"
is just one small variable in the overall efficiency equation...”
Bob Lutz...”
[1] 14 June 2014
[1] Robert Anthony Lutz (1932- ) has served as Executive Vice President for BMW, Executive Vice President of Ford Motor Company,
Head of Chrysler Global Product Development, and Vice Chairman of Global Product Development at GM. He retired from GM on 2 May
2010, and now heads his own consulting firm. In an E-mail exchange this author made reference to the advantages of the “advanced
concept”, and thereby received the comment as quoted.

“…friction would be off the chart when the thing turns......or tries to! And the weight of four more tires, wheels and related suspension and
steering bits would so negatively impact fuel economy that it would more than offset the reduction in rolling resistance. "Rolling resistance"
is
The Edsel may have failed for insubstantial reasons, but reasons which
are significant in the marketplace. For the “advanced concept” to be
marketable reasons of that type have to be addressed. As noted in
Chapter 2, simply mating conventional automotive architecture with such
small wheels (not to mention an unusual number of them to boot) results
in an appearance certain to found “silly” and reminiscent of a “kiddie
car” or “small trailer”. Present day styling trends emphasize large wheels
and tires, even to the point of decreasing performance, as demonstrated
by the Car and Driver “plus-sizing” study. The styling has to be of “an all
new car design” paradigm in accord with the all new configuration
paradigm, and it has to appeal to the emotions; an emotional commitment
generally has to precede (or supersede) the rational for mass appeal to be
attained.

Mass Properties & Advanced Automotive Design

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