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Mass Properties & Advanced Automotive Design

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The intent of this presentation is to show that a vehicle designed in true accordance with the balanced viewpoint of a professional mass properties engineer may not only demonstrate superior acceleration, braking, and handling, but superior ride, stability, fuel economy, and safety as well. If a design begins with the first principles of how mass properties affect automotive performance in all its aspects , and is optimized accordingly in an integrated manner, then the resulting advanced automotive design may truly “go where none have gone before”.

Published in: Automotive
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Mass Properties & Advanced Automotive Design

  1. 1. Brian Paul Wiegand, PE 74TH SAWE International Conference on Mass Properties Engineering Alexandria, VA, 18-22 May 2015
  2. 2. …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
  3. 3. 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. 74th SAWE International Conference 3
  4. 4. …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. 74th SAWE International Conference 4
  5. 5. …AND RE-ENGINEERING EVERTHING UPWARD FROM THOSE PRINCIPLES TO ACHIEVE TOTALLY NEW AND SUPERIOR DESIGNS. ACTUALLY, NOTHING COULD HAVE BEEN FURTHER FROM THE TRUTH… 74th SAWE International Conference 5
  6. 6. “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 74th SAWE International Conference 6
  7. 7. …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 ?!? 74th SAWE International Conference 7
  8. 8. NEWTON’S SECOND LAW: F = m a 74th SAWE International Conference 8
  9. 9. …INCLUDE THE CONCEPT OF “EFFECTIVE MASS”: F = me a 74h SAWE International Conference 9
  10. 10. TEXT 74h SAWE International Conference 10 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).
  11. 11. A REDUCTION OF “I1” AND “I4”: 1) REDUCES WEIGHT MASS 2) REDUCES EFFECTIVE MASS 3) REDUCES UNSPRUNG MASS 74h SAWE International Conference 11
  12. 12. 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 74h SAWE International Conference 12
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  15. 15. 74h SAWE International Conference 15 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
  16. 16.  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 74h SAWE International Conference 16
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  23. 23. PERFORMANCE COMPARISON OF: BASELINE VEHICLE – KNOWN ENTITY WITH: “ADVANCED CONCEPT” – DEVELOPED FROM BASELINE 74h SAWE International Conference 23
  24. 24. 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. 74h SAWE International Conference 24
  25. 25. 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% 74h SAWE International Conference 25
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  31. 31. 1) PRODUCIBILITY a) TIRE PROCUREMENT 2) MARKETIBILITY a) STYLING 74h SAWE International Conference 31
  32. 32. FIVE MINUTES ARE ALLOCATED FOR ASKING QUESTIONS OF THE AUTHOR 74TH SAWE International Conference on Mass Properties Engineering Alexandria, VA, 18-22 May 2015 32
  33. 33. 74TH SAWE International Conference on Mass Properties Engineering Alexandria, VA, 18-22 May 2015 33 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 ?
  34. 34. 74TH SAWE International Conference on Mass Properties Engineering Alexandria, VA, 18-22 May 2015 34
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  36. 36. 74TH SAWE International Conference on Mass Properties Engineering Alexandria, VA, 18-22 May 2015 36 “…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.
  37. 37. 74TH SAWE International Conference on Mass Properties Engineering Alexandria, VA, 18-22 May 2015 37 “…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.

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