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bike-project_complete.ppt

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bike-project_complete.ppt

  1. 1. bike1.ppt - 1 of 5 product dissection 09.12.2022 The Bicycle SADDLE SEAT POST GRIPS HANDLEBAR BRAKE LEVER BRAKE CABLE TOP TUBE CABLE STOP SEAT BOLT SEAT TUBE TIRE TREAD SIDEWALL REAR DERAILLEUR TENSION PULLEY DOWN TUBE FRONT DERAILLEUR HEAD TUBE CABLE YOKE FORK TUBE FORK DROPOUTS HUB FLANGE HUB SPINDLE SPIDER CHAINRINGS CHAIN TOE CLIP PEDAL BRAKE SPOKE RIM STEM STEM BOLT GEAR LEVER Used by permission, Cannondale Corp, ©1996
  2. 2. bike1.ppt - 2 of 5 product dissection 09.12.2022 Bicycle Module Contents 1. Introduction, History and Development of Bicycles 2. Biomechanics of Cycling 3. Basic Construction and Design
  3. 3. bike1.ppt - 3 of 5 product dissection 09.12.2022 Bicycle History 1490 DaVinci drawing 1815 Hobbyhorse by Karl von Drais, Germany
  4. 4. bike1.ppt - 4 of 5 product dissection 09.12.2022 1839 Treadle cycle by Kirkpatrick Macmillan, Scotland 1861 Velocipede by Pierre Michaux, France
  5. 5. bike1.ppt - 5 of 5 product dissection 09.12.2022 In the quest for more speed, the velocipede evolved into the “ordinary” The “ordinary” 1.5 m
  6. 6. bike1.ppt - 6 of 5 product dissection 09.12.2022 1885 Rover “Diamond Frame” Safety by John Starley, England 1888 Pneumatic tire by John Boyd Dunlop, Scotland 1895 Derailleur gears 1895 - 1970 Nothing significant happened in the development of the bicycle Modern Rear Derailleur Bicycle Evolution - continued Rover Safety Bicycle
  7. 7. bike1.ppt - 7 of 5 product dissection 09.12.2022 The Revolution since 1970  New materials (composites, titanium, aluminum)  Cross-over technologies (aircraft, skiing)  Mass production  Increased environmental consciousness  Bikes are “cool” again,  Mountain bikes  Human powered vehicles
  8. 8. bike1.ppt - 8 of 5 product dissection 09.12.2022 The Bicycle Today  The world’s 1 Billion bikes outnumber cars by two to one  Bike production outnumbers car manufacture by 3 to 1  In Asia alone, bicycles transport more people than do all the cars worldwide  The bike is the most energy-efficient mode of transport: one US study found that to cycle one mile burns 35 calories, to walk uses 100 calories, while a car’s engine burns 1,860 calories
  9. 9. bike1.ppt - 9 of 5 product dissection 09.12.2022 Bicycle Facts - continued  Each mile of highway consumes about 25 acres of land  The average motorist spends four hours a day either driving, maintaining, or earning the money for a car  Americans spend a billion hours a year stuck in traffic, wasting two billion gallons of gas at a cost of $10-30 billion  In one hour, a lane of highway can carry twice as many people riding bikes as those traveling by car (reference 2, pp 10-11)
  10. 10. bike1.ppt - 10 of 5 product dissection 09.12.2022 Cycling Bio-Mechanics  Basic Terminology (fill in the details as a class)  Work  Energy  Power  Force  Torque
  11. 11. bike1.ppt - 11 of 5 product dissection 09.12.2022 Things I’ve always wondered about 1. Why do we shift gears on a bicycle? 2. What determines how fast our bike goes for a given power input? 3. Are toeclips worth the trouble?
  12. 12. bike1.ppt - 12 of 5 product dissection 09.12.2022 Newton’s Second Law F = ma = m dv/dt F1 F2 F3 F4 m a C.G. A Rigid Body
  13. 13. bike1.ppt - 13 of 5 product dissection 09.12.2022 External Forces acting on Bike RIDER WEIGHT WIND RESISTANCE HANDLEBAR FORCE BIKE WEIGHT GROUND REACTION FORCES PEDAL FORCE
  14. 14. bike1.ppt - 14 of 5 product dissection 09.12.2022 Force Transmission Purpose of bike transmission is to convert the high force, low velocity at the pedal to a higher velocity (and necessarily lower force) at the wheel. The power at pedal (F1 x V1) equals the power at the wheel (F4 x V4) (assuming no friction losses) L1 L2 L3 F1 F2 F3=F2 F4 L4 F4 = F1 x ?
  15. 15. bike1.ppt - 15 of 5 product dissection 09.12.2022 Pedal Forces (ref 3, pg 105) A clock diagram showing the total foot force for a group of elite pursuit riders using toe clips, at 100 rpm and 400 W. Note the orientation of the force vector during the first half of the revolution and the absence of pull-up forces in the second half. used by permission of Human Kinetics Books, ©1986, all rights reserved
  16. 16. bike1.ppt - 16 of 5 product dissection 09.12.2022 Pedal Force Components Fr = Total Foot Force Fe=Effective Force (causes useful Torque) The total foot force can be resolved into vector components PEDAL CRANK
  17. 17. bike1.ppt - 17 of 5 product dissection 09.12.2022 Effective Pedal Force (ref 3, pg 106) EFFECTIVE FORCE RESULTANT FORCE UNUSED FORCE NEGATIVE EFFECTIVE FORCE CRANK ANGLE (Degrees) FORCE (N) 0 180 360 used by permission of Human Kinetics Books, ©1986, all rights reserved
  18. 18. bike1.ppt - 18 of 5 product dissection 09.12.2022 Human Power Output  Most adults can deliver .1 HP (75 watts) continuously while pedaling which results in a typical speed of 12 mph  Well-trained cyclists can produce .25 to.40 HP continuously resulting in 20 to 24 mph  World champion cyclists can produce almost .6 HP (450 watts) for periods of one hour or more - resulting in 27 to 30 mph Why do the champion cyclists only go about twice as fast if they can produce nearly 6 times as much power?
  19. 19. bike1.ppt - 19 of 5 product dissection 09.12.2022 (ref 3. pg 112) Human Power Output The maximum power output that can be sustained for various time durations for champion cyclists. Average power output over long distances is less than 400 W. used by permission of Human Kinetics Books, ©1986, all rights reserved
  20. 20. bike1.ppt - 20 of 5 product dissection 09.12.2022 The Forces Working Against Us Drag Force due to air resistance: Fdrag =CdragV2 A Cdrag = drag coefficient (a function of the shape of the body and the density of the fluid) A = frontal area of body V = velocity and since: Power = Force x Velocity This means that, to double your speed requires 8 times as much power just to overcome air drag (since power ~ velocity3)
  21. 21. bike1.ppt - 21 of 5 product dissection 09.12.2022 Some Empirical Data (ref 3, pg 126) Drag force on a cycle versus speed showing the effect of rider position. The wind tunnel measurements are less than the coast-down data because the wheels were stationary and rolling resistance was absent. used by permission of Human Kinetics Books, ©1986, all rights reserved
  22. 22. bike1.ppt - 22 of 5 product dissection 09.12.2022 Forces - continued  Rolling Resistance Frr=Crr x Weight  typical values for Crr:  knobby tires .014  road racing tires .004  Mechanical Friction (bearings, gear train)  absorbs typically only 3-5% of power input if well maintained
  23. 23. bike1.ppt - 23 of 5 product dissection 09.12.2022 Other Energy Absorbers  Hills (energy storage or potential energy)  Change in Potential Energy = Weight x Change in elevation (Dh) Dh Here, the rider has stored up energy equal to the combined weight of rider and bike times the vertical distance climbed.
  24. 24. bike1.ppt - 24 of 5 product dissection 09.12.2022 The First Law of Thermodynamics  Conservation of Energy, for any system: Energyin = Energyout +Change in Stored Energy SYSTEM Energy input Energy Output Internal Energy of System
  25. 25. bike1.ppt - 25 of 5 product dissection 09.12.2022 Now Put it All Together: Velocity = f [ power input (pedal rpm, pedal force), road slope, rider weight, bike weight, frontal area, rider position, gear ratio, tire type and inflation, maintenance ...] Your task: (as homework, due in one week, use computer (spreadsheet program like EXCEL) for analysis and presentation of results) 1. Using first law of thermodynamics, derive the relation between the relevant factors to calculate V (bike velocity). Clearly state all assumptions. 2. Generate a graph relating speed to hill grade (from 0% to 20%) for riders weighing 120, 140, 160, 180 and 200 pounds who are exerting a continuous power of 0.1 HP. 3. Determine the terminal velocity of the 160 lb rider coasting going down a 10% grade.
  26. 26. bike1.ppt - 26 of 5 product dissection 09.12.2022 Bicycle Construction and Design from ref. 4, used by permission of Rodale Press, ©1994, all rights reserved
  27. 27. bike1.ppt - 27 of 5 product dissection 09.12.2022 Look at one simple subsystem - frame tubing  This is an excellent example of the trade-offs inherent in the design process and the sometimes arbitrary decisions (not justifiable based on purely analytical terms) which are often made  There are lots of possibilities (variables) for even this simple element – material (steel, aluminum, titanium, composite, ...) – cross section shape » shape (square, round, oval or other) » hollow or solid » constant cross section, or variable  How do you handle all this information and make a proper choice ?
  28. 28. bike1.ppt - 28 of 5 product dissection 09.12.2022 Design Process 1. My first step in design - ASK QUESTIONS – intended use of product – desired or important performance qualities » for bike - low weight, riding efficiency, comfort, durability, low cost ... – potential failure modes – how does the part fit into overall system 2. Identify design variables (things you as the designer can specify) make a list here
  29. 29. bike1.ppt - 29 of 5 product dissection 09.12.2022 Design Process - continued 3. Quantify the performance qualities in terms of the design variables 4. Identify the constraints based on potential failure modes and performance qualities 5. Formulate a measure of the design’s “goodness” (quantitative if possible)
  30. 30. bike1.ppt - 30 of 5 product dissection 09.12.2022  6. Apply an appropriate design method for choosing the actual values of the design variables and then iterate – Trial and error (OK for simple problems) – Past experience (extrapolation or interpolation) – Intuition, dumb luck – Numerical optimization methods ( a necessity if the number of design variables and constraints are large) Design Process - continued
  31. 31. bike1.ppt - 31 of 5 product dissection 09.12.2022 Different Frame Construction Philosophies Cannondale - welded aluminum frames, hand crafted Specialized - steel or chrome-moly (a steel alloy), welded Trek - glued aluminum frames, or welded steel Bicycle companies tend to have different design philosophies, to give them a unique market “niche”
  32. 32. bike1.ppt - 32 of 5 product dissection 09.12.2022 Back to the Tube Let’s assume that the most important qualities of this tube are its: Design Variables:
  33. 33. bike1.ppt - 33 of 5 product dissection 09.12.2022 Back to the Tube Let’s assume that the most important qualities of this tube are its: – Low Flexibility (= high stiffness) – Low Weight (want as light as possible) – High Bending and Crush Strength – Long Life Design Variables: – Material – Wall thickness – Tube OD – Joining method (weld, glue, braze)
  34. 34. bike1.ppt - 34 of 5 product dissection 09.12.2022 Bike Tubing Better tubes are thicker at ends to give greater strength at joints How are these made? plain gage tube single-butted tube double-butted tube triple-butted tube from ref. 4, used by permission of Rodale Press, ©1994, all rights reserved
  35. 35. bike1.ppt - 35 of 5 product dissection 09.12.2022 Materials Issues  Why was aluminum used?  What are its advantages and disadvantages?  Other possibilities: – Steels » Low Carbon, High Carbon, Chrome-molybdenum, Stainless ... – Titanium – Magnesium – Carbon fiber composite (Carbon Fiber, Kevlar)
  36. 36. bike1.ppt - 36 of 5 product dissection 09.12.2022 Important Material Properties  Weight (density)  Stiffness (elastic modulus)  Strength (tensile strength, endurance limit)  Impact resistance (hardness)  Corrosion resistance  Joining  Recycling potential
  37. 37. bike1.ppt - 37 of 5 product dissection 09.12.2022 Material Properties Comparison Elastic Yield Tensile Density Brinell Cost Material Modulus Strength Strength lb/in3 Hardness $/lb Mpsi Kpsi Kpsi Aluminum 6061 T6 10 40 45 .10 95 7075 T6 10 72 82 .10 150 Steel 1040 HR (med carbon) 30 42 76 .283 149 1040 CD 30 71 85 .283 170 4140 HR (chrome/moly) 30 63 90 .283 187 4140 CD 30 90 102 .283 223 Graphite/Epoxy* 1-20 N/A 30-200 .06 HR = Hot Rolled CD=Cold Drawn * Actual properties depend on the amount of reinforcing material
  38. 38. bike1.ppt - 38 of 5 product dissection 09.12.2022 Static Strength results from a typical tensile test of a steel sample from Manufacturing Engineering and Technology, by S. Kalpaakjian, used by permission of Addison Wesley, ©1992, all rights reserved
  39. 39. bike1.ppt - 39 of 5 product dissection 09.12.2022 Cyclic Strength The fatigue properties are highly dependent on the material type. Steels have an endurance limit - a stress level which can be endured for an unlimited number of cycles (no fatigue). Aluminum does not have an endurance limit and fatigues no matter what the stress level. An aluminum bike must be built with extra strength to account for fatigue effects. 1045 Steel Endurance Limit 2014-T6 Aluminum alloy Number of Cycles, N Stress Amplitude, S (MPa) Kpsi 80 500 0 103 1010 0
  40. 40. bike1.ppt - 40 of 5 product dissection 09.12.2022 Cannondale Tube Cannondale chose: aluminum tubing, 1.75” OD, .085” constant wall thickness - a good compromise between weight and flexibility WALL THICKNESS - inches 0 0.05 0.1 0.15 0.2 0.25 WEIGHT FLEXIBILITY OD - 1.75”
  41. 41. bike1.ppt - 41 of 5 product dissection 09.12.2022 Bicycle Reverse Engineering  learn how to build them ourselves (without paying royalties for the design)  improve on existing designs if possible  another reason for reverse engineering - need to replace a part for which you have no drawing or technical information Let’s say we are trying to get a quick start in the bicycle business. We could buy a bunch of new bikes and “reverse engineer” them to:
  42. 42. bike1.ppt - 42 of 5 product dissection 09.12.2022 Reverse Engineering Process  Document the design (usually in the form of detailed engineering drawings) – Dimensions (metrology) – Materials (destructive or non-destructive measures) – Manufacturing processes – Estimate costs (materials, labor, etc)  Attempt to understand the design constraints and reasons for various design decisions

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