Category: Photos

MONDAY

• Introductions, students shared the most memorable thing from Professor Arnold’s previous presentation

Guest speaker: Bill Becker (architect, economist, engineer, motorcyclist) on Motorcycle Wheels

• Why do motorcycles fail? Under-engineered, material failure. Reverse engineering can make materials stronger/faster
• Focus: motorcycle wheel
• History of wheel
  • First wheel: something round. Stone, wood.
  • Wooden rim, spokes: not used on motorcycles
  • 1895 Germany: first motorcycle, basically a bicycle
    • Front wheel attached to hub, center point: axel, no brake
    • Rear wheel solid
  • Modern motorcycles: cast wheels > spoke wheels because labor is cheaper
  • Triumph Tiger Cub wheel: spokes, larger on one side for brake
• Topics: thinking as designers and engineers, material science, geometry, engineering and stress tests
• Terms
  • Mass: how much matter is in something, gives things weight, intertia and momentum (energy needed to start/stop mass)
    • Motorcycle wheel has evolved to combat weight
  • Forces: acting on mass. Torque, etc.

• • Vectors: direction and amount of force in object
• Materials in a wheel: what they are and their properties

• • Strong steel, lightweight aluminum
• What forces do to structure diagram
• Materials can resist one force easily and buckle under another force
• Young’s Modulus: relationship between stress and strain

• • Stress: force, strain: reaction of material to force
  • Steel takes high stress, has high strain with little deformation
  • There’s a limit to elastic deformation (snaps back to original form), yield point to plastic deformation (not failure but doesn’t come back to original form) until point of fracture.
  • Rubber band example
  • Any material is a matrix of atoms
  • Steel plastic deformation: a wheel

• Littman – Airplanes: pressure + altitude
• Jon – Also why things fail: temperature. Bending a rubber band quickly = high temperature at the molecular level, so bending a rubber band slowly saves its elasticity more than bending it quickly
• Forces acting on a wheel diagram

• • Gravity caused by: load
  • Impact caused by: mass resisted by object
  • Acceleration: motor’s power torque goes to transmission to chain to sprocket to hub and torqueing transmitted from hub to rim through spokes
  • Deceleration: similar to accel: acting
• Most motorcycles: 36 spokes, British motorcycles 40 spokes
• Spokes work in tension, they’re not securely fashioned to the rim
  • When you’re accelerating hub, only half of the spokes are contributing
  • When they work in compression and spokes are too long, they’ll poke your inner tube
  • Spokes don’t go straight to center of wheel because there’s torque on hub and on where tire meets the road. Better when some are off set (so spokes can lengthen/shorten under strain)
  • Rim tension hub compression: spokes are in tension
    • Web of 40 objects, all of them in tension. Pre-stressed structure
  • Unique geometry of wheel: triangular sub structures
    • Spokes positioned forward and backward, left and right, creating triangles
    • Spokes in wheels also allow air movement: wheels not tipped over by wind

• • Bike wheel: brake applied on rim. Motorcycle: braking at hub, so spokes have to transfer work to rim
  • Spokes aren’t universal; they’re made for specific wheel on specific type of specific motorcycle
    • Inside and outside spokes
    • Tap the spokes: each give the same musical note, because every one is in harmony
  • Jon: all Triumph and British motorcycle repair videos are available to stream on Amazon Prime!
  • Wednesday reading: chapters 5 and 6

 

WEDNESDAY

Show and Tell!

• Littman: wheel with spokes (20 spokes leading, 20 trailing)
  • When spokes are in tension, hub rotates -> rim rotates

• Rupert: “Meg the 2001 MGF”

• • at first: didn’t start, very dirty

• • repair: trickle charge the battery

• • careless design in the “boot”, battery doesn’t fit in the bay so made a makeshift part
  • clean the engine, clean and check the fuel system (fuel injectors)
  • alternator belt was fixed
  • it ran!

• • It’s a negative ground battery (negative side connected to the frame)
• Jake: Bike

• • It’s a 2-stroke engine, so there’s no top end
    • Power stroke every two strokes, so if there’s a compression problem, it’s bad
    • Problems with fuel being pumped in
  • Spark plug worked
  • Got it running
  • Recently got a chain breaker
    • Master link: the one section of the chain that can be manually detached to fix the chain
  • 1:20 ratio of oil to fuel
  • Shearing issue
  • 110 cc engine
  • 2 stroke: a little less than 2x power of 4 stroke
  • No battery, bump start it, shift and the clutch starts it
  • Mountain bike transformed with motorized kit
• Taylor: “Duster” car
  • Before: red car sitting in a field

• • After: green car, doors and fenders not on it right now

• • 3-18 specs of motor

• • Not original motor; it’s a racing engine
  • ’67 Shelby in the shop

• • Better heating/AC: more efficient, less space
  • Unibody car: doesn’t have a frame

• • Fuel injection: Holley Sniper
  • Gas mileage on truck: 18mpg
• Macey: Land Rover

• • Defender model, 110 inch wheel base
  • Leaks, hard to drive
• Kate: 1962 Buick Special, recently fixed up

• Fun fact: gas is currently $1
• Jon: motorcycle
• Anna: car

Reading: Chapters 5 and 6

• Motorcycle references
• Resistance to the flow: friction
• Voltage and current
• If you hold a bearing in the center and put compressed air into it, it will spin at high speeds and explode
• Self-absorption: digging too deeply into motorcycle repair (going out of your way to find problems to fix) vs. value of work
  • Better safe than sorry: fix it anyway
  • Caring too much vs Pirsig’s “idiot” not caring enough. There’s a middle ground
• Silicon Valley work benefits: Google water, swimming pools, laundry service, college education at work
  • Attracting workers, keeping them there, keeping them at work longer to increase work hours/productivity
• Teamwork vs individual work as a member of the crew
• Happiness at work: a good job “satisfies the desire to know”
• Can you find fulfillment in having knowledge but not applying it?

For next week: finish Shop Class as Soulcraft