Reading Assignment
- Shop Class as Soulcraft: Chapter 4
In-Class Discussion
Zen and the Art of Motorcycle Maintenance
Chapter 10:
- Theme: Scientific method – Discussion of Phaedrus’ qualms with the scientific method: From one hypotheses, many emerge; it is virtually impossible to test them all. The more we test, the more we move towards chaos, rather than away from it.
- Theme: Scientific method (cont.) – The purpose of scientific method is to select a single truth from among hypothetical truths.
Chapter 11:
- Theme: Classical vs. romantic; West vs. Orient; theoretic vs. esthetic
- Metaphor: Ascending into high country ~ “Climbing” arguments. Realization that philosophy tops the hierarchy of knowledge.
- Theme: Philosophy – Kant, Hume: Hume argues that sensory information is what matters, and Kant floats a priori notion of viewing the world, where we have preconceived ideas of what things are.
- Mechanics: Engine backfire – May result from lack of oxygen when mixture runs too lean. Exhaust pipes get hot and engine overheats. Can adjust idle – two parts – adjust mixture and then speed.
Calculations
Finding the engine torque:
Rear wheel – coulomb friction/slipping force:
- We calculated the torque necessary to slip the rear wheels. (We used the friction coefficient of rubber on asphalt (~1) and assumed a total burden of 400 lbs on the wheels.)
- We know F = μ*n , that the frictional force is equal to the friction coefficient multiplied by the normal force (200 lbs on the rear wheel), so the force needed is 200 ft. Since W = F*d (work = force*distance), and the radius of the back wheel is 1 ft, the torque at the rear wheel is 200 ft*lbs.
Engine torque:
- The engine torque multiplied by the gear ratio is this rear wheel torque, 200 ft*lbs (Energy is conserved in mechanical systems.) The gear ratio, which is reflected in the ratio of rates at which the flywheel and rear wheel sprocket turn (6000 RPM: 840 RPM), comes out to be ~7.13. The engine torque comes out to be 200 ft*lbs/7.13 = 28 ft*lbs.
High gear vs. low gear:
- The mechanical advantage is best in low gear. Using the Triumph manual, we found that the gear ratio in low gear was 21.14 as opposed to that in top gear, which was 7.13. This means that in low gear, about one-third (~21.14/7.13) of the motor torque is required to provide the energy necessary to slip the wheels.
Lab
- Frames: Wet-sanded gas tank. (Advantage of wet-sanding: keeps particles off paper; prevents paper from getting clogged)
- Bottom end: Cleaned engine case. Tested oil pump using mock distributor to spin gear and start pump. Checked springs (4) and balls (2) comprising check valves.
- Electrical: Analyzed measurements of gap in spark advance.
- Top: Parts cleaning.
S.Y.