Notes by Noelle Goudy
Assignment for Tuesday: Think of questions for Professor Martinelli
Assignment for Thursday: Introduction and chapter 1 of Shop Class as Soulcraft
Announcements:
- Get stuff to be powder-coated or chromed together
- We might be missing frame parts
- Make sure we have anything that will be painted ready to be powder-coated
- Example: battery box
- Next Tuesday: Professor Martinelli
- Come up with a set of questions for him
- Week four scribe: take notes next week
Housekeeping:
- Ricky: Found a taillight at the bunker and got that working; checked the spark plug on the red motorcycle
- Noelle: With Alex, assembled carburetor; flooded the carburetor and it leaked; lathed out the top plate because it was warped; reattached it and it no longer leaked
- Eric: Determined which front and back hub to use; began plugging it up for powder coating
- David: With Alex, found that half of a split-ring washer is missing (but there was one at the bunker)
- Connor: With Grace, cleaned the engine plates and put them back together; going to sandblast it today
- Charlie: Tried to disassemble the headlight; put it in a new chromed case
- Brendan: Cleaned the light; organized parts for powder coating
- Alex: Worked with Charlie
- Grace: Worked with Connor
- Jordan: With Emily, put together the jacks for the wheels
- Julianne: With Charlie and Ricky, went to the bunker; finished cleaning top end parts
- Sarah: With Ricky, attached the light and tested it; watch the dem for the spark plug
- Jake: Searched on ebay
- Hannah was out
Tiger Cub Engine Calculations Reading:
- Octane is C8H18
- Air is 20% O2
- Nitrogen goes in and out of engine
- While it is a spectator, it still starts to react to form NOx
- A problem with engines
- Sulfur present – emissions
- Carbon dioxide and water vapor are also products
- Energy release is 44,400 J per gram octane
- Air to fuel ratio is about 15:1 by weight
- 14.7:1 grams in industry
- What limits the amount of power output is the amount of oxygen
- Could make the engine larger
- Compress the air
- Super/turbocharging
- Use pure oxygen or
- Nitrous oxide
- Nitromethane
- ⅕ liter -> .257 g of air and .0171 g fuel yields 759 J
- 37,950 Watts out of the engine (100% efficiency)
- 50.9 horsepower (if the engine was fully efficient)
- Engine has about 20% efficiency in actuality
Demo:
- Two cylinders (pipettes) with a platinum wire
- They are bubbling with the top open
- When the top is closed, the bubbles cannot escape
- The gas inside the left cylinder is going down more quickly than the right
- This cylinder holds the hydrogen (H2O -> two moles hydrogen for only one mole oxygen)
- The gas inside the left cylinder is going down more quickly than the right
- When the hydrogen got to the bottom, a spark was lit and the ping pong ball moved upwards about a foot and a half
- The product is water
- The pressure increases because of heat (PV=nRT)
- Thus, the ball is launched
- On the second launch, the ball went up about three feet
- On the third launch, the ball went up about two and a half feet
Brake dynamometer:
- A device that allows you to figure out the torque and power of a motor
- A rope is wrapped around the shaft of the motor (called a rope brake)
- This motor is an electric motor
- The ropes are pulled tighter and the differences of the tensions in the ropes will allow you to find the torque as a function of speed for this motor at a certain voltage
- The speed of the motor will also be recorded
- As the rope is pulled tighter, the engine slows down
- For an electric motor, torque vs speed is linear
- The torque is greatest at stall
- Power = Force (Torque) * Velocity
- To get a power vs speed graph, multiply the two axes together and graph with respect to speed
- The graph is a parabola (opening downwards)
- The greatest power to the motor will be at the center of the parabola, which is half of the possible velocity
- Homan force vs velocity is called the Hill Curve
- Concave and with a downward slope
- The power vs velocity graph for a human on a bike also has a peak, where it will be easiest to get up a hill
- Efficiency of an electric motor would be the power curve divided by the force (torque) curve
- Graphed with respect to velocity, it is a straight line with a positive slope
- The most efficient is using the least amount of energy
Questions for Professor Martinelli:
- Where does air flow play a role in our motorcycle?
- Carberation
- Cooling
- Windage in the engine
- Exhaust
- Aerodynamic drag
- Streamlining shapes
- On the wheels
- Fluid in the engine
- Lubrication