Drew Somers, Craig Baron, Rebecca White

Webster’s Dictionary defines the liger as "half lion, half tiger, all terror."

(as drawn by Napoleon Dynamite)

Goals

• Carry up a bunch of weight in under 5 minutes

• Aiming for a time of 4 minutes (240 secs) up the ramp

Methods

• Slow and steady, so that all time and energy is spent transporting payload

• Light vehicle so that minimal energy is spent transporting the car itself

• Rigid vehicle frame so that energy is not wasted in flexing

Options

• Belts vs. gears

• Size of wheels

• Shape of car

• Weight distribution

• 4 wheel drive

• Pulling weight up

Belts vs. Gears

• Considered belts vs. gears:– Belts are about 98% efficient– Belts can slip if there is not enough constant

tension, is too much weight• Can solve this with teeth or sticky substance

– Gears lose about 2% efficiency with every reduction

• If we use gears, we should aim for fewer reductions: just one or two (larger gear ratio)

Wheel size

• Wheels are just another gear, so we have to figure them into the gear ratio.

Shape of Car

• Rectangular is easy, stable, and basic

• Trapezoid is lighter, race car shaped– With drive wheels set

wider, steering is more stable?

• Fish shape is just awesome.

Weight distribution

• Considered putting more weight over drive wheels for traction, but front wheels will need traction too to keep the car on course

• Weight should be over both wheels– More traction = more efficiency and straighter

course (won’t be set off course by sand or dirt)

Discarded Ideas

• Pull weight up via winch– Would give more flexibility in pulling up multiple loads– How would you transfer power from the wheels to the

winch once the vehicle reached the top of the ramp?– Torque would vary as more string wound around

winch, increasing the power required of the motor as the batteries’ energy was depleted (ideally it would be the other way around)

• Four wheel drive– Would give more power, but because of slipping or

slightly different gearing, the wheels might go at different speeds, which would mean that the motor would be working against itself.

Ramp length• Angle of ramp = 4.48 degrees

• Ramp is 9.754 m long

• We aim to go up it in 240 seconds

• Our target velocity is .041 m/s (or 4.1 cm/s)

.762 m

9.754 m

How much weight will we carry?

• We don’t know yet!

• We need to know how the battery interacts with the motor before we can feel comfortable making any calculations.

• But it will be a lot.

• Somewhere around 300 kg.

Summary

• Slow and steady

• Light vehicle

• Still deciding on gears vs. belt

• Need more info before making more predictions and plans

• We hope to do best at the competition for total weight brought up.