Presentation on theme: "Design Project Motorized Vehicles!. Bicycles How many of you ride a bicycle that allows you to change gears? How do you use the gears when riding."— Presentation transcript:
Bicycles How many of you ride a bicycle that allows you to change gears? How do you use the gears when riding a bicycle? What do gears do on a bicycle?
Terminology Gear: we will use this term to refer to an individual gear Sprocket: a gear that is connected to another gear with a chain Pedal Sprockets: Sprockets connected to the pedal crank Wheel Sprocket: sprockets on the rear hub Derailleur: mechanism that moves a chain
Gear and Gear Combinations Bicycles are often identified by the number of gears or speeds they have A ten speed bicycle has 2 sprockets on the pedal crank and 5 sprockets on the rear wheel hub which allows for 10 different combinations! Mountain bikes have 3 pedal sprockets and 7 rear wheel sprockets which allows for 21 different combinations!
Things to Consider! How is the motion of the pedal transferred to the rear wheel? The pedal sprocket drives the chain, which turns the wheel sprockets; both turn in the same direction
What sprocket combination would you use to go as fast as possible? The largest pedal sprocket with the smallest wheel sprocket
Why don’t we use this sprocket combination all the time? It takes a lot of force to get this combination going
What sprocket combination would you use to go up a steep hill? The smallest pedal sprocket with the largest wheel sprocket (low gear)
Why don’t we use this sprocket combination all the time? The bicycle doesn’t move very far with each pedal rotation
The sprocket combination easiest to pedal is……. The sprocket combination hardest to pedal is…….
WHAT DO GEARS DO! Gear allow the rider to change the number of times the rear wheel rotates for each pedal rotation This affects the distance the bicycle travels with each pedal rotation Gears also allow the rider to change the force with which the rear wheel turns