Gearing

1
Gearing

• Increase speed or increase torque

2
Gears change the speed at which kinetic energy is
delivered.

• Gears generally are used for 4 things
• Increase speed (or Gearing up)
• Decrease speed (or Gearing down)
• Change direction (clockwise to anticlockwise or
  VV)
• Transfer the motion (Gear trains)

3
Gearing UP

• Gearing Up means the energy is transferred
  quickly but remember you never get something for
  nothing. More speed means less force (or more
  precisely Torque which is a combination of Force
  and radial distance)

4
Gearing Down

• Gearing Down means slower but stronger. Great for
  pushing objects or carrying heavy weights. You
  get better control too when using power levels
  with LEGO motors.

5
Changing Direction

• Changing Direction is useful for opposing
  movements such as paper feeder.
• Using Gear trains to transfer the motion further
  away.

Idler gears
6
Bicycle Gears

• The gears at the front are called the chain
  wheels. Most bikes have two or three chain
  wheels.
• Attached to the rear wheel is the freewheel. Most
  bikes have 5 to 9 free wheels.

7
Working out your speed
26 wheel

• The task of gears is to let you change the
  distance that the bike moves forward with each
  pedal stroke
• For example, a normal bicycle has wheels that are
  26 inches (65 cm) in diameter. The "lowest" gear
  ratio on the bike might be a front chain wheel
  with 22 teeth and a rear gear having 30 teeth.
  That means that the gear ratio is 0.73-to-1. For
  each pedal stroke, the rear wheel turns 0.73
  times. In other words, for each pedal stroke, the
  bike moves forward about 60 inches (1.5 meters)
• (about 3.4 mph / 5.4 kph at a 60-rpm pedalling
  rate).

30 teeth
22 teeth
Distance moved per stroke Gear ratio x
circumference of wheel 22 x 2pr 22 x 2 x
3.14 x 32.5 30 30 150cm Speed
distance x pedalling rate 1.5 x 60
x 60 5.4 km/h 1000
8
The "highest" gear ratio on the bike might be a
front chain wheel with 44 teeth and a rear gear
having 11 teeth. That creates a 4-to-1 gear
ratio. With 26-inch wheels, the bike moves
forward 326 inches with each pedal stroke. At a
60-rpm pedalling rate, the speed of the bike is
18.5 mph (30 kph). By doubling the pedalling rate
to 120 rpm, the bike has a maximum speed of 37
mph (60 kph). A range of 3.4 mph to 37 mph is
fantastic, and it lets the rider climb the
steepest hill very slowly or race almost as fast
as a car! That is why a bike has gears.