Mechanical Systems

1
Mechanical Systems

• Topic 2 Wheel and Axle, Gears, and Pulleys

2
The Wheel and Axle

• Two turning objects attached to each other at
  their centres. Turning one object turns the
  other.
• If you turn the larger wheel to move the smaller
  axle, you decrease the amount of effort you have
  to use, but you have to move the wheel a larger
  distance than the axle moves.
• Examples of this set includes door knobs and
  steering wheels.

3
Wheel and Axles Contd

• A bicycle wheel has an opposite setup. The rider
  moves the axle a smaller distance with more
  effort to move the large wheel a longer distance.
• A sprocket is special type of gear train where
  the gears do not touch but instead are connected
  by a chain. Examples include the front and back
  gears in a bike connected by the bicycle chain.

4
Gears

• Gears are special types of wheels and axle
  machines. Two wheels with teeth are placed
  besides each other. Moving one moves the other.
• A series of gears is called a gear train. The
  gear that sets the train in motion is called the
  driver gear. All other gears in the train are
  called follower gears.
• Multiplying Gear a larger driver gear turning a
  smaller follower gear allows for a large
  mechanical advantage and high acceleration (1st
  gear in a standard transmission)
• Reducing Gear a smaller driver gear turning a
  larger follower gear allows for a large amount of
  distance to be covered with each turn of the
  driver gear (5th gear in a standard
  transmission).

5
Speed Ratio

• Speed Ratio Distanceinput Distanceoutput
• The more teeth a gear has, the slower it turns in
  a speed train. Smaller gears with fewer teeth
  move faster.
• Speed ratio is the relationship between the speed
  of the driver gear and a follower gear.
• Speed ratio of driver gear teeth
• of follower gear teeth

6
Pulleys

• A pulley is made up of an axle and a rope. One
  end of the rope is attached to the load and the
  effort force pulls on one end pulling up the load
  with it.
• Pulleys are simple machines which change the
  direction of the effort force.
• There are two types of pulleys fixed (the axle
  attached to something that doesnt move) and
  movable (the axle is attached to a movable heavy
  weight)