1. Topic 1.2 – The complex Machine
Unit 4 – Mechanical Systems

2. The complex World
Simple machines are great, but in our complex world we NEED machines with an effort other than people.
Today, we are almost completely dependent on machines.
What would happen to us if we could not use machines?!

3. Complex Machines
Complex machines are devices that are made up of several simple machines that work together.
A system is a group of parts that work together to perform a function.

4. Example A bicycle is a system for moving a person around.
A subsystem is something within a system that have just one function. (subsystems work together to help the device accomplish what it was built to do)
BIKES
SYSTEM – Moving people around
SUBSYSTEM – Braking, Steering

5. Brakes use levers to increase the force your apply with your hands
Gears reduce the force that you need to apply
Pedals are levers that increase the force you apply to the wheel and axle

6. YOUR TURN Analyze the following mechanical device.
THE PENCIL SHARPENER
What is the function of the device?
How many subsystems can you identify in the device?
Do any of the subsystems contain a simple machine?

7. MACHINE
SIMPLE MACHINES
SUBSYSTEMS
Pencil Sharpener
Wedges
Wheel and Axle
Handle to turn
Blades to sharpen
Holder for shavings
Can Opener
Wedge
Lever
Handles to squeeze
Cutter to cut
Place that holds the can

8. Systems that transfer forces
A linkage is the part that transfers your energy from one part to another.
They transfer small amounts of energy
EXAMPLES:
Chain on a bike
Belts in car engines

9. A transmission transfers energy from engines to the wheels.
They transfer large forces

10. Subsystems that transfer energy
Energy needs to be converted from one subsystem to another so energy converters are used.
SOLAR ENERGY SOLAR PANEL ENERGY

11. Gears
Gears consist of a pair of wheels that have teeth that interlink.
When they rotate, one gearwheel transfers the turning motion and force to the other.
The larger the gearwheel, the more slowly it turns but it has a GREATER FORCE
The smaller the gearwheel, the more quickly it turns

12. How gears work Almost every device that uses spinning parts has gears
Gears control the transfer of energy in the system
In a bike the gears allow the rider to change and control the speed of the wheels

13. Driving vs. Driven
The driving gear is the gearwheel where the force is applied.
The driven gear is the gearwheel that moves as a result of the other gearwheels moving.

14. How gears affect speed
If the DRIVING GEAR is larger than the DRIVEN GEAR, the turning speed in the system increases.
The larger gear will turn around once and the smaller gear will turn around more than that.
Gears that increase the speed are called multiplying gears
EXAMPLE: Egg beater

15. Reducing gears decrease the turning speed in a device.
The driving gear is smaller than the driven gear
Parallel gears have two gears of the same size working together.

16. Summary Multiplying gear – large to small gears
Reducing gear – small to large gears
Parallel Gears – same size of gears