Topic 1.2 – The complex Machine Unit 4 – Mechanical Systems

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?!

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.

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

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

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?

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

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

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

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

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

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

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.

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

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.

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