Mechanisms 👍 Flashcards
What are mechanisms
•They make a job easier to do.
•They involve some kind of movement.
•They involve some kind of force.
•They need an input to make them work.
•They produce some kind of output.
A mechanism is a system of moving parts that performs some function. They are used to reduce the effort in relation to work
What is a lever
A lever is a long, rigid object with a pivot somewhere along its length.
•The pivot is sometimes called the fulcrum.
1st class lever
Class 1 levers have the load at one end, the effort at the other and the fulcrum in the middle.
•E.g.: A workman pushing a trolley. Or scissors or a crowbar.
I Effort
\/
—————————————
I /\
I Fulcrum
\/
Load
2nd class lever
Class 2 Levers have the load in the middle and the effort and fulcrum on the outside.
•E.g.: A gardener lifting a wheelbarrow
3rd class lever
Class 3 levers has the fulcrum at one end, the load and the other and the effort somewhere in the middle.
•E.g.: A fisherman catching a fish. Or tweezers
How can we remember the lever classes
FLE
123
What is a rack and pinion gear system
The ‘pinion’ is the normal round gear and the ‘rack’ is straight or flat. The pinion rotates and moves the rack in a straight line - another way of describing this is to say ‘rotary motion’ changes to ‘linear motion’.
Worm and wheel gear system
The worm gear is usually found on an electric motor.
For one rotation of the worm the wheel rotates by one tooth
Bevel gears system
Gears are cone-shaped. The angle is known as a bevel. They transfer rotary motion through 90 degrees.
What are the 4 types of motion and how do they move
Linear motion is straight line motion
•Reciprocating motion is straight line motion going both forwards and backwards
•Rotary motion is going round and round
•Oscillating motion swings back and forward about a pivot
Now name some types of mechanisms
Levers and linkages
Wheels
Pulleys
Gears
What are three basic build blocks of mechanical control
Input. The input is usually a force and initiates the process.
Process. The process will change the magnitude or direction of the force.
Output The output put is what performs the desired task
For starting a car what is the
Input
Process
And output
Foot on pedal
Mechanisms allow petrol into engine
Car moves
Sum up what a mechanism can do
• Has an input, process and output
• Can change the direction in which a force acts
• Can change the size of the force
• Can change the place where the force acts
What are gears
Gears are wheels with teeth which mesh to transmit rotary motion. When two or more gears mesh it is called a gear train. There are two types: Simple and Compound.
