Mechanical Systems
How engineered products change movement: types of motion, linkages that change direction, gear trains and pulleys that pass on rotary motion, cams that create up and down movement, and bearings that reduce friction.
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Systems that move
Engineered products often need to change movement. A motor may only turn round and round, but the product might need something to move up and down, or in a straight line, or to change direction. Mechanisms such as linkages, gears, cams, pulleys and bearings do this work, taking one kind of movement in and giving another kind out.
Words for mechanisms
Learn these four terms before you study how movement is changed.
Three mechanisms
Each mechanism changes movement in its own way.
What it does to the movement
Top answers say what a mechanism does to the movement, not just its name. For a gear train, a larger driven gear turns more slowly but with more turning force. If the driven gear has twice as many teeth as the driver, the driver turns twice for every one turn of the driven gear.
Match the mechanism
- linkage
- gear train
- cam and follower
- bearing
- changes the direction or type of a movement
- passes on rotary motion using toothed wheels
- changes rotary motion into up and down motion
- reduces friction so a shaft turns smoothly
Match the type of motion
- linear motion
- rotary motion
- reciprocating motion
- oscillating motion
- movement in a straight line in one direction
- movement turning around in a circle
- movement backwards and forwards in a straight line
- movement swinging backwards and forwards along a curve
What does a cam do?
What does a cam and follower do?
- It changes rotary motion into up and down reciprocating motion.
- It passes rotary motion from one shaft to another without changing it.
- It reduces friction between two moving parts.
- It changes reciprocating motion into rotary motion.
Spot the types of motion
Select the TWO types of motion.
- Rotary motion.
- Reciprocating motion.
- Gear train.
- Linkage.
Order the movement
A toy uses a motor and a cam. Put the flow of movement in order, earliest first.
- A motor turns and produces rotary motion
- A gear train passes on the rotary motion
- A cam changes it into up and down motion
- The follower moves up and down
Summarise the mechanisms
A _____ is a set of rods pinned together that changes the direction of a movement. A _____ uses toothed wheels to pass on rotary motion, and a bigger gear turns more slowly. A cam turns rotary motion into _____ motion, which moves a follower up and down. A _____ reduces friction so a shaft turns smoothly. Movement that turns around in a circle is called _____ motion.
Work out the gear ratio
A driver gear has 20 teeth and the driven gear has 40 teeth. How many times does the driver gear turn for one full turn of the driven gear?
Find the rotary carriers
Tap the TWO mechanisms that pass on rotary motion.
- Gear train
- Cam and follower
- Pulley system
- Linkage
- Bearing
Which mechanism is it?
Decide which mechanism each description is.
- Two meshed toothed wheels transmit turning motion, one turning faster than the other
- A rotating shaped disc pushes a follower up and down
- Rods pinned together reverse the direction of a push
Explain a mechanism
Choose a product that uses a gear train, a cam or a linkage. Explain which mechanism it uses and how that mechanism changes the movement to make the product work.
- Name the product and the mechanism it uses
- Describe the movement going into the mechanism
- Explain how the mechanism changes that movement