Bell crank and lazy-tong linkages | Design and technology

Starter quiz

Match the linkage to the description.
- push pull linkage
  
  ⇔
  
  The output moves in the same direction as the input. ✓
- reverse motion linkage
  
  ⇔
  
  The output moves in the opposite direction to the input. ✓
- parallel linkage
  
  ⇔
  
  Works in the same way as the push pull linkage. ✓
Which of these best describes a mechanism?
- A solid, rigid bar.
- The point where levers connect.
- A movement needed to make something happen.
- A set of moving parts. ✓
What type of linkage is this?
- reverse motion
- parallel ✓
- push pull
- slider
Which of these would be the most suitable for a pivot point in cardboard?
- screw
- paper clip
- split pin ✓
- stapler
Fill in the missing word. A simple lever mechanism uses a __________ to reduce the effort needed to lift a load.
- box
- handle
- fulcrum ✓
Which of these is NOT an example of a simple lever mechanism?
- scissors
- bus ✓
- wheelbarrow
- light switch

Why do the pivot points on the levers of a lazy-tong linkage have to be in the same place on each lever?
- so it looks even
- so the levers can move on their own
- so the levers can all make the same movements ✓
- so there is room to fit them all on
Which two things do you need to use to safely make a hole for a pivot in cardboard?
- pencil ✓
- scissors
- sticky tack ✓
What type of linkage is this?
- lazy-tong
- reverse motion
- parallel
- bell crank ✓
What type of linkage is this?
- bell crank
- push pull
- lazy-tong ✓
- reverse motion
What does a linkage connect together?
- mechanisms
- pivot points
- levers ✓
In a bell crank linkage, what connects the levers to the central 'bell' shaped piece?
- loose pivots ✓
- fixed pivots
- right angle pivots

A bell crank linkage moves levers at angles from each other.
A lazy-tong linkage is made of levers which lengthen or shorten when one end is pushed or pulled.

It doesn't matter where you place the pivots on a lazy-tong linkage.

Where the pivots are placed is very important on a lazy-tong linkage. If they are not placed correctly, the mechanism will not function correctly.