Bell crank and lazy-tong linkages
Lesson details
Learning outcome
I can make bell crank and lazy-tong linkages.
Key learning points
- 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.
Keywords
Linkage - A mechanism connecting levers together.
Input - The motion used to start a mechanism.
Output - The motion created by the input.
Loose pivot - A free moving point that connects two levers together.
Fixed pivot - A point that connects a lever to one place.
Common misconception
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.
Teacher tip
Have a pre-made working example of each of the linkages to show in the lesson.
Equipment
See additional resources document for a list of materials needed for this lesson.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
Loading...
Prior knowledge starter quiz
6 Questions
Q1.Match the linkage to the description.
Q2.Which of these best describes a mechanism?
Q3.What type of linkage is this?
Q4.Which of these would be the most suitable for a pivot point in cardboard?
Q5.Fill in the missing word. A simple lever mechanism uses a __________ to reduce the effort needed to lift a load.
Q6.Which of these is not an example of a simple lever mechanism?
Assessment exit quiz
6 Questions
Q1.Why do the pivot points on the levers of a lazy-tong linkage have to be in the same place on each lever?
Q2.Which things do you need to use to safely make a hole for a pivot in cardboard?
Q3.What type of linkage is this?
Q4.What type of linkage is this?
Q5.What does a linkage connect together?
Q6.In a bell crank linkage, what connects the levers to the central 'bell' shaped piece?
To help you plan your 4 design and technology lesson on: Bell crank and lazy-tong linkages, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 4 design and technology lesson on: Bell crank and lazy-tong linkages, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 2 design and technology lessons from the Levers and linkages: interactive books unit, dive into the full primary design and technology curriculum, or learn more about lesson planning.