1 - Getting Started ~5 mins
Watch this. One small push at the side makes something else move. How can a push in one place make a different movement somewhere else?
Hands up: what everyday things turn one movement into another?
Have one finished lever-and-linkage example ready to show (e.g. a bird with a flapping wing). If you also have a finished cam toy, keep it aside for a ten-second reveal later, not yet. Do not explain the parts yet. Give one short push so the class sees the output, then freeze.
Key questions: What did the hand on the strip do? What moved on the picture? Did anything stay still?
Accept everyday ideas: bicycle pedals turning the wheel, scissors, a playground see-saw, a farm gate latch, and the handle or catch on our own classroom door. Keep this beat light. The build kit comes out later.
2 - What Is a Mechanism? ~7 mins
That push on the strip is the input. The wing going up is the output. The split pin that lets the wing swing is a pivot. All the parts working together make a mechanism: parts that transfer movement from one place to another.
Watch the bird again. Where does the movement start, and where does it end?
Point at the finished lever-and-linkage from the hook as you name only these four core words on the board: input, output, pivot and mechanism. Keep cam and follower off the board for now; name them only if you later show a finished cam toy in the demo step (stretch path).
Keep the board short; the table below is your reference for the core path.
| Concept | Why it matters | Example |
|---|---|---|
| Mechanism — a set of parts that work together to transfer movement from one place to another | Almost every machine, from a bike to a crane, is built from mechanisms that turn one movement into a more useful one | Pushing a side strip makes a bird's wing flap on a card moving picture |
| Input — the movement you make to start the mechanism (a push, pull or turn) | Engineers always ask where the force goes in, because that is what the user will do | Your hand pushing the lever strip is the input |
| Output — the movement that comes out at the other end | The output is the job the mechanism is meant to do, so we judge success by whether it happens clearly | The wing rising and falling is the output |
| Pivot — a joint that lets a part turn around a fixed point | Without a pivot on this kind of picture, the wing cannot swing, so the push cannot turn into a flap | A split pin through the wing and base lets the wing swing up and down |
If you have a finished cam toy (stretch only, later): a cam is an off-centre shape on an axle; the follower rests on it and bobs. Keep those two labels for the brief reveal in the next step, not this board.
Misconception to head off: pupils often say the whole picture "moves by itself". Name the chain: input → linkage → output. Nothing moves without an input.
Nature of STEM: designing parts so one movement becomes another is everyday mechanical engineering — the same idea behind a farm gate latch, bicycle gears, and a canal lock gate that transfers a long push on a balance beam into the swing of a heavy gate.
3 - Watch One Being Made ~6 mins
Watch carefully while a simple moving picture is joined together. When the strip is pushed, which part of the bird will move?
Before the step
Do not cut the demo from blank card in this slot. Pre-cut the demo parts before the lesson: base, bird body, one wing, and a long thin input strip. Have two split pins, scissors (only if a tiny trim is needed) and a pencil ready. Join live on the desk facing the class so pupils see each pin. Adult trims only if a piece is fiddly. Keep a finished cam toy (or a simple pre-made cam and follower on a short dowel) ready for a quick side-by-side show after the bird works — only if you have one.
Modeled cycle (say this thinking aloud)
- I wonder: Can I make a push at the side flap a bird's wing?
- I predict: If I join a strip to the wing with a split pin and fix the wing to the base with another pin, pushing the strip should lift the wing.
- I test: Pin the wing to the body so it can swing. Pin the strip to the wing so a push turns into a lift. Leave a little free play so it does not jam.
- I notice: A short push lifts the wing; pulling the strip lowers it. The body stays still. The two split pins are the pivots.
- I think: The input is the hand on the strip. The output is the wing flapping. The linkage transfers the movement from strip to wing around the pivots.
What to expect: if the wing does not lift, the strip pin is too close to the wing pivot, or a hole is too tight. Move the strip pin further from the wing pivot for a bigger flap, or loosen the pin slightly.
Fold the class in: before you push, take a quick hands-up on the prediction options. After the reveal, ask: Where did the movement start? Where did it end? What stayed still?
Cam stretch preview (about 20 seconds, only if a finished cam is on the side table): hold up the finished cam toy beside the bird. Turn the axle once: "This other design uses a cam, an off-centre disc on an axle, and a follower that bobs. Most groups will build a strip-and-pivot picture like the bird. If your group finishes a working linkage early and the finished cam is on the side table, you may try a cam with that model as a guide." If no finished cam is available, skip this preview entirely and do not name cam or follower on the board.
4 - Build Your Mechanism ~18 mins
In your group, build a lever-and-linkage moving picture so one input movement makes a clear output movement. Use at least one pivot. It is fine if the first pin position is awkward — adjusting is part of the engineering. Work in this order:
- Agree what your scene is and what should move (for example a bird wing or a waving arm).
- Use the pre-cut base and strip if you have them, or sketch lightly on card and cut the parts.
- Join the moving part to the base with a split pin so it can swing.
- Pin on the input strip the user will push or pull.
- Test gently and adjust until the output is clear. Stop when you can name the input and the output.
If your group finishes a working linkage early and the finished cam model is on the side table, you may try a simple cam toy. A cam needs three parts: an axle, an off-centre disc on that axle, and a follower that rests on the disc and bobs. Use the finished model as your guide.
Take your Investigation Journal page now and keep it beside you for the test and drawing steps.
Before the lesson
- Gather stiff card (cereal-box card is fine), split pins, scissors, pencils, glue or tape, and short dowels or wooden skewers with blunt tips for any stretch cam group.
- Default support path: pre-cut bases, simple body/scene shapes, and input strips for every group so cutting does not eat the whole build slot. Full cutting from blank card is stretch for groups that want extra challenge after a working linkage, not the only route.
- Pre-snip spare strips and off-centre cam discs so groups that struggle with cutting can still join parts.
- Push desks so each group has a clear flat build space.
- Have the finished cam toy on a side table as a stretch reference only. If you have no finished cam, do not offer the cam stretch on the board.
- Hand out one Investigation Journal page per pupil (or per pair) with the build materials so pages are already on desks before testing.
During the build
Groups of three work well. Default path for every group: a lever-and-linkage moving picture (base scene such as a bird, person waving, or goalkeeper diving) with one moving part joined by split pins to an input strip the user pushes or pulls. Start groups on pre-cut bases and strips so every group can reach a testable linkage inside the slot.
Stretch only (after a clear working linkage, and only if the finished cam is on the side table): a simple cam toy using a card or box frame, a dowel axle with an off-centre card cam, and a follower that rises and falls. Point them at the finished cam model and pre-cut cam blanks. Remind them of the three parts: axle, off-centre disc, follower.
Success looks like: one clear input the user controls; one clear output the class can see; parts stay joined at the pivots; the group can point to input and output without prompting.
Differentiation: support groups with a two-piece linkage only (base + one moving arm) and pre-cut strips. Stretch groups add a second linkage so one push moves two parts, cut a full scene from blank card, or move on to a cam with the finished reference beside them.
Common snags: pins too tight (movement jams); pins too loose (parts fall apart); cam centred on the axle (no rise and fall — it must be off-centre); input strip glued solid instead of pinned (nothing turns).
Circulate and ask: Show me the input. Show me the output. What is the pivot doing?
5 - Test the Input and Output ~8 mins
Now investigate your own mechanism. You are the tester: change one thing and see what the mechanism tells you. Choose one thing about the input to change: how far you push, how fast you move, or which direction you go. Predict what the output will do, then try it. Try a second change after the first. On your Investigation Journal page, jot a quick prediction and what you noticed; you will draw the mechanism later.
This is the open-ended beat: groups design the small test, not a recipe. They already built the mechanism; now they choose which input change to try. Journal pages should already be on desks from the build step; if any pupil is missing one, hand it out now before notes begin.
Prompt groups: Change only one thing about the input at a time so you know what caused the new output. Keep the same starting position for a fair comparison between trials.
Recording now: pupils use the Investigation Journal page for short notes only (prediction and what changed). The labelled drawing comes in the next draw step, so do not wait for a finished diagram before testing.
What good talk sounds like: "I pushed the strip further and the wing rose higher." "Turning the cam slowly made the figure bob more smoothly." "When I pushed the other way, the wing went down."
Misconception: if nothing changes, pupils may say the mechanism "is broken". Often the input change was too small, or a pin is binding. Help them enlarge the push or free the pivot, then re-test.
Fold watchers in: when one group demonstrates at the front, ask the class What is their input? What do you predict their output will do if they push further?
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