- Difficulty
- Intermediate
- Build time
- 75-110 min
- Estimated cost
- $0-$10
- Age range
- 11-17
- Workspace
- A clear table about 90 cm wide
The finish line
What you will build
The platform rises at least 15 cm, stays within 10 degrees of level, and lifts a 50-gram load without a pivot separating.
Learning goals
- Identify how horizontal motion between lower pivots produces vertical platform lift.
- Construct and explain a linear input-to-vertical translation system.
- Measure how the number of scissor stages changes performance.
- Diagnose losses caused by pivot friction and link bending.
Before you build
Materials, tools, and safety
Reuse-material cost: $0-$3 with reused materials. Supervision: Adult help recommended for sharp or heated tools.
Tools
- Ruler
- Pencil
- Scissors
- Masking tape
Low-cost swaps
- Use clean recycled packaging whenever it has similar stiffness.
- Substitute paper clips, binder clips, or twist ties for specialty fasteners.
- Use doubled cardboard strips with punched holes instead of craft sticks.
Project-specific safety
- Wear eye protection when stretched elastic, magnets, or spinning parts are present.
- Test at floor or tabletop height and keep the path clear of people.
- Keep fingers away from folding diamonds and never use the lift for hands, people, or heavy objects.
Orient the build
Place the build so horizontal motion between lower pivots is on your left and vertical platform lift is on your right. Call the side facing you the front, the far side the back, the tabletop the bottom, and the opposite face the top.
Build it
Step-by-step instructions
Step 1
Pair and mark sticks
Stack equal sticks and mark center and end holes from one template.
An adult should pierce aligned holes.
Step 2
Build four X units
Join each pair at its center with free pivots.
Check equal arm lengths on both sides.
Step 3
Connect the first side chain
Join two X units end to end to make a two-level scissor side.
Keep links in alternating depth planes.
Builder checkpoint: After connect the first side chain, the first subassembly should stay aligned when handled gently.
Step 4
Build the matching side
Duplicate the chain and overlay it with the first.
Correct any unequal center distance.
Watch for: If this stage binds or drifts, inspect platform tilt before adding more parts.
Step 5
Mount fixed base pivots
Attach one lower end on each side to the base.
Place the opposite lower ends in parallel slots.
Step 6
Attach the platform
Fix one upper end on each side and guide the opposite ends in top slots.
Keep left and right sides synchronized with crossbars.
Builder checkpoint: After attach the platform, operate the build slowly and confirm that vertical platform lift begins without binding.
Step 7
Add the input handle
Connect the sliding lower pivots to a pull bar or slow screw.
Add stops before links fully flatten or straighten.
Step 8
Lift and load
Raise empty through the full range, then add 50 grams at center.
Measure height, level angle, and input travel.
Builder checkpoint: At the final checkpoint, The platform rises at least 15 cm, stays within 10 degrees of level, and lifts a 50-gram load without a pivot separating.
See the engineering
Why it works
- Input
- horizontal motion between lower pivots
- Output
- vertical platform lift
- Motion
- linear input-to-vertical translation
- Energy losses
- pivot friction, link bending, slot rubbing, platform tilt
Why this works
Scissor geometry
Crossed equal links form changing diamonds. Pulling lower pivots together increases link angle and raises the top, while stacked stages multiply height and alignment demands.
Look for: Measure input distance and platform height at several angles instead of assuming a constant ratio.
Where the energy goes
Efficiency and losses
The ideal model leaves out pivot friction, link bending, slot rubbing, platform tilt. These effects turn some input energy into heat, sound, vibration, or unwanted motion, so measured performance will be lower than an ideal calculation.
Look for: Run the build slowly and locate the first place where pivot friction becomes visible or audible.
Math bite
Estimate one-stage height
Formula: height = 2L × sin(θ)
- Half-link length L = 60 mm
- Link angle θ = 30°
- sin(30°) = 0.5
Substitute: height = 2 × 60 × 0.5 = 60 mm
Result: One ideal scissor diamond is 60 mm high at 30 degrees.
More stages add height but also flexibility.
Joint offsets and slot geometry change the real value.
Make it behave
Test, troubleshoot, and tune
Controlled test
Start here: Raise the empty platform from its lowest safe position.
Success looks like: It reaches 15 cm, stays within 10 degrees of level, and carries 50 grams.
Measure: Platform height, level angle, and input distance.
Change: the number of scissor stages
Keep constant: link length, base, platform, load position, input, and stops
- one stage
- two stages
- two stages with centered load
| Symptom | Likely cause | Confirm it | Fix |
|---|---|---|---|
| The platform tilts | Left and right link chains differ or move separately | Measure both side heights | Match geometry and add crossbars |
| The lift locks low | Links start too flat or input lacks force | Raise slightly by hand and test | Set a higher minimum stop |
| A pivot tears out | Hole is close to an edge or overtight | Inspect whitening around holes | Reinforce ends and loosen pivots |
| Slots bind | Moving pins tilt or slots differ | Move empty and watch each slider | Widen and align guide slots |
Choose your tradeoff
Avoid near-flat and near-straight extremes, where force or locking becomes severe. More stages increase height but lower stiffness; cross-connect both sides before adding load.
Keep experimenting
Try another version
Single-stage lift
Build one X pair per side with an empty platform.
Lead-screw input
Add a slow threaded drive to control height.
Force curve
Measure input force at several platform heights.
Build together
Classroom and access options
Classroom version
Teams can compare the number of scissor stages while keeping link length, base, platform, load position, input, and stops. Assign builder, tester, recorder, and explainer roles; have each team predict the result before collecting three trials.
Access adaptations
- Offer pre-cut parts and tactile or high-contrast measurement marks.
- Split roles so one builder can hold, another assemble, and another measure.
- Use a large threaded knob or pull handle and color-code fixed versus sliding pivots.
Reflect on the design
- How did the number of scissor stages change the measured result?
- Where did pivot friction affect the build most strongly?
- What evidence shows that scissor geometry explains the motion?
- Which change would improve vertical platform lift without creating a new problem?
Glossary
- Scissor geometry
- Crossed equal links form changing diamonds.
- Input
- The action or energy supplied to a system; here it is horizontal motion between lower pivots.
- Output
- The useful response produced by a system; here it is vertical platform lift.
- Efficiency
- The fraction of input energy that becomes useful output instead of friction, sound, heat, or unwanted motion.
Build your dreams
One build can start the next.
Share what you learned, change one variable, and help another builder understand what worked.
Explore more guidesSources and build notes
A familiar household engineering activity implemented with original instructions and controlled tests.
- Classroom engineering basis: A common educational challenge implemented with original dimensions, tests, diagrams, and instructions.
Written and edited by BrickLabClips. Published 2026-07-22; updated 2026-07-22.