Mechanical Engineering · Fluid Systems
Design a hydraulic arm from syringes
Build a three-joint arm moved by water-filled syringes that picks up and places an object.
- DifficultyEasy
- Estimated time1–2 weeks
- Budget₹250–₹500
- ClassClass 7–11
- Team2–3 people
- You needHousehold materials
Prerequisites: None beyond your class work
Original · by TechnifyedEngineering DesignWorking ModelBeginner friendlyLow costWell documented
Overview
Build a three-joint arm moved by water-filled syringes that picks up and places an object.
Why build this?
It is a favourite exhibition model because visitors can operate it themselves.
What you will learn
- How hydraulic force is transmitted
- How joints and levers give movement
- How to build without leaks
Skills you will use
Safety
- This project uses a blade or sharp tool. Cut away from your body on a cutting mat, and ask an adult to help younger students.
Materials and tools
- Eight 10 ml syringes
- Clear tubing
- Thick cardboard or ice-cream sticks
- Skewers as pivots
- Glue
- Coloured water
Tools and software
Step-by-step roadmap
Start
You will finish with: a working arm that picks up, turns and places an object, with a diagram of the hydraulics.
- 1
Prerequisites
Nothing special to know first. Then collect the 6 items in the materials list.
- 2
Learn
- How hydraulic force is transmitted
- How joints and levers give movement
- How to build without leaks
- 3
Plan
Sketch the design, list every part with its price and decide how you will know it works.
- 4
Build
- Cut arm segments and a base from stiff card.
- Join the segments with skewer pivots.
- Fix a syringe across each joint and connect it by tube to a control syringe.
- Fill each pair with water and remove air bubbles.
- Add a gripper driven by a fourth pair.
- Practise picking up and moving a small object.
- 5
Test
Run it ten times in a row. Note every failure, fix the cause and test again.
- 6
Document
Photograph each build stage, keep the circuit or drawing, and note what failed and how you fixed it. Report structure
- 7
Present
Demonstrate it working first, then explain how it works and what you would improve. Presentation structure · Viva questions
- 8
Publish
Share a short video, the parts list and the drawing or code so someone else can build it.
Expected outcome
A working arm that picks up, turns and places an object, with a diagram of the hydraulics.
Other versions of this project
Beginner version
Build a single joint that lifts and lowers.
Advanced version
Use syringes of two sizes and measure the force multiplication.
Make this project better
- BasicBuild a single joint that lifts and lowers.
- This projectDesign a hydraulic arm from syringes
- AdvancedUse syringes of two sizes and measure the force multiplication.
Science fair mode
Text marked "You write this" is a prompt for your own work; everything else is specific to this project.
- Problem
- You write thisWrite your question as: How does [what you change] affect [what you measure]?
- Hypothesis
- You write thisWrite it as: If [I change this], then [this will happen], because [reason].
- Variables
- You write thisName the one thing you change (independent), the thing you measure (dependent) and what you keep the same (controlled).
Materials and procedure are in Materials and the Roadmap.
Observation table
You write thisDraw a table with one column for what you change, one for each repeat reading and one for the average.
- Graph
- You write thisPlot what you changed along the bottom and what you measured up the side; use a bar chart for categories and a line graph for numbers.
- Results
- You write thisState what the graph shows in one or two sentences, with numbers.
- Conclusion
- You write thisSay whether the result supports your hypothesis and why you think so.
Display board
- Title and your name
- Question
- Hypothesis
- Materials
- Procedure (with photos)
- Data table and graph
- Conclusion
- What you would do next
Questions judges ask
- Why does it use water?
- What causes a spongy response?
- Where are real hydraulic arms used?
- What would you change if you did this again?
- What was your biggest source of error, and how did you reduce it?
- Where is this idea used in real life?
Working as a team
2–3 people. Suggested roles:
Report and presentation
Report structure
- Title and aim
- The problem it solves
- How it works (principle)
- Parts list with cost
- Design: drawing, circuit or block diagram
- Build steps
- Testing and results
- Problems faced and fixes
- Limitations
- Future improvements
- References
Presentation structure
- The problem
- The idea
- How it works (one diagram)
- Parts and cost
- The build (photos)
- Live demo or video
- Test results
- What did not work
- Next version
Viva questions
Try answering before you open each one.
Why does it use water?
Water is almost incompressible, so movement is transmitted directly.
What causes a spongy response?
Air bubbles in the tube.
Where are real hydraulic arms used?
Excavators, cranes and vehicle lifts.
Resources
Source and attribution
Original
Written by Technifyed. Free to use for your own school or college project; write the report in your own words. Added 1 Oct 2026.
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