Build a hydraulic device
Build a simple hydraulic arm using plastic syringes, tubing, cardboard, and water, exploring fluid pressure and force to move joints safely and predictably.
About this activity
Build a simple hydraulic arm using plastic syringes, tubing, cardboard, and water, exploring fluid pressure and force to move joints safely and predictably.
What you need
Step by step
- 1
Step 1
Gather all materials and set them on a clear flat workspace so everything is easy to reach.
- 2
Step 2
Cut two cardboard strips about 20 cm long and one base rectangle about 10 cm by 8 cm to use as the arm parts and mount.
- 3
Step 3
Use the ruler and marker to mark a joint hole near one end of each strip and mark a spot on one strip and on the base for mounting the syringes.
- 4
Step 4
Make small holes at each marked joint and mounting spot by poking carefully with the tip of the scissors or a pen under adult supervision.
- 5
Step 5
Push the paper brad through the two strip holes and spread the ends so the two cardboard strips join and can swing freely like an elbow.
- 6
Step 6
Tape one syringe (the actuator) along the inner side of the lower arm strip with its nozzle pointing toward the joint and the plunger free to move.
- 7
Step 7
Tape the second syringe (the pump) securely to the base so its plunger is easy to push and pull by hand.
- 8
Step 8
Push one end of the tubing firmly onto the pump syringe nozzle and the other end firmly onto the actuator syringe nozzle to make a snug connection.
- 9
Step 9
Put the pump syringe nozzle into the small cup of water and pull the pump plunger back to draw water into the pump and tubing until the actuator syringe fills and no air bubbles remain.
- 10
Step 10
Slowly push and pull the pump syringe plunger to move the arm and watch how small plunger movements make the joint bend and straighten.
- 11
Step 11
If you see water leaks or air bubbles return stop and press the tubing and tape connections tighter then repeat filling until the system is sealed.
- 12
Step 12
Take a photo or video of your working hydraulic arm and share your finished creation on DIY.org
Fun facts
How do you build a simple hydraulic arm using syringes and cardboard?
Start by cutting cardboard pieces for the base, arm segments, and a claw. Join segments with brads or strong tape to make hinged joints. Attach one syringe to each joint as an actuator, connecting syringe tips with clear tubing. Fill the syringes and tubing with water, removing air bubbles, then secure syringes to the base. Push and pull plungers slowly to move the joints, adjust linkage lengths for smoother movement, and test under adult supervision.
What materials do I need to make a DIY hydraulic arm?
You’ll need plastic syringes (10–20 mL) without needles, clear flexible tubing that fits syringe tips, sturdy cardboard, brads or split pins for hinges, strong tape or hot glue, scissors and a craft knife (adult use), a small container of water, optional food coloring, a ruler and marker, and a stable base (wood or thick cardboard). Also have paper towels and a tray to catch spills and an adult to help with cutting and assembly.
What ages is a homemade hydraulic arm suitable for?
This project suits children about 8 years and up with adult guidance for cutting and assembly. Younger kids (5–7) can participate by designing, filling syringes, and testing while adults handle sharp tools and connections. Teenagers can build and modify independently, exploring more syringes and linkages. Match complexity to the child’s skill: simpler two-joint arms for beginners, more joints and controls for older kids learning physics and engineering basics.
What safety tips should parents follow when doing a syringe hydraulic arm?
Always supervise children when cutting, gluing, or assembling. Use syringes without needles and avoid pressurizing the system—push plungers gently to prevent leaks or popping connections. Seal tubing snugly but avoid airtight systems that could trap pressure. Keep work area dry and use trays for spills. Wear goggles if cutting cardboard or tubing. Teach children not to point syringes at people and to check for leaks; replace cracked tubing immediately.
Watch & Learn
Need help?
What can I use if I can't find paper brads, syringes, or clear tubing?
Use a small brass fastener or a short nail as the joint instead of a paper brad, swap the syringes for disposable medical syringes or a cut turkey-baster nozzle, and replace the clear tubing with aquarium tubing or a snug flexible drinking straw when connecting the two syringe nozzles.
If the arm doesn't move smoothly or water leaks, what should I check and fix?
Check the tubing-to-nozzle and tape connections described in the instructions, press the tubing firmly onto both syringe nozzles, tighten or re-tape the syringe mounts on the cardboard strips and base, then repeat the filling step until no air bubbles remain.
How can I adapt this hydraulic arm activity for younger or older kids?
For younger children have an adult pre-cut the two 20 cm cardboard strips, make the joint and mounting holes, and tape the syringes so the child only operates the pump syringe, while older kids can add extra joints, lengthen the arm, or attach a second actuator syringe to the lower strip to explore more complex motion.
How can we extend or personalize the finished hydraulic arm?
Decorate the 10 cm by 8 cm base and cardboard strips, attach a clay or paper claw to the arm tip, or add a second actuator syringe and a marked scale on the syringe barrel to measure plunger displacement during the push-pull step.