Cardboard Hydraulic Robot Arm

A grabbing arm powered by water in syringes — no motors, all physics.

Materials

• —4–6 plastic syringes (10 ml) and clear tubing to fit
• —Corrugated cardboard
• —Brass split pins or skewers for joints
• —Zip ties, tape, glue
• —Water and a towel
• —Notebook

Steps

1. 1. Feel the physics15 min

   Connect two syringes with tubing full of water. Push one; watch the other. Write why water works better than air.

2. 2. Cut the parts45 min

   Cut a base, two arm segments and a two-finger gripper from cardboard.

3. 3. Join and mount45 min

   Use split pins for joints. Zip-tie one syringe to each joint.

4. 4. Plumb it45 min

   Fill syringe pairs with water, connect tubing, and test each joint.

5. 5. Challenge and look again30 min

   Try to pick up a paper cup. Let a friend operate it and note what confuses them. Fix one thing.

Field Notes

Write these in your notebook when you finish:

• □What leaked or bent
• □What my friend changed
• □Next upgrade