Learners build a cardboard claw and power it with air, using pneumatics, so pushing one piston opens and closes the claw at the other end. It is a careful ten-step build that ends with a working machine, a gripper relay race, and a first look at hydraulics.
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Get the materials that pair with this educator guide.
Quick Start gets the main resources in hand. The guide below helps with the decisions that happen before, during, and after students build.
What students build and how the activity works.
Prep questions and pro tips.
Classroom sequence and prompts.
Learning goals and curriculum connections.
Fixes, adaptations, and extensions.
Learners build the claw from six cardboard levers joined with connectors, then attach two pistons and a tube. Pushing or pulling one handle moves air to the other piston and works the claw. Plan on learners following the visual guide closely. Once it works, they improve the grippers for a relay race, redesign parts from scrap cardboard, or try water instead of air.
Subject connections
Everything needed for the core build is inside the Spark bag. No extra materials are required to complete the basic pneumatic claw.
Optional for extensions: scrap cardboard, scissors, craft supplies (markers, colored paper, stickers, tape) for custom gripper designs; water and food coloring for the hydraulics extension; small objects of varying size and weight for a relay race.
Question: What do you notice about the different holes on each lever? Why do you think they have different shapes?
Question: What do you think will happen when we connect these two pieces with just one connector? How is that different from using two?
Question: How do you know which hole to use next? What clues are you looking at?
Question: How is this half different from the long half you just built? What will you use it for?
Question: This step is the most important of the whole build. What do you think makes a circle connection different from a triangle or square connection?
Question: What are pneumatics? What do you think happens inside a piston and cylinder when you push or pull on the handle?
Question: Why do you think we need foam holders on the cylinder at all? What job do they do?
Question: What is different about this second piston? Why would one stay closed and the other stay open?
Question: How is air going to travel between the two cylinders? What do you think will happen when you push one piston in?
Question: Now that your Monster Claw grabs, how could you make it even better? What could it pick up that it can't right now?
RI.3-5.3 – Explain relationships between concepts in a text: Example: Learners explain the cause-and-effect relationship between pulling a piston handle and the claw closing by tracing how air travels from one cylinder, through the connecting tube, and into the other cylinder - connecting what the printed visual guide shows to the physical pneumatic system they built.
W.3-5.2 – Write informative texts to examine a topic and convey ideas clearly: Example: Learners write or dictate a short "how it works" paragraph for their Monster Claw, identifying the piston, cylinder, and tube and explaining how a push or pull on the handle transfers air through the system to open or close the claw.
RST.6-8.3 – Follow a multistep procedure when carrying out experiments: Example: Learners follow the ten-step Monster Claws build sequence precisely - including the critical rule that one piston has to be fully pushed in and the other fully pulled out before the tube is connected - understanding that reversing the order or skipping the balance step means the pneumatic system won't transfer air correctly.
SL.6-8.1 – Engage in collaborative discussions with diverse partners: Example: Learners debate the trade-offs between pneumatics and hydraulics during the extension activity, using their Monster Claws to compare how force transfers through air versus colored water, and arguing which approach is better for specific real-world applications like dental chairs, construction equipment, or robot grippers.
3.MD.B.4 – Generate measurement data by measuring lengths: Example: Learners measure how far the piston handle moves when they push or pull it and compare it to how far the claw jaws open or close, generating data about the one-to-one relationship between handle motion and claw motion in their pneumatic system.
4.OA.C.5 – Generate and analyze patterns: Example: Learners observe the inverse push-pull pattern of the pneumatic system - when they pull one piston out, the claw closes; when they push the piston in, the claw opens - recognizing this as a consistent, repeating inverse relationship and predicting the claw's motion before every push or pull.
6.RP.A.1 – Understand ratio concepts and use ratio reasoning: Example: Learners count the lever segments that make up each half of their claw - three straight and bent levers fastened together for the long half, two for the short half - expressing this as a 3:2 ratio and reasoning about why the long half, built from more segments, sweeps through a wider arc than the short half when the claw opens and closes.
8.G.C.9 – Know the formulas for the volumes of cones, cylinders, and spheres and use them to solve problems: Example: Learners calculate the volume of air inside a closed cylinder using πr²h before and after the piston is pushed in, connecting the change in cylinder volume to the force and range of motion they feel in the claw - then predict how a wider or a longer cylinder would change both.
3-PS2-1 – Forces and Interactions: Cause and Effect: Example: Learners investigate how the force of pulling a piston handle causes the claw jaws to close, testing different pull strengths to observe how the claw responds - establishing a clear cause-and-effect relationship between applied force, air pressure transfer through the tube, and the opening/closing motion of the claw.
3-5-ETS1-3 – Plan and carry out fair tests to identify failure points: Example: Learners systematically troubleshoot a claw that will not fully open or close by checking one variable at a time - is one piston fully closed and the other fully open? Are both tube connections snug? Are the connectors firmly pushed through? - isolating each possible failure point until the system works.
MS-PS3-5 – Energy Transfer: Construct an explanation of energy transfer: Example: Learners explain how energy transfers through their Monster Claws pneumatic system - the mechanical energy of pulling the piston handle converts to pneumatic energy as air is compressed and pushed through the tube, then converts back to mechanical energy on the other side when the second piston extends and pulls the claw jaws closed.
MS-ETS1-2 – Evaluate competing design solutions: Example: Learners compare their Monster Claw's performance when driven by air versus colored water during the hydraulics extension, evaluating which fluid produces stronger, more controlled gripping force - and discussing the trade-offs engineers make between the simplicity and speed of pneumatics and the consistent force of hydraulics in real-world gripper design.
The cylinders are unbalanced. Disconnect the tube, push one piston all the way in, pull the other piston all the way out, then reconnect the tube by push-and-twisting both ends firmly. The claw should now have full range of motion when you push or pull the free handle.
Check the tube connections - both ends of the tube must be fully pushed and twisted onto the cylinder tips. A loose connection lets air escape. Also check that one piston is pushed in and the other is pulled out (the "one closed, one open" rule). If both are in or both are out, air has nowhere to flow.
Hold the cardboard flat on both sides of the connector and pull it straight back out. Then re-check the printed guide and place the connector in the correct hole.
Trace the damaged lever onto a piece of scrap cardboard, poke through the holes with a pencil to mark their positions, cut the shape out, and press the connectors into the replacement piece. This lets learners recover from mis-placed connectors or accidental bends without scrapping the whole build.
One or more cardboard connections may be loose. Check that every connector is pushed all the way through, with its head flat against the cardboard. Wiggly connections absorb the force that should be moving the claw.
