Practice: Intake

Frame today as a capstone for Stage 1C — they've learned sketches, extrudes, components, and joints; now they combine all of it. Stress that real FRC intakes are simple: plates, a shaft, rollers, a motor. Tell them an over-the-bumper intake reaches OVER the robot's bumper to pull a piece in, vs an under-the-bumper that scoops low. Common beginner mistake: overcomplicating geometry. Keep it boxy.

This is the Fusion version of Onshape Variables. Demo adding a parameter live, then show typing the parameter NAME into a sketch dimension box instead of a number. Sell the payoff: change one number, whole model updates. Common mistake: students type the value instead of the name, losing the link. Units matter — set the design to inches first (Document Settings).

Circumscribed polygon sets the across-flats distance, which is what 1/2in hex means — not the corner-to-corner. Make them create a Component first (right-click in browser > New Component, or the Assemble menu) so it shows in the tree as its own thing. This is the backbone everything else references. Mistake: drawing the hex with a flat on top vs a point on top — doesn't matter functionally but tell them to be consistent.

The hex BORE is the key idea — the roller's hole matches the shaft so it can't slip and transmits torque. Show Modify > Combine or a Cut extrude using the hex sketch for the bore. For spacing, demonstrate either a Rectangular Pattern of the component or copy-paste-joint. Rigid joint = roller and shaft move as one. Mistake: forgetting the bore is hex, making it round (would spin freely).

The bore hole must line up exactly with the shaft axis — teach them to project the shaft (Project/Include, press P) so the hole is on-axis automatically. Use Mirror across the origin plane for the second plate so they stay symmetric and parametric. Mistake: eyeballing the second plate's position so the shaft ends up crooked. Keep plates parallel and the shaft perpendicular.

Revolute = one rotational degree of freedom, the Fusion equivalent of Onshape's revolute mate. This is what lets the shaft spin while the plates stay still. Grounding (right-click component > Ground) pins the plates so they don't fly off when you drag. Have them actually drag-test the motion — if rollers don't spin with the shaft, their rigid joints from Step 3 are missing.

Don't make them model a perfect motor — a stand-in cylinder with the correct bolt circle is fine for practice. The point is the belt offset: the motor sits a fixed center distance from the shaft so the 5mm HTD belt is tensioned. Mention real teams insert the actual NEO 550 STEP file (we cover STEP imports next lesson). Rigid joints because the motor body doesn't move relative to the mount.

Walk through each of these — they're the exact failures you'll see at the work tables. The 'all one body' problem is huge for beginners: if they never hit New Component, everything merges and joints become impossible. Tell them the browser tree should show HexShaft, Roller(s), SidePlate x2, MotorMount as separate nodes. If it's flat, they skipped components.