Gussets & Plates

Open with a real robot photo from last season. Point out that almost every joint on a robot is a gusset of some kind. Stress that gussets turn a pile of tubes into a rigid frame. Beginners think the tube does all the work, but a bad gusset is where robots actually break.

The #1 Fusion habit: every new part is its own Component, activated before you sketch. Demo activating the gusset component. Common mistake: students model the gusset inside a tube body, then can't move or count it. In Fusion, the active component is where new sketches and bodies land.

Sketching directly on a face is the Fusion equivalent of Onshape's in-context. The gusset becomes parametrically tied to that surface. Tell students: never sketch on the origin planes for a gusset, always on the actual mating face, so it follows the tube.

This is the heart of the lesson. Press P for Project. Projected geometry is associative, if the tube hole moves, the gusset hole follows. The classic FRC failure is hand-typing a 1in hole spacing and being 0.5mm off, so bolts don't go through. Projecting kills that error forever.

Edge distance rule of thumb: keep at least one bolt diameter of aluminum between a hole and the edge, two is safer. Show how a sketch turns black when fully constrained. Unconstrained (blue) sketches drift later and break the model. Add fillets to avoid stress risers and sharp cut hazards.

Use real stock: 0.090, 0.125, or 0.25in aluminum. Remind them to pick New Body, not Join, or it merges into the tube. Then a second extrude with Cut and 'All' extent punches the projected holes through. Type fractions directly, Fusion does the math.

Multi-tube gussets are where superstructure design gets real, think the plate tying a swerve module mount to two cross members. Stress checking coplanarity: if faces aren't flush, the flat plate won't sit right. Project from each tube separately so all patterns are captured.

Onshape calls these Mates; in Fusion they're Joints. A bolted gusset is Rigid, no motion. Revolute and Slider are for things that actually rotate or slide. Tell students: jointing makes mass properties and the parts list accurate, which matters for weight budgets near the 125lb limit.