How frames and beams hold loads up: members that pull or push, triangles that keep their shape, long pushed members that buckle, and beams whose shape matters more than their weight. It ends with a bridge to a budget, tested to failure.
Each lesson works two ways. Students can work through the online tutorial at their own pace (it checks their answers and saves their progress in their browser), or you can teach it to the whole class from the slides, then send students into the tutorial for the Modify and Make steps.
Every lesson guide has plain-language notes, the answers to every check, a solution for every task, and slides and a worksheet for Waypoints Prepare. These guide pages are not linked from student pages, but they are not secret either: keep printed Teacher editions for answers you do not want students to find.
Whole-course cheat sheet: Open to print (every command, grouped by unit: a handout for the final challenge)
Tension and compression, triangles, buckling, and a bridge to a budget.
A truss is a frame of straight members joined by pins. Each member only pulls (tension) or pushes (compression) along its length. Slanted members carry more than their share; flatter frames have bigger forces.
A triangle can't change shape; a square on pins leans over. Brace squares with diagonals. For a flat frame on a pin and a roller, members + 3 = 2 × joints.
A pull only fails when a member snaps. A push buckles a long thin member at a much smaller force, falling with length squared. Good trusses keep pushed members short and make long members pull. Testing to failure gives the safety factor (failure load ÷ working load).
truss, member, joint (pin), support (pin, roller), tension, compression, brace, buckling, safety factor.
Cheat sheet: Open to print (A4, with board pictures) · Markdown
Support forces and why depth matters most.
A beam carries a load across a gap. Its supports share the load like a lever: each holds load × the far distance ÷ the span, so the nearer support holds more.
A beam sags less the stiffer its cross-section is, and stiffness grows with depth cubed (a rectangle: width × depth³ ÷ 12). The same strip on its edge is 100 times stiffer than flat. I-beams and tubes put material far from the middle, where it adds most stiffness.
beam, span, support, reaction, sag (deflection), cross-section, I-beam, stiffness.
Cheat sheet: Open to print (A4, with board pictures) · Markdown