Machines rarely want the motion a motor gives them. A crank and slider turns rotation into back and forth, a cam's shape becomes a follower's path, and four bars turn a crank into a rocking arm, if their lengths allow it.
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)
Cranks and sliders, cams and followers, and four-bar linkages.
Motors turn. Machines often need something else: back and forth, up and down at set times, or a swing. Three mechanisms change one motion into another.
A crank and slider: a pin on a turning wheel, a rod, and a slider on a track. One turn is one stroke out and back; the stroke is twice the crank's radius. Pumps use it one way, engines the other.
A cam and follower: a shaped wheel and a rod resting on it. The cam's shape decides the follower's path, shown on a displacement graph (height against angle). Eccentric: smooth wave, lift = 2 × offset. Pear: rests half a turn. Snail: slow rise, sudden drop (one way only). Heart: steady rise and fall.
A four-bar linkage: a frame, a crank, a coupler and a rocker. The crank turns all the way only if shortest + longest ≤ the other two (Grashof's rule) and the crank is the shortest. A longer crank gives a bigger swing, up to that limit.
crank, connecting rod, slider, stroke, cam, follower, dwell, displacement graph, linkage, coupler, rocker, frame.
Cheat sheet: Open to print (A4, with board pictures) · Markdown