ENGINEERING COMMISSION #7973 (Dr. F approved, build before astronaut set): touchable motion transformations — gears, cams, linkages, escapements — every one a WORKING model (#7971); the mechanics table (6.1) is its classroom bench.
The Lever, First and Last
Everything on this wall is a lever wearing different clothes. Class one, two and three; the fulcrum moved and the whole world changes. Archimedes was not boasting about strength — he was describing a ratio.
Gear Ratio
Twelve teeth driving thirty-six: one turn in, a third of a turn out, three times the torque. The wall lets a student turn the input by hand and count the output. Ratio stops being a fraction on paper the moment your wrist feels it.
The Four-Bar Linkage
Four rods and four pins, and from that almost nothing you can draw a straight line, a figure of eight, or the motion of a bird's wing. The four-bar is the most useful mechanism nobody outside the trade can name.
The Cam
A shaft turns steadily; the cam turns steady rotation into a shaped, repeatable, irregular motion. Every engine valve, every music box, every automated loom. The cam is how a machine remembers a sequence without a computer.
Escapement
The mechanism that lets a clock give back its stored energy one measured bite at a time. Escapement is why time could be carried, and once time could be carried, ships could find longitude and factories could keep shifts.
Mechanical Advantage, Counted
The bench: lift the same weight with a lever, a pulley block, a screw jack and a gear train. Record the effort each time. The load never changes. The number you record does. That column is the lesson.
Gear trains, a four-bar linkage caught mid-stroke, a cam and its follower, an escapement engaged.