WAP — WARNING! Air Pockets — is a paper automaton about a very small airplane having a very difficult day.
Caught in an unruly sky, our little pilot is tossed up and down, rocked from side to side, and carried along by winds that seem determined to send him anywhere except where he wants to go. Every sudden drop feels like an air pocket; every brief moment of calm is followed by another unexpected jolt. The flight has no apparent logic, and the poor aircraft seems entirely at the mercy of the air.
Behind this erratic journey, however, everything is precisely controlled. Gears, cranks and oscillations combine their regular movements to produce something that looks wonderfully unpredictable. The mechanism turns order into apparent chaos, giving the little airplane its wandering, precarious flight.
But there is no need to worry too much about our hero. However rough the air becomes, however wildly his airplane bounces through the sky, we know something he does not yet know: in the end, he will make it safely back to earth.
The main mechanism
WAP is a paper automaton whose main mechanism is Redtenbacher’s variation of the Cartwright straight-line mechanism: a twin gear driving a common slider crank. When the two gears have different numbers of teeth, the up-and-down motion of the bar results from the addition and subtraction of two sinusoidal functions.
Straight-line generation, determined here by the vertical motion of the bar, was an important problem in the early history of mechanics. In WAP, the apparently random motion of the unlucky airplane is generated at the centre of the beam, which is free to rotate. At that point the two sinusoidal movements produce an oscillation which, combined with the vertical displacement of the bar, creates the characteristic air-pocket-like shaking.
The main mechanism in WAP uses two gears with a ratio of 1.2 (18/15 teeth). The complete motion cycle is produced after five turns of the handle.
Leave a Reply