Fig 26 shows a schematic of the mechanism layout for a mechanical toy. Turning a handle on the side makes a figure wave its arm up and down while simultaneo...

(a) A cam and follower mechanism converts the rotary motion of the handle into the up-and-down motion of the figure's arm. [1] This is the standard mechanism for producing controlled reciprocating or oscillating output from a rotary input, and it is widely used in toys, engines, and automated machinery.

(b) A cam is a specially shaped disc (or lobe) fixed to the rotating handle shaft. As the handle turns, the cam rotates with it. The cam profile has a varying radius from its centre: some portions bulge outward (the "rise") while others sit closer to the centre (the "fall"). [1] A follower, which is a rod or lever connected to the figure's arm, rests against the cam surface. As the cam rotates, the changing radius pushes the follower upward when the high-radius lobe passes underneath it, then allows the follower to drop back down (under gravity or spring return) as the low-radius portion comes around. [1] This continuous rotation produces the repetitive waving motion of the arm.

(c) Bevel gears transmit rotary motion through a 90-degree angle. [1] A pair of bevel gears has cone-shaped teeth cut along angled faces, and the two gear shafts meet at right angles. When one bevel gear turns, its angled teeth mesh with the partner gear and redirect the rotation by 90 degrees, making them ideal for driving the horizontal turntable from the vertical handle shaft.

(d) The gear ratio is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driver gear:

\[ \text{Gear ratio} = \frac{\text{Teeth on driven gear}}{\text{Teeth on driver gear}} = \frac{36}{12} = 3 : 1 \]

The turntable gear is three times larger than the handle gear. [1]

(e) 3 complete turns of the handle are needed for one full rotation of the turntable. [1] Because the gear ratio is 3:1, the driven gear (turntable) turns three times slower than the driver gear (handle). For every three rotations of the smaller 12-tooth gear, the larger 36-tooth gear completes exactly one rotation. This speed reduction also means the torque at the turntable is three times greater than the torque applied at the handle, though speed is sacrificed.