Compound Rod

For illustrating expansion by heating and contraction by cooling.

Comprising a mild steel bar 110 x 10 mm. length x diameter, on rod with wood handle, overall length approx. 280 mm. with metal cast gauge, sliding fit over ends of bar and with hole 10 mm. bore in one Arm.

Represents a typical air cooled, side-valve four-stroke petrol engine with the operation of the valves clearly evident, cams being driven by a gear train from rear of the main crank. As with the two-stroke model, simulated spark plug uses a small lamp to indicate the firing point. Screw terminals are provided for connection to 3 Volts battery. Cross-section of carburetter is shown. Mounted on base