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Steam Reversing Gear.

The action of the reversing gear is, briefly, as follows:—

When the lever in the cab is moved, steam is admitted to a steam cylinder placed in line with another cylinder filled with an emulsion. This is called the cataract cylinder. The steam piston is directly connected by a piston rod to a piston in the cataract cylinder, so that both move together. The motion of the cataract piston is controlled by the emulsion passing from one side to the other, through suitable mechanism, giving a slow, even motion to the crossheads, which are fixed to the ends of the piston rod. One crosshead is connected by a reach rod to the weigh bar shaft on the leading power bogie, and the other to the corresponding shaft on the trailing power bogie. Any movement of the reversing gear is therefore transmitted directly, and without jar, to the reversing gear of the locomotive.

Owing to the large diameter (6ft. 6in.) of the boiler, it has been necessary for sand domes to be dispensed with, the sand boxes being placed in various positions about the wheels they will serve with sand. For the same reason the locomotives are fitted with an unusually low funnel, the height of which is only 8in.

The Pyle-National turbo-generator supplying electricity to the headlights, cab lights, inspection points, etc., is placed on the running board alongside the smokebox, and the whistle lies fore-and-aft along the boiler, on the side of the dome.

These locomotives (which have undergone successful trial runs) have been classified “G,” and will carry the numbers 98, 99 and 100. For the present they will operate from Taihape to Taumarunui, on the North Island Main Trunk line.