G class

G class or Class G may refer to:

Locomotives

Ships

Other uses

NZR G class (1928)

The NZR G class was a type of Garratt steam locomotive used in New Zealand, the only such Garratt type steam locomotives ever used by New Zealand Government Railways. They were ordered to deal with traffic growth over the heavy gradients of the North Island Main Trunk and to do away with the use of banking engines on steep grades. They were one of the few Garratt designs to employ six cylinders. A mechanical stoker was used to feed coal into the locomotive.

Introduction

In 1928, New Zealand Government Railways obtained and operated three unusual Garratt locomotives in the 4-6-2 + 2-6-4 layout from Beyer, Peacock and Company of the United Kingdom. These engines had three cylinders (16.5-by-24-inch or 419-by-610-millimetre) on each of the two set of engine frames, thus creating a 6-cylinder Garratt. The engines entered service in 1929.

Walschaerts valve gear operated the outside cylinders with the inner third cylinder operated by a Gresley mechanism. The locomotives proved a disaster on the light NZR tracks. W. W. Stewart, in his book When Steam was King (pp. 98–104) suggested the most likely reason was because the engines were too powerful for the system and also the valve gear mechanisms were complicated. Stewart stated, and existing photos verify, that the design was most unusual in that the coal bunker was carried on an extension to the boiler frame rather than the normal Garratt positioning on the rear engine frame.

G3 battlecruiser

The G3 battlecruisers were a class of battlecruisers planned by the Royal Navy after the end of World War I in response to naval expansion programs by the United States and Japan. The four ships of this class would have been larger, faster and more heavily armed than any existing battleship (although several projected foreign ships would be larger). The G3s have been considered to be proper "fast battleships" since they were well-balanced designs with adequate protection. Nonetheless the class was officially designated as a "battlecruiser" due to their higher speed and lesser firepower and armour relative to the planned N3 class battleship design. The G3s carried nine 16-inch (406 mm) guns and were expected to achieve 32 knots (59 km/h; 37 mph), while the N3s would carry nine 18-inch (457 mm) guns on the same displacement at the expense of a slower speed.

The G3 design was approved by the Board of Admiralty on 12 August 1921. Orders were placed in October—November, but were suspended later in November with the beginning of the Washington Naval Conference which limited battleship numbers. The orders were cancelled in February 1922 with the ratification of the Washington Naval Treaty which limited construction to ships of no more than 35,000 long tons (36,000 t) displacement.