8in Gun on Railway Mount Model 1918

The 8in Gun on Railway Mount Model 1918 saw US coastal defence guns and their barbettes mounted on a low loading railway carriage. Three actually made it to France in 1918, but none saw action.

Seven different types of Army and Navy guns could be mounted on this railway carriage. The Army guns were all 32 calibres in length, and were a mix of Model 1888, Model 1888 M.I and Model 1888 M.II. The Navy guns ranged from 30 calibres to 40 calibres in length, and were a mix of Mk I, Mk II, Mk III and Mk IV guns.

The Army guns used a hydro-spring recoil system. There was one hydraulic recoil cylinder and four spring recuperator cylinders, arranged symmetrically around the outside of the cradle.

The original elevation and traverse systems were rather too slow, and it took more than a minute to move it through its full range of motion in either direction. Anti- friction devices were then installed, reducing this to just over 20 seconds.

Elevation was controlled via a segmented circular rack attached to the bottom of the cradle. This was connected to a worm gear, which was connected by gears to a hand wheel. One turn of the hand wheel moved the gun up or down by 0.333 degrees, and it could be moved from 0 to 42 degrees. It thus took 126 complete turns of the handle to move the gun through its full range of elevation.

The traverse system was based around a circular rack that was mounted on the base ring. The upper part of the gun was carried on conical rollers carried on the outside of the base of the barbette. A pinion was mounted on the barbette and engaged with the teeth of the rack. This was connected by worm gears to a hand wheel. One turn of the hand wheel rotated the gun by just over 1 degree.

The railway carriage was a low loader type, with two axle bogies at each end. A fairly elaborate firing platform needed to be built before the gun could be fired. First the entire gun carriage was lifted up using four hydraulic jacks built into the carriage. Two lines of ‘H-beams’ (girders) were placed length ways under the carriage, sitting on the railway ties outside the rails. Six wooden cross ties were then placed across these beams, running sideways under the carriage. The entire carriage was then lowered onto these wooden beams. This system was put in place to absorb the horizontal element of the recoil and prevent damage to the tracks. Four outriggers were provided on each side to keep the carriage stable. It took at least 45 minutes to emplace the gun, and 25 minutes to prepare it for movement.

Ammo was carried in a separate ammunition car, which ended with a track and trolley to carry shells out towards the gun carriage. A series of two cranes could then be used to move the shells to the breech. If the gun was being fired at more than 35 degrees from the line of the track then the shells had to be unloaded and placed by the side of the carriage, where the second crane could reach them.

The 8in railway guns were produced as part of a programme to build 75 ton naval guns with all round traverse. Eighteen were completed by the end of the war, of which three actually reached France, but the war ended before they got into action.

Between the wars the railway guns went to the Coastal Artillery. The 8in guns, with their 360 degrees of traverse, were kept throughout the period and some were still in service in 1941. Some were used as coastal defence guns on Hawaii, while one reached the Philippines where it was placed at Corregidor, but wasn’t assembled in time to take part in the Japanese siege. 

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