The Arrol Gantry was a large steel structure built by Sir William Arrol & Co. at the Harland and Wolff shipyard in Belfast, Northern Ireland. It was built to act as overhead cranes for the building of the three Olympic-class liners.
Beardmore's gantry at Dalmuir
From 1900 to 1906, Arrol had constructed a shipyard for William Beardmore and Company at Dalmuir on the Clyde. This included a large gantry structure over the building berth. In 1906 it was used for the construction of the pre-dreadnought battleship , then the largest battleship launched on the Clyde.
The Beardmore gantry was long, wide and high, spanning a single building berth. The structure was of two long steel truss girders, supported on ten pairs of steel truss towers, braced by cross trusses above. Nine electric cranes were provided, with four jib cranes along each side girder, each having a 5-ton capacity and 30 foot jib. These were travelling cranes and could be moved along the girder, or grouped together to share a heavier lift. They were intended to place the main hull plates into position, with a dedicated gang for each crane, forming the plates and riveting them into place. A central 15 ton travelling gantry crane was also provided, for lifting machinery along the centreline of the hull.
The Belfast gantry would be very similar to this first gantry, although larger at long and spanning two building berths. The central girder between the berths allowed the addition of a larger cantilever crane.
The Beardmore gantry had used tapered towers, with size and strength proportional to the load upon them. The base of each was spread into a triangular arch, giving a more stable base and also allowing a railway line to be laid through the towers, bringing construction materials. For the Belfast gantry, the towers were more parallel, with straight inner faces. This allowed temporary working platforms to be attached and relocated upwards as a hull was constructed, giving an additional working space and easy access to the outside of the hull, even with heavy equipment. The access within the gantry was also improved, with long sloping walkways and electric lifts, rather than the previous slow and hazardous use of ladders.
Construction
The Belfast gantry was commissioned by the White Star Line and Harland and Wolff and built by Sir William Arrol & Co. in 1908. It was feet long, feet wide and feet high. It was an essential part of the infrastructure needed for the construction of the and and remained in use until it was demolished in the 1960s to create space for storage and car parking.
Before the Gantry, the northern end of the Queen's Island shipyard had four building slipways, each with gantry cranes above them. The cranes formed three crosswise gantries over each slip, with jib cranes working from each upright. To make space for the two new slipways, three of the old slipways were given up. No 1 slipway remained and continued in use, with its original gantries, and was used for building liners such as the . The two new slipways were numbered 2 & 3. There were nine slipways at Queen's Island before this, eight afterwards but the other remained numbered as 5...9 and there was no longer a No 4 slipway.
The Gantry was built on three rows, apart, of eleven steel truss towers with three large truss girders between them, and lighter crosswise Warren trusses above this. The large girders provided runways for a pair of 10-ton overhead cranes above each way and lighter 5-ton jib cranes from the sides. Along the centre line ran a light Titan crane, with a reach of 135 feet and able to carry a 3-ton load at full radius, and 5 tons closer in. The cranes were electrically-powered and built by Stothert & Pitt of Bath. Access to the high girders was provided by three long ramps and also electric lifts for the shipyard workers. As Harland and Wolff were primarily a commercial yard, there was no need for the huge Titan cranes being built at this time for the naval shipyards of the Clyde, where heavy lifts of armour plate, or even entire turrets, were needed.
Olympic-class liners
Olympic and Titanic were built together, with Olympic in the No 2 slipway. Olympic was launched first, in October 1910, with Titanic seven months later. To provide better photographs against the steelwork of the gantry, Olympic's hull was painted white during building, then repainted after launch. Titanic was painted in White Star's black hull livery from the outset. was then constructed on the Olympic ways.