Upper and lower trolleys are driven by trolley travel gears and all trackwheels can be driven or braked. A maintenance slewing crane of 13 tonnes capacity is arranged on top of the pier leg, and can directly pick up components out of the trolleys and the machinery room and lower these to the ground. The radius and lifting capacity of this crane is suitable for the heaviest machinery components.

The cranes run on an 800m track which spans the dock and the block assembly area where large weldments are made up. The loaded weight of each crane - approximately 4000 tonnes - is taken on 64 special anti-friction bearing mounted wheels, each of 90.2cm (35½ins.) diameter. Twelve identical driving motors are fitted - six to each leg - so arranged to provide direct drive to 36 of the wheels. Hydraulically-operated rail clamps are fitted to prevent the crane from being blown along the track in high winds. In operation each crane moves along the track at a speed of about 30 metres (98 feet) per minute, although this can be increased to 45 metres (147 feet) per minute for loads of 100 tonnes or less.

Special devices ensure that the legs move at identical speeds, thus preventing skewing.

If, however, the legs should become more than 250 mm out of step the drive to all wheels is automatically cut off.

In the skewed position only the sheer leg can be moved until correct alignment is regained with the pier leg.

Extensive safety devices and electrical interlocks are provided for all movements and operating conditions.

An interesting and unique feature of the cranes is that they are powered by electricity generated on board.

The generating plant is installed in the top section of the pier leg and consists of the following: - Two Ruston AR2 1350 b.h.p. 750 r.p.m. main diesel engines, each driving two x 365 KW. 600V D.C. generators directly coupled, and one 90 KW 600V D.C. and one 45 KW 300V. D.C. generators belt-driven at twice engine speed. The two 365 Kw. generators supply power for the main hoisting movements, while the smaller generators supply power for the Upper Trolley and Lower Trolley cross-travel motors respectively. A braking alternator is also directly attached to each main diesel engine shaft to provide regenerative braking when necessary.

In addition to the two main diesel-generating installations each crane is also equipped with two 170 h.p. Ruston diesels which each drive a 120 KW 440V three-phase alternator to give supplies to pumps, lighting, lift, and maintenance crane and also control voltages through transformers.

Speciffically, only one of these diesel alternators is needed for the operation of the Samson crane, the second merely acting as standby. For full operation Goliath requires both engines running.

Now much beloved Belfast landmarks, their future was assured in 2003 when they were scheduled for preservation.