The Gogar depot, serving the new Edinburgh tram network, is using a double girder 6.3 tonne travelling crane to maintain the fleet of 27 trams and support the Unimog track maintenance vehicle. The UK’s largest overhead crane manufacturer, Street Crane Company, installed the crane.
At 42.9 metres long the seven-section articulated Edinburgh trams weigh in at 56 tonnes per vehicle and are the largest operating in the UK. Easy passenger access is provided by a low floor that is just 300mm from the rail. This has been made possible by the adoption of compact axle and drive design and the repositioning of all but essential auxiliary equipment to the roof of the vehicle. The overhead crane is essential for access and maintenance of the roof pantographs and to service the pods on the roof containing air-conditioning and other key electrical equipment.
The 19 metre crane, with a 5.5 metre height of lift, spans three tracks within the depot and runs almost the full length of the building to give maximum flexibility in transporting materials. Elevated access platforms at the eastern end of the building allow engineers easy access to the vehicle roof and covered pits permit access to the undercarriage. Jacks, located in the floor in the western end of the building, enable carriage bodies to be lifted from the tram bogies.
The crane has been installed within a limited height envelope. A top running carriage is therefore installed, permitting the maximum height of hook lift and for greater safety in transporting of loads. The Street Crane ZX84 wire rope hoist includes safety and productivity features such as overload protection, positive braking on the primary gear box shaft, a fully enclosed permanently lubricated gear box and a rope guide to clamp the rope in position.
In addition to servicing the trams, the crane will also be used to load and unload the track engineering vehicle, a specially designed Unimog truck that can straddle the track for maintenance and repairs.
Dual speed operation is provided on all crane motions with 40/10 metres per minute in long travel, 20/5 metres per minute in cross travel and 5/1.25 metres per minute for lift. All crane movements are controlled from a radio remote device so that the operator can always work from the location that gives best visibility and greatest safety. A conventional pendant control is also provided as a back-up.