Changing Trains

10 May 1998

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Overhead travelling cranes have now been fitted in a state-of-the-art railway workshop in London

A new landmark building in east London is an architecturally-acclaimed train shed, built as part of London Underground’s $4.4bn Jubilee Line Extension project which extends the “Tube” rail network from the centre through the Docklands district to the East End of the city.

The Stratford Market Depot is a crucial element in LU’s efforts to maximise train availability and has advanced overhead travelling cranes for high speed train servicing.

Three cranes have been installed in a contract won by Street Crane, a regular LU supplier for 25 years. The contract included supply, delivery, installation, testing and the provision of on-site training to LU staff.

The package comprises two double-girder cranes of 10t capacity and a single girder 2.5t-capacity special bridge crane. One of the 10t cranes is installed in the 13m-span workshop and stores bay; the other two cranes are in the 25m-span overhaul shop.

The 10t cranes have Street’s NS4 open-barrel hoists designed to aid accuracy on lifting and placement. They also have dual speeds on all motions to improve performance and safety in final manoeuvring.

The smallest of the three is used for power transfer. Trains entering the building take power from overhead wires up to the building perimeter, so to move within the building they need an auxiliary power supply. This is delivered by a moving trolley on the bridge crane that has power lines which hook up to the traction units.

A 650V DC supply is drawn from bus bars running along the length of the bridge. These bus bars themselves draw power from a similar bus bar installed parallel within the crane rails.

SC Smartdrive, inverter based, infinitely variable motion control, allows the the long-travel speed of the crane to be matched to that of the locomotive as it is moved slowly in the depot.

The bridge crane and working cranes are operated by pendants that are mobile across the crane span.

The cranes may be now in place but the trains have yet to begin running on the new line. Operations were scheduled to begin in March this year but gremlins have got into the high-tech railway signalling software.

The new target is to get a partial service running sometime in spring 1999, and trials are scheduled for the second half of the year. The only firm assurance that the London Underground board feels confident to give is that the whole service will be fully operational by 1 January 2000.