BACK injuries can be a problem for maintenance staff working underneath trains, so Metronet asked Harmill Systems to develop a trolley-mounted access seat which would improve the ergonomics of working in a depot inspection pit on London Underground.

The 60m long pit at the Waterloo & City Line depot is only chest-deep, making it awkward to access the underside of trains. To make it easier for staff to carry out work on the rolling stock, Harmill designed a moving chassis which runs on rails installed along the bottom of the pit. Across this chassis are two stainless steel shafts, held in place by shaft blocks, which act as runners for four low friction linear bearings supplied by SKF Engineering Products. These in turn support a small platform on which a 19 tonne bottle jack is mounted, topped by a seat and seatbelt assembly from a fork-lift truck.

An engineer strapped in the seat can move around and along under the full length of the train. From the seat he has full control of his movements in three dimensions, and he can swivel and recline to increase his reach. Metronet installed the first trolley for testing last summer, and a second trolley is now being supplied for an inspection pit at another Underground depot.

Harmill Systems, UK