Video tapes and 3D printers

Hearne House, home to London Underground's technical services section, offered guided tours at the last opening of London Transport Museum's Depot. It was a wonderful mixture of old and new technology, as well as a fascinating glimpse behind the scenes of the Tube. 

 

First stop was track monitoring. Since every bit of the track needs to be checked regularly, some trains are fitted with equipment to film and monitor it. The data is then reviewed at Hearne House, and necessary repairs can be ordered. An Automatic Track Monitoring System has been developed: it records track condition using images, laser measurements, and noise and vibration data. RFID tags map the location and the data is sent to Hearne House via wifi. Faults can be identified, and their rate of degradation as well as their current state can be monitored. 

However, its predecessor has not fallen out of use yet: Auto Video Inspection uses VHS tapes to record images of the track. While you might think the cameras could be replaced with digital versions, other parts of the system such as specialist DOS software pinpointing the location of each image are harder to update. Thus the near-obsolete technology will enjoy a little more use on the Underground (at least as long as old equipment can be cannibalised for spare parts).
 

By contrast, the experimental workshop has some state-of-the-art equipment including a 3D printer. It's invaluable for producing prototypes which can, for example, be used to check that a part can actually be fitted. While CAD can ensure that once in place, the part has the space it needs, getting it there can be another story! Having a plastic model to experiment with therefore saves much time and money.

However, for our visit the printer produced Big Ben and the Gherkin, as well as roundel keyrings. The white material supports overhanging parts of the model during printing, and is washed away when the piece is complete: hence the yellow models apparently emerging from cocoons. 

There's a lot of other testing going on in the workshop, with plenty of specialist machinery including a dust chamber to test how well-sealed components are, another chamber which can create variable levels of heat and cold for sustained periods, and machines which replicate the ranges of movement different parts will endure in use. 

A thermal camera produced an oddly disconcerting self-portrait! Other equipment such as an abrasive water jet cutter weren't on view, but we did see video of them in operation. Overall, this was an amazing opportunity to understand a little more of the incredible work required to keep the city moving.

If you haven't been to the Acton Depot, it's well worth a visit. The next open weekend is in September; Hearne House tours may not be available but there are more than enough other activities and things to see to ensure a fascinating visit.