Memories of working on APT


If you have any memories of working on the APT - Please let me know !

Tony Randall

The commissioning of the APT-P trains was in the hands of a specialised Commissioning Team and we just installed the required test instrumentation and analysed the results. As a completely new train, it would have to go through our full programme of tests for such trains. Only two major criteria applied - that they would not apply any high lateral (sideways) or vertical forces to the rails on curved track whilst in operation and that the train would give a good ride to the passengers when finally in service. The heavy axle-hung motors on the electric locomotives in use on WCML at the time were causing a lot of track damage so moving the traction motors inside the body was expected to alleviate this problem.

When the Power Car 49001 arrived at the RTC Derby weeks before the first Trailer Rake 370001, we started initial test on this. We had a multi-channel weighbridge at Derby and individual wheel weights for most vehicles on BR could be taken. This could check whether the bogie primary springs were set correctly and there was no excessive weight on any individual wheel.  One cell could be lifted or lowered under one of the wheelsets and the other wheels lifted onto packing pieces to simulate the Power Car being on a canted curve but statically. Historical information has allowed engineers to determine that, if no wheelset did not lose more than 60% of its normal load in this condition, then the vehicle safe to run. We then installed any measurement transducers known to be needed for the test programme around the Power Car ready for when we had the full set of vehicles. Any measurement transducers available at this time were fairly basic and any computers very slow and not able to cope with large amounts of data. We put a Tacho generator on the end of one axle to give us a speed unit (our instruments could also use the Tacho pulses to get a linear distance), linear potentiometers, standard accelerometers, strain gauges for any stresses and pressure transducers plumbed into the air system to measure various air pressures as required. Output voltages were then recorded onto a basic 12 channel magnetic tape recorder or onto paper chart records for manual analysis. Load cells and accelerometers were also installed onto the current collecting head of the pantograph together with a potentiometer on the operating arm to get height and stagger measurements on the overhead 25KV wire (we do these measurements regularly with specialised Test Cars). The pantograph is mounted directly on the bogie and the body tilts around it, so no problems were expected with a dewirement on a sharp curve.

We could carry out some testing locally because we had Laboratory Coaches which could supply the auxiliary power supplies needed to work the tilt system, etc. and used the time for familiarisation for the various systems.

The 3-car trailer rake 370001 was converted to a laboratory unit by removing all seats and installing racks to hold the recording equipment. The kettle and teapot area was the most important area on the whole train after the loo facilities!

After similar initial tests to 49001 at Derby (the articulation caused major problems using the weighbridge), we transferred al vehicles to Crewe ETD and Shields Depot in Glasgow for running tests under the wire. We computed the track forces using accelerometers on the bogies and Newton's Law of Motion F = Ma.

Various recordings were carried out on behalf of the Commissioning Team to help them to set up the tilt system to the best setting for passenger comfort. We installed accelerometers at various points on the floor of various vehicles to assess the vehicle ride for the best passenger comfort. Tests in the past had shown that a frequency of 1 Hz on the vehicle body would cause travel sickness so modern vehicle suspensions are designed to eliminate this frequency (5 Hz is perfectly acceptable). Travel sickness on APT was probably caused by passenger being able to see out of the windows. We tilted by up to 15 degrees on top of the standard track cant of 6".

TR1 Test Rake
Layout of APT-P Test Trailer Rake No 1 (TR1)

Test Trailer Rake 1Test Trailer Rake 1Test Trailer Rake 1

Test Trailer Rake 1Test Trailer Rake 1Test Trailer Rake 1

If you have any memories of working on the APT - Please let me know !


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Last Revised: 09.08.2018 10:00
by R G Latham
© 1998