Nice pictures. The destination displays are the original backlit LCD ones. As with nearly all such displays of that time they failed quite quickly and were replaced after a few years by the LED ones currently fitted.
From the list in the other thread linked earlier this appears to have been the trip on 13/7/93. I'm pretty sure that was when investigating low voltage performance, as an extreme case, as we were having trouble with operation at lowish voltage accelerating out of Ealing Broadway at the time. The Ongar trip provided data that ABB used to adjust some traction parameters. Later Ongar trips were to prove those fixes, but I can't recall what the 4-car trip was for. Eeek- nearly 30 years ago!
A reminder that the Central line was still not ATC at that time, you can see the external tripcock reset rope and a yellow switch below the driver's side front that may have been the tripcock cut-out switch, later Tripcock/ATC changeover? Design relics from a time when I suppose it was thought that having the rope dangerous to get at would instil more care not to SPAD. A bit of a nonsense really and a hazard for daily prep. Brought inside on later builds and on a D78 mod. The isolation switch outside was visible indication to 'operating officials' that the tripcock was cut-out, but it took a while for the logic to work through that since from 73TS onwards cutting out the trip enforced Slow Manual, that wasn't going to be something done unthinkingly. So again the switch could be brought in cab.
Yes. Doesn't stand a logical safety assessment overall though. Especially given that the track remains live, you have to either lean out of M door holding on with one hand and pulling the rope with the other, or actually descend the slippy coupler to the track to reach the rope on the earliest types. And maintainers were expected to do this even over depot pits. And as proved oh so often, time interval is a terrible protection from collision with the train in front.
Anyway, it will be interesting if anyone else has memories of 92TS to Ongar.
My recollection is that it had already been decided to close the Ongar service. Management didn't really want the traction voltage testing done up there in case it gave the wrong public impression - that the service might stay open. We had to justify the test trips as the most efficient way of gathering data and testing the solution. As mentioned I don't recall why the 4 car trip was made. Perhaps it was to show there wasn't really enough power even for a 4 car!
The original plan for electrification of the the section east of Stratford to Epping, and Ongar was to have a substation at Blake Hall this did not come about due the lack of money in the 1950’s after the 2nd World World War.
Of course, post-war intention was for Loughton to be the outer terminus of much of the cross-London service through the pipe. Even Epping was to be mostly a shuttle service from Loughton, replicating the GER/LNER pattern, let alone Ongar