1986ts Prototype Trains & 2024ts Pre-Production Trains

[jimbo]

It was mentioned in a recent thread that 1992ts' large curved windows weakened the body structure, and became loose. But this was trialed on 1986ts units, so why was it not revealed at that stage? I now realise that the 1986ts probably only traveled the Central Line once for display at Woodford bay platform. It sometimes ran in passenger service on the Jubilee Line to Charing Cross, which doesn't have the tight twists and turns of the Central Line, so perhaps never revealed the problem. Why was it trialed from Neasden on the Jubilee Line, which would have given it an easier time than its intended line? 

Why did the 1986ts trials come to an abrupt end after the Neasden derailment? Were they close to the end of the trial period anyway? Or was a design fault to blame which would have been expensive to rectify on the prototypes?

Is the same thing about to occur with the new Piccadilly Line trains, which are purely computer designed without prototypes. They feature walk-through car ends, thus loosing a lot of body rigidity. If the pre-production trains are trialed on the Old Dalby test track, they will not experience the twists and turns of service life. The Piccadilly is far less demanding than the original Central Line tunnels, but a later batch is destined for that line!

[t697]

I don't think body twist was the prime reason for glass debonding on 92TS. I think water trapping and resultant corrosion at the bond line was the prime cause. Even assuming the 1986TS was properly representative of 92TS in the window detailing, it would probably have been many years before the problem became fully apparent.

A bit of both reasons for the Neasden derailment bringing the end of trial 86TS service. Secondary retention of the gearbox torque reaction link needed adding and quite a bit of useful experience had been obtained anyway.

Computer modelling of structures has advanced a lot since the 1986TS so as with 09TS and S stock, no prototype designs this time round.

[Tom]

From what I remember (having been in the cab of the Green train several years later) the cab layout was very similar to that of 1983 Tube Stock - hence running it on the Jubilee line.

At the time various parts of the Central line used 33⅓Hz track circuits (the Ealing Broadway branch was one such section) and the 1986 stock with various experimental electronic devices would have probably been prohibited due to Electro-Magnetic Interference concerns.

[100andthirty]

Feb 14, 2022 18:18:53 GMT Tom said:

From what I remember (having been in the cab of the Green train several years later) the cab layout was very similar to that of 1983 Tube Stock - hence running it on the Jubilee line.

At the time various parts of the Central line used 33⅓Hz track circuits (the Ealing Broadway branch was one such section) and the 1986 stock with various experimental electronic devices would have probably been prohibited due to Electro-Magnetic Interference concerns.

Indeed, the control desk was the same as in 1983 tube stock as extras were bought and free issued for the 1986 tube stock. In addition LU managed the contract with Plessey (now Siemens) for the control and monitoring system so that it could ensure that the electronic systems across the three trains from two different manufacturers would talk to each other.

1986 tube stock was helpful in a number of ways. It showed that welded aluminium bodies would work well, that steering bogies were a step too far and that overhead door operators using rubber belt drives (as per the concurrent class 508/317 designs) didn't work well on the curved doors of tube stock. The most efficient structure was the version supplied by BREL. Sadly when they won the contract, they adopted the Metro-Cammell layout instead.

And finally, the first two trains of 2009 tube stock were, effectively prototypes. Once their testing work was complete, they were returned to Derby to be brought up to the standard of the others. They changes were VERY extensive.

[Chris L]

The blue train featured the large windows and it looked like the apertures were cut with an old fashioned can opener.

[100andthirty]

Many welded aluminium bodyshells are manufactured with no window apertures and they are cut out later.....think giant can opener!

[d7666]

I'm more than a bit puzzled why in one part people are refering to body corrosion around windows yet in another part are refering to aluminuim which does not corrode (well not in the sense meant here).

[100andthirty]

Aluminium does corrode, but unlike most steel, the corrosion sticks to and protects the metal underneath. Another factor is that the volume of aluminium oxide is much bigger than one might expect. And if water, mixed with, say, cleaning fluid gets lodged in "nooks and crannies" then some comparatively large amounts of aluminium oxide powder can be produced. I remember this being demonstrated in chemistry lessons at school many years ago.

the original glazing system for 1992 tube stock involved bonding the windows to the body rather like the process for securing most modern car windscreens. This requires an excellent chemical bond to the glass and to the aluminium aperture. This involved meticulously preparing the aperture and treating the surface that receives the adhesive with a suitable etch primer to deliver a much better bond than would be achieved if the adhesive was applied to the bare aluminium. Based on what was found both in replacing loose windows and later when the new window frames were fitted, attention to detail on both the quality of the manufactured apertures and the quality of the etch priming was sometimes not up to the standard. Thus there were some of the "nooks and crannies" that allowed water to collect.

[jimbo]

It wasn't just the windows that came loose on 92TS. The car ends and cabs came adrift and had to be taped up for some years! Did these follow a design trialed on 86TS? Perhaps the trials didn't run long enough to reveal these problems. Then the destination displays gave out after a short while!

[Tom]

The destination display issues came first - I can remember the temporary cards in the 'M' door before the tape.

Were the original destination displays LED Matrices too? I can't remember.

[rincew1nd]

At one point (not sure if it's still the case) the longest thread on the Central Line board was dedicated to that fact that there was "Less tape on cabs".

[metman]

Yes I recall that too!

I have also seen a lot of tape on the 1996 tube stock too so perhaps it’s a modern construction technique issue?

[100andthirty]

Both the 1986 tube stock and 1992 tube stock had the body ends constructed separately from the rest of the car and were fitted later. 1986 tube stock used composite materials for the body ends and 1992 tube stock used aluminium. I think it's well known that many of the body ends "didn't survive very well" (delicately put!). The joints between the body and the ends were sealed with what was claimed to be a "flexible for life" sealer. I remember escorting a senior employee from the supplier around one of the depots and explaining about the flexible for life sealer, before stopping adjacent to a body end, and digging out a piece of filler which I snapped in two in front of him. The material had set solid and wasn't sealing anything. This was the reason for all the tape!

[Chris M]

Feb 21, 2022 21:06:18 GMT rincew1nd said:

At one point (not sure if it's still the case) the longest thread on the Central Line board was dedicated to that fact that there was "Less tape on cabs".

It turns out that it was three years ago tomorrow that I compiled the list of longest threads. Seems like a good time to see what has changed since then.