Safety of EPB and SUB southern EMUs

[Bikeman78]

Would it have stopped the body overriding?

Buckeyes are generally considered better at keeping trains coupled and in line during a collision. I think it's quite rare for vehicles within a train to over-ride if they have buckeye couplers. That being said, I've read the Lewisham report. The force of the crash broke the buckeye between the eighth and ninth carriages of the EPB train with the ninth over-riding the eighth. The tenth carriage was relatively undamaged despite having 34066 embedded in the rear cab.

 

[Taunton]

The severity of the Cannon Street incident surprised me too. In the way of the time passengers had swung the carriage doors open shortly before coming to a stand, and some had actually alighted onto the platform before the collision. It wasn't going that fast.

Must have been early 1979 that I arrived midday at Liverpool Street. There had obviously been a buffer stop collision on the westerly of the two platforms that used to extend further into the concourse (No 10 ?). Not only were the stop blocks damaged but it had struck right back into the concourse/platform asphalt surface, which was all buckled up and cracked. Stock removed and a large civils gang were working full speed inside some erected fencing to fix it all. Never heard anything more about it, yet the speed, and indeed likely age of whatever stock it was, would have been much the same.

 

[PG]

Must have been early 1979 that I arrived midday at Liverpool Street. There had obviously been a buffer stop collision on the westerly of the two platforms that used to extend further into the concourse (No 10 ?). Not only were the stop blocks damaged but it had struck right back into the concourse/platform asphalt surface, which was all buckled up and cracked. Stock removed and a large civils gang were working full speed inside some erected fencing to fix it all. Never heard anything more about it, yet the speed, and indeed likely age of whatever stock it was, would have been much the same.

Maybe an ECS movement involved? Which if no injuries resulted wouldn't have attracted media attention back then.

 

[matchmaker]

Buckeyes are generally considered better at keeping trains coupled and in line during a collision. I think it's quite rare for vehicles within a train to over-ride if they have buckeye couplers. That being said, I've read the Lewisham report. The force of the crash broke the buckeye between the eighth and ninth carriages of the EPB train with the ninth over-riding the eighth. The tenth carriage was relatively undamaged despite having 34066 embedded in the rear cab.

If you look at photos of the 1937 Castlecary disaster you will see how well the buckeyes kept the coaches in line.

 

[BayPaul]

The severity of the Cannon Street incident surprised me too. In the way of the time passengers had swung the carriage doors open shortly before coming to a stand, and some had actually alighted onto the platform before the collision. It wasn't going that fast.

Must have been early 1979 that I arrived midday at Liverpool Street. There had obviously been a buffer stop collision on the westerly of the two platforms that used to extend further into the concourse (No 10 ?). Not only were the stop blocks damaged but it had struck right back into the concourse/platform asphalt surface, which was all buckled up and cracked. Stock removed and a large civils gang were working full speed inside some erected fencing to fix it all. Never heard anything more about it, yet the speed, and indeed likely age of whatever stock it was, would have been much the same.

Presumably the number of open doors would have contributed to the damage? I would guess that an open door is even more of a structural weakness than a closed one (apologies if I am stating the obvious - I only just thought of it).

 

[Taunton]

I don't think the physical door being open/closed contributes anything. It is held in position by one latch.

Regarding the vehicle structural integrity with multiple door openings (and the same to a lesser extent for windows) that is pretty much down to the design of the load-bearing paths in the remainder of the structure. Before integral designs, which only came along with the Mk 2, the roof was never a structural part of the vehicle; in fact only a few years before the Cannon Street vehicles were built Eastleigh was turning out the same underframe and body design on 4-SUB units but with timber & canvas roofs; even steel roofs were decidedly post-WW2 for Southern electric stock.

 

[hexagon789]

Buckeyes are generally considered better at keeping trains coupled and in line during a collision. I think it's quite rare for vehicles within a train to over-ride if they have buckeye couplers. That being said, I've read the Lewisham report. The force of the crash broke the buckeye between the eighth and ninth carriages of the EPB train with the ninth over-riding the eighth. The tenth carriage was relatively undamaged despite having 34066 embedded in the rear cab.

I was thinking because there's nothing in the design to stop vertical movement, but I suppose they are much more effective than a three-link coupling and centre buffer

 

[edwin_m]

The severity of the Cannon Street incident surprised me too. In the way of the time passengers had swung the carriage doors open shortly before coming to a stand, and some had actually alighted onto the platform before the collision. It wasn't going that fast.

Must have been early 1979 that I arrived midday at Liverpool Street. There had obviously been a buffer stop collision on the westerly of the two platforms that used to extend further into the concourse (No 10 ?). Not only were the stop blocks damaged but it had struck right back into the concourse/platform asphalt surface, which was all buckled up and cracked. Stock removed and a large civils gang were working full speed inside some erected fencing to fix it all. Never heard anything more about it, yet the speed, and indeed likely age of whatever stock it was, would have been much the same.

Having re-read the report in response to this thread, the train was formed of three units, the middle one of which was of an older (Southern rather than BR Mk1-derived) design, though apparently still all-steel construction. This unit sustained the most damage despite not being in the lead, and the Inspector recommends that these designs are eliminated first as the Networkers come in to replace the EPBs. You don't state, and possibly don't know, what type of train was involved at Liverpool Street but the long platforms tended to be used by loco-hauled Cambridge and Norwich services which would have been at least Mk1 and possibly Mk2 by then. Even if an EMU, only the LNER-design Shenfield units were pre-Mk1 and I think they would be using other platforms. As you mention, the speed at Liverpool Street was unknown.

The other factor might be the nature of the buffer stop. Cannon Street had the traditional hydraulic ones providing retardation over a distance of two feet, after which they were fully compressed and became essentially an immovable object. Due to limited platform length a more modern friction buffer stop could not be fitted; these can retard the train with gradually increasing force over several metres and therefore produce much lower decelerations and forces within the train. A quick search finds the photo below shows traditional fixed buffer stops in Liverpool Street P9 and P10 in 1977, but the fact the train or the buffer stop had ploughed through the platform surface suggests that these or the rails they were bolted to would have been broken through to give a longer retardation distance, by design or otherwise, than at Cannon Street.

Pin on Bishopsgate

Oct 29, 2018 - Tweets about stuff including #Hackney, #London #history #media & despairing of politics. Hedging bets so also to be found on Mastodon @Li*****@*****

www.pinterest.co.uk

 

[Taunton]

There was still a 1950s belief that coaching stock might be rebodied during its life - initial specifications of the Mk 1 were to last 40 years, but with a rebody done after 20 years. Corrosion of the thin sheet steel of bodywork was a longstanding issue until (somewhat) overcome. Much of the construction cost is in the underframe and running gear. Not really followed through, but one such vehicle was done around 1960 by Eastleigh with a fibreglass body, which could have been even worse in a collision (ironically built on the underframe of the most damaged Mk 1 vehicle from the Lewisham accident), and another done in the 1970s, with a Pacer-style body from British Leyland. It still wasn't seen that overall structural integrity was an issue. And note that road vehicles have a long history of separate body (none too strong) and chassis.

Longitudinal telescoping protection is one direction to design against, but that's not going to protect against other directions, such as the overbridge falling down on top at Lewisham (there was a comparable one in Sydney, Australia), or the recent lorry falling onto a passing, and fortunately lightly loaded, Class 455 from a bridge