Collision and derailment at Neville Hill Depot (13/11/2019)

[ainsworth74]

There are no guarantees but, from a safety point of view, give me a new train that's passed modern crash-worthiness standards over an HST any day; the risk is so, so much lower.

Yes mostly because, as much as people seem to be trying to ignore it(!), on a modern train like the 800 the cab is part of the structure of the train that is protected by crumple zones and similar mechanisms whilst on older trains, like the HST, the cab is very much part of the crumple zone!

 

[hwl]

There always is a certain amount of luck. Look at seat maps of air crashes and you see a whole row died with a single survivor who somehow got away with it.

But at crashes at that speed there is a limit to what can be engineered to protect the driver and then a mix of luck and the laws of physics take the reigns

Indeed - the driver of that 66 whose the side of cab was hardly damaged ended up being drowned by ballast/soil when it over turned and ploughed through the garden as there was less room to manoeuvre round the drivers seat and escape.

 

[richw]

The 800 cab (see above drawing) didn't get damaged the nose cone did.

I’ve read unconfirmed reports the HST cab was damaged with the desk moved. Yet everyone seems focused on the cosmetic damage to a piece of fibre glass

 

[Raul_Duke]

I’ve read unconfirmed reports the HST cab was damaged with the desk moved. Yet everyone seems focused on the cosmetic damage to a piece of fibre glass

I’d be surprised if it wasn’t. There’s very little to an HST cab. Solid as they look.

 

[LOL The Irony]

The instructior in the second mans seat in the 66 at Great Heck survived a closing speed impact at 142mph on his side of the cab.

His side of the cab tore open the DVT.

I’ve read unconfirmed reports the HST cab was damaged with the desk moved. Yet everyone seems focused on the cosmetic damage to a piece of fibre glass

It's because we probably expect a trains crumple to be similar to that of a car.

 

[option]

If the entire nose cone was destroyed at 15mph, that means a dead driver at higher speed collisions. Not great. What's the maximum speed collision possible on the ECML?

As already said, 250mph.
Your not going to design anything that could survive those forces, & you'll have a lot more than 2 dead drivers.
So, you design other safety systems to prevent the event happening.

 

[158747]

It derails, albeit across a set of points, on an impact speed of 9 mph.
One does wonder of all the computer collison simulations were done on the basis of a straight line impact and nobody though about impacts involving the set straddling a set of points!

The derailed vehicles were on straight track, it was the rear three vehicles which were over the points, these vehicles along with the three vehicles ahead of them remained on the track.

 

[Swimbar]

The derailed vehicles were on straight track, it was the rear three vehicles which were over the points, these vehicles along with the three vehicles ahead of them remained on the track.

The point I was making is that the set was still straddling a set of points when the impact occurred albeit the rear part of the train.
The fact that the whole set was not straight may have contributed to what happened.
Would it have behaved differently if all the train had been on a straight track?

 

[swt_passenger]

The point I was making is that the set was still straddling a set of points when the impact occurred albeit the rear part of the train.
The fact that the whole set was not straight may have contributed to what happened.
Would it have behaved differently if all the train had been on a straight track?

That’s what some of us have been asking for almost a fortnight. I’d expect the RAIB report will be the first clarification...

 

[Dieseldriver]

The instructior in the second mans seat in the 66 at Great Heck survived a closing speed impact at 142mph on his side of the cab.

You are correct however he wasn't sat in the seat at the time as he had partially evacuated the cab into the corridor behind. Had he been sat in the seat at the point of impact I don't think he'd have lived (or at the very least he'd have been seriously injured). For such a high speed impact, the class 66 actually stood up remarkably well. The DVT on the GNER train on the other hand was completely destroyed due to the sheer difference in weight between the two trains and the differing heights of them due to the DVT being on the ballast.

 

[158747]

The point I was making is that the set was still straddling a set of points when the impact occurred albeit the rear part of the train.
The fact that the whole set was not straight may have contributed to what happened.
Would it have behaved differently if all the train had been on a straight track?

I don’t believe that the rear of the train straddling the points is relevant to the the derailment, I believe what may have happened was that the rear of the second and third coaches moved upwards in the impact causing the wheels to momentarily leave the rails. In this instant due to a combination of the length of the coupling bars between vehicles and the dampers between vehicle ends and coupling bars, the dampers extended causing the vehicles to move to the right, as can be seen from the photo of the train earlier in this thread that both vehicles moved the same distance and in the same direction.

 

[Meerkat]

125mph, crashing into something coming 125mph the other way. Impact speed = 250mph.

someone once told me that calculating an impact speed like that wasn’t hugely relevant. Not sure I fully understood the physics, but I think it was on the lines of hitting a car head on, both doing 70, was no worse than hitting a wall at 70, as you were still going from 70 to zero. I assume it only works if both vehicles are matched so they both stop dead asbsorbing only their own energy, rather than one being bounced back.
Anyone clarify the (in)accuracy of this?

 

[PG]

I don’t believe that the rear of the train straddling the points is relevant to the the derailment, I believe what may have happened was that the rear of the second and third coaches moved upwards in the impact causing the wheels to momentarily leave the rails. In this instant due to a combination of the length of the coupling bars between vehicles and the dampers between vehicle ends and coupling bars, the dampers extended causing the vehicles to move to the right, as can be seen from the photo of the train earlier in this thread that both vehicles moved the same distance and in the same direction.

On the face of it that is a plausible theory... I guess in around 10 months the RAIB report will reveal all.

 

[swt_passenger]

someone once told me that calculating an impact speed like that wasn’t hugely relevant. Not sure I fully understood the physics, but I think it was on the lines of hitting a car head on, both doing 70, was no worse than hitting a wall at 70, as you were still going from 70 to zero. I assume it only works if both vehicles are matched so they both stop dead asbsorbing only their own energy, rather than one being bounced back.
Anyone clarify the (in)accuracy of this?

[Googles...]
There is a myth busters episode on YouTube that seems to demonstrate exactly what you’re saying.

 

[dosxuk]

someone once told me that calculating an impact speed like that wasn’t hugely relevant. Not sure I fully understood the physics, but I think it was on the lines of hitting a car head on, both doing 70, was no worse than hitting a wall at 70, as you were still going from 70 to zero. I assume it only works if both vehicles are matched so they both stop dead asbsorbing only their own energy, rather than one being bounced back.
Anyone clarify the (in)accuracy of this?

It depends what you're looking at. If you look at the overall vehicle, then yes, it's decelerating from 70 - 0, and the g-forces on an occupant will be in line with that.

If you look at an individual component, which relative to the vehicle is traveling at 0, it will come into contact with an object traveling at 140, and have to deal with the energy of that collision.

The amount of energy involved in a -70/+70 collision is the same as a 0/+140 collision. How the effects of that energy is handled would be different though.

 

[Meerkat]

Double the energy, but dissipated across two vehicles - one of the vehicles doesn’t absorb the energy of both???
And the individual component is doing zero relative to the car at the start and finish. It still doesn’t decelerate by 140mph

 

[158747]

On the face of it that is a plausible theory... I guess in around 10 months the RAIB report will reveal all.

It will be interesting to read when the RAIB report is published.

 

[dosxuk]

Double the energy, but dissipated across two vehicles - one of the vehicles doesn’t absorb the energy of both???
And the individual component is doing zero relative to the car at the start and finish. It still doesn’t decelerate by 140mph

At some points during an impact it may well be going at -140 compared to its owner vehicle. The coupling doors on the front of the IEP in this incident have been moving in the opposite direction to those at the back at times during the impact.

It's only in a perfectly matched collision that impact forces will be shared equally between the vehicles, as soon as there are differences in mass, velocity, design or impact location, both vehicles will behave differently, with their component parts being subject to wildly different amounts of impact energy.

 

[superkev]

Any update on this. Theres a rumour going round that 4 new coaches or bodyshells are required.
K

 

[LOL The Irony]

Any update on this. Theres a rumour going round that 4 new coaches or bodyshells are required.
K

And the HST could get away with just a new cab, right?

 

[swt_passenger]

Any update on this. Theres a rumour going round that 4 new coaches or bodyshells are required.
K

There’s been rumours like that almost since this thread started, and I suspect they’re mostly rubbish...

 

[43096]

And the HST could get away with just a new cab, right?

"Could" being the operative word.

 

[westv]

There’s been rumours like that almost since this thread started, and I suspect they’re mostly rubbish...

Why not info from LNER seeing as this appears to be affecting their services.

 

[AndrewE]

I’d be surprised if it wasn’t. There’s very little to an HST cab. Solid as they look.

But didn't a class 47 come off a lot worse in a similar depot collision with an HST 30 or 40 years ago?

 

[Taunton]

But didn't a class 47 come off a lot worse in a similar depot collision with an HST 30 or 40 years ago?

You are correct, it was reported at the time. The HST broke the nosecone, the 47 cab was crushed back to the bulkhead. And it was described as "demonstrating the crashworthiness of a modern unit".

This comes up elsewhere too. Mk 3 coaches are derided for not being adequately crashworthy. Yet when they were new and involved in some substantial collisions, they were praised for being able to stand up to the forces. The same even was said about Mk 1 stock in the 1950s, how steel construction and buckeyes made them very resistant.

 

[Raul_Duke]

But didn't a class 47 come off a lot worse in a similar depot collision with an HST 30 or 40 years ago?

You are correct, it was reported at the time. The HST broke the nosecone, the 47 cab was crushed back to the bulkhead. And it was described as "demonstrating the crashworthiness of a modern unit".

This comes up elsewhere too. Mk 3 coaches are derided for not being adequately crashworthy. Yet when they were new and involved in some substantial collisions, they were praised for being able to stand up to the forces. The same even was said about Mk 1 stock in the 1950s, how steel construction and buckeyes made them very resistant.

It’s similar to cars.

If I crash an old armour plated steel 60’s car (with seatbelts), the car will look like it’s taken much less damage than a modern Volvo for example.

However, I will be splattered to a much smoother jelly over the inside of the old car than I would the Volvo.

Coaches are different as obviously you don’t want them telescoping and crumpling in the same way.

If you ever see a 222 without it’s cab shell then it’s a very substantial cage of steel bars and you can certainly see the “survivable area,” in it.

Whereas a HST is more or less some 70’s fibreglass bolted to the frames.

 

[AndrewE]

It’s similar to cars. If I crash an old armour plated steel 60’s car (with seatbelts), the car will look like it’s taken much less damage than a modern Volvo for example.

However, I will be splattered to a much smoother jelly over the inside of the old car than I would the Volvo.

Coaches are different as obviously you don’t want them telescoping and crumpling in the same way.

If you ever see a 222 without it’s cab shell then it’s a very substantial cage of steel bars and you can certainly see the “survivable area,” in it. Whereas a HST is more or less some 70’s fibreglass bolted to the frames.

I don't think that's a very convincing explanation. Your seatbelts in the old car will probably have injured you more (and you will have got worse whiplash) because of the faster deceleration from not having a crumple zone.
The HST's fibreglass nose / cab did a lot more damage to the old sheet steel on a substantial steel framework than anyone expected, and might have been providing the survivable area by itself. The "70s fibreglass" obviously wasn't designed as a crumple zone, but equally I assume the class 47 front was designed to protect the driver from most things that it might impact.

 

[Raul_Duke]

I don't think that's a very convincing explanation. Your seatbelts in the old car will probably have injured you more (and you will have got worse whiplash) because of the faster deceleration from not having a crumple zone.
The HST's fibreglass nose / cab did a lot more damage to the old sheet steel on a substantial steel framework than anyone expected, and might have been providing the survivable area by itself. The "70s fibreglass" obviously wasn't designed as a crumple zone, but equally I assume the class 47 front was designed to protect the driver from most things that it might impact.

Fair enough. I know what traction I’d rather hit an obstruction in though.

 

[Chris M]

I also remember the Mark 3 coaches being extensively praised after the Ladbroke Grove and/or Southall accidents, obviously compared to to earlier generations of rolling stock.

 

[JN114]

I also remember the Mark 3 coaches being extensively praised after the Ladbroke Grove and/or Southall accidents, obviously compared to to earlier generations of rolling stock.

And then criticised after Ufton, particularly with regard to window resilience in a rollover event.