Hitachi 800 cracks
Discussion
Anyone here know anything about what is happeneing to the Hitachi trains with 'hairline cracks' ??
BBC article
Could be fatigue, but in steel components in trains... that stuff was surely sorted out donkey's years ago ?
Wrong steel used ?
Design errors ??
Anyway, my commiserations to anyone stuck becuase of delays today.
BBC article
Could be fatigue, but in steel components in trains... that stuff was surely sorted out donkey's years ago ?
Wrong steel used ?
Design errors ??
Anyway, my commiserations to anyone stuck becuase of delays today.
They're made from ally, rather than steel, so seemingly that makes any welding repairs more complicated. They've found cracks around the jacking points, which is a sort of ledge moulded into the bottom of bodyshell towards either end of the coaches to allow them to be lifted on jacks in the depot. It's structural, so a bit of a headache...
A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
I was in London last week and noticed that some of the GWR ones had white jacking points and others didn't. I did wonder if that was to show they had been checked.
Talking of HST, this week will be the last to catch one to the capital.
What magnificent service they have given to front line expresses over the last 40+ years.
Their loss wouldn't be so bad if anything that had come since was better for the passenger experience. Sadly they are not. Either more uncomfortable, noisy or both.
Talking of HST, this week will be the last to catch one to the capital.
What magnificent service they have given to front line expresses over the last 40+ years.
Their loss wouldn't be so bad if anything that had come since was better for the passenger experience. Sadly they are not. Either more uncomfortable, noisy or both.
Rich1973 said:
I was in London last week and noticed that some of the GWR ones had white jacking points and others didn't. I did wonder if that was to show they had been checked.
Talking of HST, this week will be the last to catch one to the capital.
What magnificent service they have given to front line expresses over the last 40+ years.
Their loss wouldn't be so bad if anything that had come since was better for the passenger experience. Sadly they are not. Either more uncomfortable, noisy or both.
Talking of HST, this week will be the last to catch one to the capital.
What magnificent service they have given to front line expresses over the last 40+ years.
Their loss wouldn't be so bad if anything that had come since was better for the passenger experience. Sadly they are not. Either more uncomfortable, noisy or both.
The HST, what an utter British design hero! Sadly missed!
The white jacking points is the paintwork; GWR's first batch are painted white and then vinylled green, so the body ends and fiddly bits like the door openings etc are still in white. The later batches are painted green.
Southerner said:
They're made from ally, rather than steel, so seemingly that makes any welding repairs more complicated. They've found cracks around the jacking points, which is a sort of ledge moulded into the bottom of bodyshell towards either end of the coaches to allow them to be lifted on jacks in the depot. It's structural, so a bit of a headache...
A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
Hmmm, why would you make these from ally rather than steel ??A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
(I guess casting something fiddly shaped in ally would be cheaper than in steel, so that's probably why.)
Given Hitachi must know to expect fatigue in these ally components, this might indicate they got their stress calcs wrong, or they're under unexpetedly higher load.
As said the bodyshells are aluminium which makes repairs and re-design more difficult (steel and ali have very different fatigue properties). I suspect the big worry, over and above the initial appearance of the cracks and short term solution, is where the cracks are propagating to. Both the yaw damper brackets and the lifting pockets are extensions of the bolster, If they are moving into the bolster seams that will be a real problem!
911newbie said:
Hmmm, why would you make these from ally rather than steel ??
(I guess casting something fiddly shaped in ally would be cheaper than in steel, so that's probably why.)
Given Hitachi must know to expect fatigue in these ally components, this might indicate they got their stress calcs wrong, or they're under unexpetedly higher load.
You're correct, bodyshells are easier/quicker to manufacture from extruded aluminium planks than steel and it offers a reasonable weight saving (around 10%).(I guess casting something fiddly shaped in ally would be cheaper than in steel, so that's probably why.)
Given Hitachi must know to expect fatigue in these ally components, this might indicate they got their stress calcs wrong, or they're under unexpetedly higher load.
I worked on the first aluminium bodied trains in the UK and (Cl 158) they had issues with bodyshell cracks around yaw dampers and door portals(fatigue related). There the issue was the current state of analysis available (mid 80's so early days of FEA) and lack of experience with the material/construction in this application meant the fatigue cycles and calculations were misunderstood.
In this instance they look like fatigue issues (I'm not involved so only a spectator); the issues on the Northern (CAF) units are I believe more to do with structural overload due to the design not respecting the tight curves in depots (<70m) so they are most likely UTS failures as the system locks up under rotation resulting in the bracket being ripped out.
Edited by nc107 on Saturday 8th May 13:54
911newbie said:
Anyone here know anything about what is happeneing to the Hitachi trains with 'hairline cracks' ??
BBC article
Could be fatigue, but in steel components in trains... that stuff was surely sorted out donkey's years ago ?
Wrong steel used ?
Design errors ??
Anyway, my commiserations to anyone stuck becuase of delays today.
I don't know about the 800 series but similar is happening on the 195's, yaw dampers pulling out from the body mounts. BBC article
Could be fatigue, but in steel components in trains... that stuff was surely sorted out donkey's years ago ?
Wrong steel used ?
Design errors ??
Anyway, my commiserations to anyone stuck becuase of delays today.
911newbie said:
Southerner said:
They're made from ally, rather than steel, so seemingly that makes any welding repairs more complicated. They've found cracks around the jacking points, which is a sort of ledge moulded into the bottom of bodyshell towards either end of the coaches to allow them to be lifted on jacks in the depot. It's structural, so a bit of a headache...
A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
Hmmm, why would you make these from ally rather than steel ??A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
(I guess casting something fiddly shaped in ally would be cheaper than in steel, so that's probably why.)
Given Hitachi must know to expect fatigue in these ally components, this might indicate they got their stress calcs wrong, or they're under unexpetedly higher load.
The mounting points look undersized to me but that's just my opinion.
911newbie said:
Hmmm, why would you make these from ally rather than steel ??
(I guess casting something fiddly shaped in ally would be cheaper than in steel, so that's probably why.)
Given Hitachi must know to expect fatigue in these ally components, this might indicate they got their stress calcs wrong, or they're under unexpetedly higher load.
Weight was the reason and the ability to manufacture more cost effectivly in aluminium.... If designed correctly by knowledgable people this is still the best way . (I guess casting something fiddly shaped in ally would be cheaper than in steel, so that's probably why.)
Given Hitachi must know to expect fatigue in these ally components, this might indicate they got their stress calcs wrong, or they're under unexpetedly higher load.
Southerner said:
They're made from ally, rather than steel, so seemingly that makes any welding repairs more complicated. They've found cracks around the jacking points, which is a sort of ledge moulded into the bottom of bodyshell towards either end of the coaches to allow them to be lifted on jacks in the depot. It's structural, so a bit of a headache...
A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
Probably naive questions, but are cracks around the jacking points an issue other than when the trains are being jacked ? And what would be the effect of failure of the yaw damper mountings - anything more than a bumpier than usual ride (though I appreciate that could cause issues elsewhere) ?A few weeks back they also found some cracks around the yaw dampers, which in turn was due to inspections after Northern had to withdraw a load of their new stuff (from a different manufacturer) for repairs!
Eeek!
I believe that there's a lot of electronic gubbins that needs to be removed prior to welding the cracks. With the sheer ubiquity of the class 800's on both the East Coast Mainline and the South West lines it's going to be a rather grim time for the travelling public - just when travel restrictions are being eased.
SD.
SD.
Lily the Pink said:
Probably naive questions, but are cracks around the jacking points an issue other than when the trains are being jacked ? And what would be the effect of failure of the yaw damper mountings - anything more than a bumpier than usual ride (though I appreciate that could cause issues elsewhere) ?
Yes and no, you need to know where the cracks came from and where they will go (that whole area is highly stressed and flexes in service). But failure in itself, if unrelated, will only be an issue when jacked. But having one break when 10 ft up on a carriage weighing 40t is not good! A jack broke when lifting a class 222 at Crofton about 15 years ago - the repairs to the vehicle were over £1m and it was purely luck none of the maintenance crew were killed.The yaw damper failure will "just" result on a hard ride but that has implications. It damages the bumps stops which are sized to prevent the bodyshell from going out of gauge. It also causes additional bogie movement which can increase the risk of derailment. So when a damper does fail you run at reduce speed. Failure of the bracket is rather more serious as you now have a big piece of metal flailing around at 125mph, or even worse, flying off. That's "News at 10" territory.
Edited by nc107 on Saturday 8th May 19:24
Edited by nc107 on Saturday 8th May 19:25
nc107 said:
Lily the Pink said:
Probably naive questions, but are cracks around the jacking points an issue other than when the trains are being jacked ? And what would be the effect of failure of the yaw damper mountings - anything more than a bumpier than usual ride (though I appreciate that could cause issues elsewhere) ?
Yes and no, you need to know where the cracks came from and where they will go (that whole area is highly stressed and flexes in service). But failure in itself, if unrelated, will only be an issue when jacked. But having one break when 10 ft up on a carriage weighing 40t is not good! A jack broke when lifting a class 222 at Crofton about 15 years ago - the repairs to the vehicle were over £1m and it was purely luck none of the maintenance crew were killed.The yaw damper failure will "just" result on a hard ride but that has implications. It damages the bumps stops which are sized to prevent the bodyshell from going out of gauge. It also causes additional bogie movement which can increase the risk of derailment. So when a damper does fail you run at reduce speed. Failure of the bracket is rather more serious as you now have a big piece of metal flailing around at 125mph, or even worse, flying off. That's "News at 10" territory.
nc107 said:
As said the bodyshells are aluminium which makes repairs and re-design more difficult (steel and ali have very different fatigue properties). I suspect the big worry, over and above the initial appearance of the cracks and short term solution, is where the cracks are propagating to. Both the yaw damper brackets and the lifting pockets are extensions of the bolster, If they are moving into the bolster seams that will be a real problem!
I assume the stop service order would be to provide Hitachi the opportunity to throughly inspect the bolster area for signs of crack propagation beyond the lifting point and yaw damper bracket? With the time out of service being a function of how long it will take to inspect this area of each car? So potentially if the problem is isolated to just the brackets and pockets they’ll be able start returning some to service after the weekend but with more frequent inspections until a long term solution is developed and fitted. That’s probably the best case. I’m not involved so this is just speculation, albeit I’ve had some experience in similar things in the railway. At the moment it’s all about containment to protect staff and the public. The failure is obviously serious enough that the consequences and likelihood of separation are bad enough that the fleet has been stopped for an immediate check.
From this they will do three things; identify those cracked and those not, and gather some basic information on maintenance and service history to give some confidence in if they can release the vehicles and when they should next examine. Now the risk could be evaluated as so low that a relatively small inspection at a long frequency is considered acceptable in the first instance. Not likely in this case I think. So they will likely end up with a criteria for allowing trains back into service and an inspection regime. I suspect they may find that some need immediate repair and the likelihood of others cracking is high so any inspection regime will be both regular and intrusive.
Hence the statement from the railway minister that disruption will be prolonged.
There will be another team going through calculations, load cases, FEA models trying to reverse engineer the crack to a cause to understand the failure a find a long term solution That team will probably be in Japan. The seriousness with which this is being treated suggests it could be very serious.
From this they will do three things; identify those cracked and those not, and gather some basic information on maintenance and service history to give some confidence in if they can release the vehicles and when they should next examine. Now the risk could be evaluated as so low that a relatively small inspection at a long frequency is considered acceptable in the first instance. Not likely in this case I think. So they will likely end up with a criteria for allowing trains back into service and an inspection regime. I suspect they may find that some need immediate repair and the likelihood of others cracking is high so any inspection regime will be both regular and intrusive.
Hence the statement from the railway minister that disruption will be prolonged.
There will be another team going through calculations, load cases, FEA models trying to reverse engineer the crack to a cause to understand the failure a find a long term solution That team will probably be in Japan. The seriousness with which this is being treated suggests it could be very serious.
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