INFORMED SOURCES e-Preview June 2021
INFORMED SOURCES e-Preview June 2021
Just as I was producing a provocative graph for the final item for this month’s column, the news broke that all Hitachi 800 series trains plus the ScotRail Class 385s had been withdrawn from service because of cracking in the jacking pocket area. So out went the provocative piece and I started a new report on jacking pockets.
I had already written an extensively illustrated analysis of the yaw damper bracket cracking problems with CAF and Hitachi trains, so I have linked the various problems as a Rolling Stock Crisis special
Jacking point cracking hits Hitachi fleets
Yaw damper bracket problems hit CAF and Hitachi
Southern considers future operations processes
Baptism of fire for Luminate at Liverpool Street
Recovery of vehicles after a derailment or other incident will involve lifting or jacking. To simplify this process, since the 1970s the lifting and jacking points on traction and rolling stock have been standardised to accept the lifting brackets used during recovery.
Jacking points add to the complexity of an already difficult part of the body-shell when it comes to design. With a body-shell formed from long aluminium extrusions welded together, the floor panel will be a double sided extrusion with external skins braced by internal stiffening webs. This is not strong enough to take the static and dynamic forces generated by a bogie or accept the end loads at coupler level. Thus a fabricated aluminium ‘bolster’ is welded to the under-frame at the vehicle ends. Lifting pockets or pads have to be integrated with the bolster, as do attachments for yaw dampers.
According to Informed Sources, the concern with the Hitachi jacking pockets was that the cracking found might lead to complete failure. This could result in all or part of the section of the bolster which takes the load of the vehicle on the lifting bracket becoming detached.
Following a risk assessment, the affected trains were allowed to return to service subject to daily monitoring and specified maximum length of crack. Both Great Western and LNER have trains out of service as a result. A press briefing on 20 May reported that Hitachi has yet to find the cause of the jacking pocket and yaw damper bracket cracks.
Complicating analysis are the other forces on the bolster at the yaw damper bracket. This is not straight forward, because the yaw damper bracket is also subject to vertical forces from the anti-roll bar.
Yaw damper bracket problems for CAF and Hitachi
On 3 April Northern Trains revealed that a maintenance examination at Newton Heath Depot had found a yaw damper arm which had become detached from the body of a CAF Class 195 Diesel Multiple Unit. A yaw damper restrains rotation of the bogie about the centre pivot and is fitted to prevent hunting at high speeds.
According to Northern, out of 1160 yaw dampers assemblies inspected subsequently, 33 were found to have cracks in the body-shell where the bracket is attached. This resulted in 23 trains being withdrawn from service.
Eight days later Great Western Railway issued a similar notification of the discovery of cracks on a Class 800 vehicle in the area where the yaw damper arm is bolted to a bracket on the side of the car body. Visual inspection and Non-Destructive Testing of the 93-strong Class 800/802 fleet had resulted, initially, in eight trains being withdrawn from service.
With the 800 series bogie, the yaw damper arm is bolted to a bracket on the vehicle body. This is the conventional design approach.
However, in the CAF design, the yaw damper arm is bolted directly to the underside of the body-shell itself, using T-slots in the wide extruded aluminium sections which are welded together to produce the body structure. With the arm secured by just four bolts clamped on narrow strips of aluminium about 5mm thick, none of the engineers I have talked to are surprised that the fastening failed.
In the article I explain, with copious illustrations, why yaw dampers are needed, what they do, how they work and previous problems with yaw damper brackets cracking. I also explain why aluminium body-shells have presented a particular problem when it comes to attaching yaw damper arms.
Briefly, steel has a higher fatigue limit than aluminium but also has an endurance limit or stress level. Below this stress it will not fatigue and fail due to the cyclic forces from the damper. In contrast, aluminium doesn’t have an endurance level and will fail after it has been subjected to sufficient cycles. This number of cycles depends on the local stress in the metal, which is why Finite Element Analysis of stresses in components is such an important tool when designing aluminium vehicles.
For designers of yaw damper arm attachments there are two semi-unknowns. The first is the maximum force generated by the damper across its operating range. Second are the stresses this generates in the attachment point which are not easy to calculate, even with today’s FEA.
Understanding these complex stresses will be central to the modifications proposed to remedy these failures. Instrumenting a vehicle with strain gauges and other measuring devices will provide real-life data to feed into the FEA computer models used in the original design.
CAF moved fast and had an instrumented Class 195 DMU gathering data during the second week May. Surprisingly, Hitachi was not expected to have a strain-gauged Class 800 running until this coming week.
During a railway press briefing at Hitachi’s North Pole depot on 20 May, we were told that it was too early to discuss possible remedial measures. And according into Informed Sources, as non-destructive testing of yaw damper brackets continues as part of the routing monitoring by GWR and LNER, further sets are having to be withdrawn.
When it comes to a solution for the failures, CAF probably has the easier task. One solution would be a cast or fabricated plate with attachments for the yaw damper arm bolted over the area where the T-slots proved inadequate. Bolting is preferred because welded repairs to aluminium vehicles are not straightforward.
When welding a body-shell, the welding torch is putting electric current into the aluminium and generating electro-magnetic white noise containing nasty frequencies. Modern trains are stuffed full of electronic equipment.
Memory chips and processors could be fried by stray current from a welding torch. So before starting welding repairs, all the electronic kit has to be removed or isolated.
This is not a trivial matter. And when you have put the equipment back, it all has to be tested.
A recent welding repair on a Class 387 is reported to have taken two days to strip out the electrical equipment, followed by three days to reinstall and test after the repair was completed.
All in all, this resurgence of fatigue cracking is a timely, if unwelcome, reminder that for all the talk of ‘digitalisation’, the railway remains dependent on mechanical engineering for safe and reliable operation. And despite computer-aided design, engineering remains an art, not a precise science. Over 6,000 yaw damper brackets in the CAF and Hitachi fleets attest to that.
Southern ponders operations processes
Intrigued by the Notice published by Network Rail’s Southern Region in the Official Journal of the European Union (Informed Sources May 2021), I followed it up with the ever-helpful media folk at Southern. They arranged a background briefing for me with Paul Harwood, Southern Region Director Investment and Stewart Firth, Director of Operating Strategy.
Stuart explained that the OJEU was sparked by the transfer of responsibility for the Traffic Management (TM) component of the Thameslink resignalling project to Southern. While Hitachi’s Tranista TM at Three Bridges Rail Operating Centre was still under development, it was unclear whether the development programme was aimed at adapting TM to work with the Network Rail operations systems or vice versa.
Shouldn’t you know what you want before you ask people what they can do for you, I asked? Well, yes and Southern has already held workshops where its train operator customers were asked what was hindering their operations, what didn’t work and what made it difficult to run the plan and recover from disruption?
These sessions made Southern better informed on what was needed. However, before firming up the new requirement, as a sense check, it needed to ensure that the new approach wouldn’t be asking manufacturers for the impossible or, contrarily, overlooking the potential of some new technology. Hence the OJEU Notice.
Reactions to the problem statement included the advice ‘you shouldn’t do any of this until you have got your processes mapped out’. And, as Stewart remarked dryly, ‘introducing a new system without having a baseline process in the first place is pretty difficult’. In retrospect that was one of the lessons of Network Rail’s original TMS procurement exercise back in 2009.
In the article I describe how Southern is analysing its core operational processes, how well they are understood and, critically, what are the opportunities to improve them.
Southern believes that the focus of the original TMS procurement was more on the ability to de-conflict the train plan and load a new one. Being able to constantly alter the train plan is undoubtedly important but, in Southern’s view, equally important is enhancing the overall ‘situational awareness’ within the Route Control Room. For example, currently Control has to interrogate multiple system to pull together the variables of a problem before developing the solution.
What Stewart is looking for is technology which will extend to all its operators the benefits, such as avoidance of multiple data entry, which Luminate has already brought to the Train Running Controllers at Swindon/Didcot and Liverpool Street. ‘We want to use technology to allow people to do what they do best and concentrate on the really-challenging and difficult.
Where does the programme go from here? With the current financial pressures the likelihood of funding for a large scheme is obviously ‘pretty slim’.
That said there are opportunities. Where a system is becoming life-expired, the current work could inform the operational requirements which could be met, potentially, by any new technology emerging from the OJEU Notice follow-up. Control room IT systems are one example.
TM handles Liverpool Street disruption
On the day of my interview with Network Rail’s Southern Region, a powerful demonstration of what can be achieved with Integrated Traffic Management was playing out at Liverpool Street station following Overhead Line Equipment problems that morning which affected access to three platforms. Liverpool Street Integrated Electronic Control Centre (IECC) is the second application of Resonate’s Luminate Integrated Traffic Management System which went live on 11 April.
In the column I have extracts from the control log for that day. Instead of implementing a contingency plan, Luminate was used to re-plan a full evening peak service, including re-platforming.
As a result, everyone went into the peak with a published plan, which had been tested off-line. For the passenger this meant normal passenger information displays and, in this digital age, up-to-date information on their smartphone apps.
For controllers and signallers, implementation of the new timetable through the IECC’s Automatic Route Setting, reduced their workload, giving them time to manage any other issues.
A feature of TM is the ability to prepare, and test off-line, contingency plans for potential disruption – for example failure of a set of points – which can be implemented in an emergency. But when you can re-plan the evening peak at Liverpool Street on the fly to meet a specific set of circumstances, how relevant are contingency plans based on generic service changes and cancellations?
Running the full peak also avoided the knock-on effects of emergency timetables, such as trains terminating at the wrong locations over-night. Without TM Liverpool Street would still have been recovering from the impact of the failure next morning.
New Train TIN-Watch
My thanks to all those readers who responded to last month’s request for suggestions on how TIN-Watch should develop. There was agreement that the ‘promotion ceiling’, should be reduced from 50,000 MTIN to 20,000 MTIN, given the pitifully slow improvement with most new fleets. As a result, this month we have lost the GTR Siemens Class 700 fleet and the Hull Trains Class 802s.
On the topic of how to deal with fleets which are no longer ‘new’, a reader reminded me of the view of Depot engineers, that once you get to 15,000 MTIN, fleet is not a major factor in service reliability.
Finally, a criticism of the table has been that it does not show trends. I think the solution here is to highlight fleets where reliability has improved on the previous month. This will complement my periodic analyses of long term trends.
These changes will be implemented next month with the start of the 2021-22 railway reporting year.
Roger’s blog
Well, the big excitement last month came on Saturday 8 May when I was woken by a phone call from the BBC Radio ‘Today’ programme, asking to comment on the mass withdrawal of the Hitachi 800 series fleets; I assumed that the yaw damper bracket problems had worsened.
Having gone from slumber to radio interview in 20 minutes flat, and fluently explained yaw dampers, I checked my e-mail. Messages included a Network Rail Western Route Control ‘Black Incident’ notification covering the new problem with the jacking pockets. I got it right on later TV appearances!
April ended with the RIA virtual Innovation Conference which had some interesting presentations and Q&A sessions. While I record the audio, habit means that I also get out my reporter’s notebook and take notes.
Last week’s Zoom time included a 15 minute interview with Keith Williams, for a briefing on his review, or more correctly the resulting white paper jointly authored with Transport Secretary Grant Shapps. With publication next day, the Modern Railways team was kept busy providing expert comment for the broadcast media.
I handled the local radio afternoon drive-time slot, with six interviews in 45 minutes. Great fun, plus useful feed-back on particular concerns around the country.
Also on that day GWR had arranged a visit to Hitachi’s North Pole Depot for a briefing on the cracking problems described above. Neither Mr Walmsley nor I could attend in person, so the GWR media team fixed up a Zoom link.
This not only included the Q&A session, but took us on the subsequent tour of the depot to see the problems in the metal. I gather there were complaints that we got better views of the cracking than those on the spot.
Luckily, the next few weeks are fairly quiet, since, in addition to completing the held-over provocative piece and updating the cracking crisis, I also have to get to grips with the White Paper and the challenges of implementing Great British Railways, which will probably require some detailed analysis.
Roger
