Loughborough University tests new generation point work on the Great Central

[mwmbwls]

https://www.lboro.ac.uk/enterprise/repoint/

The University of Loughborough have released an interesting video having gone back to basics on the causes of point failure. Their solution is elegant.

https://www.lboro.ac.uk/enterprise/repoint/technology/delay-reduction/
Switches present a single point of failure to the rail infrastructure, in an era when most others have already been eliminated. In the UK, this means switch failures present a disproportionally high impact from service affecting failures.

The effect is compounded as switches are almost always sited at key locations, with a failure affecting more than just the traffic on immediate approach. Failures require emergency intervention by the maintenance organisation to restore operation, which potentially means rushing to put boots on ballast at rush hour.

Repoint offers multi-channel redundancy of actuation, locking and detection.

Should a channel become faulty, it can be isolated, and the maintenance organisation informed. The switch will continue to operate, and trains can continue to run, until such a time as replacement of faulty components becomes convenient. The result is a significant reduction in service delays.

Modelling for the British mainline network indicates Repoint would have prevented around 90% of points failures (2010-2013).

A last sentence contains a breath taking claim and as a bean-counter I learnt the hard way to sceptical of bald percentages. Does anybody know the amount of delay minutes caused by point failures in the United Kingdom?

 

[Legolash2o]

I wonder how they would work in high heat or freezing temperatures.

 

[Chris125]

I wonder how they would work high heat or freezing temperatures.

Is there any reason to think it would be more affected than existing designs?

 

[tiptoptaff]

Is there any reason to think it would be more affected than existing designs?

AS this is when points tend to fail, their performance in extremes of weather will have a large impact on the number of failures they reduce. If they perform no better than existing designs in those conditions, then I personally don't see this a step forward in design.

 

[Ken H]

It looks like they are building in redundancy. That will always improve reliability. but what would be the cost?

BTW, points dont fail. Its usually the detection that fails. Ensuring points have thrown correctly and telling electronics that is so is always difficult in a dirty, wet and high high physical shock environment.

 

[atraindriver]

<deleted>

 

[Ediswan]

This would have three actuators in parallel, only one needed. Great if one or two fail 'free', but what if one fails 'stuck'? Have they just multiplied the risk of the points becoming stuck by three?

The 'up and over' passive locking is interesting. That does appear to simplify the system.

 

[Richard Ingram]

Looking at the mechanism diagrams, it looks to me that the cannot fail stuck, as if the cam fails to move, the blades can still be lifted by the other motors, leaving the failed motor where it is, since the cams are not connected to the tie rod (is that the right name?). It would even be able to join in with the reverse motion, if the only reason it failed to move was something like a power loss.

For detection, how bad would it be to have 3 detectors, and if you get mismatch on the warnings, to ask local ground staff, or the next train to pass, to stop and check it manually, then mark one of the sensors as faulty until it can be replaced? I remember reading somewhere on this forum that drivers are expected to check point blades in the event of passing a signal at danger under authority (on the thread about the derailment on the GCR, possibly), so they might already have the training. If you currently only have one detector, this way, even after a failure, you are no worse off than currently.

 

[Ken H]

Looking at the mechanism diagrams, it looks to me that the cannot fail stuck, as if the cam fails to move, the blades can still be lifted by the other motors, leaving the failed motor where it is, since the cams are not connected to the tie rod (is that the right name?). It would even be able to join in with the reverse motion, if the only reason it failed to move was something like a power loss.

For detection, how bad would it be to have 3 detectors, and if you get mismatch on the warnings, to ask local ground staff, or the next train to pass, to stop and check it manually, then mark one of the sensors as faulty until it can be replaced? I remember reading somewhere on this forum that drivers are expected to check point blades in the event of passing a signal at danger under authority (on the thread about the derailment on the GCR, possibly), so they might already have the training. If you currently only have one detector, this way, even after a failure, you are no worse off than currently.

when SSI first started they had 3 computers who did the interlocking. If 2 said one thing and the 3rd said something else, the 3rd would be switched out and the interlocking runs on 2 computers until its fixed. This could use the same logic, perhaps?

 

[mwmbwls]

The Loughborough Team make some interesting observations about whole life costs and ahave also considered nor producing just a one size fits all solution:

https://www.lboro.ac.uk/enterprise/repoint/technology/whole-life-cost/

“Of course, at first glance, many people have observed, ‘three point machines equals three times the cost’, but this is simply not true!

As existing machines are single-channel, they have been significantly over-engineered. Revising the design of traditional machines has led to many opportunities for cost savings. Repoint is constructed almost entirely from COTS (commercial, off-the-shelf) components. The actuators and gearboxes are simple, designed for mass-manufacture, and standardised. Wear components are low-cost and easily replaced. The lift-move-drop motion eliminates the requirement for back-drives on a large portion switches.

Significant savings also come from the reduction in maintenance and fault rectification which having several channels offers. Should a channel fail, it can be isolated, and the maintenance organisation informed. The switch can continue to operate, and trains can continue to run, until replacement of faulty components becomes convenient. The delay reduction itself is a significant cost saving.

Whilst the system demonstrator has been constructed with three channels, it is possible to add or remove channels as demanded by the installation location. Perhaps points at the entry to key stations could be fitted with four channels, and lesser used rural lines, two.”

As they point out , inherent redundancy comes built in.

One of the benefits of this technology should it prove operationally viable would be its self funding nature in that delay payments are only a poor consolation prize to operators and passengers alike. Would fellow contributors care to suggest sites where this technology would be a boon – for me the Castlefield corridor and the Windsor Link/Ordsall Chord would be high on the list.

 

[edwin_m]

Part of the problem with existing point detection is that it has to be set up within millimetres so that it only detects closed when the gap between the switch and stock rail is too narrow for any risk of a flange getting into it. I think with the suggested "stub switch layout", not adopted for this demo, the detection would be much simpler because effectively the moveable rail is either there or it isn't.

 

[Ken H]

Part of the problem with existing point detection is that it has to be set up within millimetres so that it only detects closed when the gap between the switch and stock rail is too narrow for any risk of a flange getting into it. I think with the suggested "stub switch layout", not adopted for this demo, the detection would be much simpler because effectively the moveable rail is either there or it isn't.

With Alsthom using CCTV to check pendolinos state and highlighting maintenance issues, like brake pad wear, Maybe CCTV could be used to check points rather than detection in the mechanism itself. The camera could be well out of the way of dirt and vibration, and the 'clever' bit elsewhere.

 

[edwin_m]

With Alsthom using CCTV to check pendolinos state and highlighting maintenance issues, like brake pad wear, Maybe CCTV could be used to check points rather than detection in the mechanism itself. The camera could be well out of the way of dirt and vibration, and the 'clever' bit elsewhere.

Perhaps I didn't explain it very well. The switch gap needs to be within a couple of millimetres (don't recall the exact figure) to get detection. A lot of the problem is about reliably getting it within that distance when it is subject to thermal movements and clogging by debris, not about how to detect whether it is close enough.

 

[Ediswan]

Looking at the mechanism diagrams, it looks to me that the cannot fail stuck, as if the cam fails to move, the blades can still be lifted by the other motors

Thanks. I had not spotted that level of detail. That gives the possibility of a cam getting stuck mid travel, preventing the blades from falling back down.

 

[Ken H]

Perhaps I didn't explain it very well. The switch gap needs to be within a couple of millimetres (don't recall the exact figure) to get detection. A lot of the problem is about reliably getting it within that distance when it is subject to thermal movements and clogging by debris, not about how to detect whether it is close enough.

so how close to point have to be to fully closed do they have to be to be safe? 10mm? 5mm? 2mm?

 

[Richard Ingram]

Thanks. I had not spotted that level of detail. That gives the possibility of a cam getting stuck mid travel, preventing the blades from falling back down.

That's a good point, I wonder if anything could be done to mitigate that. And is that a likely failure mode? I can imagine the failure of a servo to start moving is much more likely than a mid point stop, but I have no evidence of this. Maybe someone else has an idea?

 

[edwin_m]

so how close to point have to be to fully closed do they have to be to be safe? 10mm? 5mm? 2mm?

I think it's about 2mm but I there must be someone else on here with a better figure.

 

[Lucan]

Rather a bad start by calling "points" "switches", the US term and ambiguous in this context. Of course, "points" is also ambiguous but at least we are used to that in the UK.

The tech in the video is only from 0:42 to 1:42 and the rest is hype. This video is aimed at railway professionals, who don't need to be lectured on how critical points are to the system, so it was a bit irritating.

Nevertheless the idea of the point blades lifting over to the other position is interesting and worth a try in real use. I am not sure if it would be better or worse than sliding. Sliding can push stuff like a piece of ballast out of the way, and a lifted point blade could be prevented from getting sitting back down by that piece. Experience would tell.

 

[edwin_m]

Rather a bad start by calling "points" "switches", the US term and ambiguous in this context. Of course, "points" is also ambiguous but at least we are used to that in the UK.

The tech in the video is only from 0:42 to 1:42 and the rest is hype. This video is aimed at railway professionals, who don't need to be lectured on how critical points are to the system, so it was a bit irritating.

Nevertheless the idea of the point blades lifting over to the other position is interesting and worth a try in real use. I am not sure if it would be better or worse than sliding. Sliding can push stuff like a piece of ballast out of the way, and a lifted point blade could be prevented from getting sitting back down by that piece. Experience would tell.

The official term in the UK is "switches and crossings" and since they are only interested in the switch part it is entirely appropriate to call it that.

 

[moggie]

I wonder whether they've analysed NR's point failure data to ascertain how many 'point failures' are due to a failure of the point drive mechanism? Because I'd wager that the vast majority of 'failures' are a failure to detect the points switch (not a failure of the detection system) due to rail expansion / impaired mechanical set up or obstruction / detritus wedges in the blade.
The downward travel of their switch blade action when moving from one position to another provides a compacting action similar to the lateral compacting movement of conventional switches. This has the same potential to prevent completion of the full travel of the point blade and therefore the same potential for detection failure.
Three point drives (per end?) is also significantly more kit than conventional points except for the longest switches on HS lines. The drive mechanism may be good but the weakness will be the extra complexity in the control and detection arrangement. While redundancy is achieved it all still needs maintaining in good operation but with three times the effort / end?
Have they solved the wrong problem at an inflated cost while introducing yet another variation into the rail system to be maintained?
(there's a good reason why HW machines are still being installed decades after they were introduced - they do what they are supposed to do consistently and reliably)

 

[whhistle]

I didn't understand how it would work until I saw a video.
The media seemed to go on the approach that the sliding mechanic of the point operation catches debris, so the point fails. By lifting the rail and placing it in a cradle lock, it means no debris.
There are three or four motors for the lifting action so if one fails, the point will still work.

 

[Lucan]

The media seemed to go on the approach that the sliding mechanic of the point operation catches debris, so the point fails. By lifting the rail and placing it in a cradle lock, it means no debris.

There could still be debris like ballast stones in the cradle where the point blade is put down. If it were up to me I would give this idea a trial in a secondary location and see how it works out. Are there any proposals for a trial on the railway?

 

[sng7]

There could still be debris like ballast stones in the cradle where the point blade is put down. If it were up to me I would give this idea a trial in a secondary location and see how it works out. Are there any proposals for a trial on the railway?

From the first post it informs us they are trialing it on the grnd central heritage railway at the moment.

 

[coppercapped]

There could still be debris like ballast stones in the cradle where the point blade is put down. If it were up to me I would give this idea a trial in a secondary location and see how it works out. Are there any proposals for a trial on the railway?

From the way I read the drawings and the video there is no cradle to take the point blade. The stretcher connecting the two switch blades has 'U'-shaped cutouts in the lower edge which fit over horizontal rods. The mechanism lifts the stretcher, moves it sideways and drops it again. For the locking mechanism to jam an object (ballast stone, errant chunk of metal, etc.) would have to balance on the curved surface of the top of the rods and then be trapped as the stretcher descends. I would suggest that the chances of this happening are small.

The lower faces of the point blades look as if they rest on the normal sliding surface of a rail chair to take the train loads. It is, of course, possible that a piece of ballast, or other foreign object, gets in the way but I can't see why the chances of this happening would be any higher than with a conventional set of switch blades. I suspect that the designers are well aware of all the possible fault modes and are able to design as many as possible of such fault modes out of the final design

What should be remembered is that the device shown is a 'proof of principle' and as such it seems to me to be a good idea. Before any such design is adopted on a wide scale there will certainly be all sorts of further design and evolution work.

 

[edwin_m]

I got the impression this was only part of an intended solution. The bit where the switch rails themselves are lifted up may come later.

 

[NeilNX]

A different approach to pointwork, im no engineer, but looks interesting proposition

 

[Belperpete]

In my experience, the problem with something that costs more initially but gives whole-life savings, is that projects are decided on their up-front cost. There.may be lots of whaffle about reliabibility in the specification, but the contractor with the cheapest up-front quote almost always gets the job.

 

[whhistle]

If you watch the One Show from last Thursday there's a short report on the point with demonstration:

https://www.bbc.co.uk/iplayer/episode/m00038kk/the-one-show-14032019

It's around 25:00 in.

 

[squizzler]

How does the One Show end up running a segment on railway engineering? It strikes me as an unusual place to find news on industrial technology.

 

[duffield]

How does the One Show end up running a segment on railway engineering? It strikes me as an unusual place to find news on industrial technology.

Yes, I only flipped to BBC 1 to look at the news text and was pleasantly surprised to see one of my local heritage lines demonstrating a new bit of railway kit, though it was disappointing they didn't mention the line at all, just saying "And here we are at the Great Central heritage railway to demonstate..." would have been nice.