rippled railhead

[507 001]

Hello!

Now to be honest, this I only something I've really noticed on metrolink, so mods please feel free to move this thread if necessary.

In certain places on the system, the railhead has become "rippled". In other words there are small indentations across the top of the rail. Its quite noticeable in places as it makes the track brakes rattle :mad:
Anybody got any idea what could cause something like this? It only seems to occur in particularly heavily used areas such as Cornbrook.
It's been puzzling me for weeks.
Cheers
Rob

 

[Katada]

I think it's caused as the metal heats up and cools down and expands and contracts. With the amount of metal on tracks this has quite an effect in some places.

 

[transmanche]

In certain places on the system, the railhead has become "rippled". In other words there are small indentations across the top of the rail. Its quite noticeable in places as it makes the track brakes rattle :mad:
Anybody got any idea what could cause something like this?

Just for elimination purposes, it's not something like the 'wiggly line' discussed in this thread is it?

Otherwise could it be the action of the track brakes themselves, in the same place (and perhaps 'bouncing' slightly on initial application) that is wearing out the railhead?

 

[TheKnightWho]

Just for elimination purposes, it's not something like the 'wiggly line' discussed in this thread is it?

Otherwise could it be the action of the track brakes themselves, in the same place (and perhaps 'bouncing' slightly on initial application) that is wearing out the railhead?

No. It's like cross-hatching on the rails, and I've seen it in the Newcastle bay platforms.

 

[Nym]

If it's what I think you're on about, it's caused in areas where a significant torque is caused in the same direction repeatedly. (For example, up to a braking point)

Next time I'm trackside I'll photo an example of what that causes.

 

[The Planner]

Not cyclic top is it? normally ESR city if that occurs.

 

[507 001]

Just for elimination purposes, it's not something like the 'wiggly line' discussed in this thread is it?

Otherwise could it be the action of the track brakes themselves, in the same place (and perhaps 'bouncing' slightly on initial application) that is wearing out the railhead?

Nope, definitely not.

If it's what I think you're on about, it's caused in areas where a significant torque is caused in the same direction repeatedly. (For example, up to a braking point)

Next time I'm trackside I'll photo an example of what that causes.

Now that sounds plausible!

Not cyclic top is it? normally ESR city if that occurs.

No I don't believe so, it's the actual rail head has visible ripples in it, but the rail itself is usually fairly straight and level.

So, if your looking down on the rail, it looks like this;

_____________________________
00000000000000000000000000000
-----------------------------------------

Poor drawing, but the best I can do, I'll try and get a photo later.

 

[Sir_Clagalot]

usually found near the stops on bay platforms/terminus platforms as due to the amount of rubbish that accumulates on the rail the train disappears from the track circuits, so the bit of metal on top helps to maintain the track circuit. They do sometimes crop up in other locations where it is a problem (usually only low speed as well)

 

[snowball]

usually found near the stops on bay platforms/terminus platforms as due to the amount of rubbish that accumulates on the rail the train disappears from the track circuits, so the bit of metal on top helps to maintain the track circuit. They do sometimes crop up in other locations where it is a problem (usually only low speed as well)

The original poster has already said it's not that.

 

[Bag of Badgers]

I think it's Corrugated track, that is meant.

Used to happen on tram tracks at Blackpool, would make a hell of a noise. It would be ground back, they had to get a special machine in from Europe to do it. In the end it was relaid with a rubberised compound, it was around Fleetwood that you could sample it the best. I believe it is caused by the harmonics of the foundation/support/track/wheels/suspension. I have seen it referred to as Washboarding?

Hope that helps?

Just found this with pictures, does it help http://www.corrugation.eu/research/

 

[edwin_m]

It does indeed sound like rail corrugation - Google image search brings up some pictures. No doubt it also brings up more details but as far as I recall nobody is totally sure why it happens but it clearly does and rail grinding is one solution. I think it's responsible for the "howling" noise you used to hear many years ago on some sections when riding in Mk1 and Mk2 stock at speed.

 

[L&Y Robert]

When the (then) new driverless Victoria Line opened, I read somewhere that after a while, some sort of randomising effect had had to be introduced into the control systems to avoid the trains always decelarating on the same rails and then stopping in exactly the same spot. It was causing something similar to the railhead.

 

[user15681]

When the (then) new driverless Victoria Line opened, I read somewhere that after a while, some sort of randomising effect had had to be introduced into the control systems to avoid the trains always decelarating on the same rails and then stopping in exactly the same spot. It was causing something similar to the railhead.

I have noticed at Euston on the Victoria line, pretty much under the cab, there is wear on the 4th rail. Possibly unrelated.

 

[D1009]

It does indeed sound like rail corrugation - Google image search brings up some pictures. No doubt it also brings up more details but as far as I recall nobody is totally sure why it happens but it clearly does and rail grinding is one solution. I think it's responsible for the "howling" noise you used to hear many years ago on some sections when riding in Mk1 and Mk2 stock at speed.

Isn'It that the same as cyclic top? I'd call it more of a roaring noise from the track. It tends to affect freight more than passenger in terms of Emergency Speed Restrictions. Coincidentally I was going north through Tamworth High Level yesterday and saw a warning board on the down line showing 30 over 125, which means 30 for freight but line speed for passenger, and this is the sort of restriction which tends to be imposed for cyclic top. It's usually very bad news on lines like that with a 125 line speed and
heavy freight usage.

 

[rebmcr]

It only seems to occur in particularly heavily used areas such as Cornbrook.

Which bit of Cornbrook? I've noticed since TMS went live, on the Altrincham line northbound, when rounding the bend in the underpass and drawing up to the signal for the joining Eccles line, that the superelevation is far too severe for the speeds now normally being used to prepare for a potentially restrictive aspect.

 

[Nym]

I have noticed at Euston on the Victoria line, pretty much under the cab, there is wear on the 4th rail. Possibly unrelated.

Thats due to all of the traction going in / out of the track at that point, you'll find it at the points on the conrail where there's shoegear.

 

[user15681]

Thats due to all of the traction going in / out of the track at that point, you'll find it at the points on the conrail where there's shoegear.

I had assumed so, as it's at the point where the shoe comes to a rest. There's a similar patch of wear about a foot or so before it, presumably where another shoe is.

 

[Nym]

I had assumed so, as it's at the point where the shoe comes to a rest. There's a similar patch of wear about a foot or so before it, presumably where another shoe is.

The shoegear is near enough in the centre of each bogie (around 12m), the other point will be from the regen braking (before the pneumatics take over).

 

[edwin_m]

Isn'It that the same as cyclic top? I'd call it more of a roaring noise from the track. It tends to affect freight more than passenger in terms of Emergency Speed Restrictions. Coincidentally I was going north through Tamworth High Level yesterday and saw a warning board on the down line showing 30 over 125, which means 30 for freight but line speed for passenger, and this is the sort of restriction which tends to be imposed for cyclic top. It's usually very bad news on lines like that with a 125 line speed and
heavy freight usage.

No. Cyclic top is on a wavelength of several tens of metres and is caused by a lot of similar freight trains passing at similar speeds and the dips in the rails coinciding with the pitching frequency of the wagons. Once cyclic top starts developing it increases the pitching and hence makes itself worse. One common giveaway is yellow paint splodges from the track recording train visible every few seconds from a train on another track.

Rail corrugation is on a wavelength of several centimetres. Roaring is probably a better word for it too!

 

[507 001]

I think it's Corrugated track, that is meant.

Used to happen on tram tracks at Blackpool, would make a hell of a noise. It would be ground back, they had to get a special machine in from Europe to do it. In the end it was relaid with a rubberised compound, it was around Fleetwood that you could sample it the best. I believe it is caused by the harmonics of the foundation/support/track/wheels/suspension. I have seen it referred to as Washboarding?

Hope that helps?

Just found this with pictures, does it help http://www.corrugation.eu/research/

It does indeed sound like rail corrugation - Google image search brings up some pictures. No doubt it also brings up more details but as far as I recall nobody is totally sure why it happens but it clearly does and rail grinding is one solution. I think it's responsible for the "howling" noise you used to hear many years ago on some sections when riding in Mk1 and Mk2 stock at speed.

Yep that looks like it! It tends to be confined to stations where the track is a few years old, so cornbrook, timperley, navi road, bury etc.

Which bit of Cornbrook? I've noticed since TMS went live, on the Altrincham line northbound, when rounding the bend in the underpass and drawing up to the signal for the joining Eccles line, that the superelevation is far too severe for the speeds now normally being used to prepare for a potentially restrictive aspect.

Both inbound and outbound platforms....

I would imagine that the cant will be reduced when the track through there is relayed in the next year or so. Current rumours are that pretty much the entire Alti line will be done as all the track circuits etc will be removed when TMS goes live.

 

[Starmill]

I was under the impression that the rippling you describe was the much-fabled 'track wear pattern' caused by the T68s! We will (sadly ) soon see the truth of that I guess! Perhaps it isn't as often talked about on here and I'm thinking of SSC.

I have always wondered if this is either responsible for, or (more likely) a side-effect of what ever really causes the awful M5000 ride!

 

[edwin_m]

Based on my own experience the M5000 problem seems to be lateral oscillation (hunting). The usual cause for this is mismatch between wheel and rail profiles, or insufficient damping of the bogie rotation (a particular problem for trams as the bogies have to rotate easily to get round 25m curves). I'm not aware of any link between hunting and rail corrugation, though I recall those Mk2s I mentioned back up the thread were pretty good at both!

 

[507 001]

Don't let TfGM fool you, the M5000 poor ride quality is nothing to do with the T68s. It's completely an M5000 problem. The K5000s in köln (which are identical) have been taken off high speed running in favour of older statbahn b cars, and many have had their centre sections rebuilt completely because they're shaking themselves to pieces.
There are areas of the Rochdale line where ride quality has deteriorated quite badly, same for east dids.

I believe that with an M5000 it is partly to do with rail profile (3 areas have had rail grinding work completed recently and the ride quality is much better, although again it is starting to deteriorate) and (lack of) suspension.
I believe air suspension would help, the T68s have it, the m5000s don't. At the moment every little imperfection is transmitted to the body. In the case of the hunting I get the impression that it's one lurch at first but it takes ages for the tram to regain a straight line.


I think in a couple of years were going to have big problems with the M5000s. I mean, if your home now, go and pick up your PC or laptop and give it a damn good shaking and see how well it works afterwards. The M5000s are giant PCs on wheels so imagine the problems it must cause!

 

[Starmill]

Indeed. I have always thought there were more imperfections in the design on an M5000 than we should be putting up with. The doors slam far too hard, the suspension is awful, the hazard braking is too extreme, the cab door is on the wrong side, they're prone to software issues...

But on the flipside, air suspension you say - well yes it's self-leveling isn't it, and by definition better (some M5000s when overloaded had the doors jamming on the platform edge!) ... but how much cheaper and lighter and easier to maintain is the M5000 suspension? Just a thought. Again maybe we'll have major problems in a few years time but I hear the T68s' ride was atrocious back in 92 also, and it took a good few years to find the optimum settings for it so maybe things will improve...

 

[Daniel Pyke]

As already said the longitudinal ripple along the rail head is likely to be rail corrugation.

Usually far more prevelant in the light rail and metro rail systems than in "heavy rail" ones.

Usually seen where there is hard acceleration/braking or severe curves. The wavelength is typically 25-50mm but it can be longer on higher speed sections. It is usually seen as alternate light and dark patches on the running band (essentially the running band changing width cyclicly)

The only way to rectify is to grind the rail. Once it has developed it will get worse and causes accelerated degradation of both the track/sub structure and the vehicle driving over it. It commonly causes a "roaring" noise as the vehicle passes over it which can also result in excessive noise complaints.

I used to spend a fair amount of my time looking at it for various networks and it can be a significant cause of cost to a network to keep on top of it.
(details of the sort of work can be found here )

You can try to mitigate against it by using harder rail grades such as our ML330, (I work for Tata Steel), and controlling the friction co-efficient of the rail (where possible), but it is one of those things that if you have it can really only be managed by grinding it out (consuming rail life) and potentially fixing the issue that may have initiated the ripple, e.g., a dipped joint or weld.

If there is interest from people, I'll see if I can find a good photo to illustrate the problem.

 

[507 001]

The one thing I disagree with in your post is about hazard braking, I think it's just right, got me out of a few sticky situations with dozy pedestrians etc.
Other than that though, your completely right.
Poorly built, poorly designed, poor ride quality.

They are perfect proof that an off the shelf design doesn't work on metrolink and that something bespoke is needed.

 

[edwin_m]

The M5000s have a lot of similarities, both in technical specification and in operating duty, with the CR4000s in Croydon. After the best part of 15 years in service, have these suffered from any major problems?

 

[507 001]

The M5000s have a lot of similarities, both in technical specification and in operating duty, with the CR4000s in Croydon. After the best part of 15 years in service, have these suffered from any major problems?

I'm not aware of any, but I dare say the CR4000s don't get half the hammering that the M5000s get.

 

[transmanche]

but I dare say the CR4000s don't get half the hammering that the M5000s get.

Why so? Why would the 4000s get an easier life than the 5000s?

 

[507 001]

but I dare say the CR4000s don't get half the hammering that the M5000s get.

Why so? Why would the 4000s get an easier life than the 5000s?

Because AFAIK the Croydon service is nowhere near as intensive, or as big.