setting the track camber

[truckman060473]

when the rail laying machine is installing new track and sleepers on a curve how is the side of the sleeper on the outer edge raised to produce the required tilt or camber? if you think about it for a bit it seems like a tricky thing to do and get right, so that high speed trains can run into the curve smoothly from a section of straight where the camber is 0 degrees or flat. and the camber needs to be gentle at start of curved part raising to a higher amount further on to avoid the coach lifting up abruptly on one side when it leaves the straight part which would not be nice for travelling. how is this done?

 

[Old Timer]

The track is laid to the formation ballast and when the top ballast is installed (the ballast between the sleepers) the track geometry is introduced by the use of a tamping machine.

This will elevate one side of the track as part of the lifting process.

The section of track through which the track is curved is gradually raised from zero to up to 150mm, and then gradually lowered back down. The length of this is related to the line speed and the amount of cant (superelevation) that is applied. The section of line from the commencement of the curve until the curve becomes a true curve (in other words the radius stabilises) is called the "transition".

There is a computer programme that is used to design the track geometry, and the elctronic version (the front offset file) is installed into the tamper computer.

You will see the curve design marked onto the sleepers so that any follow up tamping or track geometry checks have the design information on site against which the actual values can be checked.

I prefer to operate a system which profiles the ballast formation to match the degree of cant, thus reducing the amount of lift that is required using the tamping machine. This reduces the subsequent compaction of the ballast under trains, and reduces the follow up tamp work. This also allows a higher handback speed.

In North and South America, curves are generally flat and have no cant applied, except for passenger lines.

 

[DaveNewcastle]

I guess O T has answered your question already - particularly your specific concern about the gradient profile over which the cant is progressively introduced.
But it might also be worth noting the purpose of cant and reflecting on the penalties that it incurs in the process.
Clearly, by tilting a vehicle in towards the centre of a curve then its centre of gravity is also shifted inwards, which, when coupled with the centifugal force of the moving mass of vehicle, will tend to compensate and allow the centre of gravity to somewhere near the midpoint between the 2 rails. That would tend to put a fast vehicle at risk of tipping over. Cant works well at speed. It reduces the risk of the centre of gravity of a high speed train moving too close to the outside wheel flange and helps to keep the wheel-rail contact in control of the vehicle's motion. (Its not just to make the passengers feel comfortable and to keep their drinks on the table!)

But, imagine this scenario - a long and very heavy freight train has to stop on such a curve. The cant will be of no benefit as the train begins to move at just a few mph. In fact the strongest forces will be gravity and the tension pulling from the front of the train - and that "pull" is not in a straight line, its from the vehicle in front which is moving slightly towards the centre of the curve, and simultaneously, the track's cant is tipping the vehicle towards the centre of the curve. In this case, there are two consequences of cant which actually reduce stability!
Gladly, there are good designs for couplings and specifications for freight loadings which keeps these risks in proportion. But its not all so simple, is it?

 

[Old Timer]

All the above is taken into account in the track geometry design, however a vehicle moving away from a stand will tend towards the high rail, thus reducing but not stopping, frictional resistance and rail head sidewear.

Because of the variation in train speeds it is not always possible to introduce the optimum degree of cant for high speed passenger train operation, and thus the amount will be at a figure below optimal. This negative variation is known as "Cant Deficiency" and can be felt when travelling at speed as either a slight jerk of the vehicle, or as a sideways pull on the body, towards the outside of the curve.

In other areas such as the approaches to Paddington, and in a couple of other areas on the GW, the cant is actually derogated to 30mm above the normal maximum in order to maintain speed and reduce rail head sidewear.

 

[kestrel]

All the above is taken into account in the track geometry design, however a vehicle moving away from a stand will tend towards the high rail, thus reducing but not stopping, frictional resistance and rail head sidewear.

Because of the variation in train speeds it is not always possible to introduce the optimum degree of cant for high speed passenger train operation, and thus the amount will be at a figure below optimal. This negative variation is known as "Cant Deficiency" and can be felt when travelling at speed as either a slight jerk of the vehicle, or as a sideways pull on the body, towards the outside of the curve.

In other areas such as the approaches to Paddington, and in a couple of other areas on the GW, the cant is actually derogated to 30mm above the normal maximum in order to maintain speed and reduce rail head sidewear.

Line 4 particularily between subway junc an royal oak

 

[Vlad the Impaler]

...... the elctronic version (the front offset file) is installed into the tamper computer.

You will see the curve design marked onto the sleepers so that any follow up tamping or track geometry checks have the design information on site against which the actual values can be checked.

I prefer to operate a system which profiles the ballast formation to match the degree of cant, thus reducing the amount of lift that is required using the tamping machine. This reduces the subsequent compaction of the ballast under trains, and reduces the follow up tamp work. This also allows a higher handback speed.

.

OT,

V value file on a dongle (probably with the rest of the scheme on there as well) , luxury as they say . (what did Harold McMillan say to the masses years ago, "You've never had so good " ???)

Much more fun with the transition(s) (if theres a rad change part way along the curve) marked up (if you are lucky the TO also marks up the v offset value as you go up the transition, if not, its out with the chart and work it out yourself), along with winding on the cant lift, and any design slew as you go.


Like the sound of profiling the ballast to lessen the lifts, not only from the compaction angle, but whilst an 07 tamper will lift and lift and lift some more (just keep winding it on !! and if thats not enough, lean on the lift wires But by then the tracks resting on the rocks, not in it !) , IIRC, the more modern stuff tends to wimp out a bit earlier on the lift front.

We always know we are in for a good shift when the TO siddles up and asks how much we can lift it by in one pass (as they've dropped it in low or something) .

 

[Old Timer]

Poor old Vlad

You need to do more renewals work, preferably on my sites ?

We like to look after our tamper guys most of the time

 

[Trog]

You havent lived until you have run a laser dozer through a cant reverse co-incident with a vertical curve. Walking backwards over the ballast equivilent of a ploughed field, while putting the required settings into a control box connected to the front of the bulldozer by a fifteen foot cable.


I remember back in the good old days we always tried to get the 09 tampers on our relaying items, as they could do much bigger lifts than the old 07's. Hard work keeping in front of them with the chalking up though.

 

[Old Timer]

You havent lived until you have run a laser dozer through a cant reverse co-incident with a vertical curve. Walking backwards over the ballast equivilent of a ploughed field, while putting the required settings into a control box connected to the front of the bulldozer by a fifteen foot cable.

Up Birmingham Flyover, perchance ?

 

[Vlad the Impaler]

Poor old Vlad

You need to do more renewals work, preferably on my sites ?

We like to look after our tamper guys most of the time

OT,

Haven't done a renewals job in about six months !

Our local renewals depot prefers to do it on the dongle (and hence a compact 08 with alc), which rules out me and my beloved 07's .

Whilst at the start of this "famine" I fretted about missing the buzz of being like a demented octopus in the tower (front) cab as the tamper goes up and down a transition (OK, well just a little bit for about five minutes..... ).

Now I find I have got used to having my Sundays off and knowing what time I will finish (ish) by just being on NR maintenance tamps. So do I miss doing renewals ???? Not really

Listening to the compact boys in the yard cabin moaning about having to stay on etc just confirms it.


That said, just noticed on my latest orders, I have two sundays of renewals coming in the next month. :cry: :cry: (hopefully they will change their minds and order a compact 08 instead).


Happy new year to all the pway and renewals bods out there, particularly those (lucky or unlucky depending on your viewpoint) who worked over christmas or are in over new year.

Cheers

V

 

[Old Timer]

Compacts are for maintenance. They cannot work with stone around the rail head.

An 07 will do fine, if not an 09.

I think we shall have to start spoiling your weekends again old chap !

You know you are wasting your time on maintenance, and you never do any blasted work when you get there anyway because they have never prepared for you !

Still trying to tamp with rail in the four-foot, or on the shoulders ?

Still just doing an ALC run and a smooth tamp ?

Only need train drivers for that you know !

Now change your squeeze time and pressures and come work with me ?

I always expose the sleepers, at least by the fittings But you know that anyway !

Happy New Year
Old Timer

On a BIG job !

 

[Trog]

Up Birmingham Flyover, perchance ?

Walked over that a few times but never got to relay it.



I was one of the original generation of STO's who were told by BR that we were going to be using laser controlled dozers from now on, and that you can figure out how it works on Sunday morning.

BR had three local plant firms fit a dozer up with the laser control gear, two of them we used for several weeks, and a third had worked for the ACE at Birmingham. After a few weeks the dozer from this third firm was allocated to a job of mine at Cricklewood, as well as the driver one of the firms owners came to site. It seems the Birmingham Technical Staff had failed to set the machine up, and had just been using it manually. The plant firm were worried about their investment so the owner had come along to find out what was happening. As he was telling us this myself and my collegue smiled at each other, and once the dig was begun we fell on this machine and had it rigged up and working in minutes.

He was half right to be worried though as his dozer was smaller than the other two and not really man enough for the job, so it remained very much our third choice machine.

 

[TheSlash]

Vlad, where is this railway you speak of that puts Track Geometry markings on the sleepers?
I have had countless arguements with a certain Tech office about lack of Cant markings. Several times i have breezed through the office and things have been so busy that there was people queueing for Tarot card readings from the resident Pagan Priest and it seems part time STO.

I believe it is time we cut out the middle man and kept Track Geometry a closely guarded secret between the local Trackchargeman and the Tamper Operator.

 

[Old Timer]

Vlad, where is this railway you speak of that puts Track Geometry markings on the sleepers?
I have had countless arguements with a certain Tech office about lack of Cant markings. Several times i have breezed through the office and things have been so busy that there was people queueing for Tarot card readings from the resident Pagan Priest and it seems part time STO.

I believe it is time we cut out the middle man and kept Track Geometry a closely guarded secret between the local Trackchargeman and the Tamper Operator.

They should go on as part of any renewal as they are part of the Contractual Requirements, and the Network Rail handback should not be taken if they are missing !

They also form part of the Health and Safety File which is passed over to the Maintainer.

So a question.

Without these markings or the track geometry design, how can you raise the linespeed after any incident/suspected track defect ??????

 

[TheSlash]

OT,

The markings are of course put down following any renewal. However there are large sections of our infrastructure that are over thirty years old and have long since lost any cant markings.
I was very annoyed recently when whilst lifting and packing next to a structure, i was told to ignore the Datum plates as they were wrong!

As to removing a speed restriction post incident {rough ride} alot of this comes down to wandering up and down with the gauge doing trial and error with the cant adjustment part of the cross level on sections of track believed to be reasonably level.
This was basically suggested on a Track Geometry course i attended, but we have already discussed that

 

[Old Timer]

OT,

The markings are of course put down following any renewal. However there are large sections of our infrastructure that are over thirty years old and have long since lost any cant markings.
I was very annoyed recently when whilst lifting and packing next to a structure, i was told to ignore the Datum plates as they were wrong!

As to removing a speed restriction post incident {rough ride} alot of this comes down to wandering up and down with the gauge doing trial and error with the cant adjustment part of the cross level on sections of track believed to be reasonably level.
This was basically suggested on a Track Geometry course i attended, but we have already discussed that

Yes and all that does is put the poor old man on the ground in the firing line (literally and figuratively speaking).

So much for the "new order" that was going to be a shining example of how to manage maintenance, indeed it is, but in how NOT to

 

[Trog]

I was out and about a few weeks ago and under one bridge with recently relayed track there were three sets of cant marks.


The posh new ones from the current relay on the sleepers.

A set on yellow patches painted on the bridge wall when the linespeed was altered.

Plus higher up the wall a set in my handwriting from the last time it was reballasted.

 

[Vlad the Impaler]

OT,

Compacts are for maintenance. They cannot work with stone around the rail head.

An 07 will do fine, if not an 09.

Please tell that to your oppo's sarf of the river ! It seems to be group think down here, 07's bad, 08's good (was it Brave new world, Animal farm or 1984 that had group think ??? ). No 09's down here (and the arrival of our new matisa(s) seem to be vanishing mirage-like into the future). Even a blown silencer on a tamper fails to drown out the whinging and whining from the techs when an 07 rolls up.

Don't know whether they don't like the marking up, or they think a computer is better (unless the techs transpose the design on the dongle - has happened!!). Maybe they don't realise, the more practice at renewals the crews get on 07's , the better at it they become

You know you are wasting your time on maintenance, ..........

At the risk of a parody of a certain George Lucas film, (so should you be Obi-Wan Old Timer??)

You have a choice Luke, either join us (renewals) or the dark side.....

The good is within you, etc etc etc.

Yes, spot on again OT- rails in the four foot, treadles not removed from the rails , crossings still in ....computer (alc or tgcs), smooth top etc.

Churning out endless yardage. whether its all bad or not, as your brain goes to jelly and autopilot kicks in, all you have to do is stop the machine in the right place . Computer does it all if allowed (line, x-level, cant the works).

Its like being on the production line putting a nut on a car as it goes by or something. Only good thing is each stick is one closer to going home!

Now change your squeeze time and pressures and come work with me ?

I always expose the sleepers, at least by the fittings But you know that anyway !

I think we shall have to start spoiling your weekends again old chap !

tempting - better than the "production line" ,

yes, know you've said in the past about clearing the fittings, and thats all we need (and ask for) ...apart from the odd tea break, bottles of water when its hot .....(and KFC if it drags towards 18+ hrs on site )


Cheers


V

PS always like to give it a good squeeze anyway, even on maintenance, you can't beat a bit good of consolidation !!
--- old post above --- --- new post below ---

Vlad, where is this railway you speak of that puts Track Geometry markings on the sleepers?

I believe it is time we cut out the middle man and kept Track Geometry a closely guarded secret between the local Trackchargeman and the Tamper Operator. Sounds good to me !!!

Block Joint,

As both you and OT have rightly said, they are there when its renewed but the years pass etc and they get covered in crud

This Utopian land of marked up track exists for us where the TQS's roam (some are better than others round here at marking up upcoming sites).

However I believe thats not as easy for them to do these days (after a little "skirmish" down our way (along the lines of a fault being looked at and an emergency brake app IIRC - but I stand to be corrected on that one ) stopped people going out without look outs...).


Still if we waste time looking for transition markings, thats less time for tamping .

As the old army saying goes ..." If you marching, you ain't fighting " (or something like that)

That said, apparently there are plans to fills the gaps in the TQS ranks, they are talking about recruiting more TQS's from the gangs...who knows maybe one day, it will be a world class fully marked up railway ( I won't hold my breath!!)

V

 

[Trog]

Several times i have breezed through the office and things have been so busy that there was people queueing for Tarot card readings from the resident Pagan Priest and it seems part time STO.

We used to have a TO at the ACE's office I worked in years ago who was a Pagan. When asked if it involved dancing naked round oak trees in Epping Forest. He was rather put out and said "No we wear robes." So presumably the dancing round oak trees in Epping Forest bit was right.

 

[krus_aragon]

It seems to be group think down here, 07's bad, 08's good (was it Brave new world, Animal farm or 1984 that had group think ??? ).

Doublethink is from 1984, 'four legs good, two legs bad' is Animal Farm. Groupthink is a clinical term coined back in the 50s. Finally I can contribute to the conversation on some level!

Honestly, I'm finding this conversation quite fascinating, and learning stuff I never thought enough about before.

 

[Vlad the Impaler]

k_a,

Thanks for that, thought it was one of them - which reminds me, it was Animal Farm that said

"All animals are equal, but some are more equal than others".

Nice to know that quote lives on on the railways (when it comes to rdw allocation by the roster clerks....).

Those who have been the unequal animals will know what I mean!!

chunter chunter....

V