Jump to content

Recommended Posts

51 minutes ago, Philou said:

is there an approximate date when there was a changeover from individual canting of tracks to when the formation itself was canted?

 

I'm not aware that Pontrilas had any of its curves sharing a superelevated bed.

 

pontrilas-superelevation.jpg.fc05044d5b2394cf4fcb99159799020b.jpg

 

Looking north. The curves have individual canting. The cant gradient (probably 1:400) allows a gradual change to a shared flat section at the crossover (no doubt some timbers were shared), which is also straight, so there are lots of subtle transitions in radius and height. North of the crossover, the curve takes a contrary direction, with individual track cants prevailing.

 

I think the Pontrilas superelevations might be a bit more pronounced nowadays, probably because of an increased 'line speed'.

 

The shared/not shared superelevation was not a hard and fast rule. PW engineers would not have wanted to use more ballast than was necessary. Check out Tram Inn though, were the level crossing dictates a shared superelevation. Some beds through stations shared their superlevation bed merely because that's the way they were built.

 

If you know what the Pontrilas 'line speed' was (45mph?, or is that too Edwardian), and the radius through the platforms, you can work out what the max superelevation would have been applied.

 

Share this post


Link to post
Share on other sites

@Miss Prism Aah .... It was probably the way I phrased the question. From the photos I have, it certainly seems that the tracks are canted individually (can't post the photos here as they're probably copyrighted), but I was asking in general way if there was a period when individual canting was superseded by formation 'superelevation' - or has it always been? 

 

Cheers,

 

Philip

Share this post


Link to post
Share on other sites
16 minutes ago, Philou said:

but I was asking in general way if there was a period when individual canting was superseded by formation 'superelevation'

 

My view is that individual canting was, and is, the norm. (No doubt there are hundreds of legitimate exceptions.)

 

Share this post


Link to post
Share on other sites
23 minutes ago, Philou said:

@Miss Prism Aah .... It was probably the way I phrased the question. From the photos I have, it certainly seems that the tracks are canted individually (can't post the photos here as they're probably copyrighted), but I was asking in general way if there was a period when individual canting was superseded by formation 'superelevation' - or has it always been? 

 

Cheers,

 

Philip

Alas I can't find it at the moment - as it is a small card foldout - but somewhere I have the GWR data for calculating curve radius off chord measurements and I'm sure it also includes cant allowances against radius.  It would therefore be individual as the radius varied from line to line to line.

 

I'm reasonably sure that the 12inch cant that was used near  Cullompton about 25-30 years ago (claimed to be the highest on BR) was only applied to one running line and a lesser cant was used on the line on the outside of the curve.

Share this post


Link to post
Share on other sites
10 minutes ago, Miss Prism said:

 

My view is that individual canting was, and is, the norm. (No doubt there are hundreds of legitimate exceptions.)

 

Your original reply on this said that the modern practice was "usually" that the outer track was above the inner, ie they were canted together along one plane and not individually?

Share this post


Link to post
Share on other sites
3 minutes ago, njee20 said:

Your original reply on this said that the modern practice was "usually" that the outer track was above the inner, ie they were canted together along one plane and not individually?

 

Sorry. I misread the intention of that bit of Philou's OP, confusing outer 'rail' with outer 'track'.  Post now corrected.

 

 

  • Thanks 1

Share this post


Link to post
Share on other sites
1 hour ago, Miss Prism said:

 

If you know what the Pontrilas 'line speed' was (45mph?, or is that too Edwardian), and the radius through the platforms, you can work out what the max superelevation would have been applied.

 

You could work out the maximum superelevation but not necessary the superelevation that was actually used [aside: from here I'll use "cant" instead as it means the same but is easier to type]. 

 

There is an "equilibrium speed" where a train going round a canted curve experiences no net lateral force and the wear on both rails will be equal.  But trains may be going slower than that, and therefore wearing the inner rail more, or faster and wearing the outer rail more.  So the choice of cant at a particular location depends on the mix of train speeds arising from stopping versus non-stop and also passenger versus freight, with tonnage also taken into account because a heavy train causes a lot of wear on the lower rail if it is going a lot slower than equilibrium speed. 

  • Like 2

Share this post


Link to post
Share on other sites

There do seem to be a lot of variables when taking cant into account - I'm glad I raised the question.

 

Insofar as I know, there were a fair number of stopping trains at the station and a fair amount of freight going through as it was the LNWR line into S. Wales. The Stationmaster is a most-knowledgeable chap regarding this line. I suspect that as the station has now gone together with all the pointwork therein and with improvements to rolling stock, the line speeds will have increased together with the cant.

 

Anyway, thanks for the replies. I shall be applying some cant on the through lines within the station as this is what is shown photographically AND my curves will be true to the prototype. What happens on exit stage right (and left), we shall see.

 

Cheers,

 

Philip

Edited by Philou
Edit: Missed a word or three.
  • Like 1

Share this post


Link to post
Share on other sites
10 hours ago, Philou said:

 

Those that are in the know, is there an approximate date when there was a changeover from individual canting of tracks to when the formation itself was canted? I'm not proposing to model any HS1 or 2 track - just an enquiring mind and all that.

 

Cheers,

 

Philip

 

There is no such date a P-W Engineer except perhaps when working on a new line would only bother to make two roads co-planar if there was a good reason to go to the trouble of doing so such as a crossover or a level crossing.

 

Also remember if putting canted track through a platform to adjust the rail to platform level difference by half the applied cant. Less if the platform is on the inside of the curve, more if on the outside.

Share this post


Link to post
Share on other sites
8 hours ago, The Stationmaster said:

I'm reasonably sure that the 12inch cant that was used near  Cullompton about 25-30 years ago (claimed to be the highest on BR) was only applied to one running line and a lesser cant was used on the line on the outside of the curve.

 

Are you sure I thought that Cullompton and perhaps one other place at 8" were the two exceptions to the normal 6" maximum cant rule. The exception being made because using 6" of cant would have put a speed restriction in the middle of what would otherwise have been a nice long stretch of fast track.

Share this post


Link to post
Share on other sites
14 minutes ago, Trog said:

 

Are you sure I thought that Cullompton and perhaps one other place at 8" were the two exceptions to the normal 6" maximum cant rule. The exception being made because using 6" of cant would have put a speed restriction in the middle of what would otherwise have been a nice long stretch of fast track.

I was told 12" by somebody in the WR CCE's organisation and it certainly is one heck of a cant when you go round it on a train.  But it mightw ell have been less and somebody  thought it was more.  I know there was some very significant cant put in on various curves in the west after HSTs were introduced on the West of England route.  As I no longer go to the 'right' OFs lunch I very rarely see any Civils from that area nowadays but I'll try to remember the next time I come across the DCE who was involved. 

Share this post


Link to post
Share on other sites

I remember the old platform 4 at Reading always felt like a major cant when you got onto an HST certainly, although I suspect it was just because the train was stationary.

Share this post


Link to post
Share on other sites

I wonder what the cant is at Cramlington station? On the one occasion I went there by train, I almost dislocated my shoulder when I opened the door.

Someone mentione Pontrilas; there is still a trailing crossover between the Down and Up lines, as well as an Up Goods Loop. There was mention on the BBC News site , earlier this week, of a campaign to re-open the station.

Share this post


Link to post
Share on other sites

'Twas I that mentioned Pontrilas - the location of my proposed layout. I was aware of a siding still in place together with the signal box but I had overlooked the crossover which, unless I am mistaken, lies within two reverse curves and therefore little cant.

 

Interesting that they have a campaign to re-open the station. Where will they put the platforms as the station building proper is now a private dwelling?

 

Thanks for the info from Trog regarding co-planar tracks - though I do recall seeing somewhere a cross-sectional drawing showing such a construction - might have been related to TGV trackwork.

 

Cheers,

 

Philip

Share this post


Link to post
Share on other sites
16 hours ago, The Stationmaster said:

I was told 12" by somebody in the WR CCE's organisation and it certainly is one heck of a cant when you go round it on a train.  But it mightw ell have been less and somebody  thought it was more.  I know there was some very significant cant put in on various curves in the west after HSTs were introduced on the West of England route. 

 

I don't know how much it is either but I remember doing ballast turns there - two weeks on the  trot some 10 or 15 years ago - and it certainly feels a lot when you are stationary or dribbling around the curves at 2mph or so 

I also remember it was bloody hard to reach up to the handrails of a class 66 on the outside of the curve too! :D

  • Like 2

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.