Diamond Crossings

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This may seem like a very silly question, but diamond crossings are considered to be trailing points in both ways, yes? So that being the case, from a signallers points of view when letting a train pass over, there is nothing to lock, correct? The train would simply sail on through them without having to do anything to the points?

Cheers
(signaller in week 1 training :D)
 
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30907

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Fixed diamond crossings have no moving parts to lock.

Switch diamonds are locked in either direction, as the risk is the same as with facing points (if not greater?).

You might find this site interesting http://signalbox.org.

The box diagram for Balham (listed under LBSCR) shows movable diamonds - that's what confirmed my view.
 
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Tomnick

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As above really, you don't need to worry about fixed diamonds at all. Switch diamonds are probably best thought of as two point ends, toe-to-toe, which obviously have to be worked as a pair so that trains can only ever take the straight route across - that's how, in my limited experience, they're numbered too.

Hope you're getting on with it all anyway - there's no such thing as a silly question (the only daft question is the one that you don't ask), and I for one am happy to help as much as I can.
 

edwin_m

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There was an accident a few years ago when an engineering train ran over a wrongly-set switch diamond and was diverted onto the other route. However at anything greater than a very low speed this would result in a derailment instead.

https://www.gov.uk/raib-reports/una...-subsequent-derailment-at-haymarket-edinburgh

There was another one where the two ends of the switch diamond were out of correspondence due to incorrect wiring of detector circuits. Very fortunately the first train to use them trailed through the incorrectly set end - if it had been in the other direction there would have been an extremely nasty high-speed derailment.

https://www.gov.uk/raib-reports/incident-at-greenhill-upper-junction-near-falkirk
 

Sunset route

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There was an accident a few years ago when an engineering train ran over a wrongly-set switch diamond and was diverted onto the other route. However at anything greater than a very low speed this would result in a derailment instead.

Been involved in one of those myself, loco plus 5 auto ballast wagons, mangled the switched diamonds nicely but all stayed on the track, must of been about 12yrs back. Only came across my report for the investigation while shredding old paperwork a few months ago.
 

Mugby

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Some years ago, Attenborough Junction, between Trent and Nottingham had swing nose crossings which gave continual trouble, they were replaced by switch diamonds which solved the problem.

I often wondered why it didn't have switch diamonds in the first place!
 

edwin_m

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Some years ago, Attenborough Junction, between Trent and Nottingham had swing nose crossings which gave continual trouble, they were replaced by switch diamonds which solved the problem.

I often wondered why it didn't have switch diamonds in the first place!

But I think at Sheet Stores the switch diamonds were replaced by fixed diamonds. I believe use of new types of steel in the crossings means fixed diamonds are less of a problem for maintenance than they used to be.
 

The Planner

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We don't use swing nose crossings, we tried as part of WCRM and it didn't work for various reasons of our own making.
 

Bald Rick

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Some years ago, Attenborough Junction, between Trent and Nottingham had swing nose crossings which gave continual trouble, they were replaced by switch diamonds which solved the problem.

I often wondered why it didn't have switch diamonds in the first place!

Reasonably sure this was the trial site to prove the concept of swing nose crossings on the UK network. Close to Derby research, and even closer to the Switch manufacturing plant at Beeston.
 
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It's more than just the Americans, the modelling sector uses frog thanks to Peco descriptions. Personally I had never heard of 'nose'....
 

D Foster

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The term for the whole area in which one rail crosses the other is called the "common crossing" and the pointy bit is called the nose. The term frog is used because of the overall X shape of the construction.
Not so many years ago there was a big thing about "calling it a frog" was wrong - but I have seen C19 railway/engineering documents in which the common crossing is called a frog. In my experience people working on the railway are a bit more likely to be familiar with the term frog than common crossing.
I would admit though - the expression "swing nose" rather than "moveable frog" had me guessing for a short while.
I'm wondering whether the same element(s) of the crossing move in a swing nose and a moveable frog - or - if different moving parts are involved.

I know that at least one moveable frog was installed in the last few years (in the UK) but I don't know where it was - as in where the picture was taken.

Thanks for the links :D

;)
 

edwin_m

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I know that at least one moveable frog was installed in the last few years (in the UK) but I don't know where it was - as in where the picture was taken.

Swing nose crossings tend to be used on high speed lines where the crossing angles are very shallow, so they are probably on HS1 but I can't confirm that for definite. I've an idea they may also be used on Network Rail's only 125mph turnouts at Colton.
 

John Webb

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Interestingly, in the early days of my railway modelling, as assistant to my father, we then used Wrenn track, which was based on fibre sleepers rather than plastic. The points were so arranged that the whole of a point blade pivoted about its centre-point, causing the end of the blade at the frog to press up against the frog and close off the gap between frog and blade so that wheels had a continuous run through the point. Seemed to work well.
 

louis97

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Swing nose crossings tend to be used on high speed lines where the crossing angles are very shallow, so they are probably on HS1 but I can't confirm that for definite. I've an idea they may also be used on Network Rail's only 125mph turnouts at Colton.

Can confirm Swing Nose Crossings are used on HS1, and not at Colton Junction.
 

Railsigns

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Swing nose crossings tend to be used on high speed lines where the crossing angles are very shallow, so they are probably on HS1 but I can't confirm that for definite. I've an idea they may also be used on Network Rail's only 125mph turnouts at Colton.

HS1 has lots of swingnose crossings. There's one at Stratford International that can be viewed closely from the platform.

There are no swingnose crossings at Colton Junction. Despite having a permissible speed of 125 mph in both directions, the angle of the crossings aren't shallow enough to require a swingnose because these are 'split lead' points (Y shaped) - there's no straight route. Network Rail has another 125 mph turnout at Rugby North Junction, where the same applies.
 

Senex

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HS1 has lots of swingnose crossings. There's one at Stratford International that can be viewed closely from the platform.

There are no swingnose crossings at Colton Junction. Despite having a permissible speed of 125 mph in both directions, the angle of the crossings aren't shallow enough to require a swingnose because these are 'split lead' points (Y shaped) - there's no straight route. Network Rail has another 125 mph turnout at Rugby North Junction, where the same applies.
But then HS1 is effectively a French railway on English soil. Germany too makes extensive use of swing-nose crossings on high-speed lines.

As you note Colton is a "Y", which involved slewing the Normanton lines eastwards for a short distance to get the necessary curvature. At that time the idea was still that XC traffic would be running via Normanton and both the Y&NM line and the NM line would be upgraded for higher speeds (including restoring the original alignment at Castleford).

Haven't Colton-design switches been used in a number of other layouts, but never for anything more than 100 on the divergence (often less)? I'm thinking of Weaver, Cogload, Worting, and now Norton Bridge.
 

coppercapped

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Swing nose crossings tend to be used on high speed lines where the crossing angles are very shallow, so they are probably on HS1 but I can't confirm that for definite. I've an idea they may also be used on Network Rail's only 125mph turnouts at Colton.

The original turnouts at Airport Junction near Hayes and Harlington on the Western used swing nose crossings laid out for 90mph on the divergence and 125mph on the straight route. They seemed to be very difficult to keep properly aligned - there was often a sideways lurch when passing over them - and after a few years were replaced by conventional crossings with a 75mph divergence.

There were also some used on the Main lines near Ladbroke Grove in the 1990's Paddington resignalling at the point where the layout changed from 4 (Mains and Reliefs) to 6 bi-directional tracks and the speed was maintained at 90mph through the turnouts. These were also removed later and the limit reduced to 75mph.
 

Bald Rick

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Swing nose crossings are required on all lines in this country with a speed above 125mph, as that is the limit above which having discontinuity in the rail starts getting challenging.

Hencewhen the WCML was going to be a 140mph railway, all the junctions north of Wembley were going to have to be replaced, and indeed Ledburn Junction was actually installed with swing nose crossings. And then subsequently replaced.
 

Joseph_Locke

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Swing nose crossings are required on all lines in this country with a speed above 125mph, as that is the limit above which having discontinuity in the rail starts getting challenging.

Hencewhen the WCML was going to be a 140mph railway, all the junctions north of Wembley were going to have to be replaced, and indeed Ledburn Junction was actually installed with swing nose crossings. And then subsequently replaced.

As was Basford Hall Junction at Crewe, for reasons now forgotten.

J. Locke Snr. was heavily involved in the work BR did in the 1970's on SNX. This was another example of the UK thinking that J. Foreigner esq. couldn't possibly understand such things properly, despite all evidence to the contrary. (cf. moving block signalling, high speed S&C on concrete, CWR, etc.)

Curious that France, Germany and even South Africa have fully functional SNX designs, and we don't, over 40 years after the trials of the BR Mk1 SNX
 
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