Switched Diamonds

[martin_wynne]

The North Eastern Railway was using "Switch Diamonds" or "K Crossings" as they called them by c1910, I have the drawings to prove it.

Hi Mick,

 

Yes, they are in the excellent NERA reprint of the NER 1912 track standards.

 

Also, C. J. Allen (1915) shows at Fig. 119 -- "Messrs. Sykes and Howard's Patent Movable Diamond Crossing". He says one such had been "recently laid by the LBSCR at the new Victoria station".

 

There is an alternative idea at Fig. 117 -- "Messrs Henry Williams' Patent Diamond Crossing Point Protector" in which a component is raised vertically into the flangeway gap at the K-crossing, to prevent wheel flanges striking, or going the wrong side of, the point rails. That would make an interesting model!

 

regards,

 

Martin.

[DIW]

Going off at a slight angle here.....

 

How about this - a switched diamond crossing on a rack railway at Grindelwald Grund station (beyond the point in the foreground, of course).

 

 

The rack section swivels in order to provide continuous rack through the crossing. The adjacent signal indicates which route is set.

 

This crossing was installed in recent years when the station was re-laid and re-signalled.

 

Dave

[phil-b259]

Swing nose points are used at Colton junction just south of York where the Selby diversion turns off the Leeds line and they are the only 125mph points in the UK as far as I know.

 

 

That depends on whether you include HS1 / CTRL in your deffination of UK mainlines as all points on this route outside St Pancras use swing nose crossings (i.e. the frog in model terms), which is not suprising given that in Kent they are travelled through at 186mph comfortably beeting Colton Junction.

[Glorious NSE]

There is an alternative idea at Fig. 117 -- "Messrs Henry Williams' Patent Diamond Crossing Point Protector" in which a component is raised vertically into the flangeway gap at the K-crossing, to prevent wheel flanges striking, or going the wrong side of, the point rails. That would make an interesting model!

 

Going totally off at a tangent now, some locations in the US are now using what they call OWLS diamonds (One Way Low Speed) - if the site has one route that's a main line with high traffic or high speed being crossed by a low density route these effectively lift the lower speed route over the main routes rail, the flange of trains on the low speed route runs across the rail head of the high speed route, the high speed route has a solid piece of rail to run on so no bounce, lower maintainence requirements, no moving parts and no speed limit.

http://www.flickr.com/photos/jonroma/1487082642/in/photostream/

 

That's why I was surprised a Class 66 managed it at Haymarket without the driver apparently noticing.

 

RAIB report if you fancy a read: http://www.raib.gov.uk/publications/investigation_reports/reports_2007/report032007.cfm

 

36 The train passed over the junction and ran through 173B switch diamonds, which diverted it onto the down south line. The driver realised that his train was heading in the up direction on the down line and stopped the train in platform 4 of Haymarket station, after the locomotive had travelled about 400 m past the junction; he immediately contacted the signaller. The rear of the train was still on the down Midcalder line.

37 In order to ensure that it had not been damaged as it went through the switch diamond points, arrangements were then made to examine the train before it was moved onto the correct line. At 16:14 hrs a member of EWS engineering staff asked the driver to release the train brakes so that he could carry out a functional brake test. The wagons of the train rolled back a short distance and the wagon that was standing on the switch diamond points (173B), the fifth from last in the train, became derailed by one pair of wheels (see paragraph 44).

43 Following this incident, one wagon of the train became derailed. The EWS fitter who attended the train at Haymarket was not aware that the train was still standing with its rear end over 173B switch diamonds and therefore did not consider the risks of doing a functional brake test at that location. When the brakes were released, the rear of the train rolled a short distance back, and one pair of wheels which were standing on the switch diamonds were derailed towards the six-foot. The movement was probably caused by the release of the compressed buffers of the wagons, since the Edinburgh and Glasgow lines are level at this point.

44 The movement of the train was extremely limited, and there was no risk to any person or other train from this derailment.

[Edwin_m]

Going totally off at a tangent now, some locations in the US are now using what they call OWLS diamonds (One Way Low Speed) - if the site has one route that's a main line with high traffic or high speed being crossed by a low density route these effectively lift the lower speed route over the main routes rail, the flange of trains on the low speed route runs across the rail head of the high speed route, the high speed route has a solid piece of rail to run on so no bounce, lower maintainence requirements, no moving parts and no speed limit.

 

Some points on street tramways in the UK do something similar. A couple of years ago they replaced a crossover at Nottingham just next to the theatre and concert hall, where I believe vibrations were a problems. The rarely-used curved rail now raises up as described to pass over the other one with a gap for the wheel on the straight rail to go through. I noticed another one on the relaid street track on Aytoun Street in Manchester. I guess this trick will only work with small-radius tramway points otherwise the gap would be too long.

[Southernman46]

I would be very surprised if slips with switched diamonds have disappeared, there were lots about much more recently than 25 years ago. See Jim Smith Wright's topic on Birmingham New Street for examples. And a quick look at 192.com's super zoom photos found half a dozen in the Kings Cross throat. It doesn't give direct links to the pic so you have to search for Kings Cross then zoom in.

192.com

Waterloo on the other hand seems to be all cast manganese crossings, but they are only for larger crossing angles, 1:8 and less have to be switch diamonds.

Regards

Keith

By the way, 192.com photos can be printed out to modelling scales and used as templates for track building, but you need to use 'print screen' to download them.

 

 

 

Yes I can confirm that the double slips at Waterloo in the throat off the ends of plat 9-13 (1514/1515) & 1524/1525) points are all 1 in 7.5 angle cast manganese crossings.

 

There is a set of slip switched diamonds in the London end ladder on the Windsor side at Clapham Jn - 654 points from the Down Windsor Slow into the yard - these were a nightmare to maintain - and were replaced like for like at Xmas 2008 when the entire ladder was renewed.

[D6975]

A switch diamond was partly blamed for the Colwich crash involving 86211/429.

One of the trains (Northbound towards Stoke/Manchester) overshot a red and was derailed on the switch diamond, leaving the loco across the path of an oncoming Southbound on the main. Because the train was derailed, the driver couldn't reverse it clear of the crossing, which he apparently would have had time to do had it been a plain diamond.

[beast66606]

A switch diamond was partly blamed for the Colwich crash involving 86211/429.

One of the trains (Northbound towards Stoke/Manchester) overshot a red and was derailed on the switch diamond, leaving the loco across the path of an oncoming Southbound on the main. Because the train was derailed, the driver couldn't reverse it clear of the crossing, which he apparently would have had time to do had it been a plain diamond.

 

I assume this is the accident to which you refer http://www.railwaysarchive.co.uk/documents/DoT_Colwich1988.pdf

 

I'm not sure this is true - can you quote references please - the driver of the Manchester train hadn't even reached the crossing when the Liverpool train was first spotted, so I can't see any chance of any reversal taking place and the switch diamonds are not blamed in the conclusions and recommendations

[DY444]

I believe the first, experimental, installation in a fast running line on BR was that at West Drayton East back in the late 1970s or therereabouts.

 

The very first one was installed at Burton On Trent in 1969. It was in a trailing turnout on the Up Goods line.

[DY444]

I assume this is the accident to which you refer http://www.railwaysa...Colwich1988.pdf

 

I'm not sure this is true - can you quote references please - the driver of the Manchester train hadn't even reached the crossing when the Liverpool train was first spotted, so I can't see any chance of any reversal taking place and the switch diamonds are not blamed in the conclusions and recommendations

 

I am sure and can confirm it is not true. The switch diamonds played no part. The locomotive of the Manchester train was stationary on the diamond when the impact occured. The driver, having seen the approaching Up Liverpool train, had jumped clear.

[LNERGE]

Here is an excellent picture from Mick Nicholson showing a flat-bottom double-slip with movable K-crossings (switch diamond):

 

© Mick Nicholson

 

Martin.

 

This plan came my way today..

 

 

Any use to anyone?

[Grovenor]

Switch diamonds (called movable elbows on the Western) are a pre-requisite where the crossing speed is 40 mph or greater although they have appeared more widely on lower speed diamonds since the late 1960s/early'70s.

The speed is not the primary reason for switch diamonds, the main indicators are the crossing angle, flatter than 1:8 have to be switched as its not possible to check correctly at flatter angles. (Hence why the double slips in Toronto are switched but not the crossings between which are at double the angle) If the crossings are on a curve then switch diamonds are often used at greater angles. In the past with built up crossings wear and tear was a big issue hence the use of switch diamonds for higher speeds. Nowadays cast manganese crossings would be used in these situations.

 

This is from the Railtrack 2003 track design handbook

3. The flattest fixed obtuse crossing is 1 in 7.5, exceptionally 1 in 8.25 when all

four crossing legs are straight.

4. The limiting radii for fixed obtuse crossings (switch diamonds must be used if

the radius is sharper) are:

 

Angle Desirable Radius Minimum Radius

1 in 7.5 500 000 400 000

1 in 6.25 250 000 210 000

1 in 5.25 180 000 160 000

1 in 4.375 170 000 150 000

The tables give standard dimensions of switch diamonds from 1:5.25 up to 1:44.5

(Swing noses, which are, as noted above, a different animal, are given from 1:13.5 up to 1:56)

Keith

[winterbournecm]

Has Peco ever produced a set?

 

Mike: I saw the picture of the "stranded" class 50 in Westbury panel from my MOM days. Along with an array of other Westbury mishaps on the board there.

[David Bigcheeseplant]

There is a swiched diamond in the 1910 film of the Met line taken at Aylesbury, I will post the link if anyone is interested.

 

David