Sprung-Frog Turnouts

[trisonic]

In the August 2013 edition of Model Railroader there is a quite interesting one page article "How a sprung-frog turnout works" with two photographs on the BNSF track at Pauls Valley, Okla (p.18).

 

This kind of switch moves at both the frog and the switch points - but only for the diverging route. For the Mainline the frog is "closed" which makes for a smoother transition (and presumably higher speed). If switched to the diverging route then the guardrail pulls the each axle set over meaning  the rear of the wheel on the frog side literally pulls open the frog. I'm not sure how else to explain it...

 

The wing rails are not symmetrical.

 

If Martin (Wynne) had written the original article he would have explained it better, in less words and maybe a couple of diagrams!

 

Unfortunately I have never seen this style of turnout over here and have no photographs to show you.

 

Do these exist in the UK or anywhere else???

 

Best, Pete.

[Colin_McLeod]

See this discussion on another forum.

 

Scroll down a bit until you come to the photograph and relevant posts.

 

http://cs.trains.com/trn/f/111/p/120779/1816676.aspx

[martin_wynne]

Do these exist in the UK or anywhere else???

 

Hi Pete,

 

Flexible Wing (Spring) Crossings are (or at least were) certainly used in the UK, where a lightly-used siding makes connection with a busy running line, and for little-used trailing crossovers.

 

BRT3 (published 1964) has drawings and photographs for both bullhead and flat-bottom examples. In the case of bullhead spring crossings, the wing rail is held against the crossing nose by means of a coil spring. Flat-bottom spring crossings rely on the stiffness of the flat-bottom rail section to hold the wing rail against the crossing nose. In both cases devices were sometimes added to retard the closing of the wing rail, so that after being opened by the first wheel it remains open, or partially open, for the passage of the whole train. If it opens and closes between each wheel, wear and tear becomes excessive.

 

Such crossings rely entirely on the integrity of the check rail (guard rail) for safe working, and for this reason are never used in facing positions. The check rail needs regular inspection and maintenance to ensure safety, and the moving wing rail needs regular lubrication.

 

In BRT4 (published 1971) all reference to such spring crossings has been removed, so we can assume that by then they were no longer being installed. By now there must be very few, if any, left in service.

 

Generally cast crossings have taken over, with no moving parts and a much lower maintenance load.

 

Where a smoother high-speed ride is needed, powered swing-nose crossings are now sometimes used instead. In these it is the crossing nose which moves, not the wing rail. These are not restricted to trailing positions, don't need check rails, and provide an unbroken ride over both routes. However, the extra cost and complexity over a fixed cast crossing mean they are quite rare in the UK. This is a German swing-nose crossing:  

 

This is a file from the Wikimedia Commons.

Description: Swing-nose Crossing. Photographed in Bonn main railway station. Date: 10 February 2005. Source: Own work. Author: user:Qualle

 

This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

 

 

In contrast, here is another swing-nose crossing:

 

 

Thanks to Brian O’Donovan. See: http://85a.co.uk/forum/view_topic.php?id=2178&forum_id=22

 

regards,

 

Martin.

[trisonic]

Fascinating!

 

Many thanks, Martin.

 

Best, Pete.

[gordon s]

I seem to recall in the very distant past that a UK manufacturer made 00 track like that.  It may have been Wrenn or Farish Formoway?  

 

Someone on here will know...unless this is another senior moment.

[steve22]

Gordon, I believe it was Wrenn who produced the track you're thinking of.  From the back cover of my September 1960 Railway Modeller: "Universal Straight Point. 24'' Radius... designed for extra smooth running by continuous support for wheels across the nose of the frog."  I think it may also be the kind of point work visible in the December 1968 RM, Railway of the Month, 'Huntshire'.  Page 359 of that issue gives a good example.  Whichever make those points are, they don't actually look too bad and there's times I'd use point work like that at 'troublesome' spots on my layout.  I'm sure my Trix three rail points worked in the same way.  Some of the point work made by Fleischmann for a great many years now uses a switching frog as well as switching rails.    

[highpeak]

They are a useful idea when properly maintained and used with consistent wheel standards. When I worked at a streetcar museum we had a couple of these switches and while they worked well with most streetcars, they could cause a lot of trouble when cars with worn wheels negotiated them. If you ran a worn railroad profile wheelset (much wider tread than streetcars) through them there was a risk of the wheelset splitting the switch.

 

You also needed to avoid the trap of running a double truck car part way through the switch and then reversing, since one truck would go one way and the other would be guided down the other track. I don't remember the exact circumstances but my ex-wife dropped a car in the dirt by not realising that the lead truck had gone through the spring switch but the trailing truck hadn't, she then reversed the car and oops! My three-year old daughter ratted her out: "Mummy backed up".

[stewartingram]

Talking of tramways, I've seen pictures of points with no moving parts, and have actually made these in 00 too. Difficult to describe, but judicious use of checkrails and staggering of the fixed point blades, forces the tram to always take the same route (ie diverging left but never straight on).

 

Stewart

[shortliner]

Our good friend, Prof Klyzlr, has written about these - http://www.zelmeroz.com/album_model/members/klyzlr/DynamiteCanyon.pdf - and I built a pair - watching a train happily run through a turnout that you know is soldered up solidly, and can't move,  is amazing     

[BR60103]

Long time ago (up to the early 60s) TruScale made American points that looked like a sprung frog. The points, rails and the wing rails on the frog were a single unit and the wing rails moved to close the gap, as appropriate, when the points changed.

I've still got one somewhere in my collection...

[The Stationmaster]

I seem to recall in the very distant past that a UK manufacturer made 00 track like that.  It may have been Wrenn or Farish Formoway?  

 

Someone on here will know...unless this is another senior moment.

Wrenn universal - something like code 140 rail or thereabouts but they worked fairly well, I even converted some from 3 rail to 2 rail but then along came Peco Streamline, and Graham Farish so they gradually vanished from the layout (crikey - that was about 50 years ago ).

 

There was a running junction between West Drayton and Dawley on the GWML installed in the 1970s that had swing nose crossings and once bedded in they seem to have been fairly reliable but I don't think the experiment was repeated and I'm reasonably sure they went when the layout changed in connection with the construction of Airport Junction.

[hartleymartin]

Code 140? That's a heavy O gauge rail section these days!