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topic: 1400check-rails through crossovers
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posted: 3 Mar 2011 18:06

from:

geoff
 
 

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Hi,

Is there anyone out there ( doesn't have to be Martin ) who can explain the thinking/rules about the use of check rails in the middle of a crossover?  I've noticed in my Rhyl photographs that these exist in the D12 crossovers between fast-slow lines.

Just in case I'm not making it clear, the effect is that the wing-rail in the turnout road on one side is extended until it joins the check rail of the other turnout.

Thanks,

Geoff

posted: 3 Mar 2011 21:00

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Geoff,

These are called "parallel-wing crossings". They are used where the crossover tracks are sharply curved, or where the check and wing rails are so close together that there isn't room for at least two clear timbers between them. I'm not sure this is a formal rule though, practice seems to vary a lot. Anyone?

Here's a full-size crop from your uploaded Rhyl picture, showing four parallel wings:

1870_031520_550000000.jpg1870_031520_550000000.jpg

Here's a clearer picture on RMweb showing a parallel wing crossing:

http://www.rmweb.co.uk/community/index.php/gallery/image/14841-fabricated-parallel-wing-xing/

Full-size version:

http://www.rmweb.co.uk/community/uploads/1266273518/gallery_7181_438_43278.jpg

To do them in Templot you would omit the check rail on the one template, split the the wing rail out on the other template as a separate partial template, and increase its wing rail reach length at real > customize V-crossing > wing and check rails ... menu item.

regards,

Martin.

posted: 5 Mar 2011 19:02

from:

geoff
 
 

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Martin,
Thanks for your reply.

The parallel wings are sort of understandable for the fast-slow crossover shown in the photograph but the parallel wings in the down slow line where trains are moving straight ahead still intrigue me. I wondered whether it was related to expected speed through the crossover. The trains arriving at Rhyl used to go quite smartly through the fast-slow crossover.

Geoff

posted: 5 Mar 2011 22:36

from:

JFS
 
United Kingdom

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Hi Geoff,

Perhaps it is because the wing and checks would be very close together but it might also be due to the superelevation (at least on the "high" rail side where there is a risk of the backs of wheels contacting the wing rail at low speeds). Bear in mind that the degree of cant will be same for the slow as the fast - due to the continuous timbers - and will be calculated to suit the higher speed.

But all guess work of course!

Howard.

posted: 12 Mar 2011 12:16

from:

geoff
 
 

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Howard,
Thank you.

Geoff

posted: 8 Feb 2012 13:58

from:

David R
 
Hatfield Heath - United Kingdom

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One not-so obvious question arises from the above to which I'm sure somebody knows the answer.

As check-rails are vertical and wing-rails are, like running rails, inclined at 1:20 what is the prototype's solution when a wing-rail is extended to become a check-rail?  Does the check-rail bit remain inclined or is a twist put into the rail?  Or is there another way?

This is applicable to tandem turnouts as well as the crossovers pictured above.

Regards
Dave R

posted: 9 Feb 2012 14:39

from:

Tony W
 
North Notts. - United Kingdom

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David R wrote:
As check-rails are vertical and wing-rails are, like running rails, inclined at 1:20 what is the prototype's solution when a wing-rail is extended to become a check-rail?  Does the check-rail bit remain inclined or is a twist put into the rail?  Or is there another way?

Regards
Dave R
Hi David.
I think you will find that the check rails are actually inclined at 1:20 toward their respective running rail.
<Edit Apparently not, see below.> This makes the bending of the wing rail quite complex as the axis of the bend has to be off the vertical to maintain the 1:20 inclination either side of the bend. The check rail extention is therefore just fishplated onto the end of the parallel wing rail.  Modern flatbottom  P&C is of course different as the rails within the Turnout are vertical and incorporate a twist in the rail between adjacent timbers to change between vertical and 1:20 inclination at the outer ends.
Tony.
Last edited on 10 Feb 2012 16:10 by Tony W
posted: 9 Feb 2012 14:51

from:

Tony W
 
North Notts. - United Kingdom

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2151_090947_130000000.jpg2151_090947_130000000.jpg
Martin Wynne wrote:
Hi Geoff,

These are called "parallel-wing crossings". They are used where the crossover tracks are sharply curved, or where the check and wing rails are so close together that there isn't room for at least two clear timbers between them. I'm not sure this is a formal rule though, practice seems to vary a lot. Anyone?

Martin.
Hi Martin, Geoff.
Sometimes they don't seem to have been able to make up their mind either way. Here is one for the prototype for everything department.
Tony.

posted: 10 Feb 2012 13:11

from:

David R
 
Hatfield Heath - United Kingdom

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Tony W wrote:
I think you will find that the check rails are actually inclined at 1:20 toward their respective running rail. This makes the bending of the wing rail quite complex as the axis of the bend has to be off the vertical to maintain the 1:20 inclination either side of the bend.

According to the LNER* book check-rails are vertical; at least the CC chair drawings show the check-rails as vertical.  This gives a larger area of rail-head to bear against the rear of the wheels.

The chairs holding wing-rails are shown as inclined hence the requirement for conical curves (rather than simpler cylinderical ones) at the knuckle and end-flare.

Which still leaves my question unanswered: where/when/how does the inclined extended parallel wing-rail become a vertical check rail?

* Other railway companies are also available, a pity detailed drawings of their trackwork aren't more widely published.

Regards, David R


posted: 10 Feb 2012 15:38

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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David R wrote:
Other railway companies are also available
Hi David,

Indeed. :?

For the GWR, just looking at Paddington drawing R1782 (Nov 1948) states "The check rail is always vertical".

I think that goes for the REA designs too, as evidence from the LNER book.

However, in older designs the check rail was inclined -- the NER check rail drawings certainly show that.

The point and splice rails at the vee nose are vertical, and a twist is put in the rails to return them to 1:20 inclined. The twist is made between the end of the spliced section and the next special crossing chair, i.e. for our typical model sizes between the B and C chairs.

For parallel wing crossings a similar twist is needed in the wing/check rail, from inclined to vertical, but I'm not sure where the twist is made. Parallel wing crossings require special crossing chairs to accommodate the check rail beyond the B chair, presumably setting it vertical after a twist in the REA designs. The NER drawings show the layout of such chairs on page 39, but no drawings of them. Parallel wing chair drawings, anyone?

regards,

Martin.

posted: 10 Feb 2012 16:07

from:

Tony W
 
North Notts. - United Kingdom

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Hi David, Martin.
Further to the above, I was going by the British Railway Track book third edition published by the Permanent Way Institute. This has a drawing on page 67 showing Flangeway clearances and this gives the impression that the check rail is inclined. However I have subsequently discovered on page 410 in a section that deals with check rails a statement that says "Check rails in Bull Head track are usually fixed vertically in special chairs", implying the drawing is incorrect. The sectional drawing through the A chair on page 103 certainly shows the wing rails inclined toward the nose. This implies as Martin suggests that there must be a twist in the parallel wing rail presumably between the B chair and the first special parallel wing rail chair. As the rail head alignment must be maintained, the twist must push the foot of the rail closer to the running rail as a consequence. It would certainly make sense for the check rail to be vertical as the sides of the rail head were parallel prior to the introduction of 113A section FB rail, and this maximises the contact area and hopefully minimises wear.
Tony.
Last edited on 10 Feb 2012 16:14 by Tony W
posted: 10 Feb 2012 16:50

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Tony W wrote:
However I have subsequently discovered on page 410 in a section that deals with check rails a statement that says "Check rails in Bull Head track are usually fixed vertically in special chairs"
Hi Tony,

Thanks for the page reference. :)

I was sure I had seen it somewhere in BRT3 but couldn't find the page.

That para is omitted in BRT4, which deals mainly with FB track.

Detailed drawings of parallel wing arrangements seem elusive. The Paddington drawings (1936) contain a reference to modified 4C chairs for parallel wings, but no details.

regards,

Martin.

posted: 13 Feb 2012 18:29

from:

David R
 
Hatfield Heath - United Kingdom

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Martin Wynne wrote:
 The NER drawings show the layout of such chairs on page 39, but no drawings of them. Parallel wing chair drawings, anyone?

The LNER book on page 38A has drawings for the PW, L1PW and PWR chairs.  All show quite clearly (well they do if you've got a good magnifying glass!) both rails are inclined at 1:20.  Page 38 shows the CCR, CC and CCL chairs with one rail vertical.

So, does anybody have any evidence of if/when/where an extended wing rail changed its inclination to become a check rail when a checking action was required?  Is this another case of "we've done it this way for years so there's no need to write down" or "the ganger on-site knows what to do with it"?

Please bear in mind that an extended wing -- check rail exists in many tandem turnouts so the question is not quite so esoteric as you may at first think as these are common formations, at least on models!

Regards
David R



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