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1st message | this message only posted: 9 Dec 2011 17:42
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John Palmer
 

 

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This is my first post on this forum, and I’ll begin with a big thank you to Martin for having provided such a powerful and useful software tool as Templot.

I am attaching the box file for the most recent evolution of my projected West Highland model: an alternative to the Mallaig Extension based on the premise of a railway along the west shore of Loch Shiel to a terminus on South Loch Moidart via Acharacle. The box file shows the current layout for the terminus, any resemblance to Mallaig being entirely intentional.

In the late 'eighties I was fortunate enough to have the opportunity to measure and photograph a North British turnout at Rannoch with interlaced timbering. The turnouts on the attached drawing reflect the data collected at Rannoch.

The projected layout features one tandem turnout, the employment of which is fairly critical as I haven’t found a satisfactory alternative way to fit in the required facilities. Whilst I am reasonably content with the geometry of this tandem unit, I am much less happy about the interlacing of the timbers. I have scoured every photograph available to me of NBR trackwork, but have yet to find one that clearly shows a tandem, let alone reveals any clues as to North British timbering practice for such a unit. I am even beginning to wonder whether, exceptionally, the NBR made use of timbers extending across the full width of a tandem formation.

So, if anyone out there can provide me with any information about how the NBR went about timbering a tandem, it would be much appreciated.


<edit> Aagh! Sorry, seem to have posted this to the wrong sub-forum; hope it will be of some interest nonetheless. </edit>

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2nd message | this message only posted: 9 Dec 2011 21:20
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Tony W
North Notts., United Kingdom

 

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Hello John.
First off let me admit that I am no expert on pre-group railways let alone the NBR. The few pictures I have seen appear to show that standard 9 footers are used throughout. That said, the options for timbering a tandem in such a fashion are quite limited. My suggested solution is attached. I do not claim this is the only solution and if someone knows better then I hope they will let you know. You just have to tidy up the rails through the crossings now. Well done for what you have achieved so far.
Tony.

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3rd message | this message only posted: 9 Dec 2011 22:06
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John Palmer
 

 

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Tony, thank you for the revised version. I will study this carefully and come back to you after I have done so.

Is there something you think needs particular attention as regards cleaning up the rails through the crossings? So far as I can see all one can do is superimpose the first crossing on the diverging closure rails - is there a trick I've missed here?
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4th message | this message only posted: 9 Dec 2011 22:25
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Tony W
North Notts., United Kingdom

 

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John Palmer wrote: Tony, thank you for the revised version. I will study this carefully and come back to you after I have done so.

Is there something you think needs particular attention as regards cleaning up the rails through the crossings? So far as I can see all one can do is superimpose the first crossing on the diverging closure rails - is there a trick I've missed here?
Hi John. At the moment you have as you say got the crossing superimposed on the stock rail and it is perfectly possible to print the template and construct it from this, however it may not be so easy to see exactly where the tip of the crossing nose comes. Using partial templates one can remove the stock rails for the crossing areas. Give me a while and I will show you what I mean. There is a tutorial for this under the tandem turnout section of the forum.
Tony.

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5th message | this message only posted: 9 Dec 2011 23:08
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Tony W
North Notts., United Kingdom

 

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Hi John.
Load the Templot file attached, open the storage box and step through the templates from the highest number and work down and you will see what I mean. To achieve this in version 0.91c you need to go Do > Omit rails and joint marks Ctrl+O and deselect the rail in question. Then store and background to save it, next right click the mouse and click the hide control to make it visible again. Then Ctrl+O again, this time click every box to invert all the rail settings. Now go Real > Timbering > No timbering and you should have only one rail visible. The visible length can now be adjusted by using either F4 to adjust the overall length or Ctrl+F3 to adjust the blanking length. It will make sense when you try it.
Tony.

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6th message | this message only posted: 10 Dec 2011 09:59
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Jim Guthrie
United Kingdom

 

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John Palmer wrote
The projected layout features one tandem turnout, the employment of which is fairly critical as I haven’t found a satisfactory alternative way to fit in the required facilities. Whilst I am reasonably content with the geometry of this tandem unit, I am much less happy about the interlacing of the timbers. I have scoured every photograph available to me of NBR trackwork, but have yet to find one that clearly shows a tandem, let alone reveals any clues as to North British timbering practice for such a unit. I am even beginning to wonder whether, exceptionally, the NBR made use of timbers extending across the full width of a tandem formation.

So, if anyone out there can provide me with any information about how the NBR went about timbering a tandem, it would be much appreciated.
John,

It's not NB but Caley and it's not a tandem,   but here's a picture of a three way at Crow Road station on Glasgow showing that sleepers were used throughout.    I think that there were some detail variations on NB and Caledonian practices but I'm sure that they all followed the same general rules.



A lot of pre-Grouping interlaced turnouts survived well into the BR period in Scotland - this picture was taken in 1953 and the turnout would probably have survived until the line was closed in the 1960s.   I've got another picture somewhere of interlaced turnouts taken in the early 1980s in Scotland which showed that the timbers and the chairs had obviously been replaced at some time in its history in the LMS or BR period so Scottish PWay crews were still carrying out full maintenance on them. :D

Jim.

EDIT - Just having a close look again at the picture,  I see that I am wrong and that longer timbers were being used - i.e. on the crossing closest to the camera,  the two chairs closest to the crossing are on interlaced sleepers,  but the next chair along is on the same sleeper as the nearest stock rail.  I can foresee Martin doing some wizardry with Gimp to to an overhead plan of the turnout. :D

Jim.

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7th message | this message only posted: 10 Dec 2011 14:27
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grahamroberts
 

 

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Hi John,

I'm very interested in your box file since I'm in the throes of Templotting interlaced timbering myself, albeit for a GNS prototype. I've drawn an almost complete blank in finding any GNS-specific details so am working from an NBR plan for a "simple junction", drawn at 1:48 in 1901. (I can't remember where this came from but I have the feeling it was referred to in a post on Templot Club).

Now, the said plan shows rather variable sleeper spacing: 33" centres along the switches; 24" at the heel chairs; 30" from the heel to crossing; and 33" or 36" at the crossing. There is also a distinctive 18"-spaced pair of sleepers directly on the crossing side of the heel chairs, after which the interlacing starts.

Your design simply has 27" spacing before the interlacing and 36" spacing afterwards, and the interlacing starts directly after the switch heel without a close-spaced sleeper pair. I would be very interested to know if this is exactly what you measured at Rannoch, or whether it's an average.

When I tell you I'm planning to model in 2mm finescale, you will probably laugh, since the 6" difference in interlaced spacing works out at a scale millimetre... except that, as you've no doubt already found out, these few inches add up as you work along the interlacing and you can end up with an awkward space! I am not at all fussed about being "exactly right", but it is always interesting to know what was really used on the ground.

I'm a bit suspicious of the NBR plan, since who knows why it was prepared - maybe to impress the Board of Trade rather than for the PW gang - and I'm sure the Scottish companies would have used 36" spacing rather than 30" if it provided adequate support... less wood to buy...

The other "gotcha" with interlaced sleepers, which applies to any of the compromise-flangeway scales including 2mmFS, was pointed out by Stewart McSporran in a post on this form a few years back: the wider-than-scale flangeway at the crossing pushes the knuckle away from the crossing nose and it is impossible to place the crossing sleepers to accurately support the nose and knuckle. You won't have this problem in S4 at least! I am still pondering which will look better - accurate support, with uneven sleeper spacing; or inaccurate support but even sleeper spacing. I think probably the latter.

Finally, regarding your original question... you may be familiar with the Iain Rice "Layout Design: Finescale in small spaces" published by Wild Swan. This has a nice photo from a raised viewpoint of North Leith yard in mid-LNE days by C.L. Mowat, with two tandems visible in the middle distance, one of which looks close enough to give useful detail. Unfortunately the screen used for reproduction is too coarse to say for sure whether there are timbers or sleepers at the crossings but it looks to me like sleepers. If you could get hold of an original print it might shed some light: I believe Mowat's photos were held by LGRP and have passed to the NRM, but I have no idea whether or how they can be accessed - doubtless others can help. There were at least two more tandems at North Leith: I can only find side views of them in albums, and not of the crossing area, so it's hard to say how they were made. I found another view of a tandem in the yard at Gullane, but too far off to be useful.

Hope this is of interest, and thanks again for posting you box file,

regards
Graham Roberts
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8th message | this message only posted: 10 Dec 2011 14:49
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John Palmer
 

 

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Tony, thank you so much for taking the time to set up the file so as to show how the crossings’ appearance can be cleaned up. I really ought to have worked this out for myself, having partially applied the necessary techniques when creating the trap points. I’ve now applied them to the tandem and taken the opportunity to clean up the check rails too, as the attached boxfile will show.

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9th message | this message only posted: 10 Dec 2011 14:51
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John Palmer
 

 

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Jim, many thanks for the photograph of a 3-way at Crow Road. I agree that there seem to have been substantial similarities in the practices of the Scottish companies and I counted myself very fortunate to have encountered a North British interlaced turnout as late as the 1980’s. At the time I measured it, its through-timbered replacement was lying on the adjacent loading bank, so it was an opportunity not to be missed.

Re-examination of photographs available to me revealed a Lens of Sutton shot taken in the late 30’s of a Yorkie tank departing Helensburgh, with an interlaced tandem in the foreground. Unfortunately it lacks sufficient depth of field to make interpretation of the timbering easy, but it appears to have a mix of standard nine foot sleepers and longer, heavier crossing timbers. As best as I have been able to divine it from the photograph, I have reproduced this timbering arrangement in the tandem in the latest version of boxfile attached to my post in reply to Tony. The use of such longer timbers chimes with the comment in your edit.

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10th message | this message only posted: 10 Dec 2011 16:26
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from:
John Palmer
 

 

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Graham, how right you are about those odd few inches progressively adding up and leaving you with an awkward space! This becomes all the more significant when you bump into spacing constraints that apply both at the crossing and the switch end of a turnout.

At the crossing end, timber positions need to take account of the pitch between timbers that is built into the castings of the specialist chairs. This largely determines where any standard sleepers must be placed, bearing in mind their restricted width. But then you come up against a similar constraint at the heel of the switch, since at least on North British loose heel switches, the switch and closure rails are mounted on cast heel plates that incorporate the chairs adjacent to the ends of these rails. I’ve attached the photograph I took of the heel plate of the Rannoch turnout to illustrate this.

I’m still working from the pencilled sketches and notes on this turnout that I made ‘on site’ (probably still bearing traces of squashed midge), so I can’t readily post a table of the dimensions taken. Moving towards the toe of the switch from the heel plate, sleepers were mostly pitched at between 31 and 34 inches. Moving forward towards the crossing from the heel plate, sleeper pitch fluctuated between 31 and 36 inches, the majority being between 34 and 35 inches apart. The joint in the stock rails adjacent to the heel plate I noted as being 13.25 inches distant from the from the centre of the nearest chair cast into the heel plate, implying a sleeper pitch adjacent to the joint of 27 inches.

One of the most distinctive features of the North British turnout was the very pronounced flare on wing and check rails, such as to leave a gap of 5 inches between checking face and running rail face at the extremity of the flare – I have tried to reflect this in my Templot drawings. Similarly, my timber positioning attempts to reflect the constraints described above that are imposed on the formation by the specialist castings and chairs.

Unfortunately I don’t have a copy of Ian Rice’s book, but the mention of North Leith set me off on a Google session that revealed a tandem at North Leith in the photo here:

http://www.edinphoto.org.uk/0_edin_t/0_edinburgh_transport_railways_dy_north_leith_0861.htm

I also came across a picture here:

http://www.disused-stations.org.uk/s/st.boswells/index1.shtml

 of part of a tandem at St Boswells. Judging by pitch between chairs in particular I suspect that both of these formations include timbers spanning (and supporting) multiple tracks. I also suspect that in the case of a tandem this may have been unavoidable, as otherwise it seems to be impossible to provide adequate support for each pair of rails whilst still making it practicable to get a jack under the timbers for maintenance purposes.

Interesting that compromises are forced upon you even in 2mm fine. How glad I am that I shall be able to dodge them in the larger scale!


 

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11th message | this message only posted: 10 Dec 2011 22:43
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from:
Tony W
North Notts., United Kingdom

 

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John Palmer wrote:
Tony, thank you so much for taking the time to set up the file so as to show how the crossings’ appearance can be cleaned up. I really ought to have worked this out for myself, having partially applied the necessary techniques when creating the trap points. I’ve now applied them to the tandem and taken the opportunity to clean up the check rails too, as the attached boxfile will show.
Hi John.
Unless you know the facility is there you don't necessarily think to look for it. I thought you would sort out the check rails once you realised. It does look a lot better. With regard to the sleeper / timber spacings, As you so rightly say, the spacings of the crossing and switch timbers are pre set by the geometry of the chairs and those for the closure rails are fitted in between. Although each company had its own standards, as long as the maximum spacing between adjacent timbers was not exceeded, some flexibility was necessary to get things to fit, as you have discovered. The give away as to whether long timbers were used at the crossings is the number of crossing chairs visible in pictures, long timbers use far less as I am sure you realise.
Anyway, wish you well with your project.
Tony.


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