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topic: 1377Questions on the basic fundamentals on prototype (and scale model) turnout dimensions and design met
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posted: 20 Feb 2011 15:04

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi All,

Please excuse me for asking what might seem to be some dumb questions, but something has been bugging me for a little while now.

First let me explain why I am asking the questions, on several occasions I have been placing turnouts onto my background track layout plan, and have found that in these cases, no matter what I do I cannot get both the main and turnout sides to align with the plan track lines.
In some of these cases, I have aligned the main side and then altered the adjoining track-work for the turnout side to mate up with that end (but I am not absolutely sure this is what I should really do), (I know, someone will scream the dreaded words “compromise”). :)
I have tried ringing the changes, such as changing from B to C or D type turnouts (and/or visa versa) and in some cases this has worked and created alignment of both sides, but alas not in every case.

Now although I would agree that some fault may lie in possible inaccuracies of the original drawing, but it may not be that in all cases.
To achieve complete alignment, I would have to make the particular turnout side as a partial and align it to the drawing, but this would mean it is not a standard turnout, is this a good or bad idea ?

Now if I am not mistaken, I believe most, if not all, switch chairs types are made to a standard (not withstanding individual company manufacturing), and can be used for all switches ?
Thus for a longer turnout, more of appropriate chairs would be used, and the radius of the turnout would be more gradual.

This brings me to a further question, are the turnout heels of a switch (irrespective of size/length) always the same distance apart from the stock rail ?
Here again meaning for a longer heel to blade tip distance, the more gradual the radius of the turnout.

In a nutshell, believing Martin has designed all the types of turnouts in Templot to some standard (or specification), there must be some constants in the design data, since when we modellers alter the curving and swelling of the template, everything within that template is changed pro rata to the specification (or am I wildly out in my assumptions).
What I would like to ask is, would be good practice, to customize the turnout side only, by using partial templates, in order to fit the plan precisely ?
In addition, would such a thing ever have been done in the prototype world ?

Please help with my current dilemma.

Best regards, from a some what confused

Brian Nicholls.

posted: 20 Feb 2011 16:50

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi All,

As a PS to my above posting, I have attached a PDF file of a particularly awkward 3 way tandem I’ve just come across.

The tandem is at the top of the picture in the file near to the loading gauge, and is a prime candidate as to the reason for my questions.

This particular tandem can only be done with perhaps several partial templates.

Just another dilemma !

Still confused, best regards,

Brian Nicholls.
Attachment: attach_983_1377_difficult_3_way_tandem.pdf 366

posted: 20 Feb 2011 17:21

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Brian,

Can you clarify whether you are asking about tandem turnouts or plain turnouts?

Tandem turnouts will always require the use of partial templates to create a full design. The one in your PDF looks especially tricky. :)  It would help if you could upload the base plan without the overlaid Templot tracks.

Plain turnouts should be possible without using partial templates in the vast majority of cases. The controls and options in Templot should enable you to replicate any likely turnout. Of course there is always the odd exception where partial templates would be needed. This sometimes arises where the lead length has been artificially extended to bring the switch drive rodding off a bridge for example, or to within the 350yd limit from the signal box.

You can see the heel offset dimension for each of the pre-set switch sizes by clicking the show switch info button on the switch options dialog (template > switch options... menu item).

regards,

Martin.

posted: 20 Feb 2011 18:36

from:

JFS
 
United Kingdom

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Hi Brian,
How confident are you about your source data? Where did it originate and how long ago was it surveyed? (pre-grouping track might be something very different from REA standard!)
What was its original intended purpose? It might not have been intended for use as a scale track drawing!!!
I have tried working off 40 inch plans for example, and to me they are sometimes amazingly accurate and, equally, often, miles out - straights are not straight and curves are not circular! Given that they were never intended to be accurate drawings of the track and that they might have been traced / copied / scanned half a thousand times, it might be too easy to over estimate their accuracy. Your example - given that it is coloured - might not have been copied too many times, but does that mean it is an original drawing or a tracing / print?
Do you have any corroborative evidence - photos etc? I have found that counting sleepers of photos is pretty informative when compared with a drawing.

I am looking forward to seeing how the tandem turns out!!

Best Regards,

Howard.

posted: 20 Feb 2011 23:52

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi Martin,

Many thanks for your speedy response.

Martin Wynne wrote:
Can you clarify whether you are asking about tandem turnouts or plain turnouts?
Unfortunately, it’s both tandem & plain turnouts that occasionally will not line up, needless to say, it’s the tandem’s that are the worst. :(

 Tandem turnouts will always require the use of partial templates to create a full design. The one in your PDF looks especially tricky. :)
I do fully understand that tandem turnouts do require partial templates, simply because they are made up of two templates precisely overlapping in the right areas and correct orientation, with portions omitted.

My concern with non-standard partial templates (plain or tandem) is with the aspect that, the blade tip filing may be incorrect and not fit for the job, if for example one had to make the angle of the tip more acute or perhaps more flatter (less angle) at the point where it closes to the running stock rail, would this be permissible and fit for the job (this is my area of uncertainty). ?
Also of course, it may mean the switch blade heels could end up further apart from the stock rails than normal, again is this permissible and fit for purpose ?
 
It would help if you could upload the base plan without the overlaid Templot tracks.
Regarding up loading the base plan, due to a signed copyright agreement with Birmingham Central Library (BCL) I cannot distribute the whole plan without their permission, which I do not have at this time, however, I can upload just the section I put in the PDF file if that will help (I can up load this as a bitmap file if required).
 
You can see the heel ofset dimension for each of the pre-set switch sizes by clicking the show switch info button on the switch options dialog (template > switch options... menu item).
Having looked at the switch options menu I note the following:

For older type BH or FB switches of the straight heel versions, the heel offset appears to be constant for switches between, 9 ft through to 30 ft as shown:

 offset at the heel (heel spread) = 4.5 ( 1.5 model mm )

only the planning length varies.

Where as, BH (RAE) types have the following offset sizes:

     A type  =    heel offset = 11.71 ( 3.9 model mm )
     B type  =    heel offset = 9.98 ( 3.33 model mm )
     C type  =    heel offset = 10.31 ( 3.44 model mm )
     D type  =    heel offset = 9.74 ( 3.25 model mm )
     E type  =    heel offset = 10.39 ( 3.46 model mm )
     F type  =    heel offset = 10.12 ( 3.37 model mm )

Although not strictly speaking constant, there is only a spread of 2” (0.65 model mm) across the board, therefore more or less constant.

Plain turnouts should be possible without using partial templates in the vast majority of cases. The controls and options in Templot should enable you to replicate any likely turnout. Of course there is always the odd exception where partial templates would be needed. This sometimes arises where the lead length has been artificially extended to bring the switch drive rodding off a bridge for example, or to within the 350yd limit from the signal box.
I think the nub of my questioning is can the heel offset of a custom partial template turnouts be greater or smaller than those shown for the RAE switch types ?
Also is there a practical limit to the heel offset in either direction (greater or smaller) ?
And is this an acceptable and practical thing to design or would I be creating something that is never found in the prototype world ?

I am aware that for the older straight heel types, the heel offsets are almost at the minimum gap requirement for wheel flange clearances.

I am very sorry to take you away from your coding to respond to my queries, but this has been niggling me for some time now, and before I go further with my track-work, I would really like to understand any implications using partial templates that are, out of spec, so to speak before I go too far and have lots of rework to do in the near future.

Many thanks again Martin

Kindest regards,

Brian Nicholls.

posted: 21 Feb 2011 00:40

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi Howard,

Many thanks for your response.

Regarding confidence in my plan, I have so far found it to be reasonably accurate, despite having to correct the scaling in Templot due to shrinkage of the plan being poorly stored over the years.

To correct for the scaling, I measured using the Templot ruler against the scaling bar on the drawing background image.
Also I had a copy of another original LNWR drawing for one of the stations overall roof trusses, which was something like 198 ft 6 in long, this being a known dimension I could also measure on the background image as verification for accurate scaling to 4mm to 1 foot.

I take your point about pre-grouping track may be something very different from REA standard, but no matter which type of switch I use (old style or RAE) they won’t line up to the image rail lines (here I must add, that there is not a mammoth out of alignment, but it does make it awkward to get track ends square to each other, particularly regarding curves (it leaves a small discernable “kink” to what should be a smooth curve.

The plan that resides at the Birmingham Central Library (BCL) is a copy from an original drawing, and is rubber stamped 1921, that had been stored for many, many years (I suspect since that date), until just before I visited BCL when it was taken from storage and had to be professionally cleaned and flattened in order for people to view it.
Incidentally, there is also slightly later plan dated 1929, and although one can view this plan copy it has only been briefly cleaned but not yet flattened and is not available for sale of copies, it can, as I did, be photographed however, if one visits the BCL.

As to photographs, I have a number of interesting ones of the station, taken during the 1950’s and 1960’s, which I obtained from the D J Norton web site, and from his 3 books that I bought, of the “surveys of the railways of the west midlands”, however, as with most photographers the majority are of locomotives, from which only a small area of track can be seen, and I can only assume from these that, what track is visible, remained the same as from the 1920’s.
There is two photo’s of the area of the tricky tandem turnout, but the most significant parts are cut off by the platform edge and the angle of framing of the photo’s, so not so easy to count sleepers.

We shall have to see what develops regarding the tricky tandem !!

Many thanks again for responding.

All the very best,

Brian Nicholls.

posted: 21 Feb 2011 00:58

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Brian Nicholls wrote:
I think the nub of my questioning is can the heel offset of a custom partial template turnouts be greater or smaller than those shown for the RAE switch types ?
Also is there a practical limit to the heel offset in either direction (greater or smaller) ?
And is this an acceptable and practical thing to design or would I be creating something that is never found in the prototype world ?
Hi Brian,

I think what you are asking me is -- do I have the prototype data to hand for LNWR loose-heel switches?

I regret that the answer to that is no. Others on here may be able to help.

The straight switches listed in Templot are taken from the details in BRT3, which are I believe given as typical of pre-group practice, and may actually be from the LNWR for all we know. We do have full details for GWR switches, and also for NER switches, and both of those are significantly different.

You can create any custom switch within reason in Templot, you don't need partial templates. But it won't be prototypically correct if it's not based on the prototype designs. The prototype used a range of fixed switch designs, they didn't invent specials on-site to suit each individual turnout. If specials were needed in specific cases, they would have been drawn up and manufactured to special order at significant extra cost, so unlikely to be used unless absolutely unavoidable. Apart from the extra first cost, there would be the difficulty of sourcing replacement parts in the event of needing maintenance several years later. Switch blades for a non-standard planing angle for example, or special chairs for a non-standard heel offset.

On the other hand, in pre-group days the switches were usually built up and "set" on site, and often where there is contraflexure this would have resulted in a split deflection. This may give you a much greater range of effective sizes to try than seems the case at first sight.

More about split-deflections at:

 http://www.templot.com/martweb/gs_realtrack.htm#split_switch

To split the deflection in Templot you do need a partial template for the switch front. How to do that is covered in this tutorial:

 http://www.templot.com/martweb/y_symm.htm

Sorry it's a very old tutorial now.

I meant only for you to upload the immediate area of the tandem, not the whole plan. It would be easier to suggest a solution if the full details are visible.

regards,

Martin.

posted: 21 Feb 2011 17:30

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi Martin,

Many thanks for your very detailed and honest response.


Martin Wynne wrote:
I think what you are asking me is -- do I have the prototype data to hand for LNWR loose-heel switches?

I regret that the answer to that is no. Others on here may be able to help.

I think what you say here, is probably true, I do need LNWR track specs.

However, there may be a faint light at the end of the tunnel in this respect, About a week ago I contacted the archivist of the LNWR Society, a chap called Dave Pennington, he has just emailed me and informed me that he thought he had quite a lot of LNWR track-work information which I could buy copies from them at reasonable prices.
I addition he also informed me that they had in their possession an official book of track drawings for the whole system, and that there were several pages in the book of track-work at New Street, although these pages would have only covered the main line sections and not sidings.
Needless to say, I could hardly contain my excitement at this news, and am awaiting for Dave to give me a quotation for the cost of copies of all the drawings, including those pages from the system track-work book.
Can’t wait to get hold of these drawings !! :D


Regarding the remaining information of your latest posting message, here I very much appreciate the attention to detail and the informed suggestions you offer and will try as you suggest, the various options.

I think my main concern was, when alignment to the plan of the turnout side was not achieved, it meant that I had to shift the mating track connection to connect squarely with the turnout end, this in turn resulted in the whole turnout road going off track (forgive the pun !) and causing, in some cases, the adjacent track-work to be too close for comfort, or the turnout road to collide with track-side objects.
All of this is, of course, brought about by the very tight confines of the station as a whole, and not much room for manoeuvre or compromise as one would hope.


I attach a bitmap image file, New_Street_Station_1921_Sample_partA.bmp, which is a sample of the New Street plan covering the same section I placed in the previous PDF file, sent in my last message, hope you find it helpful.

Again, many thanks indeed Martin for your very informative message. :thumb:

Kindest regards,

Brian Nicholls.
Attachment: attach_986_1377_New_Street_Station_1921_Sample_partA.bmp 299

posted: 21 Feb 2011 17:36

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi Martin,

As a PS to my last message, just as a reminder, if you wish to load the sample bit map into Templot, you will need to set the scale factor to 1:492 to get the correct scaling to P4 (4mm to 1 foot).

Regards,

Brian Nicholls.

posted: 21 Feb 2011 22:22

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Brian Nicholls wrote:
I think my main concern was, when alignment to the plan of the turnout side was not achieved, it meant that I had to shift the mating track connection to connect squarely with the turnout end, this in turn resulted in the whole turnout road going off track (forgive the pun !) and causing, in some cases, the adjacent track-work to be too close for comfort, or the turnout road to collide with track-side objects.
Hi Brian,

I think you must be going wrong somewhere. It should be possible to match the turnouts quite closely using all the controls and options in Templot.

I have had a quick dabble on your plan, and I was quite surprised how well it could be made to fit. Admittedly the V-crossings in the tandem are going to be a challenge, especially the check rails -- but if the prototype could do it then it should be possible in the model, at least in P4. :)

From the right the turnouts are (all right-hand):

9ft switch + 1:5.5 curviform

15ft switch + 1:8 curviform

9ft switch + 1:8 regular

In the latter case that's an unusual combination, and as a result the regular pattern V-crossing has produced a long entry "straight". The lead length could have been adjusted by extending or shortening the entry straight, but in the event the default length fitted well. This turnout now needs the trap catch points* inserted -- over to you. :)

As usual I converted your bitmap to low-contrast negative grey-scale, and worked using the "bright night" colours:

2_211653_300000001.png2_211653_300000001.png

2_211653_290000000.png2_211653_290000000.png

2_211653_310000003.png2_211653_310000003.png

2_211653_300000002.png2_211653_300000002.png


Thanks for uploading the scan. I set 300dpi and 1:492 for 4mm scale, as your instructions. :thumb:

*let's not start that one again. To the signalman they are trap points, to the p.w. gang they are catch points. :)

regards,

Martin.

posted: 21 Feb 2011 23:22

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi Martin,

Many thanks for having a go at my sample plan, it is good news you found things would fit reasonable well.


Martin Wynne wrote:
I think you must be going wrong somewhere. It should be possible to match the turnouts quite closely using all the controls and options in Templot.

I have been half expecting for you to say the problem is the way I am doing things, and I am not surprised, I think I should start paying more attention to the data relating to the templates, rather than just shoving them around with the mouse.

I must say, that the images look really good, and the tandem has fitted very well.

I don’t suppose you saved a box file of this, as that would have been very useful for me to look at the data associated with the templates, so that I will get an idea where I am going wrong (must learn the error of my ways).

Many thanks again Martin for all your work and help, it is very encouraging news.

All the best,

Brian Nicholls

posted: 22 Feb 2011 14:18

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Brian Nicholls wrote:
I don’t suppose you saved a box file of this, as that would have been very useful for me to look at the data associated with the templates
Hi Brian,

.box file attached below.

I have had a quick dabble at the third V-crossing -- it's about 1:6.74 -- and the check rails:

2_220910_430000000.png2_220910_430000000.png

Over to you to carry on. :)

regards,

Martin.
Attachment: attach_987_1377_bns_tandem_for_brian_11_02_22_1330_10.box 341

posted: 22 Feb 2011 14:33

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi Martin,

Many thanks for the BOX file, I can only say that the service is second to none.

I will now study very carefully the template data and try to determine where I have been going wrong.

I can only conclude by saying thank you so very much for all the work you have put in, whilst trying to help with my problem and the service is, and has been always absolutely first class.

Very best regards,

Brian Nicholls.

posted: 3 Mar 2011 23:20

from:

Brian Nicholls
 
Poole - United Kingdom

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Martin Wynne wrote:
Over to you to carry on. :)

Hi Martin, Howard (JFS) and All,

As a final note, to my original posted message, I have now managed to complete (well more or less) the alignment of all the templates that go to make up the Carriage Landing section of Platform 3 of old New Street station.

Much of my thanks must go to Martin and Howard who’s advice was extremely helpful, and have attached the BOX file, for this formation, which contains a 3 way tandem.

I do however, still have a couple of niggles to sort, and perhaps re-work, before the job can finally be fully put to rest, and those are:

1. I think I will have to re-check for the correct rail lengths throughout the formation, however, I am awaiting suitable drawings which are to be sent to me from the LNWR Society.


2. The lower most check rail of the 1st switch vee in the tandem, is not quite right, and I have put a temp machined end onto it, made up of a flattened crossing vee blanked off, but there is no bent flared end on that end (not good for the wheel flanges and a possible recipe for derailment).  Must find a way around this, but am not sure about clearance of chairs etc.


Very best regards,

Brian Nicholls.
Attachment: attach_1000_1377_3_way_tandem_to_carriage_landing_access.box 299

posted: 3 Mar 2011 23:39

from:

Brian Nicholls
 
Poole - United Kingdom

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Hi All,

As a PS to my last message.

Sorry must be feeling tired, but meant to say have found some photo’s of this formation area, though not all is clear in them.

The following links are for these photo’s:

http://www.warwickshirerailways.com/lms/lnwrbns_str395.htm

http://www.warwickshirerailways.com/lms/lnwrbns_str413.htm

http://www.warwickshirerailways.com/lms/lnwrbns_str413a.htm

http://www.warwickshirerailways.com/lms/lnwrbns_str1889.htm

http://www.warwickshirerailways.com/lms/lnwrbns_str1883.htm

http://www.warwickshirerailways.com/lms/lnwrbns_str1919.htm

Very best regards,

Brian Nicholls.



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