Turnout construction - Question here please.

Discuss the prototype and how to model it.
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grovenor-2685
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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Mon Mar 29, 2021 10:14 pm

Follow the prototype, make your switch so it sits fully against the stock rail naturally without any forcing, assemble it like that. Then the tie bars pull it away to open it rather than pushing to close it.
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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Mon Mar 29, 2021 10:17 pm

Hi Keith.
That's how I do it too.
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Tue Mar 30, 2021 7:42 am

grovenor-2685 wrote:Follow the prototype, make your switch so it sits fully against the stock rail naturally without any forcing, assemble it like that. Then the tie bars pull it away to open it rather than pushing to close it.

The way flexible switches work is that the switch blades (points) are sprung against each other, with the stretcher bar(s) in tension.

This means that as the force needed to pull the one blade away from the stock rail gradually increases, the force needed to hold the other one away from the stock rail gradually reduces. The two forces cancel out, and the result is that the points can be moved across with very little additional force needed from the rodding. Much less than opening a single switch blade would need.

That's one reason why single-blade catch points* are quite common with a loose-heel (pivoted) blade, but for more modern flexible switches they are nearly always double-blade catch points. Especially in flat-bottom track, where the force needed to flex the rail is higher.

Having the stretcher bars always in tension means that they can be quite slender in relation to the rail section, and often appear at first sight to be inadequate for the job.

*if someone corrects this to say they are called trap points, I am going to jump out of the window. Image

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Re: Turnout construction - Question here please.

Postby Julian Roberts » Tue Mar 30, 2021 3:03 pm

Martin Wynne wrote:
grovenor-2685 wrote:Follow the prototype, make your switch so it sits fully against the stock rail naturally without any forcing, assemble it like that. Then the tie bars pull it away to open it rather than pushing to close it.

The way flexible switches work is that the switch blades (points) are sprung against each other, with the stretcher bar(s) in tension.

This means that as the force needed to pull the one blade away from the stock rail gradually increases, the force needed to hold the other one away from the stock rail gradually reduces. The two forces cancel out, and the result is that the points can be moved across with very little additional force needed from the rodding. Much less than opening a single switch blade would need.

Martin.


That is extremely useful to know. Thank you Martin, and Keith. I've just got to installing some E blades so I'll write on my Masokits thread if I have any further questions about the practical implications rather than take up this thread.

Martin Wynne wrote:
*if someone corrects this to say they are called trap points, I am going to jump out of the window. Image

Martin.


:o Please don't - unless it's a French window!

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Re: Turnout construction - Question here please.

Postby Winander » Tue Mar 30, 2021 3:31 pm

Tony,

Where you say "clean up the running face" of the obtuse crossing point rail in your diamond, do you mean remove burrs and restore the rounded profile to the rail edge, or is more involved?

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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Tue Mar 30, 2021 4:34 pm

Winander wrote:Tony,

Where you say "clean up the running face" of the obtuse crossing point rail in your diamond, do you mean remove burrs and restore the rounded profile to the rail edge, or is more involved?

thanks

Hi Richard.
Yes, but there is a bit more to it than that as it is likely that it bending the rail back into line of the face will not be true and you can see in the picture that the running face of the rail has a slight dogleg to the left. This needs to be removed and the easiest way to do this is to place the rail head side down on a flat file (I normal do this on top of the vice) and remove the excess metal. This is how I do it with BH rail and was covered in the BH turnout construction topic.
I will see if I can find it and post a link.
EDIT: Its under this post, 6 pictures down. viewtopic.php?f=5&t=5727#p58828

If there is anything else I appear to have skipped, please ask. I expect there will be several further edits to the main posting for a while yet.
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Tony.
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Re: Turnout construction - Question here please.

Postby Julian Roberts » Sat Apr 10, 2021 8:02 am

There is a conversation here viewtopic.php?f=5&t=7028&start=75 on E Switch chairing with several drawings.

Tony Wilkins wrote:
Julian Roberts wrote:Hello Ted

My main issue now, having been enlightened by your post, is where to first fix the switch (how far from the tip) as I think I read on Tony's turnout thread that the last two of what look like slidechairs are block chairs that allow some movement (on a B switch).


Hi Julian.
Ted's post has clarified the situation regarding E switches accompanied by a wonderful set of drawings.
Your comment above is correct in so far as it goes, but the combination of slide and block chairs is a little more complicated than that.
For most types of switch there are a number of P slide chairs followed by a number of Block chairs. So far so good.
For A, B, C and D switches the first two block chairs of each switch allow the blade to move.
For A, B and D switches, the remaining block chairs firmly hold the rail in place. D switches have four fixed block chairs, two of them beyond the joint.
C switches have three fixed block chairs before the joint.
The situation with E and F switches is different as they only have P slide chairs and fixed block chairs, the first two of which before the joint are fixed (as Ted's drawing shows), and had the keys on the inside of the rails, as there was not room for them in the usual place.
So a sprung switchrail will always be held fixed by at least two chairs before the joint.

Incidentally only the LMS and SR used REA F switches. The largest the LNER used were E switches.
Regards
Tony.


By the way Tony, I see from your post on Feb 17th 2018 in the original Bullhead turnout thread that "F switches are made of the "Straightcut" Type only". Does that oblige you to demonstrate the straightcut style of filing/planing, and making scale joggles?! :o :D

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Re: Turnout construction - Question here please.

Postby Martin Wynne » Sat Apr 10, 2021 11:02 am

Julian Roberts wrote:By the way Tony, I see from your post on Feb 17th 2018 in the original Bullhead turnout thread that "F switches are made of the "Straightcut" Type only". Does that oblige you to demonstrate the straightcut style of filing/planing, and making scale joggles?! :o :D

Hi Julian,

It is the other way round. Or at least I can't find a drawing for F straightcut switches. Here is the LMS drawing for REA F undercut switches:

f_switches_rea.png


Most of the drawings are available in the NERA reprint book, and a fuller set of drawings is available at:

http://www.lmssociety.org.uk/assets/pdf ... ay1928.pdf

cheers,

Martin.
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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Sat Apr 10, 2021 3:17 pm

Interesting. It would seem that in this case I have copied information from an authoritative source that was incorrect.
Straight cut F switches would make little sense.
Thanks Julian for spotting it.
Regards
Tony.
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Sat Apr 10, 2021 3:35 pm

Tony Wilkins wrote:It would seem that in this case I have copied information from an authoritative source that was incorrect.

Hi Tony,

That would be p.85 of BRT3. I would regard that as authoritative too. Bear in mind that the existence of a drawing doesn't necessarily mean that it was ever used. But I can't find a drawing for F straightcut switches, and the LMS is listed as using F switches.

Perhaps the SR F switches were straightcut? The SR was the leading light in p.w. developments in the grouping years, and their thinking pervades the early BRT editions.

cheers,

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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Sat Apr 10, 2021 3:54 pm

Hi Martin.
The previous edition BRT2 page 74 states the same thing although elsewhere in both editions the texts states under (b) semi-curved switches, that for Straightcut switches the planing dimensions for F switches were slightly different to other switch types, which suggests this is may not be so wrong after all.
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Re: Turnout construction - Question here please.

Postby JFS » Sat Apr 10, 2021 3:57 pm

Martin Wynne wrote: ... and a fuller set of drawings is available at:

http://www.lmssociety.org.uk/assets/pdf ... ay1928.pdf


That is an excellent source - many thanks Martin.

Edit:- just to mention that the S&T sheet from the same source has an excellent drawing of FPLs on double slips on page 58

http://www.lmssociety.org.uk/assets/pdfs/LMS_SandT.pdf

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Re: Turnout construction - Question here please.

Postby ted.stephens » Sun Apr 11, 2021 8:06 am

Martin Wynne wrote:
Perhaps the SR F switches were straightcut? The SR was the leading light in p.w. developments in the grouping years, and their thinking pervades the early BRT editions.


Here is a copy of an SR drawing for F switches straightcut.
No.17 SR 5.jpg
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Re: Turnout construction - Question here please.

Postby Terry Bendall » Sun Apr 11, 2021 9:49 am

This is a little off topic but may be interesting to some. I was sufficiently interested in this topic to look up my reference sources. My copy of British Railway Track is the fourth edition so is concerned with FB track and turnouts and I am sure they were different to BH ones but a table o page 101 confirms that the length of the planing distance for straight and curved types was different - by almost two metres.

The book "The Railway: British Track Since 1804: describes and has pictures of how the actual planing was done using a machine tool called, not surprisingly, a planing machine. This has a long bed which moves backwards and forwards under a cutting tool that can be raised and lowered and also fed across the work piece. The produced the flat planed surface. For a curved planed switch the rail was fixed to the machine so it was curved upwards and the flat surface machined. When remove from the machine the rail was straightened to produce a concave curved surface. Current practice is to use a computer controlled milling machine where the curve can be generated using the programming.

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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Sun Apr 11, 2021 12:15 pm

Terry Bendall wrote: For a curved planed switch the rail was fixed to the machine so it was curved upwards and the flat surface machined. When remove from the machine the rail was straightened to produce a concave curved surface.

Essentially just what was recommended in the original P4 instructions 55 years ago. :)
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Re: Turnout construction - Question here please.

Postby BorderCounties » Sun Dec 26, 2021 11:23 am

A quick use of the search function to try to find "spring switches" only gets a few hits for topics containing both words (luckily).

One of the more informative is Tony Wilkins' thread on turnout construction (obviously), but I can't find any mention of making model spring switches, or self closing switches, actually work. Whatever is used as the "spring" must be capable of keeping one of the switches tight against the stock rail but also not too tight as to impede or derail any vehicle being pushed through the closed switch.

Has anyone tackled this? I can think of a few ways to do it, but would welcome any input.

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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Sun Dec 26, 2021 11:41 am

I have one at the trailing end of a double junction. It has worked fine for the last 20 years.
It just has the blades set so one just closes and the other sits just open enough so a reverse move does not derail. No tie bars fitted. They are B switches.
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Sun Dec 26, 2021 12:16 pm

BorderCounties wrote:One of the more informative is Tony Wilkins' thread on turnout construction (obviously), but I can't find any mention of making model spring switches, or self closing switches, actually work. Whatever is used as the "spring" must be capable of keeping one of the switches tight against the stock rail but also not too tight as to impede or derail any vehicle being pushed through the closed switch.

It's much easier if you build a loose-heel (pivoted) switch rather than a flexible switch. To provide a light force to keep it closed, run a cord over a pulley to a falling weight (which unlike a spring applies a constant force). Add just enough weight to keep it closed and no more. For a free-working loose-heel switch it won't need much. Instead of a pulley, you could use an angle crank. Or for a thin cotton thread it could simply run over a horizontal bar.

If you have enough room for it, use an air damper plate as the weight. That's just a horizontal piece of thin card a few inches square. After the first wheels open the switch, it won't close so quickly because of air resistance around the card, and still be partly open for the following wheels. It doesn't need to be quite as heavy as this: :)

Image

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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Sun Dec 26, 2021 3:14 pm

Martin Wynne wrote:It's much easier if you build a loose-heel (pivoted) switch rather than a flexible switch. To provide a light force to keep it closed, run a cord over a pulley to a falling weight (which unlike a spring applies a constant force). Add just enough weight to keep it closed and no more. For a free-working loose-heel switch it won't need much. Instead of a pulley, you could use an angle crank. Or for a thin cotton thread it could simply run over a horizontal bar.

Well, to me that is just adding lots of complexity. IMHO its easy using spring switches, you just have to tweak the spring force to just enough and all is fine. If you don't need reverse moves at all then its trivial, if you want reverse moves for one route it just needs a bit of care. As I said I did one over 20 years ago and its worked perfectly ever since. Long before that, when still at school I made two similar ones for the two ends of a passing loop and they worked for 3 or 4 years till that layout was dismantled.
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Re: Turnout construction - Question here please.

Postby BorderCounties » Sun Dec 26, 2021 5:32 pm

Thanks chaps.

The prototype in question is here - https://www.flickr.com/photos/irishswissernie/36234004843/in/album-72157686232283623/ behind the Stevens drop flap ground signal. It was only when I came to plan point rodding runs that I noticed the total lack of a means of moving the switches. The two rods to the left of the picture control the point and FPL in the distance, there are no visible rods to the turnout to the right and no hint of any sort of hand lever. The white "line" on the photo to the left of the bush appears to be photo crap, not a hand lever.

I have built it as a loose-heeled B8, but I think the PW gang are going to have to pay a visit to change it to flexible switches sprung lightly against the out rail.

Thanks again

John

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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Sun Dec 26, 2021 6:52 pm

Hmm, that's an odd place for a sprung point, it would be good to see a signal plan to understand what was intended.
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Sun Dec 26, 2021 7:52 pm

BorderCounties wrote:It was only when I came to plan point rodding runs that I noticed the total lack of a means of moving the switches. The two rods to the left of the picture control the point and FPL in the distance, there are no visible rods to the turnout to the right and no hint of any sort of hand lever.

Hi John,

There's some boarding across to the bush on the right. I suspect there's a hand lever hidden behind the bush. It would have been moved there clear of the footway across the bridge. Otherwise I can't think of a reason for the boarding.

snipped_photo.jpg

A spring switch needs a spring, and I can't see one.

Image

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Re: Turnout construction - Question here please.

Postby John Palmer » Mon Dec 27, 2021 1:13 am

I am also interested in ways of representing spring points that operate reliably, as I am informed that the headshunt points at Burnham (which we are modelling) were sprung so as to lie normal for the excursion loop via which locomotives ran round their trains. So far we haven't attempted sprung operation. How might polarity switching of the crossing be arranged for working spring points?

Photographs of sprung switches don't appear to be common, but in those I have seen the spring is far from obvious, being usually recessed below the top of the timbering. So I don't find it surprising that a spring mechanism can't be seen in the Bellingham photograph. As to an operating lever, there may well be one lurking under that boarding, but the presence of such a lever in no way precludes this being a spring switch. After all, the spring points at Burnham to which I have referred had also to be fitted with a hand lever for the purpose of releasing an engine that arrived via the excursion loop and had to run round its train through the adjacent train shed. This is in contrast with the majority of services that arrived via the train shed line, for which the sprung headshunt points provided the convenient and customary method of engine release.

Although the Bellingham arrangement may look a bit odd, it should be borne in mind that traffic on the Border Counties line was sufficiently sparse as to render meets of opposing passenger trains unnecessary other than at Reedsmouth Junction, which (I think) was the only BCR crossing point with platforms on both sides of the crossing loop. So at Bellingham passenger trains in either direction would only use the nearest line, which has a single platform at the end of which the photographer was standing. The two additional lines visible are unlikely to have been used for vehicles actually carrying passengers, though they may well have been traversed by ECS movements in connection with Bellingham race traffic. If, as I think, there was never a need to pass a passenger train over either of the two further lines visible, I can't see a problem with the signalling arrangements adopted.

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Re: Turnout construction - Question here please.

Postby BorderCounties » Mon Dec 27, 2021 11:03 am

Keith, Martin and John

I have a photo of the signal box diagram which, unfortunately, is probably still under copyright. For the track layout itself, here is part of the 25" inch OS map - this is the final track layout from 1896.

Bellingham core.jpg


There is also a signalling sketch to help clarify what went where (if it infringes anyone's copyright I'll remove it).

Bellingham SB diagram.jpg


However, there appear to be a couple of errors:

1 - no connection between the loop line and the dock line at the left hand end,
2 - points 9 is double ended with a trap on the loop line

I have a photo from North British days which shows the lines as per the OS map with no traps on either the dock or loop lines. All subsequent photos show exactly the same features. A possible explanation for the lack of traps may be the very close proximity to the road underbridge - see map - anything derailed would have been at serious risk of going down the embankment onto the road. The line at this point is also on a rising 1 in 144 gradient steepening to 1 in 100.

Martin, I'm not convinced that there was a hand point lever in the bush - the hand levers at Bellingham were of the NB pattern - see further photos in the link to Ernie Brack's Flickr collection. The whole mechanism is well above ground and would be obvious in the photo. Also, if sited where you suggest, it would have been right at the top of the embankment.

As John has stated, Reedsmouth was the only place on the Border Counties where two passenger trains could cross, but there were several places where a passenger train could pass a freight, one of which is obviously Bellingham. Would it make sense for the turnout in question to always be set to the loop line from the main when running from the Tarset (Kielder/Riccarton/Hawick) direction?

Unfortunately, we can't go back and ask the photographers to stand further back or further forwards.

John

P.S. just filed up a new set of flexible switches!
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Re: Turnout construction - Question here please.

Postby John Palmer » Mon Dec 27, 2021 12:47 pm

It's unfortunate that there is not quite enough definition in the picture of the Bellingham turnout under discussion to be sure, but I get the strong impression that this is a common piece of North British pointwork with 12' loose heel switches, as per this photograph:
Rannoch turnout.jpg
I guess that in model form a loose heel switch probably lends itself better to spring working than a flexible switch.

The normal lie of the running line points can be discerned in Ernie Brack's collection of photographs and the signalling diagram, and is such as to direct all trains to the platform line, regardless of their direction of travel. I think that is as to be expected, given that there is but one platform face serving both Up and Down trains, and my guess is that FPL plungers 8 and 13 stand normally in. If they respectively bolt 9 and 12 points normal only, rather than both ways, the implication is that Bellingham was not designed to cross opposing passenger trains – scarcely likely to be necessary anyway, given that Reedsmouth was next station to the south.* It also seems clear that the particular turnout under discussion lies normal for the 'middle' loop rather than that serving the loading bank.

*Edited to add that in order to make the 'middle' loop fit for the passage of passenger trains, it would of course be necessary to equip facing connections in that loop with facing point locks also.
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