Joggled Stockrails

Discuss the prototype and how to model it.
Julian Roberts
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Joggled Stockrails

Postby Julian Roberts » Sun May 19, 2019 10:05 am

I am trying to properly understand something that is, I think, taken as something perfectly simple by most of us. What exactly happens with joggled stock rails?

This follows discussions on two other threads
viewtopic.php?f=5&t=6257
viewtopic.php?f=5&t=5728&start=100

Martin Wynne wrote:p.s. Dave,

If it helps to understand what's happening in a joggle, I have added a red line to the diagram:

Image

The red line shows the position of the stock rail for a plain set with no joggle. To make the joggle, imagine the stock rail being held along the red line, and then pushed sideways at B.

You can see that this means that when there is a joggle, there is also very slight bend in the stock rail at C. This angle is so small that it is normally ignored for construction purposes.

(For an A switch with 66" planing, and a tip of 3/8" thickness, that small angle is 1:176 = 0.3 degrees. For longer switches it is even smaller.)

If you like to use over-scale depth joggles, as many do, that angle will increase, and you might want to bear it in mind. It is more evident when there is a joggle in the straight (main-road) stock rail
Martin.


(My italics)

I want to confirm whether the drawing below (showing a RH turnout) is correct. Martin's diagram above shows the diverging (LH) stock rail, and I want to know if how I've drawn the main road straight stock rail, which I've inferred from the drawing above, is correct. The important point being that the normal track gauge of the straight stock rail is fully restored only at the stockgauge, the end of the planing length - is that right? (Obviously the amount it is overgauge is tiny so I'm talking about something almost invisible. The drawing is a huge exaggeration of what goes on simply for clarity. )
20190519_105329-1.jpg

The return length and depth of the joggle are not the issue here.

If this is correct then I imagine that when laying the straight stockrail first, between the stockgauge and the end of the joggle is an area of uncertainty. If using a ruler the length between A and C will not abut the ruler.

Here is a Templot A6LH with joggled stockrails.

Screenshot_2019-05-19-10-57-14-1.png

Phil O
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Re: Joggled Stockrails

Postby Phil O » Sun May 19, 2019 12:21 pm

Hi Julian,

That's the way I read it. Having played with 12ins to the foot GW turnouts. We had a preserved railway director trying to tell us it was over gauge we explained to him that this was correct for GW switches and everything was ok. I don't think he really bought it, but we weren't about to change it and it still hasn't been altered since and that was around 10 years ago.

Phil.

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Re: Joggled Stockrails

Postby Phil O » Sun May 19, 2019 12:30 pm

Julian,

If you're building GW turnouts, the timbering is square to the centreline, what Martin describes as 'equalized - incremental ' in the timbering munu.

If you're building something else, , then forget I mentioned it.

Phil.

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Martin Wynne
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Re: Joggled Stockrails

Postby Martin Wynne » Sun May 19, 2019 1:58 pm

Julian Roberts wrote:If using a ruler the length between A and C will not abut the ruler.

Hi Julian,

Your drawing is correct. It is actually very tricky to get right in a model, especially the very slight bend needed at C.

Phil wrote:
If you're building GW turnouts, the timbering is square to the centreline, what Martin describes as 'equalized - incremental ' in the timbering menu.

Not necessarily. Most GWR drawings pre-1930 show the timbers square-on. The drawings for the flexible switches introduced in 1930 show equalized timbers.

But the important point is that the timbering style shown on drawings is "TYPICAL". What actually gets built depends on the site conditions, traffic over each road, and in some cases the preference of the local p.w. gang or relaying inspector. I've written about this at length several times so I won't repeat it yet again, but it's NOT a case of right or wrong for a particular prototype company or period. At least not for bullhead track.

The same applies to the age-old misunderstanding from Studiolith days about all the rails through a V-crossing being always dead straight, simply because that arrangement is shown on a drawing somewhere. The drawings show the "TYPICAL" arrangements, they are not an actual drawing of any specific item.

Martin.
40 years developing Templot. And counting ...

Julian Roberts
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Re: Joggled Stockrails

Postby Julian Roberts » Sun May 19, 2019 3:47 pm

Hi Phil and Martin

Thanks, that's good to know I've understood correctly. I don't like to imagine these types of issues being disagreed about at 12" to the foot.

Martin Wynne wrote: It is actually very tricky to get right in a model, especially the very slight bend needed at C.


Yes it seems to me that any advantage that the blades may be easier to form than with the undercut type switch is balanced by the stock rails being a much less straightforward proposition. Have you any hints?

In your comments about filing switch blades you stress the importance and relative difficulty of filing the back of them straight so that they mate properly with the stock rail. With joggled stock rails it looks less easy to get the stockrails too as truly straight along the planing as with the undercut switch type.

Now I've added the switches to the drawing in yellow - hopefully they are basically correct as a diagram too?
20190519_155748-1.jpg

(The curving switchrail is not exactly accurately drawn to the right of the stock gauge.)

martin goodall
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Re: Joggled Stockrails

Postby martin goodall » Sun May 19, 2019 8:01 pm

My approach to all forms of engineering, including point and crossing work, is 'Suck it and see', and I apply this to (among many other things) setting out the switches of turnouts.

I found a good few years ago that a joggle in the stock rail is a far more reliable way of ensuring that wheel flanges do not try to go the wrong side of the switch blade than relying on a 'set'.

The joggle in the stock rail on the GWR was 3/8-inch (equivalent to 5-thou in 4mm scale), but in practice it needs to be more than this in the model. Mine came out larger than I intended at 20-thou, but experience has taught me that this is none too large.

It does mean that the gauge between the stock rails where they are joggled will be significantly wider than 18.83mm, but the gauge needs to be 'correct' immediately ahead of the joggle and also beyond the point at which the planing of the switches runs out. In the latter case, the gauge will, of course be measured between the stock rail and the inside of the opposite switch rail. The gauge between the stock rails where they are joggled will be whatever it turns out to be, and one doesn't need to measure it.

martin goodall
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Re: Joggled Stockrails

Postby martin goodall » Sun May 19, 2019 8:12 pm

I meant to add that my method of forming a joggle in the stock rail is to use a jig made from a small door hinge, with pieces of 20-thou nickel silver soldered to the inside of each leaf of the hinge, leaving a slight gap between them when the hinge is closed. The stock rail is then placed in this jig, in contact with the two N/S strips and squeezed in a vice - producing a neat joggle, which will be the same every time.

(I thought I had been frightfully clever in devising g this jig, only to discover that an identical jig had been described in Model Railway News way back in 1959!)

Philip Hall
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Re: Joggled Stockrails

Postby Philip Hall » Sun May 19, 2019 10:21 pm

I’m with Martin here. I model the LSWR in the South West, so stock rail joggles should not feature, but I think I am going to put them in because I think it will be more reliable and easier to build. Anyway, from side on you can hardly tell. The blades will be a trifle more robust as a result, because the joggles will be a touch overscale.

I might get rocks thrown at me but I want a thoroughly reliable main line railway with trains whizzing around at 75 or so, and I think this will help.

Philip

Julian Roberts
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Re: Joggled Stockrails

Postby Julian Roberts » Mon May 20, 2019 9:52 am

Hi Martin and Philip

Yes the reliability aspect appeals to me too. I can't recall where he wrote it on this Forum but Russ Elliott talks somewhere of "the wisdom of the joggle".

But my reason for starting this thread was to understand exactly what the stockrails do as I was unclear on several things (and I don't think I'm alone) - until Martin Wynne posted what I quoted in the OP from the related thread for which I gave the link.

Specifically, I was unclear that (1) the diverging stockrail does have both a joggle and a "set". There is a confusion that the joggle is only on the straight stockrail and the diverging one has just a set. And (2) I had no clarity when, on the straight stockrail, normal gauge is restored after the wider gauge resulting from the joggle.

The original Protofour instructions are unambiguous on the first point, but no help as to when and how the joggle ceases.

A 'set', or angle, occurs in the curved stock rail 1-2mm ahead of the toe of the switch. The angle is the same as that of the switch blade planing. Facing turnouts often have a slight joggle in both stock rails as shown in the sketch.



Well the sketch is no longer on our website, though I do have it somewhere undiscoverable on my PC, but I'm pretty sure it shows, like the Templot drawing above, simply the joggle itself. The way it returns in a straight line to track gauge at the stockgauge is not sketchable except in diagramatic form.

Of course I'm doing exactly what you do Martin (Goodall), suck it and see - but I think it's really helpful to know exactly what is meant to be happening. Thanks for the thoughts on the joggle itself. I already talked with Martin Wynne about this on viewtopic.php?f=5&t=5728&start=100

I said previously that I thought it was problematic getting a straight line on the straight stockrail between "B" and "C" (see Martin's sketch) but now see that is perfectly simple.

allanferguson
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Re: Joggled Stockrails

Postby allanferguson » Mon May 20, 2019 5:40 pm

I think it is true that joggles are relatively rarely, if atall, to be found on Scottish lines; perhaps this is true of some English lines also. The set is another matter, and is always necessary (unless your switch blades can taper to zero thickness). Certainly I have never used a joggle, and have had no resultant problems. Burntisland, which some may know, has no joggles.. The attached picture is of the demonstration turnout at the Bo'ness museum built, I assume, with the highest level of expertise, as is generally the case there.

Allan F

Set.JPG

Julian Roberts
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Re: Joggled Stockrails

Postby Julian Roberts » Tue May 21, 2019 5:40 pm

allanferguson wrote:I think it is true that joggles are relatively rarely, if at all, to be found on Scottish lines; perhaps this is true of some English lines also. The set is another matter, and is always necessary (unless your switch blades can taper to zero thickness). Certainly I have never used a joggle, and have had no resultant problems. Burntisland, which some may know, has no joggles.


Yes Allan, Martin has the advantage of modelling GWR on his wonderful Burnham, while you and I are doing Scottish themes - though in my case I'm doing a colliery line turnout.

I'm 'havering' here perhaps.

Surely the very issue that makes many people use joggles even when not modelling the GWR is that if we don't use a joggle the blades HAVE to taper to zero - at the gauging height - if they are not to be undergauge relative to the opposite stockrail at their tips?

Only by creating the joggle can the tips have a certain thickness surely? Without it a B switchblade is roughly 30mm long so if the tips are 1mm after the set they can only be roughly 0.03mm wide, given a rail width of 0.9mm. But 'undercut' means the blade guides the flanges only the first few mm surely just as the prototype does.
Capture Undercut Blade Calderside.PNG
Undercut B switch for Calderside. My first turnout so not up to the standard of more proficient modellers. LH turnout so the 'set' is not visible
Capture Undercut Blade Calderside.PNG (920.29 KiB) Viewed 1955 times

0.1mm width after 3mm length, 0.2mm width from 7mm, at normal rail height.

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grovenor-2685
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Re: Joggled Stockrails

Postby grovenor-2685 » Tue May 21, 2019 8:24 pm

Surely the very issue that makes many people use joggles even when not modelling the GWR is that if we don't use a joggle the blades HAVE to taper to zero - at the gauging height - if they are not to be undergauge relative to the opposite stockrail at their tips?

Not quite zero actually as the set is ahead of the blade tips so the gauge between stock rails at the tips is already a bit over.
File the blade to the correct angle, and get the tip as fine as you can and there should not be any tight to gauge spots.
Rgds

davebradwell
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Re: Joggled Stockrails

Postby davebradwell » Tue May 21, 2019 10:19 pm

Surely the only reason for using joggles is to better represent your favourite railway company - they are part of the atmosphere, if you like. Now, done properly they are a very subtle feature but, like Alan Ferguson, I can see no reason for using them otherwise. I use an NER drg for non-undercut heel switches and the tip of the blade is around web thickness with the sharp end created by a cunning angled chamfer on the top. This gradually brings the blade up under the wheel. Perhaps Mr Wynne has a more appropriate drg otherwise I might have to try and load this one. The trap if not joggling is insufficient filing of the blade leaving a bulging taper and narrow gauge through this area.

On the other hand, I cannot understand why you would want to use a grossly overscale 0.020" joggle (half the width of the rail head) as this looks terrible and nothing like the thing you are representing. It must increase the risk of derailment in the trailing direction if the wheel strikes the joggle. The most noticeable aspect will be the blade opening; instead of the scale 4 1/4" there's another 0.5mm making nearly 6" gap between blade and stock rail. A glaring hole.

DaveB

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Martin Wynne
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Re: Joggled Stockrails

Postby Martin Wynne » Wed May 22, 2019 2:19 am

Hi Dave,

Well I have this drawing of how to represent an undercut switch tip in simplified model form (assuming vertical rail):

Image

Julian you asked if I have any suggestions for joggles, and the answer is yes -- don't use them. Image

I don't understand your difficulty in creating a knife edge at the extreme tip? It appears automatically if you file the inside planing at an angle. Then you clip the blade against the stock rail and fettle it with abrasive paper until the extreme tip drops a fraction below the rail top to allow for the top corner radius on the stock rail.

The stock rail is then plain rail. Which avoids the big problem with joggles -- they are next to impossible to make to scale.

Here is photo of a GWR joggled switch, taken yesterday at Worcester Shrub Hill (platform 3):

Image

You can see that the joggle is barely visible even at full size from any normal viewing distance. In a model it is just not visible if made to scale size. The resolving power of the human eye is about 3 thou at 12" distance, which is the same order of magnitude as a scale model joggle in 4mm/ft scale. If you can see the joggles on a P4 model, they must almost certainly be over scale size. You are talking about a 5 thou deflection in a rail 36 thou wide. Your eye can't resolve that unless you rest your chin on the track.

Many hundreds (thousands?) of model switches have been built over the decades using the simplified undercut design in my drawing above, and a plain set on one side, and they all work just fine. The most important thing is to get the stock gauge set correctly before you try to fit the blades.

cheers,

Martin.
40 years developing Templot. And counting ...

Julian Roberts
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Re: Joggled Stockrails

Postby Julian Roberts » Wed May 22, 2019 10:11 am

Keith David and Martin thanks for your replies.

David I was intending to try a 0.2mm joggle not 20 thou. In fact I was lazy and made it 0.25 as I had that thickness of suitable strips which I glued onto opposite jaws of my parallel pliers at a 3mm distance.

Martin and Keith, what bothers me about the non joggled type is exactly what happens at the tip of the blade, where on a B switch there is 0.03mm gauge space available! - i.e. effectively no space at all! - is that not right?

This is what Tony Wilkins wrote on the related thread. He is saying exactly the same as you, except what I've italicised clarifies the aspect that seems critical to me.
Here is a diagram of an undercut switch showing the section at the toe or tip of the blade. Obviously we cannot hope to produce such a section and the reality is that the back of our switch blades will be flat as per the vertical line down the middle of the switch blade. The important thing to note though is the chamfer to the top edge of the running face. This is pretty much the last operation described in making the switch blade.
Switches006.JPG
Switches006.JPG (14.7 KiB) Viewed 1824 times


The idea of this chamfer is to deflect the flange and guide it away from the stock rail. It will continue to do this for some distance as the head of the switch blade rises until the tread of the wheel makes contact with it.


(My italics)

I think what would clarify this is a diagram of the very tip showing the wheel too. Is this correct? The arrows will meet at the gauge face of wheel and rail? The blade as it first presents itself is at or just below this point? The angle of the blade must be equal or steeper but not shallower than the angle of the flange? Not less than 60 degrees from horizontal? (As per Waverley Gardens derailment)....correct?
20190522_111959-1.jpg


Here are some pictures I took on a goods transhipment line by the Rhine. The blade tip is almost invisible even in the third picture unless you can turn up the screen brightness. This is an exaggeration of what I mean above.
20171031_115101.jpg

20171031_115040.jpg
Tip difficult to see

20171031_115049.jpg
Tip lurking in the dark there


Obviously in the model, to function as intended the height of the blade will need to be controlled, while the real thing is heavy enough not to stand proud of the slideplates. I soldered arms to the stretcher bars to go under the stockrails so the blades cannot rise.

I do wonder whether the hundreds or thousands of successful users of this design are P4 modellers. I can easily see that in 00 or EM there is no problem, but Philip and Martin G (both practical types emphasizing reliability) indicate their scepticism - in MG's case with his famous EM flanges! Pictures on the Forum that include turnouts mostly seem to show the joggled type. The CLAG website indicates too that it is not so simple and advocates trying a 0.1 wide gauge through the whole switch area on both roads. Meanwhile I proved to myself at least that this design is perfectly practical and reliable, and looks right, but for the sake of going with club policy am trying a joggle type next. Here is progress so far
20190522_124524-1.jpg
Aiming for a compromise between realism practicality and reliability. Overscale but hopefully not too badly

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Guy Rixon
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Re: Joggled Stockrails

Postby Guy Rixon » Wed May 22, 2019 11:01 am

What happens if, instead of joggling, one files away the rail head to the same extent as the joggle? This would be filing a vertical-sided rebate, not cutting away under the railhead to house the toe of the switch.

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Martin Wynne
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Re: Joggled Stockrails

Postby Martin Wynne » Wed May 22, 2019 1:03 pm

Julian Roberts wrote:Obviously in the model, to function as intended the height of the blade will need to be controlled, while the real thing is heavy enough not to stand proud of the slideplates. I soldered arms to the stretcher bars to go under the stockrails so the blades cannot rise

Hi Julian,

An essential function of stretcher bars, both prototype and model, is to hold the switch rail down onto to slide chairs, and prevent the tip from kicking up between wheelsets under traffic. The switch rails don't stay down under their own weight. This essential element of stretcher bar design is often missing in some designs of model stretcher bars and "turnout operating units".

I think you are wasting your time trying to base the planing of model switch tips too closely on prototype designs, because:

a. the top corner radius on model rail section is often very different from the scale equivalent.

b. the web thickness of model rail section is always very much over-scale.

But if you follow the method suggested by many modellers, what happens is that it works. Image

1. ensure there is a proper set in the diverging stock rail.

2. check and double check that the stock gauge is correct before fitting the switch blades.

3. file a simplified version of undercut planing as in my diagram.

4. final fettling of the blade tip is done in situ using abrasive paper while the blade is clipped to the stock rail.

For some further notes and a suggested filing aid for this, see:

http://85a.co.uk/forum/view_topic.php?i ... d=6#p19571

cheers,

Martin.
40 years developing Templot. And counting ...

Tony Wilkins
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Re: Joggled Stockrails

Postby Tony Wilkins » Wed May 22, 2019 4:08 pm

Julian Roberts wrote: This is what Tony Wilkins wrote on the related thread. He is saying exactly the same as you, except what I've italicised clarifies the aspect that seems critical to me.
Here is a diagram of an undercut switch showing the section at the toe or tip of the blade. Obviously we cannot hope to produce such a section and the reality is that the back of our switch blades will be flat as per the vertical line down the middle of the switch blade. The important thing to note though is the chamfer to the top edge of the running face. This is pretty much the last operation described in making the switch blade.
Switches006.JPG

The idea of this chamfer is to deflect the flange and guide it away from the stock rail. It will continue to do this for some distance as the head of the switch blade rises until the tread of the wheel makes contact with it.


(My italics)

I think what would clarify this is a diagram of the very tip showing the wheel too. Is this correct? The arrows will meet at the gauge face of wheel and rail? The blade as it first presents itself is at or just below this point? The angle of the blade must be equal or steeper but not shallower than the angle of the flange? Not less than 60 degrees from horizontal? (As per Waverley Gardens derailment)....correct?
20190522_111959-1.jpg


I know this is not going to display correctly, but never mind.
In essence that is correct. The tip of the blade should be low enough that the wheel does not make contact with the top or inner face of it until it has passed some way beyond the toe of the switch blade. It then continues to rise to progressively take the full load of the wheel tread.
Joggled switch blades take the full load almost from the toe onwards.
Regards
Tony.

Julian Roberts
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Re: Joggled Stockrails

Postby Julian Roberts » Thu May 23, 2019 10:03 am

Hi Martin

I absolutely take on board what you say and followed your filing instructions on previous turnouts. However as I filed the chamfer ever thinner towards the tip, what happens is that it begins to slightly lose height... :idea: exactly what is needed! It's perfectly simple! - though to get reliable running did take more work with fine sandpaper. Heavy locos were not a problem, it was light wagons that were. (Back to the weight and suspension issues ;) )
20190523_114131-1.jpg
Simple blade shape

I haven't ever seen pointed out the simple maths involved. A 0.9mm width rail tapers to zero width at the set. A 29mm B blade plus 1mm to the set gives 0.03mm taper per 1mm distance.

The thickness of the blade cannot exceed the numbers without gauge narrowing. In the case of a B switch, if my minimum blade thickness is 0.1 that can't occur before 3mm from the tips. If it's 0.2 it can't occur before 6mm from the tips.
20190523_113743-1.jpg
B switch distances/thicknesses. Almost to scale

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Martin Wynne
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Re: Joggled Stockrails

Postby Martin Wynne » Thu May 23, 2019 12:06 pm

Tony Wilkins wrote:The tip of the blade should be low enough that the wheel does not make contact with the top or inner face of it until it has passed some way beyond the toe of the switch blade. It then continues to rise to progressively take the full load of the wheel tread.
Joggled switch blades take the full load almost from the toe onwards.

Hi Tony, Julian,

An important point is that the top of the blade should not be so low that it is below the wheel flange. Otherwise the wheel would be able to ride over it instead of being deflected sideways.

This seems self-evident, but on a large P4 layout you need to keep on top of your wheel cleaning, especially in a dusty exhibition hall. The accumulation of crud on wheels can mean that the effective flange depth is much reduced. Loco wheels need to be kept clean for electrical purposes, but rolling-stock wheels tend to be forgotten and can often accumulate a lot of crud before they start derailing. But when they do, it will usually be by climbing over undercut switches.

This is a situation where the full-height switch tips in a joggled switch can tolerate much dirtier wheels before causing problems.

Whether it makes sense to build a large exhibition layout in P4 is a separate issue. Count your wheels, look for Sunday-morning wheel cleaning volunteers, and then maybe insist on air-conditioned venues only. Image

Martin.
40 years developing Templot. And counting ...

Tony Wilkins
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Re: Joggled Stockrails

Postby Tony Wilkins » Thu May 23, 2019 2:47 pm

I had some experience of this many years since, with Heckmondwike, wagons began to derail mysteriously. On examination there was very little flange showing above a thick layer of crud. The finer your flanges the more susceptible they are to this. It is not just on switch blades either. Slightly misaligned rail ends, especially on curves can pick up the flange and derail it. The solution was simple but basic. All rolling stock was inspected and wheels cleaned and checked before each exhibition. Deeper flanges are not an excuse to neglect such basic maintenance as the crud on wagon and coach wheels soon transfers itself to the rails and hence to the loco wheels with resultant poor pick up.

To put the rail top planing into perspective, for an undercut switch the rail height is reduced by a 32nd under 3/4" in the full size, which is 0.24mm at our scale and the taper runs out over the same distance as the side planing of the switch rail. For straight cut switches the figure is 1/2"

Tony.

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Re: Joggled Stockrails/undercut blade considerations

Postby Julian Roberts » Fri May 24, 2019 10:21 am

Just to make the point that if we have gauge narrowing of say 0.1mm at the tip (because the thickness of a B switch blade can't be as little as 0.33, which is little more than the width of a piece of foil) the reason we can often get away with it is our nice generous standards.

If we have maximum BB of 17.75 and the flanges are the maximum specified width 0.4 we have 0.14 running clearance each side.

Minimum BB 17.67 and minimum width flange 0.35 we have 0.23 each side.

[Whereas the real thing with maximum 1362 BB (17.874) and a nice new pair of 1 1/8th" flanges (0.375) will in our scale have 0.1 clearance each side.

With a minimum BB 1360 (17.847) and flanges worn the maximum 4mm (0.323) the clearance in our scale is 0.17 each side. :ugeek: :D (Doubt if anyone is going to be bothered to check that!?)]

So if the wheels are centred between the rails on straight track prior to the turnout we will unlikely face any problem in P4. But with more interesting curving formations which Templot is designed to facilitate this is unlikely to be the case.

JFS wrote:
Julian Roberts wrote:I take your point haha Howard but have to say the joggles on the layout this is intended for do not give any trouble in the trailing direction.


I was actually talking about the real thing - LUL has a prohibition on joggled switches which are trailed though it uses them for "A" switches used in a facing direction only (of which it has more than its fair share!). That said, I have seen a fair few derailments at exhibitions from this cause though - thankfully - mostly not on P4 layouts.

Best Wishes,

Hi Howard
Sorry I misunderstood you!
I remember there was a derailment at Camden Town that was blamed on switch issues. I can't find out much about it online but wonder if there was anything there that can be relevant to us?

What happens if, instead of joggling, one files away the rail head to the same extent as the joggle? This would be filing a vertical-sided rebate, not cutting away under the railhead to house the toe of the switch.


Guy you mentioned rebates a while back. Our group layout's original turnouts have rebates that work just fine. An underrated practical option? - perhaps because unrealistic though invisible unless inspected closely...

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Martin Wynne
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Re: Joggled Stockrails/undercut blade considerations

Postby Martin Wynne » Fri May 24, 2019 12:03 pm

Julian Roberts wrote:Just to make the point that if we have gauge narrowing of say 0.1mm at the tip (because the thickness of a B switch blade can't be as little as 0.33

Hi Julian,

There is no gauge narrowing (measured at the gauging line, 9/16" below the rail top).

It is perfectly possible for the tip thickness to be effectively zero -- it's what you get at the tip automatically if you file across the rail at a compound angle. Horizontally at the required angle to create the planing, and vertically at about 15 degrees from the vertical:

zero_tip_end.png
zero_tip_end.png (29.24 KiB) Viewed 1525 times

cheers,

Martin.
40 years developing Templot. And counting ...

davebradwell
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Re: Joggled Stockrails

Postby davebradwell » Fri May 24, 2019 2:55 pm

I have to admire your tenacity and attention to detail, Julian.

Hopefully, Martin has sorted out your main question but it follows from this discussion that if a point blade end is not sitting below the stock rail then it's at risk of causing a derailment.

I just couldn't do filed rebates - they remind me of so called universal track from 60odd years ago. I have to feel I'm moving on. Why not just follow your prototype and much good advice and not joggle? The result is completely safe.

Nobody has mentioned the addition of a slight chamfer along the lower edge of a blade on the side which contacts the stock rail. With soldered track there should be little solder fillets between the rivets and the inner edge of the stock rail which will hold the blade open, or lift it.

I check my point blades with a rigid wagon, something with a longer wheelbase (and clean wheels) like a brake van. Push it slowly while pressing a wheel flange against the blade end and stock rail and feel for any slight bump which would indicate an edge that will cause wheel lift. This is quite an eye-opener.

DaveB

martin goodall
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Joined: Fri Oct 02, 2009 6:20 pm

Re: Joggled Stockrails

Postby martin goodall » Fri May 24, 2019 4:41 pm

I mentioned the other day that I have built the turnouts on my layout with admittedly overscale joggles, but Dave Bradwell's post reminds me that in at least one case I resorted to filing a rebate in the stock rail instead.

I freely accept that this is totally unprototypical, but I I believe in taking a strictly practical approach to modelmaking. This makeshift is hardly visible from a normal viewing distance or angle, and it has worked perfectly - which is the whole object of the exercise.

The case in which I used a rebate involved two closely spaced turnouts, where the switch blade bears against the crossing vee of the next turnout, and forming a joggle in the vee of the second turnout would have been awkward. It is a device which I would have no hesitation in using in the future.

While writing, I would confirm from my own experience the importance of holding the switch blades down by means of the stretcher bar. (You won't be surprised to learn that I have resorted to using strictly non-prototypical stretchers - not the dreaded 'moving sleeper', but a slimmer version of the same sort of thing, pivoted on pins bent over and soldered along the switch blades, rather than being attached directly to the blades).

I also endorse the need to ensure that the tips of the switch blades are filed to ensure that they do not project above the top of the stock rail. Rounding off the top corner of each switch blade and gentle filing of the top of the blade is usually enough to ensure this.
Last edited by martin goodall on Sun May 26, 2019 11:50 am, edited 1 time in total.


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