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                                       Modelling GWR loose heel switches in 4mm
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1st message | this message only posted: 13 Feb 2019 12:32
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madscientist
 

 

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I have always built semi Curved bullhead track , but now I have to build some GWR ( WR ) track work and this means loose heal switches and joggles 
in 4mm , ( 00-SF) other then a slightly different geometry , is there any practical difference between loose heal and fixed heel switches.  I would have thought both would have been made from a continuous piece of nickel silver track with cosmetic fishplates 

Am I correct here , or should the switch be physically cut at the heel ? ( ie between the tongue and the lead ) 
secondly , reading the scalefour notes on loose heeled switches, there can be an issue with the stock rail to switch clearance with the switch is open , this would be exacerbated in oo-sf , is this the case , would it be better to stick with fixed heel ?

any hints on how to make the Joggle , I havent worked out  reliable way to do this ( 0.2mm joggle) 

thanks 

dave 

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2nd message | this message only posted: 13 Feb 2019 19:29
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Andrew Duncan
Reigate, United Kingdom



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madscientist wrote: I have always built semi Curved bullhead track , but now I have to build some GWR ( WR ) track work and this means loose heal switches and joggles 
in 4mm , ( 00-SF) other then a slightly different geometry , is there any practical difference between loose heal and fixed heel switches.  I would have thought both would have been made from a continuous piece of nickel silver track with cosmetic fishplates 

Am I correct here , or should the switch be physically cut at the heel ? ( ie between the tongue and the lead ) 
secondly , reading the scalefour notes on loose heeled switches, there can be an issue with the stock rail to switch clearance with the switch is open , this would be exacerbated in oo-sf , is this the case , would it be better to stick with fixed heel ?

any hints on how to make the Joggle , I havent worked out  reliable way to do this ( 0.2mm joggle) 

thanks 

dave 
Hello Dave
I think my approach to track building maybe considered a bit gung ho so you may want to take this with caution or a pinch of salt!

On Yeovil Pen Mill I’m building loose heeled switches and I do separate the switch from the closure rail at the point where they are joined on the the real thing. I say this a bit loosely (sorry) as I often move this joint back one sleeper(toward the crossing) from its intended position to give a touch more clearance that you referred to. And indeed I make the electrical break there rather than in the more usual place near the crossing. 

To give an engerneering flavour to the proceedings I hinge the the heel on a 10BA bolt that passes through the sleeper into a nut soldered to the underside of the sleeper. 

It may help to understand what I’m talking about by looking at the first page of my thread on this  I’ll try to put a link in after I’ve uploaded this. 


For making Joggles I put the rail in a vice with a sliver of thin steel either side of and opposite sides of the rail and tighten it up. As long as it’s level in the vice it seems to work ok.

Kind regards 
Andrew



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3rd message | this message only posted: 13 Feb 2019 19:48
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Nigel Brown
 

 

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madscientist wrote: I have always built semi Curved bullhead track , but now I have to build some GWR ( WR ) track work and this means loose heal switches and joggles 
in 4mm , ( 00-SF) other then a slightly different geometry , is there any practical difference between loose heal and fixed heel switches.  I would have thought both would have been made from a continuous piece of nickel silver track with cosmetic fishplates 

Am I correct here , or should the switch be physically cut at the heel ? ( ie between the tongue and the lead ) 
secondly , reading the scalefour notes on loose heeled switches, there can be an issue with the stock rail to switch clearance with the switch is open , this would be exacerbated in oo-sf , is this the case , would it be better to stick with fixed heel ?

any hints on how to make the Joggle , I havent worked out  reliable way to do this ( 0.2mm joggle) 

thanks 

dave
I build loose heel switches as loose heel switches. I use plastic chairs. Reckon there's enough give in the heel chair for the switch to move as intended. This is 3mm/ft.

Nigel

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4th message | this message only posted: 14 Feb 2019 04:24
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from:
Andrew Duncan
Reigate, United Kingdom



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Nigel Brown wrote:I build loose heel switches as loose heel switches. I use plastic chairs. Reckon there's enough give in the heel chair for the switch to move as intended. This is 3mm/ft.Hello Nigel

Would you say a bit more about this approach? What sort of plastic chair are you using and does this mean you also have the electrical break at the heel? Are there issues/cautions needed when track cleaning?

Sounds interesting. 

Kind regards 
Andrew

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5th message | this message only posted: 14 Feb 2019 07:53
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from:
Hayfield
United Kingdom

 

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Dave

Like Andrew I make the joggles in a vice using a piece of scrap brass (from an old fret) either side of the joggle point and on opposite sides of the rail

As far as a hinge on the very short switch rail, there are two methods. Either a cosmetic approach by cutting a notch in the top of the rail and soldering an etched fishplate both sides. Or (as I do for slips) use one of the Exactoscale cast brass fishplates, soldering it to the closure rail only. I use the Exactoscale plastic ones for both insulating and joining the closure rail to the wing rail, but these areas are supported by chairs as the plastic fishplates are quite delicate. I have in the past soldered etched fishplates to the closure rails, but you need to find a source of thick etched plates
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6th message | this message only posted: 14 Feb 2019 08:35
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Andrew Howlett
Torquay, United Kingdom

 

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In 7mm I also build loose-heel switches as loose heel with C&L lost wax fishplates.  In addition I drill 0.95mm hole through the rail web on the blades and 1.00mm holes through closure rails at the tie-bar.  A length of 0.9mm brass wire is passed through the 4 holes and soldered to the blades.  The wire is then cut away between the blades, thus simulating the prototype tie-bar extensions.
Andrew Howlett

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madscientist
 

 

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Can you experts enlighten me , did loose heel just pivot at the " loose" fishplate. pictures Ive seen had a chair ( not a slide) one immediately after the fishplate , was this a special one with " give " , was there more  then one of these on the " tongue"

Dave
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8th message | this message only posted: 14 Feb 2019 10:25
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from:
madscientist
 

 

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"As far as a hinge on the very short switch rail, there are two methods. Either a cosmetic approach by cutting a notch in the top of the rail and soldering an etched fishplate both sides. Or (as I do for slips) use one of the Exactoscale cast brass fishplates, soldering it to the closure rail only. I use the Exactoscale plastic ones for both insulating and joining the closure rail to the wing rail, but these areas are supported by chairs as the plastic fishplates are quite delicate. I have in the past soldered etched fishplates to the closure rails, but you need to find a source of thick etched plates "


John have you a picture to illustrate , as I dont quite follow here , what supports the tongue of the switch blade  , ie the rail  from the heel to the toe 


dave
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9th message | this message only posted: 14 Feb 2019 12:40
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RogerW
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EXPERIMENT - It was in 7mm but I feel I have to add something in here.
I was tasked with "Getting it working", the "it" being a friend's new layout that had been planned with Templot but not actually built to the correct standards. All the problem points were rebuilt for curvature on the frogs and leads to them, but on one particular three-way turnout I had to chop the fixed length blade in two, the tortoise point motor could not cope. For convenience I tried a simple brass wood screw, then soldering the now truncated point blade to the top of the screw, the tortoise had no problem with the new set up.
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Phil O
Plymouth, United Kingdom



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madscientist wrote: Can you experts enlighten me , did loose heel just pivot at the " loose" fishplate. pictures Ive seen had a chair ( not a slide) one immediately after the fishplate , was this a special one with " give " , was there more  then one of these on the " tongue"There's a picture in my thread on GW special chairs in the 'share and show's category, amongst the earliest posts.

Phil

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11th message | this message only posted: 14 Feb 2019 15:52
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from:
Ariels Girdle
 

 

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I recently used the newish Peco 'Bullhead' rail joiners on some 4mm scale loose heeled points (not GW) They work fine and look quite good. Avoids completely all the hassle of constructing a pivot.
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madscientist
 

 

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Phil O wrote: madscientist wrote: Can you experts enlighten me , did loose heel just pivot at the " loose" fishplate. pictures Ive seen had a chair ( not a slide) one immediately after the fishplate , was this a special one with " give " , was there more  then one of these on the " tongue"There's a picture in my thread on GW special chairs in the 'share and show's category, amongst the earliest posts.I had  a look at that ,
This is what confuses me , Both 2S chair and the loose heel chair look in effect , a ridig chair holding the rail tightly 

So what was the purpose of the loose fishplate, did the tongue of the switch rail , pivot in the loose heel chair , 

This is why in 4mm I wonder just what difference there is in a continuous switch rail , held in chairs until the slide chairs and a GWR loose heeled configuration , other then a a strategically placed fishplate 

The impression is often given that there was a " pivot " point  in the GWR version , but there is no overt pivot AFAIK
for example , heres a link to Keith Norgroves site heel-1.jpg, showing the tight and loose heel chairs 
but in practice in 4mm whats the difference between this and the typically arrangement of slide chairs and fixed chairs on a semi curved point , yes I accept the GWR geometry is slightly different , but in practice , the loose heel fishplate really isnt doing anything in 4mm 
or to put it another way , the Loose Heel chair in 4mm is a fiction ?

dave

Ps Im not confused about the prototype loose heeled switch , its  implementation in 4mm, that has me confused

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Martin Wynne
West Of The Severn, United Kingdom



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Hi Dave,

Loose-heel switches can only be modelled exactly to scale if you are using dead-scale flangeways. Even the overscale flangeways in P4 are border-line.

In 00-SF and EM you must extend the length of the switch rails to the position where the heel offset provides at least 1mm flangeway clearance.

Folks have many preferred ways of replicating the effect of the loose heel. Prototypically it isn't a true "pivot" in the sense of a round pin or shaft rotating in a circular housing on a fixed centre. But that is a common way of modelling them, soldering the end of the switch rail to a pin or screw head which can rotate.

cheers,

Martin.
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Martin Wynne
West Of The Severn, United Kingdom



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Here's a pic of a GWR loose-heel switch rail, as a single catch* point.



*please don't anyone say it's a trap point. We've been through that a dozen times. It's functioning as a trap, but the physical object is called a catch point. Many different track formations can function as a trap.

Martin.

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15th message | this message only posted: 15 Feb 2019 17:06
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from:
madscientist
 

 

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thanks martin , nice pic

Can templot handle the expanded switch rail heel position in 00-SF ?

( sorry if we are duplicating this conversation on Scalforum )
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Martin Wynne
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madscientist wrote: Can Templot handle the expanded switch rail heel position in 00-SF ?Hi Dave,

Sure. Click the set custom switch... button on the switch settings dialog.

Lots of info on loose-heel switches in this topic:

 http://85a.co.uk/forum/view_topic.php?id=2776&forum_id=6#p19351

cheers,

Martin.
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Phil O
Plymouth, United Kingdom



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The Loose heel chair has two jaws and with the rail slid in there's about a 3/8" gap, if the web of the rail is tight too one jaw and the other jaw, there is no no key. Two bolt fish plates secure the switch rail to the closure.

Phil.
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18th message | this message only posted: 15 Feb 2019 18:36
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Nigel Brown
 

 

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Andrew Duncan wrote: Nigel Brown wrote:I build loose heel switches as loose heel switches. I use plastic chairs. Reckon there's enough give in the heel chair for the switch to move as intended. This is 3mm/ft.Hello Nigel

Would you say a bit more about this approach? What sort of plastic chair are you using and does this mean you also have the electrical break at the heel? Are there issues/cautions needed when track cleaning?

Sounds interesting. 

Kind regards 
Andrew
Hi Andrew



There is indeed an electrical break at the heel, visible on the right of the pic. There is a dropper soldered to the underside of each rail (before laying), just to the left of the loose heel chairs, which passes straight through the baseboard. The switches are laid simply by gluing the heel chair to the timber. After that, the tiebar (gapped PCB strip) is attached, by means of bent brass pins which pivot in the the tiebar and are soldered to the switch rails.

The chairs are standard plain track chairs made by a member of the 3mm Society for members; they are fairly robust. The Society now has finer detail chairs which are possibly not as strong, but in tests I've done of them I think they're fine for this purpose.

Nigel

Edit: would add that the switches are longer than prototype, as you'd expect. The heel chairs and the adjacent chair are carved a bit to make sure they sit correctly side by side.

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Rob Manchester
Manchester



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Martin Wynne wrote: Here's a pic of a GWR loose-heel switch rail, as a single catch* point.



*please don't anyone say it's a trap point. We've been through that a dozen times. It's functioning as a trap, but the physical object is called a catch point. Many different track formations can function as a trap.

Martin.
Hi Martin,
Thanks for the excellent pic of the tr catch point. I assume that the fishplate at the heel is left with the bolts loose and the chair beside them doesn't have a key as per normal chairs ?

Rob

P.S. I see there is a new book from the 2mm Scale Association on Point Rodding. Scroll down on here if you haven't seen it.



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Martin Wynne
West Of The Severn, United Kingdom



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Rob Manchester wrote:I assume that the fishplate at the heel is left with the bolts loose and the chair beside them doesn't have a key as per normal chairs ?

Rob

P.S. I see there is a new book from the 2mm Scale Association on Point Rodding. Scroll down on here if you haven't seen it.
Hi Rob,

Yes.

It's difficult to find chapter and verse on the subject of the loose fish-bolts. Clearly they can't be too loose, otherwise the rail won't be held upright. And what means are taken to prevent them working entirely loose and eventually falling out? A simple and obvious means would be for the fishplate on one side to be tapped, so that the fish-nut could be locked against it. But I've never been able to find any reference to such an arrangement.

Also, are all 4 bolts left loose? Or only the 2 on the switch rail? Or the 2 on the fixed closure rail? Or the outer 2, with the inner 2 adjacent to the rail ends being tight? Or vice versa?

Here's another pic:



Looking at 8 o'clock in the picture, I think I can see the top left corner of the fishplate projecting away from the closure rail. Which suggests that the fishplates are bolted tight on the switch rail on the right, and are free to move on the closure rail on the left.

But despite much searching I've never been able to get definitive answers to these questions. Here is C. J. Allen on the subject, in 1915:



Which is remarkably vague, given how much precise detail he usually provides. How tight is "a little slack"? And which bolts? All of them?

Likewise the exact function of the jaw on the heel chair is unclear. The inner part of the chair supports the closed switch rail at the correct spacing from the stock rail, and resists the flange forces. But the outer jaw has a slight clearance to allow the rail to open, so it is never in firm contact with the rail. Its only purpose would seem to be to keep the rail more or less upright if the bolts do actually fall out.

Thanks for the link to the rodding book. I did see a copy, but haven't yet obtained one. Its on my list.

cheers,

Martin.

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Hi Martin

Looks to me as if the fishplate is slightly bent. If that's the case, the outer bolts could be tight, and the inner bolts tight enough without being tight enough to straighten the fish plate. The very end of the switch would then be able to move slightly. I suspect the heel chair would be only very slightly loose.

Nigel

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Rob Manchester
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Hi Martin,
Looking carefully at your 2nd picture it looks to me as if the heel chair on the near rail has a metal key. The width that you can see looks too narrow for it to just be the top of the chair casting. If the chair was just a normal one with no key surely it wouldn't be possible to hold the track gauge at that point if the fishplate bolts were loose ? Thanks for the info you provided.

I order the 'Rodding' book last night. As it follows on from the track book it is likely well worth the price. You can never have too many books.... :)

Rob


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Martin Wynne
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Hi Rob,

I didn't quite follow that? I have marked up the photo (which I should have done in the first place):



At A I think I can see the top corner of a fishplate. If it was bolted tight it would be flush with the rail head. Which suggests that the bolts in the closure rail are quite loose (and maybe tight in the switch rail?).

Here's a drawing of BH fishplates:



It's clear that if the bolts are not tight, not only can the rail move sideways as intended, but it's also not held firm in vertical alignment. So you wouldn't want to slack the bolts by more than a fraction.

At one time I was convinced that there must be some detail of these loose-heel joints that I was missing. A spring washer under the nut perhaps? Over the years I've searched many times for a proper explanation. If they were used only in sidings and yards simply leaving the bolts a bit loose is a reasonable solution. But these switches were used in fast main lines -- the GWR didn't introduce flexible switches until the 1930s for example. There must surely have been a more engineered solution than simply leaving the bolts a bit slack.

But apparently not -- David Smith on page 12 of his book on GWR track describes the switch rail rotating in the loose-fitting heel chair, saying the resulting movement at the rail joint was taken up by leaving the bolts (in the switch rail) a little slack: "Despite these technical shortcomings switches of this type were widely used because of their simplicity ... ... On the GWR attention was given to the heel joint, as necessary, in the course of normal maintenance and by this means generally ensured satisfactory performance of the switches."

I'm not convinced that passengers boarding a fast train at Paddington would have been reassured had they known that the GWR intentionally left some of its rail bolts loose. :?
 
If the truth was that they were as troublesome to maintain as they look, the later preference for flexible switches is obvious. Allen's note about the GER switches is interesting, in that they were in effect converted to flexible switches by being bolted tight.

cheers,

Martin.

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Andrew Barrowman
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According to "Railway Track Engineering"

https://books.google.com/books/about/Railway_Track_Engineering.html?id=n6XrJJIxQTEC

( page 229,  5. )

the fishplates are bent and the bolts on the tongues are finger tight :?   But that's in India.

I would have thought the idea would be to create just enough wiggle room at the middle of the fishplates to allow the tongue (point) to rotate around the fulcrum created by the chair. The apparent convex bend in the fishplate in the pic above tends to support that.

Maybe?

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Martin Wynne
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Andrew Barrowman wrote:the fishplates are bent and the bolts on the tongues are finger tight :?   But that's in India.Hi Andy,

Only finger tight? :(

How tight will they be after the first train, of say 50 wheels, has passed over them? And how many trains per day?

Doing the calcs, for say a switch rail 9ft to the heel chair, with the rail end typically 12.5" beyond the centre of the chair:

Switch opening at the toe is 4.25".

So sideways movement at the rail joint is 4.25 x 12.5 / 108 = 0.492", say half an inch. Less a bit for the freedom in the heel chair, but it is still a lot of movement to allow for in a design which is intended to be bolted up tight to securely connect the rail ends. I remain puzzled.

cheers,

Martin.

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Andrew Barrowman
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Martin Wynne wrote: Andrew Barrowman wrote:the fishplates are bent and the bolts on the tongues are finger tight :?   But that's in India.Hi Andy,

Only finger tight? :(

How tight will they be after the first train, of say 50 wheels, has passed over them? And how many trains per day?

Doing the calcs, for say a switch rail 9ft to the heel chair, with the rail end typically 12.5" beyond the centre of the chair:

Switch opening at the toe is 4.25".

So sideways movement at the rail joint is 4.25 x 12.5 / 108 = 0.492", say half an inch. Less a bit for the freedom in the heel chair, but it is still a lot of movement to allow for in a design which is intended to be bolted up tight to securely connect the rail ends. I remain puzzled.

cheers,

Martin.
I'm not buying the finger-tight story either :D

If the fishplates are bent (convex to the rail web) all the bolts can be tight but the point blade will be able to pivot around the heel chair. But were they bent?


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27th message | this message only posted: 16 Feb 2019 19:24
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Rob Manchester
Manchester



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Hi Martin,

Sorry. I must have been half asleep when writing the previous post re the sprung key in the heel chair. I hadn't noticed that the 2nd pic was reversed from the original one you posted with the ground signal. Ignore the comment about the key. Ugh :(

When were nyloc inserts first used on nuts ? Maybe the GWR express passengers would be happy to know the switch heel fishplate bolts had shake free inserts - apart from the fact you can't actually tighten these 'finger tight'.

Rob


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28th message | this message only posted: 17 Feb 2019 00:39
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from:
Nigel Brown
 

 

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Andrew Barrowman wrote: According to "Railway Track Engineering"

https://books.google.com/books/about/Railway_Track_Engineering.html?id=n6XrJJIxQTEC

( page 229,  5. )

the fishplates are bent and the bolts on the tongues are finger tight :?   But that's in India.

I would have thought the idea would be to create just enough wiggle room at the middle of the fishplates to allow the tongue (point) to rotate around the fulcrum created by the chair. The apparent convex bend in the fishplate in the pic above tends to support that.

Maybe?
That was basically my thinking when I said I thought the fishplates looked bent. If they're bent then you could tighten the middle bolts quite a lot without them straightening the fishplate.

Also wondered if the heel chair didn't have a parallel slot for the rail. If it was tighter in the middle it would allow the rail to pivot from side to side a bit.

Nigel

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from:
Andrew Barrowman
USA

 

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Nigel Brown wrote:
That was basically my thinking when I said I thought the fishplates looked bent. If they're bent then you could tighten the middle bolts quite a lot without them straightening the fishplate.

Also wondered if the heel chair didn't have a parallel slot for the rail. If it was tighter in the middle it would allow the rail to pivot from side to side a bit.

Nigel
Hi Nigel,

It was spring-boarding off your observation :)

It's interesting that they do (or did) bend the fishplates in India. I seem to remember that GWR practice had a lot of influence on the railways in India, but it's just as likely I'm making that up.

Cheers,
Andy

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from:
Matt M.
Australia

 

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Hi everyone,

I can only comment re NSWGR practice with flat bottom rail but the principles should be similar.

The inner straps or fishplates on the switch rails are given a slight set which gives the movement
for the the toe throw. Early switch fishplate bolts have no washers but the heel chock bolts did.
At some point in the 1920's to 30's spring washers start to be used on the fishplates.

The bolts are not finger tight. They are fully torqued up to hold the plates together and the plates
are locked by the bolts behind the heel.
There is a heel chock/block behind the fishplate which holds the lead rail and stock rail at the correct
distance. Heel chocks also perform the duty of keeping the formation together with regards to rail creep.

The gauge pins/rail stops, or what ever your railway company referred these as, keep the switch rail
at the correct distance from the stock rail while under load.
There was one located in the centre of the fishplate at the gap between the lead and the switch.
Never seen these modelled.

As time moved on the the heel chock moved forward and becomes part of the unit sharing the bolts
from the lead rail and stock rail with the rear of the fishplate.

The A.R.E.A. heel does away with the outer fishplate altogether and shares all bolt holes with
the inner fishplate. The first bolt on the fishplate has a ferrule which gives a bearing surface
for the switch rail web to slide plus helps maintain the correct set on the fishplate.


Hope this helps, Matt M.
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31st message | this message only posted: 17 Feb 2019 08:10
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from:
John Palmer
 

 

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The topic of loose heel switches has been touched on before at in this thread, which contains an extract from Mundrey's work.  If a fishplate is cranked then there's no need for any 'finger tight' nuts on the fishbolts; they can be pulled up tight against the outer faces of the fishplate.  However, the tongue rail's fishing surfaces appear less likely to be held in contact with the corresponding surfaces of the fishplates except at a point immediately adjacent to the fishplate bend.

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from:
Matt M.
Australia

 

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Hi John,

The switch rail is pushed against the outer fishplate under load when the wheels pass
over the heel. The set is on the inner fishplate and that is the unloaded position.

The gap at the heel between the switch and lead was not supposed to exceed 1/8th
of an inch. So you are correct that the rear bolt area of the switch rail remains reasonably
well supported on both sides.

The heavier rail 100 lb. plus, 20 foot, switch blades had just under an inch of travel at
the front bolt. But these used the A.R.E.A. heel system.

It is also possible to over tighten the fishplate bolts in some forms of installation which
will impede the smooth operation of the switch rails by pinching the end of the switch rail.
The test was one man sliding the entire mechanism to each position where it would
stay unaided. This of course was done without any connection to the point rodding.
Possibly where the concept of leaving the bolts a little slack comes from dealing with that.

Matt M.
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from:
John Palmer
 

 

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Thanks Matt, that all makes good sense to me.


This is an enlargement from a photograph I've previously posted showing components in a North British Railway loose heel switch, including the cast heel plate with chairs cast integrally.  There's no sign of a gauge pin/rail stop in the middle of the outer fishplate, but I take it this function is performed by the part of the casting I have indicated.

The lower part of the heel plate lying beneath the rails is all but invisible in the picture but must help to support the rails - and the tongue in particular - thereby resisting any tendency for the toe end of the tongue to rise as its heel end receives the weight of a passing wheelset.

The use of a ferrule to provide a bearing surface over which the web of the tongue can slide is interesting, as is your observation that there was nearly an inch of travel on the front bolt (is that the one at the toe end of the fishplate?) - that surprised me, given that the toe opening is presumably in the region of 4.5" (NBR practice seems to have allowed for a smaller toe opening of about 3.5").

I get the impression that Australian and British practices had significant diferences, and it would be interesting to see a drawing/picture of the A.R.E.A. heel system.

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from:
Andrew Duncan
Reigate, United Kingdom



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Nigel Brown wrote: Andrew Duncan wrote: Nigel Brown wrote:I build loose heel switches as loose heel switches. I use plastic chairs. Reckon there's enough give in the heel chair for the switch to move as intended. This is 3mm/ft.Hello Nigel

Would you say a bit more about this approach? What sort of plastic chair are you using and does this mean you also have the electrical break at the heel? Are there issues/cautions needed when track cleaning?

Sounds interesting. 

Kind regards 
Andrew
Hi Andrew



There is indeed an electrical break at the heel, visible on the right of the pic. There is a dropper soldered to the underside of each rail (before laying), just to the left of the loose heel chairs, which passes straight through the baseboard. The switches are laid simply by gluing the heel chair to the timber. After that, the tiebar (gapped PCB strip) is attached, by means of bent brass pins which pivot in the the tiebar and are soldered to the switch rails.

The chairs are standard plain track chairs made by a member of the 3mm Society for members; they are fairly robust. The Society now has finer detail chairs which are possibly not as strong, but in tests I've done of them I think they're fine for this purpose.

Nigel

Edit: would add that the switches are longer than prototype, as you'd expect. The heel chairs and the adjacent chair are carved a bit to make sure they sit correctly side by side.
Thanks Nigel 
That’s certainly a very neat and prototypical way of constructing a loose heeled switch. And I presume you find it durable in use as well? I think I’ll continue with my existing method for the remaining Yeovil baseboards but I have to admit it’s not as neat looking as your method.

 I was glad to read from both you and Martin that its neigh on inevitable that in everything bar S4 we have to move the “joint / pivot point” up towards the crossing. I’d always felt it was cheating a bit to do this, which of course it is, but seems I’m in good company! 

The other important consideration here for me, and you I presume, is that this where I make the electrical break for the crossing polarity,  so I need there to be a decent physical distance between that joint and the adjoining stockrail to ensure the backs of the wheels can’t touch the closure rail, unlikely as that may be?

Kind regards 
Andrew



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from:
Matt M.
Australia

 

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Hi John, 
I shouldn't post late at night while trying to do calculations in my head. 
The ferrule was over 1 inch but the movement I thought would be less that ½ an inch travel.  
Having gone through some drawings to confirm, the set could be anywhere between 7/40 and 1/4. 

So the pivot at the join is not that great a distance.  

I'll attach some drawings.  











The NSWGR didn't go through the the halfway house of bringing the heel block forward 
to integrate with the fishplate where it was bolted to the lead.  Victoria Railways and South Australia appear to have had some various versions of that type.  NSWGR went from separate heel chocks to 
the American Railway Engineering Association integrated version somewhere around 1928.   

I agree with your summation of the layout of the North British switch.  You'll see the similarities 
in the attached drawings.  Due to costs post war, following the the Depression, the NSWGR 
continued to use loose heel switches even as facing points on main lines.  
To do this they used what was termed a 'Housed' switch where, along with a joggle in the stock rails, 
the unused inner switch blade on the diverting line was under a manganese cover that also acted 
as a check rail. (Never seen one of those modelled either).  

The NSWGR started with Barlow rail. Went to Double Headed rail and then to flat bottomed rail.  
A small excursion into 90 lb. bullhead in the early 1890's but stayed with the flat bottom rail.  
So early British methodology was blended with American.  By the 1920's the NSWGR were writing 
their own manuals as they realised there was nothing to cover the methods used.  

Matt M.

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from:
Nigel Brown
 

 

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Andrew Duncan wrote: The other important consideration here for me, and you I presume, is that this where I make the electrical break for the crossing polarity,  so I need there to be a decent physical distance between that joint and the adjoining stockrail to ensure the backs of the wheels can’t touch the closure rail, unlikely as that may be?

Kind regards 
Andrew
Indeed. I generally shift the joint two sleepers worth away from the toe end of the point, which gives plenty of clearance.

On the first turnouts I built for my current layout I experimented with having the switch rails of the same polarity as the closure rails and common crossing. This allowed me to have uninsulated tiebars of prototypical shape. Was OK provided I had everything spot on so that the wheel backs wouldn't touch the switch rails, but in practice was a pain so I discontinued it.

Nigel

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madscientist
 

 

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In Nigel's pic of his excellent point work , I notice he omits the loose heeled chair completely , i.e. a key visual point of a loose heeled switch was the tight and loose chair straddling the fishplate

Again , my issue is not the prototype , as I understand the loose heeled chair allowed the rail to slide slightly to facilitate the pivot at the fishplate and the GWR ensured the rail remained upright by in effect pinning it to the stock rail by , in effect , a dowel , when it was closed

My issue is implementation in OO-SF , in practice it not possible to implement a loose heel chair , and the tongue has to move in excess of twice the difference of the prototype , so I was considering a couple of options

(a) a pivot pin under the designated" loose heel " chair and some give, using a brass fishplate only soldered to the closure rail

(b) a fake fishplate , split in two, with a " hidden " pivot pin , however this is not over a sleeper and hence is problematic

(c) not bother at all, and effectively treat the tongue and lead rail , as a rigid rail a la semi curved BH points , I would imagine this isn't a runner with FB , but at least thats not my current issue

Dave
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from:
Martin Wynne
West Of The Severn, United Kingdom



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Please do not send requests for help direct to me via email or PM.

Post your questions on the forum where everyone can see them and add helpful replies.
madscientist wrote:and the tongue has to move in excess of twice the difference of the prototypeHi Dave,

Some misunderstanding there?

The prototype blade tip opening ("switch drive") is 4.25 inches = 1.42mm in 4mm/ft scale.

For EM and 00-SF I normally recommend the thickness of a 20p coin (1.75mm) to set the tip opening.

That's only 23% more the the prototype, and a long way short of "in excess of twice". :?

And extending the length of the switch in EM and 00-SF for running clearance, actually reduces the amount of "give" needed at the heel joint.

cheers,

Martin.

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39th message | this message only posted: 18 Feb 2019 15:45
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from:
Nigel Brown
 

 

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madscientist wrote: In Nigel's pic of his excellent point work , I notice he omits the loose heeled chair completely , i.e. a key visual point of a loose heeled switch was the tight and loose chair straddling the fishplateHi Dave

Not sure what you mean here. As far as I can tell, my loose heel switch conforms to the diagrams and pics in Smith's GWR Switch and Crossing Practice. Can't see anything there which looks like a chair straddling the fishplate.

Cheers
Nigel

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Matt M.
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Hi Dave,

Apologies I didn't mean to hijack your thread. I had been reading it with interest
and there seemed to be some confusion as to how this type of switch mounting
was constructed. I only understand it as a friend of mine was the last Chief Officer of the Permanent-Way Branch of the NSWGR and we talk on research matters for early track.

To your modelling problem I did remember and confirmed that Jim Snowdon did an article
in MRJ 113 dealing with the way he got over this using wire hinges.
It is of course in 7mm so may be a little fiddly in 4mm.
I also don't know the longevity of his solution. The effect was very pronounced with
straight cut switches.

Cheers, Matt M.
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