Templot Club Archive 2007-2020                             

topic: 393Stub turnouts
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posted: 2 Apr 2008 04:27

from:

jeckardt
 
Beaverton - Oregon USA

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Can Templot handle stub turnouts?

Thanks,

Joe

posted: 2 Apr 2008 04:52

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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jeckardt wrote:
Can Templot handle stub turnouts?
Hi Joe,

Not in so many words. But it's easy to make  one up, like this. Use CTRL+F3 mouse action to blank off the switch, and then add a bit of plain track as a separate template:

stub_example.pngstub_example.png

regards,

Martin.

posted: 2 Apr 2008 05:05

from:

jeckardt
 
Beaverton - Oregon USA

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Martin Wynne wrote:
jeckardt wrote:
Can Templot handle stub turnouts?
Hi Joe,

Not in so many words. But it's easy to make  one up, like this. Use CTRL+F3 mouse action to blank off the switch, and then add a bit of plain track as a separate template.
Thanks, Martin.

So this leads to the next question which I haven't had a chance to investigate yet.  On of the main differences (at least in the US) between a point turnout and a stub turnout is how the diverging line leaves the switch.

The diverging line in a stub turnout is a constant radius curve.  The diverging line in a point turnout is a transition curve of sorts... that is, the diverging route is basically straight past the frog.

Now the question:  What geometry does Templot use for its switches?  If it uses a constant radius curve, then I can indeed just cut it off at the points as you suggested above.  But if it uses a transition curve, then cutting it off wouldn't really create a "proper" stub turnout.

Regards,

Joe

posted: 2 Apr 2008 05:20

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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jeckardt wrote
The diverging line in a stub turnout is a constant radius curve. The diverging line in a point turnout is a transition curve of sorts... that is, the diverging route is basically straight past the frog.
Hi Joe,

See the diagrams showing the difference between regular, generic and curved (curviform) types of crossings (frogs) at:

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

regards,

Martin.

posted: 2 Apr 2008 21:16

from:

jeckardt
 
Beaverton - Oregon USA

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Thank you. That is exactly what I was looking for!

Martin, I want to thank you for your patience with us newbies and your willingness to explain all these details to us.  Templot is an amazingly flexible program, but more than a little overwhelming when you first try to make it DO something.  Your help in getting us up to speed is very much appreciated.

 

Thanks,

Joe

posted: 11 Jul 2017 19:49

from:

Eric Gates
 
Bristol - United Kingdom

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With a stub turnout, how far back do you cut off the switch rails and how much gap should there be between the two converging switch rails at that point? I assume that the absolute minimum would be the clearance between a rail and a checkrail? Would there have been a practical maximum or is this trying to be too scientific about a fairly agricultural device?
2854_111445_530000000.jpg2854_111445_530000000.jpg
Best wishes
Eric

posted: 11 Jul 2017 23:03

from:

Nigel Brown
 
 

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In this context, what are the switch rails? Knowing nothing about stub points, think I'd assume that the pair of rails which move are the switch rails, whereas from your question I get the impression that you're using the term for the 3 pairs of converging rails in the pic.

If that's the case, then (again, I know nowt about this) I suspect that what is essential is that the rails adjacent to a particular pair of rails don't act like check rails. So the gap needs to be larger than the check rail gap.

For a gauge G, BtB B, flange thickness F, then:

gap > G - (B+F)

Think that's right. Don't count on it.

Nigel

posted: 11 Jul 2017 23:33

from:

Eric Gates
 
Bristol - United Kingdom

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Nigel
Thank you. You are right: I am struggling with the terminology. I need to understand the appropriate gap between the rails on which the different routes diverge. In this case, why would you not want the adjacent rail to act as a check rail?
Best wishes
Eric

posted: 12 Jul 2017 00:57

from:

Nigel Brown
 
 

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Because it's then possible for a wheel coming from the moving rail to hit the end of the adjacent rail; check rails have flared ends to avoid this, but these rails can't.

posted: 12 Jul 2017 01:21

from:

Matt M.
 
Australia

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Hi Eric,

Nigel beat me to the check rail question as I couldn't find my log in password.

The cut-off for the diverging roads on Slide Points (Stub Switch in the American parlance),
is governed by the the flexure of the switch rails.

The curve the switch rail can produce from the fixed end with given length and
still line up square to the diverging rails gives you the amount of face to face area
you have to match up with the diverging roads.

If the inner rails are working as a guard rail you run the chance that the wheel
will hit the end of the rail square on derailing the vehicle and destroying both it and the leads.
The gapping between the diverging rails should be set that there is no way that this is possible.

You also have to allow for temperature fluctuations as well. With single rail Slide Points there is the chance
in very hot weather that they will expand and lock the switch to one of the diverging roads.
In very cold weather there is a chance that the gap will become too big the passing wheel set will
destroy the heads of the rails and maybe even derail the vehicle.

Matt M.

posted: 12 Jul 2017 08:23

from:

rodney_hills
 
United Kingdom

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134_120322_500000000.jpg134_120322_500000000.jpgHello,
The 'two-foot' gauge Festiniog Railway has a notable 3-way stub point in bullhead rail.
http://www.photobydjnorton.com/FfestiniogRailway.html

It was originally part of the passenger run round arrangements at Portmadoc Harbour Station, but has been moved to Minffordd Yard, see 
http://www.festipedia.org.uk/wiki/Minffordd_Yard
this page also gives some history and also illustrates a 4-way stub.
Regards,
Rodney Hills







posted: 12 Jul 2017 10:10

from:

Ariels Girdle
 
 

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Out of sheer curiosity, are there stub points still in use in the USA? If not, when were they banned?

posted: 12 Jul 2017 13:41

from:

Matt M.
 
Australia

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Hi Ariels,

Not sure they were ever banned. Generally that method of lead design lost favour due to
its inability to take speed and weight. When researching Permanent-Way early lead design
can be a bit hard to find information on. On main lines in England that apparently used
them they were being phased out in the 1840's.

But being cheap and easy to make they were used on narrow gauge logging and
mineral lines. I believe some of those still have them in yards like the Festiniog Railway.

But the German Maglev system is using a stub switch when it flexes the concrete beam
from one road to another. So still in use in modern times.

Matt M.

posted: 12 Jul 2017 19:37

from:

Eric Gates
 
Bristol - United Kingdom

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Thanks for all the responses on this query.
Taking the easy one first, my photo above was taken at the New Jersey Museum of Transportation  http://www.njmt.org/ in April this year, which suggests that they are not illegal in the US. However, it is not on a running line for passenger traffic.  I am sure that Matt is right in saying that they would not survive long in heavy or fast service, however, the arrangement in the picture below shows the station throat at Atlanta in the pre civil war era, so they were still in use on busy locations into the 1860s.  The back to back arrangement of the two turnouts effectively creates a double slip, but, if I understand the arrangement correctly, it would apparently require the switchman to bend four lengths of rail into alignment in three possible positions, which presumably required a pretty brawny switchman! The gauge in this location is 5'.
 2854_121416_430000000.jpg2854_121416_430000000.jpg
I think I understand the issue about needing clearances greater than that for a check rail, but this then raises the question of how you keep the moving approach rails square to the diverging rails. Surely, as soon as you swing the approach rails away from dead centre, the outer one will always become fractionally short and the inner one fractionally long. The Ffestiniog 4 way must be an extreme example of this, since it seems to be set up almost like a sector plate. Or am I overthinking this? 
Incidentally, the reason behind this soul searching is described in this thread on RMWeb.
  http://www.rmweb.co.uk/community/index.php?/topic/123768-roswell-mill/
Best wishes
Eric     

posted: 12 Jul 2017 22:16

from:

Ariels Girdle
 
 

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It looks to me from the photo that the moving parts pivot at the rail joint, rather than bend.

posted: 12 Jul 2017 23:55

from:

Nigel Brown
 
 

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The "double-slip" is fascinating. All possibilities catered for by a single lever, and possibly only 3 positions needed.

posted: 13 Jul 2017 03:19

from:

Matt M.
 
Australia

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Hi Eric,

You can’t overthink this as the more you know, the more you know you don’t know.
Going through this myself with research.

Technically turntables, transverses and sectors plates are not considered switches
even though they do the same job. The difference is they carry the vehicle whilst
moving to a new position.

As crude as it is, the four road example from the Ffestiniog is a very basic Slide Switch.

And it shows some of the issues when trying to cover a large sweep. The butt joint
at the face of the switch appears to be either loose or a pivot, and has a horrible
change of angle that would severely limit the speed of anything entering the switch.

The original versions of the slide switch were not fish plated. They were butt jointed
in a joining chair for the variations of Double - Head type rail and with their own
fixing plate for flat bottomed varieties. The common use of fish plates starts
around the late 1850’s, though it does depend on the country and railway company.

With a pivot you end up with a sudden and very nasty load on the pivot if the deflection
from the fixed rail to the slide rail is sharp.
If the end of the switching rails are fixed the load may be there but with flexure of the
rail there is a smoother transition. But when the rail is fixed at one end there is a
need for the rail to flex. This adds to the weight of operation.

Even in the early days of the 1820’s to 1840’s there was an understanding that longer
transitions with pointed switches gave a smother ride and lower wear issues. Making
switch blades longer that 3 to 6 feet was a technical and manufacturing problem.
Sliding switches didn’t have that problem.

Yes some of them were pivoted Ariel. Particularly the ones that were mounted on plates.
This limited the movement of the slide rails due to that problem with change of angle.
With Double Slide Switches which is the type the one in the centre of the
Atlanta Station photo there was usually a slight curve to the ends of the slide rails that
matched the diverging road and the facing road of the switch. But that was for two roads
into one.
With this Atlanta switch if it is a three position switch, (and it may only be a two position one),
I can’t see that you could get a smooth transition in all three positions if pivoted.
Either way it would have been heavily speed restricted.

Double Slide Switches had advantages over Single Slide Switches in that the rails were
affixed to each other thus giving support against lateral movement.
Single Slide Switches are unsupported along their length except by the stretcher bars,
unless it is the plated version.

If you look at the Atlanta photo on the left is a Single Slide Switch with obvious flexure
of the switch rail visible before the road crossing.
Also, unless is is a landmark of some sort, there appears to be a crank drive switch stand
as well. These were the common choice for driving these switches in the early days due to
the weight on the action created by bending the rail. It probably allowed more accurate
positioning and locking of the switch rail.

This issue of the gap opening up due to the swing of the rail wasn’t as big a problem as
the one caused by the temperature of the seasons.

Advantages were:- Comparative ease of manufacture, (no special casting and
blacksmithing unlike blades of the period); relatively smooth passage of the train;
in areas of snowfall the closure of the switch isn’t obstructed by the compacted snow.

Disadvantages were:- Accidental derailment of vehicles due to the switch rail being incorrectly
set; expansion in summer and the switch rail jamming against the single or diverging roads;
massive gaps between rail heads in colder weather allowing degradation to the rail head
by wheel impact; lack of a quality positive alignment system for remote manual operation;
increasing operating effort with larger rail sizes, (manual operation).

The research on this sort of stuff is hard due to photographs of the period being of an overall
scene as apposed to close detail shots. Or of locos and people who are standing on,
or in front of, things you want to see. A lot of the Per-Way was buried up to the head of the rail
in the 1800’s making crossing types hard to see and to confirm what was going on at a
particular time and place. Older drawings are no longer in existence.
All in all a lot of fun.

Regards, Matthew.

posted: 13 Jul 2017 18:58

from:

Eric Gates
 
Bristol - United Kingdom

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Matthew
Thanks for your very detailed reply.
I am sure that a gap for heat expansion would have been a requirement on the prototype in the southern US. For my model, which will live in the UK and where "blistering hot" is anything in the upper 20s, it may be less of a problem!
Again, many thanks
Best wishes
Eric



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