Catch points

Discuss the prototype and how to model it.
jhock

Catch points

Postby jhock » Mon Jan 23, 2012 8:51 pm

Does any one have any advise on how to construct a a catch point? I will need one on my diorama project, I am sure there are many different types, but for my layout it is needed for a siding leading onto a single track mainline.

I had a look on Exacto scales website to see if they did a template but could not one.

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grovenor-2685
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Re: Catch points

Postby grovenor-2685 » Mon Jan 23, 2012 9:34 pm

Functionally this is a trap point, not a catch point. Depending on the expected speed a trap point can be a single blade, a pair of blades or a complete turnout.
If this is just a slow speed siding a single blade on the side away from the main line should be enough. There is no need of special templates, just use the switch section of any turnout as far as the heel. Usually it would be an 'A' switch. I'll see if I have a template section I can post here.
Regards
Keith

jhock

Re: Catch points

Postby jhock » Mon Jan 23, 2012 10:15 pm

Thanks Keith, sounds like single blade would do as speeds would be very slow at this point of the line.

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grovenor-2685
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Re: Catch points

Postby grovenor-2685 » Mon Jan 23, 2012 10:39 pm

Attached drawing shows a set of A switches, just use whichever switch suits and put a plain rail opposite to it.
gle-2.gif

Regards
Keith

Terry Bendall
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Re: Catch points

Postby Terry Bendall » Tue Jan 24, 2012 7:18 am

My method of constructing a trap point was to use a set of switches from an Exactoscale A7 turnout. Fortunately I had the switches as spares since otherwise it is a bit expensive since the rest of the kit is not used. If you ask Exactoscale nicely they may even just sell you the bits required.

Terry Bendall

martin goodall
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Re: Catch points

Postby martin goodall » Tue Jan 24, 2012 3:54 pm

jhock wrote:Thanks Keith, sounds like single blade would do as speeds would be very slow at this point of the line.


The GWR always used single-blade traps up to the 2nd World War, although they were constantly nagged by the Railway Inspectorate to use double traps.

When upgrading the DN&S for extra war traffic (in preparation for D-Day), the GWR did put double traps in the lengthened loops on that line, maybe because the government was paying for the work.

My impression was that other members of the Big Four habitually used double traps, but no doubt there were exceptions, espcially on low-speed lines in out-of-the-way places, or if inherited from pre-grouping companies that used single traps.

allanferguson
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Re: Catch points

Postby allanferguson » Tue Jan 24, 2012 11:26 pm

I think the Caledonian Railway wasn't alone in using single rail traps in low speed situations, and, as here, building them into a turnout to save space (Auldbar Rd, north of Forfar)

Auldbar Rd trap 2.jpg

martin goodall
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Re: Catch points

Postby martin goodall » Wed Jan 25, 2012 3:30 pm

Further to my previous note, Keith Ettle has kindly written to me to point out that there were two double tongued traps at Churston, certainly from the time of the rebuilding just before WW1. He points out that David Smith’s book on GWR point and crosing work has details of double tongued catches or traps. Nevertheless, it is my impression that double traps do seem to have been a rarity on the GWR. Is anyone aware of any other examples dating from before WW2?

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Jol Wilkinson
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Re: Catch points

Postby Jol Wilkinson » Wed Jan 25, 2012 4:25 pm

Trap points built into turnouts were also used by the LNWR. There are pictures in Richard Fosters Birmingham New Street showing at least two turnouts with single blade trap points built into the stock rails.

There is also a good site for photos of Warwickshire railways. This links also shows a couple of trap points in New Street;

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

Jol

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Simon_S
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Re: Catch points

Postby Simon_S » Wed Jan 25, 2012 6:21 pm

There's a great one on the far right of this photo of Birmingham Moor Street:
Birmingham Moor Street Trap Point
Seems strange to have opposing switch rails, wouldn't it be damaged if it were ever used?

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Will L
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Re: Catch points

Postby Will L » Wed Jan 25, 2012 6:40 pm

Simon_S wrote:There's a great one on the far right of this photo of Birmingham Moor Street:
Birmingham Moor Street Trap Point
Seems strange to have opposing switch rails, wouldn't it be damaged if it were ever used?


The trap points on the WHR either side of the flat crossing over the Cambrian Coast line are of this sort. I wondered if they were designed to ensure that any vehicle which overran then trap point are stopped upright and as quickly as possible by the rails hard against the back of the wheels. As for doing damage if used, I think that was accepted as inevitable what ever the design.

Will

allanferguson
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Re: Catch points

Postby allanferguson » Wed Jan 25, 2012 7:08 pm

All trap points were designed to divert a runaway away from the most dangerous side (i.e. usually away from the main line). In some situations it wasn't a good idea to divert a runaway to either side , hence the opposing switch rails. Any trap point would, if used, at least cause damage to the sleepers, and very likely to the rails as well. The only exception to this would be where a full turnout is provided, often leading into a sand drag.

Allan F

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Russ Elliott
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Re: Catch points

Postby Russ Elliott » Wed Jan 25, 2012 8:40 pm

Double-traps were quite common on LT for reversing sidings between running lines.

double-catch.jpg
double-catch.jpg (12.48 KiB) Viewed 5144 times

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grovenor-2685
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Re: Catch points

Postby grovenor-2685 » Wed Jan 25, 2012 8:59 pm

Double-traps were quite common on LT for reversing sidings between running lines.

But note this arrangement is quite different from the 'wide to gauge' traps shown in the Moor St picture.
The wide to gauge traps create an immediate strong braking effect by forcing the rails at standard gauge in between the back to back of the wheelset, unless the vehicle is light enough to climb out, or going very slowly the rails will be forced from their fastenings and the wheelset likely damaged as well.
With the LUL version the wheelset will just run through the open blade with minimal restriction and as the gauge widens out will drop onto the ballast, at which point the traction motor and/or gearbox will likely drop onto the 4th rail and these will be the bits suffering the damage.
Regards
Keith

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Mark Tatlow
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Re: Catch points

Postby Mark Tatlow » Wed Jan 25, 2012 9:54 pm

Catch points to one rail only within a turnout are not that uncommon I thought?

A rather nice prototype one here: http://www.derbysulzers.com/24047freight.jpg and one in model form by yours truely......

2548.JPG
2548.JPG (45.48 KiB) Viewed 5128 times
Mark Tatlow

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Dave K
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Re: Catch points

Postby Dave K » Thu Jan 26, 2012 7:52 am

martin goodall wrote:Further to my previous note, Keith Ettle has kindly written to me to point out that there were two double tongued traps at Churston, certainly from the time of the rebuilding just before WW1. He points out that David Smith’s book on GWR point and crosing work has details of double tongued catches or traps. Nevertheless, it is my impression that double traps do seem to have been a rarity on the GWR. Is anyone aware of any other examples dating from before WW2?

Martin,

When researching the track layout for Hallatrow we found a photo, in the Wild Swan book on the Camerton Branch, showing a double tongued trap point within the point for the up sidings to protect both the up and down lines through the station. The photo was taken in the 1930's but the caption states that these sidings the laid during the pre WW1 re-build.

martin goodall
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Re: Catch points

Postby martin goodall » Fri Jan 27, 2012 10:28 am

Mark Tatlow wrote:Catch points to one rail only within a turnout are not that uncommon I thought?


The photo of Mark's layout shows an almost identical arrangement to the one I have used in the goods yard on my Burford layout.

I don't have a photo to hand immediately which I can scan and post here, but it can be seen in one or more of the photos in my article in MRJ No.71, if you have that issue.


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