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Catch Points


D.Platt
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Good Morning All,

 

Would I be correct in thinking that to make a catch point I can print off say an A 4.5 point on TEMPLOT and it’s just a case building a point up to wear the wing rails start ?  And do you still use the same amount of sliding chairs ?

 

Dennis 

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Under the 'do' tab there is the 'snap to catch points' option. You can also omit some rails to produce a single blade unit, but it's probably just as easy to just lay what you want on the template.

 

Izzy

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3 hours ago, hayfield said:

 Also you can have things like single blade catch or are they trap

 

The difference between 'Catch' and 'Trap' points is where they are placed, and what they are used for, rather than how they operate, or the number of blades.

 

Trap Points are used to prevent conflicting movements onto a main line, such as inadvertent exit of vehicles from a goods yard onto the main line.

 

Catch Points are used to prevent vehicles from running out of control down long gradients. These are often spring loaded so a train running up hill can pass them, but runaway wagons from the rear end of the train will be caught and derailed.

 

 

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8 minutes ago, Ian Morgan said:

 

The difference between 'Catch' and 'Trap' points is where they are placed, and what they are used for

 

 

Hi Ian,

 

Dennis was asking about the physical derailing track object, which is a set of catch points, whatever it is used for.

 

"Trap" describes the signalling function, which is sometimes implemented as a set of catch points, and sometimes as a full turnout or other function within the interlocking.

 

See:  http://templot.com/companion/catch_points.php

 

cheers,

 

Martin.

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Thanks everyone for your replies, as am protecting a goods line exit onto a main line I now realise it’s a trap point that is required ?  But same building method ? 

Dennis 

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6 minutes ago, D.Platt said:

Thanks everyone for your replies, as am protecting a goods line exit onto a main line I now realise it’s a trap point that is required ?  But same building method ? 

 

Hi Dennis,

 

Yes, it's the same thing. The word "trap" describes what you are using it for.

 

The actual object is exactly the same thing. It's called a set of catch points if it has two blades, and a catch point if it has only one.

 

cheers,

 

Martin.

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Hi Martin, 

Thank you for the link on TEMPLOT I’ve watched the video and I now know what to look for, the only question left is the number of slide chairs is it still six each side ?

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29 minutes ago, D.Platt said:

Hi Martin, 

Thank you for the link on TEMPLOT I’ve watched the video and I now know what to look for, the only question left is the number of slide chairs is it still six each side ?

 

Hi Dennis,

 

That depends on the size of the catch points. An REA size "A" switch, as in in an A-5 turnout, has 5 slide chairs on each side. An REA "B" size switch, as in a B-6 turnout, has 6 slide chairs on each side.

 

Some companies, such as the GWR, designed separate catch points rather than using their standard size switches. There is a whole chapter on them in David Smith's GWR track book.

 

Many companies used older pattern short loose-heel switches as catch points, in which case there may be only 4 slide chairs on each side for the shortest ones.

 

Here's a pic of a GWR loose-heel switch blade, as a single catch point. As you can see, there are 5 slide chairs:

 

2_151216_430000000.jpg

 

cheers,

 

Martin.

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16 hours ago, martin_wynne said:

 

Hi Dennis,

 

That depends on the size of the catch points. An REA size "A" switch, as in in an A-5 turnout, has 5 slide chairs on each side. An REA "B" size switch, as in a B-6 turnout, has 6 slide chairs on each side.

 

Some companies, such as the GWR, designed separate catch points rather than using their standard size switches. There is a whole chapter on them in David Smith's GWR track book.

 

Many companies used older pattern short loose-heel switches as catch points, in which case there may be only 4 slide chairs on each side for the shortest ones.

 

Here's a pic of a GWR loose-heel switch blade, as a single catch point. As you can see, there are 5 slide chairs:

 

2_151216_430000000.jpg

 

cheers,

 

Martin.

 

Pedant alert!

 

As that particular point is worked from a signal box or ground frame and signaled, it is a trap point. Trap points are to stop errant movements running out of sidings onto a running line, catch point are on rising gradients to deflect runaway vehicles on the main line and are not signaled. Probably not many catch points about in these fully fitted days.

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2 hours ago, Poor Old Bruce said:

Pedant alert!

 

As that particular point is worked from a signal box or ground frame and signaled, it is a trap point. Trap points are to stop errant movements running out of sidings onto a running line, catch point are on rising gradients to deflect runaway vehicles on the main line and are not signaled. Probably not many catch points about in these fully fitted days.

 

It is physically a CATCH POINT. It is being used as a TRAP for errant movements.

 

The physical object is called a CATCH POINT. Refer to the GWR drawings for the damn thing.

 

The signalling term "trap" describes the purpose for which it is being used.

 

Martin.

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2 hours ago, martin_wynne said:

 

It is physically a CATCH POINT. It is being used as a TRAP for errant movements.

 

The physical object is called a CATCH POINT. Refer to the GWR drawings for the damn thing.

 

The signalling term "trap" describes the purpose for which it is being used.

 

Martin.

 

 

Per Way operatives refer to them as catch points,  whatever the use. This is an old chestnut which comes around and around.

 

 

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7 minutes ago, Siberian Snooper said:

Per Way operatives refer to them as catch points, whatever the use. 

 

Indeed they do. Not least because that is what they are called on the drawings.

 

cheers,

 

Martin.

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On ‎17‎/‎05‎/‎2019 at 13:34, Siberian Snooper said:

 

 

Per Way operatives refer to them as catch points,  whatever the use. This is an old chestnut which comes around and around.

 

 

 

Odd as I spent 36 years as a PW Renewals Engineer and in that time myself and my colleagues always described them as catch or trap points depending on what they were being used for. Surely this is another of those things where the names used for a component vary from place to place.

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On 17/05/2019 at 11:24, martin_wynne said:

 

It is physically a CATCH POINT. It is being used as a TRAP for errant movements.

 

The physical object is called a CATCH POINT. Refer to the GWR drawings for the damn thing.

 

The signalling term "trap" describes the purpose for which it is being used.

 

Martin.

Pedant mode on

 

Perhaps the 1950 revision of the Ministry of Transport Requirements should be consulted.

 

In the section referring to exits from sidings or freight lines to passenger lines this is the relevant paragraph

 

634729454_Pointstrap.JPG.dd6530ae13e99c8a6ae00497dcc5ded8.JPG

Up to the 1925 edition these were referred to as 'Safety Points'

 

Moving on to the section about safety measures on gradients we find

 

2090886474_Pointscatch.JPG.59a686b42429460e6c7fb7a241319e31.JPG

Up to the 1925 edition these were referred to as a 'Throw-off Safety Switch'

 

It's only things like old Permanent Way Institute publications which used to refer to everything as Catch Points as they never did understand much about actually operating a railway, only how to bolt together bits of wood and ironmongery.

 

Pedant mode off and back to modelling rolling stock.

(Where's the 'Tongue in Cheek' emoji when you need it?)

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19 minutes ago, Grovenor said:

But that is not one of the drawings Martin uses to make his case.:D

 

No, and Bv size means it is flat-bottom.

 

In a previous round-the-houses on this subject, after close study of BRT edition 3 and BRT edition 4, we did conclude (or at least some of us did), that the physical track object is called  "trap points" if it's flat-bottom, and "catch points" if it's bullhead (even if it is being used as a trap).

 

But I'm exhausted with this discussion after so many years. smile.gif  All I can say for certain is that the physical track object is called "catch points" in Templot, and will remain so.

 

cheers,

 

Martin.

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