catch points

[Kestrel]

make sure the catch points are in your favour otherwise this will happen https://www.youtube.com/watch?v=Yr5EztEPJS8

[52A]

What's the difference between catch points and trap points?

[Mickey]

What's the difference between catch points and trap points?

As far as i'm concerned trap points are facing to on coming traffic and catch points are trailing to on coming traffic thats the definition i use.

Come to think of it they were usually written as such on the s/box traffolyte lever badges where a set of trap & catch points were worked on the lever from a box from memory trap points were facing & catch points were trailing.

Mickey

[52A]

Catch points catch runaways, trap points trap the unwary!

[StevieG]

What's the difference between catch points and trap points?

I think there has been some interchangeability of colloquial use / meaning of these two terms in certain circumstances over very many years, but I'd say that : -
- 'catch points' [or 'spring (or run-back, or runaway) catch points' ] usually refers to the once common, normally sprung type, situated in running lines on rising gradients (usually 1 in 260 or steeper). These were sprung to lay in the 'derail' position and the wheels of trains passing normally would just trail through them against the spring pressure. Their purpose was to derail any goods vehicles without (or with insufficient numbers of) automatic brakes available, that may have broken away from the rest of a train on the rising gradient (owing to broken coupling or drawbar) and be running away in the wrong direction : Causing a derailment in this way was chosen as preferable to the 'runaway' being able to continue in the wrong direction along plain line for potentially a considerable distance through signal / Block sections (quite possibly with no opportunity to divert them, &/or perhaps gathering considerable speed) until possibly coming into violent collision with a legitimately following (possibly passenger) train.
But catch points were sometimes directly worked, or part-controlled, by a signal box if positioned where shunt movements needed to pass over them in a facing direction (e.g. to propel, set-back, or be driven back, into sidings or across to an opposite direction line).

In the event of such a steep gradient continuing for far enough that it constituted most of a long Block section or through more than one Block section, catch points could be provided at more than one location in the section, or in each section where there was more than one.

Provision of catch points was still necessary well into modern colour-light signalling days; e.g. in the early-mid 1970s, when the ex-GNR main line from London was being resignalled to Peterborough and beyond. This was because some freights of the then Classes 7, 8 & 9 [in which some or all vehicles were 'unfitted' or 'piped only' (= no automatic brake on the vehicle's own wheels) : And having a brake van at the rear], were still part of the everyday scene, and so, as the multiple-aspect colour-light signalling allowed trains to follow each other up the qualifying steep gradients more closely, a set of catch points was usually newly installed beyond each successive stop signal on the gradient.(where there was more than one running line in the rising direction, catch points would often be found only n the Slow line, thus allowing the Fast line to still consist of long lengths of uninterrupted Continuous Welded Rail).

- 'trap points' -- are nearly always signal box / ground frame-operated, and intended to derail any runaway or unauthorised movement from reaching running lines, so hopefully avoiding a possible collision.
The facing version often found at the exit from sidings, loco depots, & non-passenger running lines, and, prior to 'modern' days' and Train Protection and Warning System provision, could also be found at the exit from some bay platforms at through stations.
The trailing variety would normally be just beyond facing entry points to sidings or to the start of non-passenger running lines : (But where there was no normal requirement to be able to shunt back over such a trap point out onto the running line, the 'trap' might sometimes not be signalman-worked, and instead be merely sprung to the derail position, in the same way as catch points).

The following definitions, extracted from a sizeable, 'professional', rail encyclopaedia*, might also be of further interest (Words shown in bold are those terms which have their own entry in the book) : -

"Catch Point (CP) ... "
( Entry includes as illustrative of this term, a pair of sketch diagrams of two types of catch point : Single, and Double Tongue.)
... " An assembly of one or a pair of Switch Half Sets which Derail vehicles in the event of their Running Away in the Wrong Direction. Often employed at the lower end of gradients of 1 in 260 to Derail runaway Unfitted Vehicles. Also Unworked Catch Points. See also Double Tongue Catch Point, Single Tongue Catch Points, Worked Catch Points."

"Trap Points ...
... An assembly of one or a pair of Switch Half Sets of Facing , Worked Switches intended to Derail , Rail Vehicles in the event of their Unauthorised Movement. Often employed against Conflicting Movements onto Running Lines or on the exits from Sidings. Also Traps. Trap points consisting of one Switch Half Set are termed Single Tongue Trap Points (STT), and those with two are Double Tongue Trap Points (DTT) or Wide to Gauge Trap Points. See also Catch Points."

* - [ "Ellis' British Railway* Engineering Encyclopaedia" (3rd edition; Nov. 2014), by Iain Ellis IPWE, paperback, published through "lulu.com", ISBN 978-1-326-01063-8 ;
a not inexpensive but comprehensive book whose content is actually now far from confined to engineering terms, and features many thousands of entries throughout its 588 pages, both historical and current (and even a few from across the Atlantic Ocean), which include acronyms, project titles, operating terms, and numerous small monochrome drawings; e.g. of signalling and sectional appendix symbols, and signage.

* - ("...the Railways, Light Railways, Tramways and other guided transport systems of the United Kingdom, its Crown Dependencies and the Republic of Ireland.")

Please Note : I neither have connection with, nor benefit in any way from, this book, its author, or its publisher.

[ I hope no-one is now more confused than informed after that lot. ]

[Mickey]

An excellent post as always Stevie.

Like a number on here i still recall many locations in the past that had runaway srung worked catch points still in situ for the dwindling number of loose coupled goods trains that were still run by B.R. during the late 1960s & 1970s, i believe there was still 2 or 3 sets situated in the Down slow line on the rising gradient in the New Barnet/Green Wood/Ganwick/Potters Bar area well into the 1970s as well as at several other locations on the G.N. inner & outter suburban routes out of Kings Cross. Thinking about them again there was a set of unworked sprung catch points just outside the north end of Wood Green tunnel near to New Southgate's semaphore distant signal in the Down slow line and another set of unworked sprung catch points just outside the north end of Oakleigh Park or Barnet tunnel near to Oakleigh Park's distant signal again in the Down slow line that also come to mind as well.

Anyway one evening back in the early 1970s when i was at Welwyn Garden City box (doing the booking) Ivor one of the Station foremen came up the box with the evening newspaper and was chatting with the signalman on duty and during the course of a conversation between the both of them i remember Ivor saying something about someone had "spragged" (Ivor's word) a set of catch points in the open or throw off position and a Cravens dmu had smashed the left-hand switch and bent the thing totally and it was very lucky there hadn't been a derailment!!.

Mickey

[1H was 2E]

Interesting stuff - I hadn't realised that lever-worked catch points existed.
I understand that the exact positioning of catch points is determined by gradient and layout and is likely to be used in anger by runaway freight wagons with only the hapless guard; but has anyone else noticed that trap points are often surrounded by thoughtlessly placed infrastructure? For example, a train (possibly carrying passengers) that runs through the traps may immediately encounter an overhead gantry stanchion, the support for a footbridge, or a very substantial bridge abutment (for the last, see for example Ditton Jct 17.9.1912 on Railways Archive).
In the old layout at Liverpool St (late 60's) there were two platforms (used, ISTR for Norwich trains) that were much longer at their City ends than the others and, at the buffer stop end, there was either a crossover or Y (can't remember which). The upside track had a trap to protect the conflicting move. Now obviously if it faced away from the other track it would deflect towards the platform, so it went the other way - i.e. to prevent a train running through points and into the side of a train on the next track the trap points would deflect it err into the side of a train on the next track. Does anyone else remember this, or what the thinking was?

[Mickey]

In the old layout at Liverpool St (late 60's) there were two platforms (used, ISTR for Norwich trains) that were much longer at their City ends than the others and, at the buffer stop end, there was either a crossover or Y (can't remember which). The upside track had a trap to protect the conflicting move. Now obviously if it faced away from the other track it would deflect towards the platform, so it went the other way - i.e. to prevent a train running through points and into the side of a train on the next track the trap points would deflect it err into the side of a train on the next track. Does anyone else remember this, or what the thinking was?

I think i know what you mean 1H was 2E a set of traps which has a Y configuration i.e. x2 switches open (normally) for the 'throw off' in a siding road next to a platform road maybe at a terminal station where usually space is restricted and it's a low speed route?. If a shunt move passed the protecting ground signal coming out of the siding road the train would 'split the points' and land up right neither going to the right or left?.

I think there were sets of traps like that at Cambridge, Hertford East, Clacton and othe such places.

Another thing with trap points and some catch points they may have a 'track circuit interruptor' fitted at the end of the run off rail so if a train runs through the traps or catch points the wheels will break the 'track circuit interruptor' and puts the track circuit down i.e. shows occupied and puts any signals in that immediate area to RED we've got 'track Circuit Interruptors' fitted on a set of traps and a set of catch points at my box.

[StevieG]

" Interesting stuff - I hadn't realised that lever-worked catch points existed. .... "

I think how these operated should be explained, but I thought there was enough risk of information overload in my last post without also going into more detail on this point ( ) at that time.

There have been some instances in running lines of what look like catch points which are worked by the signalman : some of these were provided where they were not on, or near the bottom of, a rising gradient, in which case their purpose was more likely to be to protect important points and/or crossings from a powered but unauthorised movement, and so where gradient runaway incidents were most unlikely I would prefer to regard them as one example of being trap points.

But as previously mentioned, catch points (which were primarily present to derail vehicles running away in the wrong direction down a rising gradient), could also need to be worked by a signalman for legitimate shunt movements in the 'wrong' direction (the opposite-to-normal-running direction), e.g. into a siding or goods yard, or to cross to another running line.
If they were mechanically-operated by direct 'rigid' connection to a lever in the signal box, then as in the case of other worked points, they needed to be correctly set by the signalman, in this case for trains running in the normal direction as well as 'reverse' shunts :
Otherwise a 'running' move would run-through the points [ forcing the switches from the 'derail' open position towards the opposite one, against the force of their rodding connections, and so damaging any, some, or all of, the point switch/es, cranks and rodding ].

So, in many of these instances a different form of control mechanism was employed at the points, called a 'Slotted joint'. This allowed the catch points, with their signal box lever left 'Normal' (in line with the majority of levers in the frame), to be free to work in a spring-loaded fashion, just as ordinary sprung-only catch points did, ready to derail runaway vehicles, but were harmlessly trailled-through by train movements in the normal direction.
When the catch points needed to be closed by the signalman for a reverse direction move, pulling his catch points lever counteracted the springing and closed the points [and there would often be a shunt signal(s) for the move, with detection through the catch points to prove them properly closed].

In relatively recent times, an equivalent type of arrangement was still employed in resignallings at least until the early 1980s where necessary for catch points which in some circumstances needed to be under signalman control, e.g. in the Peterborough, King's Cross, and West Hampstead (St.Pancras - north of Bedford) power box schemes.
Although I daresay some power installations had also utilised the slotted-joint method, in later ones such as these, points required for 'catch' reasons were directly ('rigidly') motor-operated : They normally laid in the open position but were motored to 'closed' for a signalled normal direction move, either when the running signal that protected them was cleared, or even only on occupation of track circuit/s in passing the cleared signal:
Then when the train passed clear, they would 'self-restore' (automatically motor back to the open position) about 10 seconds after the track circuit which ended just clear of the switch tongues, went back to 'Clear'.

[Mickey]

Unworked (and worked) catch points in a block section or in signal sections between 2 s/boxes were something that always had to be taken into account by the designated Pilotman before the introduction of Single Line Working was introduced and also after SLW had been withdrawn (because the catch points would have to be un-clipped) the Pilotman would have to go through the Single Line before the introduction of SLW 'clipping up' any unworked catch points before the introduction of SLW and after SLW had been withdrawn .

Also signalmen as well had to take into account of any unworked catch points in a block section or in signal sections between 2 s/boxes especially during the time of a train failure in a block section or in a signal section were the failed train required assistance from either a light engine or another train from the front which required a light engine or a train to travel in the 'wrong direction' on the line the train that has failed requires assistance from the front.

Unworked catch points in a block section would always be shown on the signal box track diagram.

Mickey a onetime telegraph lad at Welwyn Garden City box.