Trailing Points

[ordan77]

I've seen trailing points discussed a couple of times in the context of "trailing hand points shouldn't derail a train", but I haven't yet seen a discussion of the key types of points.

As far as I know, there are at least three types of points:
** Controlled points (possibly bolted) - these should derail a train if incorrectly set for a trailing move
** Hand points - these should automatically change to the correct position as a train trails them
** Spring (or hydraulic) return points - these should allow a train to trail them, but return to their original position

We have the first, we almost have (and have been promised) the second (at least the part about them being trailable, not sure they'll move, though they should), but so far nobody has mentioned the third (that I've seen). Hydraulic return points are used on RETB controlled lines (amongst other uses), and without them, we can't properly simulate these lines.

[Tomnick]

In most cases, 'worked' points won't derail a train trailing through them - there's obviously a number of factors at play, but the result will generally be lots of smashed S&T equipment rather than a derailed train. Obviously, if there's an FPL 'in' (not often the case with a trailing move, and certainly not required) or the points are motor worked, then you're increasing the resistance of the blades to be pushed over, so the chance of a derailment is more likely. Still not an inevitable happening though!

There's mention of spring points in the 'bugs/missing features' thread, though more aimed at their uses in yards. RETB lines and other occasional uses on various lines are the use that springs to mind for me - I've not seen any mention of catch points yet though! That'd be a nice feature to have on a double line incline, but they're not much use if they derail everything in the right direction too!

[ordan77]

I've not seen any mention of catch points yet though! That'd be a nice feature to have on a double line incline, but they're not much use if they derail everything in the right direction too!

Both Catch points and Trap points would be useful.

Though some use the term Catch Point to refer interchangeably to both, I think you're using the term in the correct way - ie: A set of sprung trailable points designed to derail wrong-direction moves. Typically used on sharp climbs, they were common in the days of unfitted goods trains, but have declined in use now that all trains are fully fitted.

Trap Points on the other hand are a form of mainline protection fitted at the exit from yards or goods loops, intended to derail runaways or trains which SPAD the exit signal. These I think we can already do, sort of (though unless you're careful, you either end up without the switch blades, or with a buffer stop).

[Tomnick]

Indeed, I was referring to catch points as you know them. I'd argue that trap points are more crucial to a realistic sim, with the effects on overlaps in goods loops etc., but of course you'd do well to trail through a set of traps (not that, I hasten to add, it's impossible!)

[wolly1380]

Trailing points that are controaled by a frame or signalbox are not desined to be ran against but if you look closely at one there never locked just incase a train does run against them

Sorry I should of cotterned on and moved over to a ew topic but thanks goes to ordan77

[ordan77]

Trailing points that are controaled by a frame or signalbox are not desined to be ran against but if you look closely at one there never locked just incase a train does run against them

Never say never

I can think of a few cases in boxes I work where trailing points are routinely locked, including one where the interlocking demands it. Having said that, we also have one trailing move which is the opposite, where the interlocking demands that the FPL stands out.

However, you're quite right in saying that trailing moves are not normally bolted.

[Tomnick]

Trailing points that are controaled by a frame or signalbox are not desined to be ran against but if you look closely at one there never locked just incase a train does run against them

Sorry I should of cotterned on and moved over to a ew topic but thanks goes to ordan77

I don't think I understand. Trailing points that are purely trailing points as far as running movements, if mechanically worked, are probably not going to be locked - because there's no requirement to, not because there's a chance that something might run through. Facing points (to normal running moves) that become trailing to a 'runaway' could well be locked, especially if the last move was facing - there's certainly no chance that they'll routinely be left unlocked 'just in case', as that then stuffs you up for any facing moves you do want to make over them!

[KlausM]

At least in Germany most points are constructed in a way that in case that a train runs against a point in the wrong position the blades are mechanically unlocked. Therefore it should not cause the train to derail. This applies to both the electrically switched and manually switched points. However, this is of course not the normal operation and, as far as I know, the point needs an inspection whether it is still fully functional after such an incident. Also, for the remotely controlled points, the positions of the blades are monitored and it will cause an alarm in the switchbox.

Klaus

[AndiS]

Most of all, I support the "never say never" for anything regarding locking.
For me, the following items are clear.

- A slow moving train will (nearly) never derail on a trailing point, but it may or may not damage it, to a larger or smaller amount.

- A fast running train will always be at serious risk when going over a trailing point which is set wrong, because some parts can come loose and cause derailments or other damage, and any lock might not give in fast enough, etc. etc. The amount of actual damage depends on many factors and cannot be modelled.

- Independent of the technical implementation in the prototype, trailing switches for train movements are always conceptually locked. Whether the signaller makes a mental not to himself, whether there is some interlocking in the box, or a lock with a key at the switch, and whether the rigging has some built-in feature whereby some part gives in to prevent larger damage, differs from place to place and from time to time.

In the sim, such differences do not matter much. Running against a trailing point (set for the other direction) should be a minor error if done at low speed, and a major one when done at high speed, but it should not end the game.

Regarding catch points and trap points, I am afraid that Kuju missed another chance, although an exotic one. If you could set the resistance against the rolling wheel (Friction in MSTS) as a track parameter, you could implement such things as a switch where the diverting track has very high resistance. Since they have not, one person might be able to make a switch to an invisible buffer stop immediately behind the switch (with ultra-short diverting track). However, KRS will certainly just end the game because of derailment, since it does not have proper coupler/buffer physics, it will not let the wagon bounce back softly from the invisible buffer, or -- much better -- come to a soft halt, after "pushing the buffer" a bit away. All you might see is the wagon jumping into the air, when it hits the buffer stop.

[Tomnick]

Regarding catch points and trap points, I am afraid that Kuju missed another chance, although an exotic one. If you could set the resistance against the rolling wheel (Friction in MSTS) as a track parameter, you could implement such things as a switch where the diverting track has very high resistance. Since they have not, one person might be able to make a switch to an invisible buffer stop immediately behind the switch (with ultra-short diverting track). However, KRS will certainly just end the game because of derailment, since it does not have proper coupler/buffer physics, it will not let the wagon bounce back softly from the invisible buffer, or -- much better -- come to a soft halt, after "pushing the buffer" a bit away. All you might see is the wagon jumping into the air, when it hits the buffer stop.

Trap points, in the context that we mention, are designed specifically to derail the train - rather than bringing it to a controlled stand. That's what sand drags etc. are designed to do, and I suspect that's what you're referring to. Trap points are, in their most basic form, simply a single switch blade with the stock rail extending only a short distance before simply ending. Sometimes there'll be a corresponding switch rail on the opposite side, which again extends only a short distance. There's more complicated examples, but not by much.

Going back to handpoints, these are designed to be 'run through', so I'd suggest that these be an exception to any rule of penalising for doing such a thing - but again, this would have to apply to trailing through (sprung) catch points too.

[ordan77]

Regarding catch points and trap points, I am afraid that Kuju missed another chance, although an exotic one. If you could set the resistance against the rolling wheel (Friction in MSTS) as a track parameter, you could implement such things as a switch where the diverting track has very high resistance. Since they have not, one person might be able to make a switch to an invisible buffer stop immediately behind the switch (with ultra-short diverting track). However, KRS will certainly just end the game because of derailment, since it does not have proper coupler/buffer physics, it will not let the wagon bounce back softly from the invisible buffer, or -- much better -- come to a soft halt, after "pushing the buffer" a bit away. All you might see is the wagon jumping into the air, when it hits the buffer stop.

Trap points, in the context that we mention, are designed specifically to derail the train - rather than bringing it to a controlled stand. That's what sand drags etc. are designed to do, and I suspect that's what you're referring to. Trap points are, in their most basic form, simply a single switch blade with the stock rail extending only a short distance before simply ending. Sometimes there'll be a corresponding switch rail on the opposite side, which again extends only a short distance. There's more complicated examples, but not by much.

Indeed, we have one set of traps which look like an extremely short (4 foot) unbuffered headshunt - designed such that any runaway or SPADding train will derail without landing on (and destroying) much of the lead-away from the 'box.

Going back to handpoints, these are designed to be 'run through', so I'd suggest that these be an exception to any rule of penalising for doing such a thing - but again, this would have to apply to trailing through (sprung) catch points too.

What would be good is a way to select a 'point', and then define the properties of that point, including whether it is trailable (and whether it changes position or stays where it is after it has been trailed through, to support both handpoints and catch / RETB points).

[danielw2599]

We had a set of ponts run trough down here a couple of days ago. These were motor operated points controlled from a PSB and allthough the train did not derail, it caused alot of damage and the points were signed OOU for about 7 hours while repairs were effected.

Last year we had a set of power operated points run through and it took 5 trains to run through them before anyone realised!!They were signed OOU for some time so I still stand by my point that trains should not always derail what ever the type off point.

[wolly1380]

Trailing points that are controaled by a frame or signalbox are not desined to be ran against but if you look closely at one there never locked just incase a train does run against them

Sorry I should of cotterned on and moved over to a ew topic but thanks goes to ordan77

I don't think I understand. Trailing points that are purely trailing points as far as running movements, if mechanically worked, are probably not going to be locked - because there's no requirement to, not because there's a chance that something might run through. Facing points (to normal running moves) that become trailing to a 'runaway' could well be locked, especially if the last move was facing - there's certainly no chance that they'll routinely be left unlocked 'just in case', as that then stuffs you up for any facing moves you do want to make over them!

In normal operating situations am sure it may never happen but it could and there better to be non lockable than to fit locks to a set that don't need it and that could prevent a derailment. A damaged set of points am sure is more desirable to fix than a deraild train, damaged track and possably loss of lives!!
There is also a set of points that even though there lock points ther not always locked as the road into Allerton TMD is bidirectional as stock is moved from the up slow across to the upfast and into Allerton TMD when the stock is on the way out of the TMD the same road is used ofcaurse there is no need to lock them but that road is on a greadiant that is from Speake down hill (Speake being at the higher point) there is no risk of a runner way because of traffic movments but as it has been said never say never.

[AndiS]

My point was that basically, either by derailment or by running through sand, the train slows down more or less fast, but does not fall over or fly around like KRS simulates that now. To implement this slow down, you would need to switch it into a more or less invisible track overlapping the normal one where the friction is very high. And I am afraid that we don't have that.