Catch Points

With the introduction of animated switches in Build 98 more details on your layout’s pointwork can be modelled. This article will show you how you can build catch points into your layouts.

Introduction

The point of having catch points on a real railway is so that runaway rollingstock from a siding is derailed and hence stopped before it fouls the main line, avoiding potentially a larger accident should another train happen to be travelling on the main line. Depending on the exact situation, a catch point is normally provided between the signal controlling departures from the siding and the fouling point of the siding with the main line.

The catch point itself can be either a normal switch or just a one rail of a switch. It is usually interlocked with the points at the main line so that, when the main line points are set for main line trains, the catch points are set normal so that any train running from the siding towards the main line will be purposely derailed. In railway signalling principles, this is referred to as "flank protection" i.e. protecting the flank, or sides of vehicles travelling on the main line. When the main line points are set for main line to siding or siding to main line movements, the catch points are reversed so that trains may pass over them normally.

A device sometimes used instead of catch points for the same purposes but where the train speeds in the siding are quite slow is the Derails, and these can be modelled too.

Basic catch points

Basic catch points in Rail 3D are extremely simple to build. Providing you have the signalling set up correctly, you will never see a train traverse them, but you can see them in operation.

Assuming you have already built the main line, a connection to the siding and a signal controlling departures from the siding, all you have to do is:

Insert a node’ just after the siding departure signal.
Construct a very short section of track from this node leading from the siding in the direction of the main line but so that any train traversing it would not foul the main line.
Set the default routes of the catch point and main line switches appropriately:
- If the default route of the main line switch is from the main line to the main line, set the default route of the catch point switch to the derailling route. Make sure you enter * in the Other Route box to ensure that trains leaving the siding don’t try to derail themselves.
- If the default route of the main line switch is from the main line to the siding, set the default route of the catch point switch to the straight route.
Finally, highlight the catch point switch node by clicking on it. Right-click on the main line switch node and then select Link Points. This will ensure that when the main line switch is set for a main line to main line movement, the catch points will revert to normal (i.e. so that trains would derail if they were to travel over the catch points).

More advanced catch points

The basic catch points as above are a good start, but there are a few things other more advanced things you can also do.

Removal of check rails

You may have noticed that with basic catch points, the check rails around where the crossing frog would be are still present, despite there being no use for them since there usually is no crossing frog. To counter this, you may need to create some extra track types that do not have any check rails defined, and use these track types for the links involved in catch points.

You can suppress drawing of check rails by unselecting “draw point” in the switch dialogue, but this will also prevent the point mechanism from being drawn. — mh

Single rail catches

Many catch points are simply a break in one of the rails and derail the train by having this ‘break’ open. To model this, you need to create a separate track type that has only one rail. Ensure that you also leave out any check rails where there might normally be a frog. You might also give consideration to shortening the switch length, as the moveable part of the catch point is not as long as in a regular switch.

If the catch is correctly linked to the main line points, the moveable rail will shift towards the track centreline and away from the stock rail, thus opening up a gap. In real life, any train that were to travel over this track would then be deflected out through the gap by the wheel flange making contact with the outside of the moveable rail, and the train would then derail.

Note: the first leg of the switch that you lay determines the extra switch features that get used in drawing the point. In other words, if you lay the straight part of the catch first, then whatever track type you use for this straight part will need to have had the check rails etc. removed from it, otherwise they will be drawn by Rail 3D.