Mainline Protection - Hutt Valley

Although many of the track structures in the Hutt Valley have been lifted a few examples of mainline protection remain. In 2001 there were seven trap points extant in the Hutt Valley between Woburn and Upper Hutt. In addition there was a safety siding at Woburn and another at Upper Hutt.

This page describes these structures as they existed in November 2001. Links to detail pages are included. These detail pages use a diagram and photographs to explain the operating mechanism of the structure selected.




Track Structures: Woburn - Upper Hutt



Rule Book Extracts

The following extracts are from the 1988 Rule Book.

53. (a) Trap points are derailing switches provided for the protection of the main line, crossing loop, or other place as shown on S and I Diagrams. Except where instructions are provided otherwise they must stand in the derailing position when not in actual use for passing traffic.

(b) A Points Indicator exhibiting a Red square target by day and a Red light by night when the points are in the derailing position, and a Purple square target by day and a purple light by night when the points are reversed, is connected to and works with Trap Points.

Trap Points Indicators at night may display a red reflectorised disc and a purple reflectorised disc in place of a red or purple light as the case may be.

Where movements over Trap points are authorised by Colour Light Shunting or colour-light signals Trap Points Indicators are not provided.

55. (a) Catch Points-Catch points are placed on the main line to intercept runaway vehicles.

(b) Safety Points-Safety points are placed on crossing loops and sidings to prevent vehicles entering on or fouling the main line. Safety points are also placed on the main line where shown on S & I Diagrams.

Normal Setting-Catch points must be set for the runaway siding and safety points for the backshunt or run off road when not in actual use for passing traffic. The normal position of safety points on the main line is shown on the S & I Diagrams.

(d) Switch-locked Points-Turnouts within station limits may be fitted with electric switch-locks which secure the points. The electrical release of such switch-locked points will be given by the Signalman or as described in S & I Diagrams.



Differences

What makes the trap and safety points so interesting is the differences between installations. Items which can differ include:

  • Mechanism operated by motor, lever or rodding.
  • Rodding fitted with temperature compensator.
  • Switches detected electrically.
  • Switches individually detected or combined with a scalebeam.
  • Switches fitted with a facing point lock.
  • Switches fitted with an "Economical" facing point lock.
  • Traps protected with colour light or points indicator.
  • Mechanism located next to points or some distance away.



Specific Structures

Clicking on a link will take you to a detail page which uses a diagram and photographs to explain the operating mechanism of the selected structure.

44 Trap Points Woburn

Protect the down main from vehicles in the loop. The trap points are operated by the mainline points motor and are equipped with a facing point lock. This is an example of an "economical" facing point lock. The traps are protected by a colour light shunt signal (fixed Red since a station fire several years ago).

42 Trap Points Woburn

The trap points are protected with a Points Indicator. They are worked from the switchlock which operates the loop points.

41 Safety Points Woburn

41 points act as safety points, leading from the siding to the stub of the backshunt.

The double slip 39/41 prevents vehicles in the loop fouling the Down Main. However it does not protect the Gracefield Line so it is debatable if 39/41 can be classed as safety points. I have included them because a double slip is a rare structure.

Shunt signals 69A and 69A are both blacked out following a fire in the station building a few years ago.

33A (north) Trap Points Hutt Workshops

Operated by lever. The switchlock is still in place but is no longer released electrically (so is not shown on the S &I) as the automatic signalling has been removed from the Gracefeld Industrial Line. The mainline points have a facing point lock. The trap points do not have an FPL and their position is indicated by a points indicator.

33B (south) Trap Points Hutt Workshops

The south installation differs from the S & I diagram which shows two trap points worked off the same lever. The second trap point was probably removed when the track was altered to allow redundant Workshops land to be fenced off.

These trap points are in a state of disrepair. There is rubble piled on top of the rodding and rusting bracing rods point in the air, disconnected at one end. I suspect that when the track was removed the Points Indicator was not moved, leaving it several metres from the traps. I noted that the facing point lock on the main line points appears to have been oiled recently.

79 Trap Points Taita Storage Siding

The trap points in the exit from the Taita storage siding differ from other examples. The switch is operated by its own points motor, rather than by rodding from adjacent mainline points. 78 points and 79 traps together provide mainline protection.

The trap switch structure appears to be a "half" points mechanism. A special bracket holds the ends of rods that have been "cut-off".

A photograph of an EMU leaving the storage siding and passing over 79 points onto the down main can be viewed here.

18 Trap Points Trentham

Trap points 18 at Trentham protect the down main from vehicles in the loop. Sidings off the loop were lifted some years ago so the trap points appear to have outlived their usefulness.

The trap points are equipped with a facing point lock (FPL). The FPL is operated by a dedicated rod from the motor of 18 points so this is not an "economical" FPL installation. The switch operating rod leaves the points motor at the side; the FPL rod at the end - clearly there is flexibility in where connections can be made.

A mechanical points indicator and an electrical detector are connected to the trap switch.

18 mainline points have a 50kph authorised speed. There are two connections to each of the mainline switches.

44 Safety Points Upper Hutt

This is an example of safety points and a run-off road.The safety points are operated by rodding from the mainline points motor.

Of interest is the fact that the rodding is not fitted with a temperature compensator.The safety point switch detectors are combined by a scale beam. A rod support roller is installed between the rails of the run-off road.

48 Points Upper Hutt

48 points provide access from the Loop to the Sidings at the north end of Upper Hutt. The sidings act as a run-off road, protecting the loop. Of particular interest is the placement of the operating mechanism between the Main and the Loop. The Facing Point Lock (FPL) rod and the switch operating rod pass under the Loop to 48 points. Note also that 48 points are a small interlocked section of the siding; movements between the non-interlocked areas are controlled by an Arrow Indicator and a Points Indicator.

Note 47 traps - they are worked by a motor rather than by rodding from 49 points. 47 traps protect the loop from runaway vehicles on the north backshunt.

49 points protect the main from runaway vehicles on the loop.



Last Updated: Sat Mar 23 06:11:47 NZDT 2013

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