Sunday, 31 May 2015

NZ Rail Ferry Rail Decks and Linkspans

If you’ve ever looked inside a rail ferry you’ll understand that with the limited space the designers have a goal to get the maximum amount of track space inside the ferry so they can load the most wagons on board. This can be a challenge and has lead to some ingenious and intriguing track layouts on the linkspans which have basically interlaced as many as three tracks with parallel sets of rails in order to avoid having space-wasting points components inside the ship to the maximum degree possible.

Basically this is a photo from Google Maps (hence the two arrows each side and the copyright at the bottom) and it shows the tracks going up from the railway yard onto the linkspan. To get the switching needed in the limited space the normal type of points has been eschewed in favour of stub points. Stub points aren’t normally seen on a regular railway although bush tramways and light railways often have them, one of the issues being that they aren’t suitable for high speed operations, even when set for the straight ahead road. This is because they work by sliding a set of rails across to line up with the correct track, and the unsupported sliding rails aren’t suitable to traverse except at low speed. In this example shown you have 8 rails in total except that the two innermost aren’t running rails – they are check rails like in a level crossing. So there are three tracks going across and they fan out when they get to the join with the ferry. The first set of points appear to be conventional switchblade points and the stub points are the next set further in with two rails they can line up to. Here you can see clearly another reason why stub points are not usually used – the set of rails with nowhere to go. How are the points operated? Clearly the nearest set have a wharf lever and mechanism but how did the stubs work?

The next question to be answered is what layouts were used inside the ships.
 Aramoana (seen here at its commissioning in September 1962) had a layout with three internal tracks. Ian Robson (formerly of Christchurch/Ferrymead and latterly Wellington)  advised that Aranui shared this layout. This appears to be the basis of the three track linkspan still in use today. I presume that the next two ferries were three track also but they could have been four.

  This is the rail deck on Arahura (soon to be retired). As you can see, two sets of points have been used just inside the door to get four tracks inside the ferry. Apparently the two tracks going in were made to line up with the three track linkspan, which these days has only two tracks in use.

  This ship is, I think, in Italy and it uses 3 into 4 with one set of points within the ship. But the linkspan is interesting because it appears to have tandem pairs of switches actually on the span.