Saturday, 20 January 2018

Otago Central Railway [59A]: Taieri Estate Sidings

As of now I am putting together the aerials needed to show three generations of siding development at Taieri Estate.

Using four images from DCC GIS I am joining these together to make a 1947 image of the aerodrome, which had a siding used to load fuel until the late 1950s. Right now as can be seen from this screen dump, I just have to mask off the borders so that I can get one single continuous image.

For the 1985 era there is one single aerial photo that covers the area, and for current I just use the Linz stuff as is.

Thursday, 18 January 2018

Dunedin-Mosgiel Improvement Works 1907-1914

Few people would know today that more than 100 years ago the railway to the south of Dunedin was very different than it is today. The large embankment as it can be seen in many places, particularly between Dunedin and Caversham, simply did not exist in the original construction works as the railway was built. Moreover, by digging around and exploring the area a bit more, it is possible to discover two disused railway tunnels, one buried beneath the streets of suburban Caversham, that have been disused and virtually forgotten for more than a century. How did this come to be the case?
When the railway through South Dunedin was first constructed in the 1870s the builders were faced with issues of geography, namely the hills of Caversham, Burnside, Green Island, Abbotsford and Wingatui. In fact almost the whole of Dunedin is constructed on hills and the entire line between Oamaru and Mosgiel is the hilliest part of the Main South Line by far. From Wingatui to Invercargill on the other hand is almost completely free of such challenges. In hilly country the extra cost of construction can make various compromises inevitable, usually in regard to curvature and gradient. Bridges and tunnels being very expensive works, the early railway builders sought to keep the need for these to a minimum. Lines would be built to the steepest and sharpest alignments possible and improved later when they had proved themselves, thus Dunedin has many improvements made both to the north and the south of the central business district. The compromise that was arrived at for the line to the south of Dunedin in the 1970s entailed the following significant features:
  • From Kensington through Caversham a ruling grade of 1 in 50 to the summit then a similar downhill grade to Green Island at the bottom of the hill.
  • The line then climbed again at grades of up to 1 in 50 to the second summit at Abbotsford. There was then another drop down to Abbots Creek.
  • Another 1 in 50 climb was then faced to get to the top of the Chain Hills before descending again to Wingatui.
  • The Caversham Tunnel of 43 chains was for a significant portion of its length uphill for southbound trains at 1 in 50.
  • The Chain Hills Tunnel of 22 1/2 chains was for a significant portion of its length uphill for southbound trains at 1 in 50.
Due to the development of traffic the improvements became rapidly desirable. The goals for the project included:
  • Duplicating the main line throughout the Dunedin to Mosgiel section. (Ironically, it was singled again in the mid 1980s, and the double track embankment around Caversham was replaced by a new single track embankment so the double track alignment could be reused by a motorway)
  • Improving the gradients to make operation easier
  • Replacing the two single track tunnels with double track bores
  • Eliminating all the level crossings to make operation safer both for the railway and for traffic.
  • Improving the stations along the route.

This map sums up the nature of the improvement works between Dunedin and Mosgiel.

Otago Central Railway [38B]: Hyde maps updated

The main part of Hyde station yard. There was an engine shed from the time the station opened, until about the 1920s. Hyde had both low and high level loading banks. After the ballast pit siding at Hyde Township closed in 1952, ballast continued to be loaded by truck over the HLLB. 
The north end of Hyde yard, including the turntable which dated from the opening of the station. It was relocated to Cromwell in the 1920s. 
 1897 plan of Hyde super
1966 aerial photo of Hyde. Only three of the five houses shown on the 1897 plan remained by this stage, otherwise the yard had changed little from its inception.

Previous article about Hyde