20th-century bush tramways pushed railway technology to its extremes. As the terrain became tougher, earthworks were needed. There were tight curves: the Taupo Totara Timber Company had a section called the ‘corkscrew’, and the Ellis and Burnand tramway at Ōngarue resorted to a full spiral.
On steep grades, trains were kept under control by primitive brakes and agile brakemen working in very risky conditions. The Egmont Box Company tram at Kākahi used switchbacks to conquer a steep grade, and the Charming Creek tram used a centre rail system to provide extra braking.
The most interesting New Zealand adaptations of the rail track were the wooden trestle viaducts, and cable-worked inclines. They appeared in New Zealand when logging moved onto hilly terrain, particularly in the 20th century. A remarkable number were built, some of impressive size, using local materials and great skill.
The wooden trestle viaduct dates back at least to the time of the Ancient Romans. In New Zealand it is estimated that around 100 were built on bush tramways. While civil engineers were sometimes involved, many trestles were put up by career bridge builders who used a combination of engineers’ rules and judgement from experience. The key challenges were using local timbers, and the physical constraints of a site. A measure of the builders’ skill is that only one viaduct (at Pohangina) collapsed in service.
An incline is a steep rail track operated by cable and a winch at the summit. Inclines date from early railways, but lengthy steep inclines were only possible with the advent of steel cables in the 1870s.
Around 50 were built on New Zealand bush tramways. The first was near Waimauku about 1881. The steepest grade was 1 in 2.7, and the longest single incline was 4 kilometres. Later features included the co-ordinated operation of a series of inclines, and the use of rollers to guide the cable on curves and at changes of grade. Only one runaway tram is recorded.
Notable inclines included the 1921 Billy Goat at Kauaeranga in the Coromandel, and the Great Barrier Island system. The latter, run by the Kauri Timber Company from 1931 to 1940, was outstanding on a world scale. It comprised a series of 10 inclines, seven steam winches on high points, an operating length of 9 kilometres, and vertical falls and rises totalling 1,160 metres.