Steam haulers were used in the later period of kauri logging from the early 1900s. A steam hauler was a stationary steam engine driving a winch which could pull logs by steel cable for a distance of over a kilometre. The Billygoat Incline hauler was used instead to lower two sets of rail trucks at a time to the log skids at Billygoat Landing.
Because of the very steep grade (maximum 1:2.7) special equipment was used. The lowering hauler used a Judd steam winch which had extra braking power to control the decent. A brakeman also rode on the rear of the truck. To get around curves in the line, the steel cable was fed automatically by a bracket under the rail trucks into a series of rollers at ground level. Once unloaded, the empty trucks were pulled back up the incline by the hauler, ready for another load of logs. (source: sign at GZ)
You can take the Billygoat track on the way down from the Pinnacles. It's a slightly longer route which will go up first and is less steep (apart from the last bit) but will go up for the first part from the Hydro camp junction. It will give you a different view over the Kauearanga Valley. If you just want to do the cache it's about a 2 hour return walk from the carpark.