The Johnston Geared Locomotives

Gallery opened: Sept 2001

Updated: 5 Dec 2021

New picture, more info
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Johnston made several types of geared locomotive, but the 16-wheeler Type-D was unquestionably the most unusual.

Left: A Johnston 16-wheeler. The two-cylinder engine is mounted vertically at the rear of the cab.

The Johnston Type D 16-wheelers were built in New Zealand from 1910 onwards. They were designed to replace a team of horses for logging, and the weight on each axle on the wooden rails was supposed to be one ton only; the total weight was 16.25 tons, so that's pretty close. The design, with four powered bogies, was built under a Patent issued in 1909. It resembled a Shay locomotive in having a vertical engine, but here the engine was in the centre of the locomotive, and the drive shafts and the four universal joints required were more tidily placed between the frames.

Presumably this arrangement is denoted as a 2-2-2-2-2-2-2-2, or possibly a 2-2 + 2-2 + 2-2 + 2-2. I would happy to hear from those with strong opinions on this point.

At least 16 were built between 1910 and 1937. The average service life was around 23 years. None were preserved.

Left: The drive shafting of the Johnston. Drawing taken from the original Patent.

Note the four universal joints. The drive is applied to the centre of the arrangement.

Note that all axles are driven.

Left: This Johnston 16-wheeler was built in Invercargill for the Glenham Sawmilling Company in 1910

Here we can see that the engine was actually mounted behind the point where the drive went to the shafting. There are two cylinders, but they seem to be the same size, so it was not a compound engine. Having two cylinders prevents dead-centre problems.

Note brake-blocks on every wheel. It is not currently known how they were actuated.

Left: This Johnston 16-wheeler was built for the Egmont Box Company in 1911

This looks very similar to the Glenham locomotive above, but with minor differences in the pipework and side-panels.


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