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The Davidson Survivor

Back to G & D Davidson & Co.

The one and only surviving Davidson lokey is on display at Mawhera Reserve alongside State Highway 7 about 20 kilometres east of Greymouth. The loco has been there for many years but has recently been rebuilt and given a coat of black preserving paint. It is set on a short length of track. While not completely authentic, the rebuild has been carried out well and it nevertheless is a fine example of a Davidson engine.

Built in 1913 for the Kotuku Sawmilling Company, it saw service there until 1920 when it was sold to Westland Sawmilling at Camerons, just south of Greymouth. After four years there it spent the next six years at Redjacks Sawmilling Company in the same area where it now rests.

The loco is of 0-4-4-0 wheel arrangement and there is an additional bogie resting at the rear of the loco. When Davidson's built these engines, they did not lag the boiler, but usually the customer did by laying timber horizontally along the boiler and retaining this in place with steel bands.

A three-quarter front view of the Davidson showing the cylinders in more detail, together with the reversing lever and flywheels. A large sprocket can be seen beneath the drive crank. The extra bogie can also be seen. It was common practice to place the third bogie under the loco's tender or to support the end of the first load. By extending the drive chain arrangement, this extra bogie would provide additional traction.

Here is a close up photo of the wheel assembly showing part of the patented chain sprockets. Devised by George Davidson and patented, the chain was so made that all loadings were not carried on the pivot pins, but by shoulders machined into the links. In the original chain, sprocket wheels used were of the flat or single disc type with teeth at every link (i.e. on a pitch of 4"). It was necessary to adapt the chain for use on the bush lokeys so that misalignment could be accepted, so the sprocket wheels were a double-flanged type with the chain run between them and the teeth protruding from the bottom of the groove into every second link (i.e. on a pitch of 8").

This view illustrates the main crankshaft and herringbone gears (before rebuild) which carried the flywheel/crank discs on the outer ends and, between the frames the eccentrics for the Stephenson link motion and the two herringbone gear wheels, one for forward motion, the other for reverse. Part of the drive chain is also visible.

Finally we have a view of the crankshaft flywheel/crank disc depicting the driving gears and chains.

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