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So what kind of steam locomotive was to be used? Early engines illustrated man's ingenuity, one being a converted traction engine, but small used locomotives were becoming available from our national railway. These were light four-wheel engines and with their short wheelbase and lightweight seemed to be ideal for a bush railway.
In the beginning of the bush tramway era, only rod engines were available. A rod engine is one on which the drive from the cylinders is transmitted to the wheels by a connecting rod and the driving wheels are coupled together with coupling rods. Hence the name. Sometimes called a 'direct drive' locomotive.
Early rod engines were all of fixed wheel-base, the articulated locomotive had not yet been invented, so to be able to negotiate the rough track, and particularly very sharp curves through the standing timber, a short coupled wheelbase was the answer and a majority of the early bush locomotives were of 0-4-0 wheel arrangement.
Stiff grades were another factor of timber railways and in order that the locomotives could haul an economic load out of the forest, locomotives had to become heavier so that traction could be maintained.
The rigidity of the rod engines and their ever-increasing weight meant that the track had to be fairly graded and laid down, not too steep and not too sharp on the curves. This however did not suit the lumbermen whose prime purpose was to get into the forest, cut the timber and then move on to the next stand of millable trees. Thus they tended to simply place the tracks on the existing ground with little regard for contour, grades or foundations, because it was all going to be ripped up shortly and moved on.
So neither the early tracks nor the early locomotives were compatible and another way had to be found.
It turned out that these second-hand engines were perhaps not as useful as they might be, they were a little bit harsh in their riding and tended to damage the wooden track, particularly as their wheels had usually been built for narrow steel rails and were not suitable for wide timber ones. Also the lightweight of the engine, while acceptable on lightweight track, did not have the adhesion for the required pulling power. This was particularly evident on the bush tramways because the track was not of terribly high construction standard, had very sharp curves and tended to go up and down a lot as it followed the ground contours. The gradient of the lines, expected by the woodsmen, were far too steep for these small light engines. Never the less, the small engines did a wonderful job considering they had never been designed for such a duty.
Wooden rails were substituted for steel ones often weighing no more than 45 to 65 kilograms per metre. Tracks were built with a minimum of earthworks on grades up to 1 in 10. Trestle bridges were common as the materials were immediately to hand as were the skills to erect them, whereas earthworks meant heavy work and heavy carting.
So the bush tramway operators looked again at the problem and mainly took on a lesson learned by their overseas counterparts and introduced the geared logging locomotive.
What were the advantages of geared engines over rod engines? Certainly, it could be said that they were a bit more complicated and complex mechanisms are not exactly required in a bush-logging environment. The main advantages of geared over rod engines is their flexibility in having at least two bogies to distribute the engine weight over a large area and their gearing assists in maintaining power at low speeds.
A rod engine, with the usual two cylinders, gives four power strokes per driving wheel revolution with the characteristic 'puff-puff' of exhausting steam. A geared engine, on the other hand, would often be geared between the engine and driving wheels in a ratio of 1 to 2 and up to 1 to 7 depending on the gearing. So, a two cylinder double acting steam engine on a geared locomotive would give eight to twenty-eight power strokes per revolution of the driving wheels. In addition to this, the driving wheels of the geared engine were invariably smaller in diameter than those of the rod engine and this would add to the ability of the geared engine to haul heavy loads while surmounting severe grades and tight curves. In action they would sound like an express locomotive at high speed, yet seldom exceeded about 15 km/h.
The other main advantage of the geared bush locomotives was their wheel arrangement. A locomotive running on two small four-wheel swivelling bogies would be able to take sharper curves than a locomotive with four wheels mounted rigidly within its frame. Logging engines could have two, three or four sets of four-wheel bogies and all wheels would be driven. There were a few geared engines built very much like a rod engine, that is, having a four-coupled wheel arrangement in a rigid frame. The difference from a standard rod engine was that the cylinders drove a countershaft, which in turn was connected, to the wheels via reduction gearing. One or two of these simply drove a jackshaft mounted between the main driving wheels and connected with those wheels by the usual coupling rods.
Bush locos generally ran with their front end pointed up hill. This ensured that the firebox crown sheet was always covered with water. If this were not so, then the heat from the firebox could distort the crown sheet perhaps leading to catastrophic failure.
Locomotive braking systems were usually the manually operated brakes on the log buggies supplemented steam acting on the driving wheels and these. The log buggy brakes would be applied using a screw mechanism that pressed a wooden block on to the wheel face to provide retardation. Early log buggies simply had a wooden wedge to lodge between frame and wheel to act as a brake. It was the job of the brakeman, who was sometimes also the locomotive fireman, to walk or run alongside the loaded train and apply or release brakes as required. It was a dangerous job but a good brakeman and a good driver could act as an efficient team. Otherwise they could drive each other crazy.
Drivers often stayed with the same bush locomotive for many years and they had to be able to repair their charge if it should break down in the bush.
