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Preservation and Restoration of NSW Railway Track Vehicles |
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NSWGR Trikes |
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©Copyright NSWGR Trikes 2016 |
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Trikes and Trolleys A short history of track vehicles on the NSWGR
by Greg Lee |
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Chapter 6 The famous Fairmonts, Part 2
The MT14
The MT14 had a frame constructed from light steel channel and angle sections, bolted together. They were a medium weight car of 390 kg. They were allocated to some fettling and other gangs.
MT14s had a drive ratio of 3.89:1 in low gear, and 2.25:1 in high gear. Being low geared they had excellent pulling power in low gear, limited only by the relatively low power of the engines. They were fitted with tow bars, and had a peak power to weight ratio of 15 W/kg. They differed from the M19s and ST2s in that they had magneto ignition, with fixed timing, and so did not have a timing lever. This had the advantage of not requiring batteries, but the disadvantages of having fixed timing, and providing a relatively weak low speed spark. The fixed timing meant that low speed torque was lower than otherwise, and the relatively weak low speed spark meant that MT14s could be hard to start, particularly in damp weather.
They were capable of a top speed of about 54 kph on the level. They are ideally suited to towing moderately loaded trailers.
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The ST2
The ST2 had a frame constructed from heavy steel channel and angle sections, bolted together. They were a heavy weight car of 530 kg. They were allocated to bridge and extra gangs, and a few fettling gangs.
ST2s had a drive ratio of 2.31:1 in low gear, and 1.33:1 in high gear. It can be seen that they are much higher geared than MT14s. This gives them a very high top speed of about 80 kph on the level. Unfortunately this means that high gear is virtually useless for pulling purposes, and even low gear is geared too high for hauling heavy loads on steep grades. To make matters worse, ST2s suffer from lack of traction under load, due to their high peak power to weight ratio of 18W/kg.
ST2s were fitted with tow bars and the 8-13 horsepower engine would “pull a mountain out” if the power could be effectively harnessed. During 1985-88 GMR volunteers experimented with ways of improving the performance of a ST2 on the Glenreagh - Dorrigo line. The drive ratios were decreased by fitting a smaller pulley to the engine, and a larger pulley to the gearbox, and traction was improved by fitting rubber treaded rear tyres. With these modifications the ST2 was able to pull a vastly increased load on the 1 in 30s of the Glenreagh - Dorrigo line. During trials there was power and traction to spare and so the load was gradually increased until finally the drive belt started slipping.
ST2s were geared too high for optimum use on steeply graded lines, and even on straight flat lines their power and speed was excessive. Without modifying their drive arrangements, the only way to get satisfactory traction from them on steep grades was to load them with suitable weights so as to decrease their power to weight ratio.
This is not to say ST2s are of no use on the Glenreagh - Dorrigo line. They have done a mighty job there in the past, and a hard working ST2 is an awesome sight and sound to witness. However successfully operating them requires considerable experience and skill. |
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© Greg Lee, 1992 - 1999 |
