Narrow Gauge NM

NM 15 to 28, 31 to 38

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When the Commonwealth Railways decided to take over the Central Australia Railway operation from the South Australian Railways (SAR) they identified the need to purchase additional rollingstock, including locomotives. As the South Australian Railways would not sell the Commonwealth any of the existing locomotives being used on the line they had to look elsewhere. Originally it was thought that the "C16" design of the Queensland Railways would be suitable, but further investigation identified the "C17" as being a better purchase. A report by the South Australian Railways Engineer was favourable to the bridges on the line being able to take the additional axle load. Work on strengthening bridges had been planned since 1917, with the intention of using the South Australian Railways "T" class, but not yet carried out.

Following rapid approval tenders were called in December 1923 for 14 locomotives. Twenty overseas and 3 Australian replies were received, with "Sir W.G.Armstrong, Whitworth & Co. Ltd." of England being the cheapest at £106,381. The next nearest tender was received from "Thompson Engineering and Pipe Co Ltd" of Castlemaine, Victoria at £136,400. As the overseas tender was not suitable, due to variances from the original specification, Thomson's got he order. The Government also hoped that by awarding a local contract it would foster the establishment and expansion of the local manufacturing industry.

The order progressed well with the first locos being available for delivery, via Terowie, from May 1925. The Commonwealth was so satisfied with the delivery date and quality that an additional 8 engines were purchased for use on the new line extension being constructed from Oodnadatta to Alice Springs. This second order was expected to commence delivery in December 1926 but due to an extended British Coal strike, which closed all the British Steel Mills and force the purchase of boiler plate from America, delivery did not start until April 1927. No major problems were experienced with either order of locos and only minor alterations were requested by the union, including the provision of a screw for reversing gear in place of reversing lever due to restricted space in the cab, lids for ventilator opening in the roofs of cabs, cab lookout protection from weather, drive seat alterations and screw hand brakes on tenders in place of chains. The requested modifications were included by Thomson's in the second order. The remaining locos were fitted with these features between 1926 and 1929. Instead of using the last loco, NM38, on the Central Australia Railway it was dispatched to Darwin to assist with the extension works being undertaken from Katherine to Daly Waters. When the withdrawal of funds forced termination of construction at Birdum, instead of Daly Waters, NM38 was placed in storage pending its return to Port Augusta. Owing to difficulty in returning the locomotive south, and an unsuccessful attempt at offering it to the Queensland Railways in exchange for two lighter B15 class engines, it remained for an extended period. As it was considered far too heavy for the light track around Darwin it was only used in emergencies when no other locomotives were available. It is known to have worked a mixed train from Katherine to Birdum on at least one occasion, but seems to have never entered general service. After being stored for many years it eventually returned in September 1941 to help with the increased war traffic on the Central Australia Railway

Throughout their working life the engines remained basically unaltered apart from the provision of back bunker boards and boarding the front of the tenders. In 1927 these modifications, including a 4 in. raising of the tender sides increased coal capacity to 6½ tons. When the coaling depot at Edward's Creek was abandoned in 1943, it was necessary to increase the coal capacity to 8 tons by raising the tender sides. This work was carried out at South Australian Railways's Peterborough and Islington workshops. The only other major visible change was the provision of back cab curtains in 1932.

Note: The above text was based on the Rollingstock Files of the Commonwealth Railways and should be read in conjunction with the following comments from John Lyas who was involved in the rebuilding of NM 25.

Note on Alternations to Commonwealth Railways NM Class Engines by John Lyas"

During the rebuilding of NM 25 during 2001-2003 numerous changes to the original design were noted. It should also be mentioned that no evidence exists to support the statements above concerning the change to screw reverse equipment. The many changes encountered have been detailed below; some of these alterations are quite evident, some are not. Study of the numerous photographs that exist of the NM's will show the external changes readily when looking for them. Obviously not all engines received all the alterations.

TENDER

• Hungry boards added to the coal space of original tanks, in conjunction with a larger front tank bulkhead and larger doors to the coal space.
• Original riveted tanks were superceded where required with welded tanks that incorporated the enlarged coal capacity. Both NM 25 and NM 34 survived with original tanks, but NM 25 now has the newer design.
• A drawing show a gauge to indicate water level in the tank fitted to the outside l/h side of the tank, but no photos have been able to indicate if any of these were ever fitted.

ENGINE

• Cowcatcher changed from Queensland Railways type angle iron design to Commonwealth Railways tubular type. These were originally riveted, but later ones were welded.
• Queensland Railways style cast iron smokebox front and door changed to the South Australian Railways design.
• Cast iron funnel changed to Commonwealth Railways design fabricated mild steel one.
• Electric lighting adopted, incorporating turbo-generator, headlight and marker lamps on engine and tender.
• 3 OR type safety valves located on top of the steam dome were replaced with 2 Coale design pop safety valves located on top of the firebox.
• Air compressor moved forward 15inch to give a more convenient access to firebox cladding.
• Air compressor exhaust relocated from r/h side of smokebox to rear exhaust cavity of the right hand cylinder.
• Snifting valves replaced with drifting gauges.
• Cyclone front end added, as on NM 34, with extended smokebox.
• Original feedwater check valve casting, incorporating both checks, was replaced with individual valves for each injector.
• Cut out in the cab sides was reduced with the second batch to give the crew marginally more protection from the elements.
• "NM" classification added to the numberplates on the second batch, with an additional plate fitted to the front buffer beam on these engines.
• Steam supply to the blower was altered from the front tubeplate of the boiler, to the front of the of the steam dome on some engines. NM25 was like this at the end of its service life but has been altered to take the steam from the steam turret in the rebuiolt loco.
• Handbrake added to the tender during construction.
• Stiffening angles added to the main engine frame above the rear driving axle.
• Piston rod tails removed from the front of the cylinders.
• Design of rear cylinder covers altered to support the slidebars in a different way.
• Design of the crosshead and slippers altered twice.
• The domed ends of the front steam chest covers were removed.
• South Australian Railways style King metallic piston rod packing adopted.
• Pistons changed to incorporate 3 rings instead of 2.
• Return cranks altered to a fabricated design and mounted on the crankpin on a circular spigot instead of a square one.
• Design of the reversing shaft bracket changed; NM 25 has the old ones, NM 34 has the new design.
• Connecting rod big end bearings changed from the strap type to the floating bush style.
• Inner collars on engine axles removed.
• Spring gear details altered.
• Deck hose added to ash wetting system.
• Regulator handle altered from the pull outIpush in type to the rotary type similar to the South Australian Railways T, Rx and F classes.
• Location and type of washout plugs was altered.
• Flexible stays were fitted to some boilers.
• During overhauls at lslington during the war years steel firebox tubeplates replaced copper ones.
• Waugh type firegrates fitted to some engines. NM 25 now has these fitted so that some components are identical to the former Western Australian Government Railways W class locos, for which Pichi Richi Railway has production patterns.
• Shroud placed around the pop safety valves to prevent steam from going over the turbogenetator.
• Grease replaced cil for lubrication of rods and valve gear.
• Queensland Railways design smokebox ash ejector removed.
• Blowdown valve from rear of firebox removed.
• Pneumatic blow-off cock and control equipment removed from boiler.
• Scum cock removed from boiler.
• Superheater pyrometer equipment from smokebox and cab removed.
• Wick feed axlebox lubrication reservoirs removed from the inside of the cab walls and frame near the front of the firebox.
• Method of retaining connecting rod gudgeon pin altered.

NM 15

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 16

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 17

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 18

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 19

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 20

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 21

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 22

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 23

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 24

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 25

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 26

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 27

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 28

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 31

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 32

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 33

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 34

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 35

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 36

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 37

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.

NM 38

Steam locomotive with 4-8-0 wheel arrangement, built by Thompson of Castlemaine Victoria.