South Australian Railways 600 class
|
Number 609 of the class | |||||||||||||||||||||||
| |||||||||||||||||||||||
| |||||||||||||||||||||||
| |||||||||||||||||||||||
| |||||||||||||||||||||||
The South Australian Railways 600 class was a class of ten 4-6-2 Pacific steam locomotives built in 1925, designed to operate on 1,600 mm (5 ft 3 in) gauge lines.
History
The 10 South Australian Railways (SAR) 600 class Pacific locomotives were part of an order for thirty modern steam locomotives placed with Armstrong Whitworth in Great Britain in 1924 as part of the rehabilitation of the state's rail system being overseen by railways commissioner W. A. Webb. The 600 class design was based on the USRA Light Pacific, although modifications were made by SAR's Chief Mechanical Engineer Fred Shea to allow them to fit South Australia's tighter loading gauge. They arrived to Adelaide in 1926 and all ten were placed into service the same year.
Engine number 609 was named Duke of Gloucester after hauling the Dukes Royal Train in 1934 and so became Australia's first 'royal' engine.
The entire class received upgraded boilers and front ends from the late 1930s onwards and was reclassified as the 600C class. They were also fitted out with large smoke deflectors over their lifetime.
It was found that another lighter weight Pacific type locomotive was needed. Ten locomotives of the South Australian Railways 620 class were therefore built at Islington Workshops in 1936–1938.
All examples of the 600 class were scrapped from the late 1950s onwards.
Stocklist
| Engine Number | Builder | Date in Service | Date Condemned | Name |
|---|---|---|---|---|
| 600 | Sir W G Armstrong Whitworth & Co Ltd | 14/08/1926 | June 1959 | - |
| 601 | Sir W G Armstrong Whitworth & Co Ltd | 10/05/1926 | September 1958 | - |
| 602 | Sir W G Armstrong Whitworth & Co Ltd | 25/05/1926 | June 1959 | - |
| 603 | Sir W G Armstrong Whitworth & Co Ltd | 18/05/1926 | July 1961 | - |
| 604 | Sir W G Armstrong Whitworth & Co Ltd | 13/08/1926 | June 1959 | - |
| 605 | Sir W G Armstrong Whitworth & Co Ltd | 06/07/1926 | September 1958 | - |
| 606 | Sir W G Armstrong Whitworth & Co Ltd | 08/07/1926 | May 1960 | - |
| 607 | Sir W G Armstrong Whitworth & Co Ltd | 22/06/1926 | June 1959 | - |
| 608 | Sir W G Armstrong Whitworth & Co Ltd | 22/07/1926 | May 1960 | - |
| 609 | Sir W G Armstrong Whitworth & Co Ltd | 21/08/1926 | June 1959 | Duke of Gloucester |
Proposed duplex stokers[1]
Some of the Duplex stokers originally intended for the 600’s were fitted to the last members of the second series of 720’s (729-736), but it turns out that the Duplex stokers weren’t the only thing that the 600’s missed out on.
Despite the depression biting hard in the early ‘30’s and the aftermath of the scathing 1930 Royal Commission which inquired into the SAR (in particular expenditure and wastage) Islington kept its head down and was also quietly busy designing new locomotives, along with lots of testing, alterations and modifications to existing locos to make them more powerful and economic. Come the mid 1930’s, in particular 1936, and some of that design work came to fruition with the 620 class and in the same year the first of the 500’s received their distinctive streamlining. At this time the 600’s too received much attention from the draughtsmen and engineers.
It is well known that Webb loved the idea of the booster, any device that can increase ton miles and at the same time reduce train miles had to be good and it was his intention was to fit every large power loco with the tractive effort increasing device, 600’s included. Shea on the other hand was only ever lukewarm to the idea, and the Chief Engineer (who probably had many sleepless nights worrying about the increased axle load the booster imposed on his branch line tracks) wouldn’t be happy until they had all been removed, or better yet not fitted at all. Given these diametrically opposed feelings on the matter it is somewhat surprising that in 1936, long after Webb had gone, in an effort to increase the load hauling capacity of the 600’s design calculations and drawings were dusted off for the fitting of boosters to the 600’s.
The fitting of boosters to an existing design, particularly when the entire trailing truck arrangement had to be altered, is no easy job. The things to consider were heavy modifications to the frame extensions behind the rear driver to convert from a Hodges trailing truck to a radial delta mount style either 2 wheel or 4 wheel (delta refers to the 3 point mounting of the trailing truck to the frame), modification of the locomotive frame extensions themselves at the draw bar/safety bar area to a compact design so as to fit in between the booster and the stoker (remember that the 600’s were to get Duplex stokers and these were to be fitted at the same time as the boosters), new design ashpan and dampers to fit in between the new trailing truck, re-springing the rear of the locomotive and of course putting in all the ancillary steam and air plumbing required for booster operation. Most of this work required the boiler to be out of the frames.
Adding the booster and stoker to the existing 2 wheel trailing truck would have put the axle load of the trailing truck axle at just over 23 tons, and there was still the ancillary equipment to be added to this figure, so there was no way this was going sit well with the Chief Engineer. The only way out was a 4 wheel trailing truck to spread the weight of the booster and the firebox already supported by the trailing truck. An order was placed with Commonwealth Steel (later to become General Steel Castings) in 1928 for ten 4 wheel delta trailing trucks and these were placed in storage at Islington until required, and when required and fitted the 600’s would become Australia’s first Husdons.
Back to 1936/37, Islington had all but finished the order for ten 620 class locos, the 500’s had received a streamlined exterior as part of a makeover for the Overland and as mentioned above attention was given to the 600’s power output and look. Rough sketching was carried out for streamlining similar to the 500’s to be fitted to the 600’s, although more for aesthetics rather than any aerodynamic advantage, and these sketches were mainly for the crinolines that supported the sheet metal and of course the boosters, and at last stokers too.
But again a major change of heart to on how to increase the 600’s output came about. One fly in the ointment with boosters is the necessary factor of adhesion (FoA). The Association of American Railroads (AAR) FoA recommendation for trailing truck boosters, being a single driving axle, is 4.5. With a standard Franklin booster engine cylinder diameter of 10” the FoA for the 600 booster would come in at 4.175, this could make for a slippery booster. Calculations were done and it was found that bushing the booster cylinders down to 9” would result in a more desirable FoA of 5.16, but of course more expense for this necessary modification. So another way to increase a locomotive’s power output is to increase the boiler pressure, this also has the advantage of increasing power over the entire operating speed range and not just starting and low speed as would happen with the booster installation.
With boosters again on the back burner, again, Islington started looking at higher boiler pressure in both the 500’s and 600’s, although the 600’s were started first and it was found that a boiler pressure of 215 psi and steel inner firebox would put the boiler a tad over the AAR’s recommended safety factor of 4 ½ and would put the locomotive’s FoA a tad over the AAR’s recommendation for locomotive coupled wheels of 4.0 and other components such as connecting/coupling rods, crank pins etc would handle the extra stress of a 15 psi boiler pressure increase so this is the way that Islington went, higher boiler pressure with an all steel boiler and no boosters, and therefore no Hudsons. As for the streamlining, that never got past the sketches.
But what happened to the brand new Commonwealth Steel 4 wheel trailing trucks? In the book “600” it was assumed that they were used with the second series 720’s, this assumption is incorrect as the trailing trucks were a different design for the 600’s as they had a higher front mounting pivot due to the main frames sitting much higher with 6’ 3” drivers. The answer is they ended up under the first ten of the 520 class. This is why 520-529 had cast trailing trucks and 530-531 had fabricated trucks, only ten were ordered for the 600’s! Compare the front mounts of a 500/720 trailing truck to a 520 truck and you’ll see the difference. The 600 booster heritage of the trailing trucks fitted to 520-529 can also be seen in the rear transom, the booster ball seat mounting is clearly visible.
References
- Douglas Colquhoun, Ronald Stewien, Adrian Thomas (1971). 600 - The Pacific Locomotives of The South Australian Railways. Adelaide, South Australia: A.R.H.S. SA division.
- Drymalik, Chris. "Broad Gauge 600-class 4-6-2 (later 600C-class) locomotives". comrails.com. Retrieved 2011-05-27.
| ||||||||||||||||||||||||||