They weren't so much unwanted, but not normally avaliable for general traffic.
Unwanted locos copped an X classification, IIRC what I read in the Newnes chapter of The Shale Railways of NSW. Mention is made of some that were used in the construction of the WVR, including one Manning Wardle (I think ) that was apparently so undesirable to the Department that it was slugged with an XX tag.
Very very interesting and informative. On another point, why we're the 38s "38" and not 37? When I first became interested in steam in the early 70s my father told me that his father, who was a fitter at Eveleigh for 30 years until his premature death in 1943, told him it was in case more 36s were built. I have often wondered whether it was because there was doubt Mr Hartigan would extend the initial order of 5 38 class engines and therefore more 36s might be built or if the 1933 proposal to convert the 36 class to 4-6-2s, like half the 30 class were converted to tender engines, might be revived. I tend to think not the latter as the tender 30 class were never reclassified.
The order for the 38 class was initiated by Sir Raymond Purves of Clyde who wanted an order for five more 36 class to retain their workers through a slow period. The NSWGR design office decided that a new design would be built.
As you say, it is possible that the 3700s were regarded as reserved for more 36 class, or someone still hoped that the 30 class tender locomotives would be renumbered eventually as they should have been in 1928. Once the 36 class received new steel inner fireboxes in 1934 and were painted green to indicate their greater reliability, the conversion to 4-6-2 wasn't required any more.
I think the 30 class were not renumbered because they would have been the first conversion after the 1924 renumbering and the concept of changing the numbers was foreign since locomotive numbers, rather than class letters, did not change due to conversion before 1924.
The 30T class were superheated from 1940 onward, and since that increased their power to roughly that of the 32 class, and if this superheating proposal preceded the 38 class, the 37 class might have been reserved for the superheated 30T, but in fact the 30 continued to cover what was for traffic purposes three different types.
While the data book is not all the correct in some areas, it along with other sources have the 37series reserved for ""Proposed"" conversion of 36cl 4-6-0 to the pacific 4-6-2 wheel arrangement. Personally I could not see any real benefit in that proposal, as the belpair pigs in most respects matched the 38c' in different districts, worst part with them was their rough riding & some more than others tendency to pull the fires. On the short south, the took the same goods load as 38, standard goods & 59cl, with length limitation though.
The superheated 30T in general were only allocated the same load & conditions as the saturated versions, although capable of a 32cl load & other conditions, they rarely met them without special approval was given, & instructions issued to enginemen.
For those not familiar with the history of the 36 class, although it was a good basic design, it had serious problems with the inner firebox. This followed contemporary USA designs and was radially stayed for the crown sheet. However, the inner firebox was copper rather than steel and it was subject to additional stresses due to the different rates of expansion of copper and steel made worse by effects of the angular staying.
By 1931, this came to a head and it was reported that only twelve of the seventy five locomotives were "counted as working" and a new design of steel inner firebox with direct staying was developed to replace the original design. These were adopted for the whole class from 1934 and the modified locomotives were painted green.
During this period, at least two different designs were developed to convert the 36 class using different designs of boiler. The first, often associated with the "37 class" had a wide firebox boiler otherwise similar the the existing 36 class boiler, but with a combustion chamber and longer tubes.
Another design used a 57 class boiler which required a four wheel trailing truck but retained the cylinders and driving wheels of the 36 class. I suspect an entirely new frame would have been used.
Some confusion has concerned a locomotive diagram produced by The Superheater Company for a 4-6-2 generally in the style of a NSW locomotive with a 36 class style cab numbered 3701. This was basically advertising for their products, and included most of their equipment including an Elesco feed water heater, but this drawing has subsequently been confused with a genuine NSWGR proposal for the rebuilding of the 36 class.
However, once the steel firebox was adopted, there were no further serious proposals to rebuild the 36 class as a 4-6-2 type.
I have a copy of an early Data book put out by the NSWGR, rather than the later PTC version but I think it also shows a fairly comprehensive list of steam loco's that were used by the NSWGR as well as proposed, the pacific type 36 was shown in the book & listed as 3701, as all now know it never eventuated.
As I said & based on my numerous working of the belpair pigs, as well as 38cl, I would say from my perspective & that is all I am basing it on, I much preferred the pig over a 38cl any day, that is with drivers who were experienced in working pigs, which I am in the main thankful for, but there were a couple of exceptions.
I would perhaps assume, rightfully or wrongfully that if the 37cl proposal had been shown in some official document which has caused the proposal to show up in what is or seems to be an accepted though abandoned proposal, that the 37cl numbering had been taken up, & therefore unavailable. Of course supposition & pure speculation though.
Another possibility is that the 38 class may have been regarded as an experiment at the time and the 37 class was left to provide space for a more conventional alternative if the "advanced" 38 class did not live up to expectations.
There was also the Lima 4-8-4 design, which looked a bit like an NZR K class scaled up to standard gauge, with the large cylinders angled steeply to clear passenger platforms. This was considered seriously during WWII but as a new design could not be built in the USA during wartime. So 25 more 38 and 25 more 57 class were ordered by 1943 with cast frames to the existing designs coming from the USA. But the Lima 4-8-4, offered about the time the 38 class design was finalised, could be another candidate for the 37 class numbering (although the Lima enquiry number on the drawing was "3801").
Had WW II not occurred, it is possible that the 38 class would have remained a class of five locomotives only, if the change to diesels had still taken place in the early 1950s.
We are straying a bit from the nominal topic of NSWGR numbering.
But while thinking about WW II, while NSW missed out on any new locomotives, and only finished the first additional 38 in December 1945, one acquisition had a noticeable effect.
These were the US Army GE "44 ton" locomotives that were delivered as standard locomotives for use in the USA. Later units were built for use in more restricted clearances, and these ended up in Pakistan among other places.
But ours were straight American units, and early photos show them on the docks, presumably in Darling Harbour with handrails bent out of the way to try to fit the loading gauge, but no other changes.
When they emerged from Eveleigh, the letters "USA" were painted out, the offending handrails had been removed, the knuckle couplers had gone and buffers and screw couplers fitted. The cab roof had been cut down and new smaller cab windows installed.
But the numbers remained.
These were 7920-7923, in a US Army series used for various types of diesel locomotive.
Nominally intended for an ammunition factory at Ropes Creek, they ended up as Sydney Yard shunters, and the two not passed to the Commonwealth (again nominally for use at Woomera but more often seen in Port Pirie and Port Augusta) remained as Sydney Yard shunters into the 1970s.
But those two, 7920 and 7923 became known as 79 class, conveniently well above any allocated numbers (unlike the QR 2-8-2 locomotives, all of whose three digit US Army numbers duplicated those of existing locomotives).
When diesels came in numbers, they were numbered from 4001, but the two wartime units had so established themselves that dedicated diesel shunting locomotives were numbered from 7001 upward, forming a series with the original two whose pretty much random numbers had started a trend. (I know that electric 7100 muddied the waters a little in that respect, but the original 7101 fitted the pattern).
The 79 class was a success, and inspired the 41 class as an extension of the concept. The 41 class suffered from the inexperience of their designers, but performed good work in the hands of sympathetic crews, being able to replace 50 and 53 classes on suburban goods work on their good days.
The numbering reflected that the 41 was intended to haul trains, if only in the suburban area, while the 79s and their successors with similar numbers were seen as yard shunters.
I don't understand the weights issue (water in the firebox? would mean a burnt boiler or stays, & trouble ahead for crew) but from what I have been able to ascertain on the NW or more especially to BNWY, only the 50cl was allowed to run there, was it owing to the floating drivers as against the flanged others? My first trip on the line was in 1969, & even on a 48cl it was an unpleasant experience especially in the sections from Premer - Bnwy especially to Bomera, as the track was primarily on ash speed was 20K's max, thus I can imagine the aversion to having a freighter on the line of any type.
of course the snotty nose types were different as they tended to be lighter on their feet & more readily prone to slip than the other types, I also never found them being worked harder then half regulator as going to much past that point they would lift the water more readily as well as slip, just worked out a bit more on the screw.
As I've said earlier, both before 1924 and after, using the same class for superheated and non superheated locomotives(generally called "saturated" in NSW by reference to the steam conditions, the steam being saturated and unable to absorb more water) caused some confusion since the train loads (and as Col has pointed out, the handling) were different for superheated and saturated locomotives.
In 1924, examples of the P, T and TF classes still had saturated boilers, and these were classed the same after 1924 as well.
By contrast in Victoria, about that time, the A2 class was split into A1 (saturated) and A2 (superheated) and the Dd class into D1 (saturated) and D2 (superheated) types.
As I've said earlier, the P class and the first thirty T class remained saturated because their slide valve cylinders were unsuitable for superheated steam owing to problems with lubrication at the highersteam temperature.
By 1929, 32 class were due for cylinder replacement and the class was progressively superheated, with new frames being provided from 1937 because the extra power and speed was finding weaknesses in the original frames.
Due to the economic depression, a number of staurated 50 and 53 class were stored while others remained in service.
The NSWGR concentrated saturated 50 class in Port Waratah coal service. This consisted of collecting wooden four wheel unbraked hopper wagons at East Greta and Hexham and elsewhere and dragging them slowly to the Port of Newcastle. The addtional power and efficiency of a superheater is best obtained by continuous operation and it was felt that the stop start operation of these trains was better handled by saturated engines, which were cheaper to build and repair but had a higher fuel consumption in more normal operation.
It is hard to appreciate now with the continuous operation of fast and heavy trains that the "coal lines" were to keep the coal trains from delaying faster and higher priority trains.
With the outbreak of World War II, those stored saturated 50 and 53 class that had not been scrapped were rebuilt and superheated, including several survivors from the first thirty 50 class, so the 53 class became uniform but saturated 50 class remained in coal service and as yard shunters until the end of steam. On the day of the ceremonial last run of 6042, saturated 5069 was still in steam at Broadmeadow loco, although it didn't actually run that day.
So from a classification point of view, the 50 class was the last survivor of the locomotives that had both superheated and saturated versions at the 1924 renumbering.
However, as I said above, since 1924, the 30 class had split into tender and tank versions and the tender locomotives had split into saturated and superheated versions.
In this aspect, NSW classification was less flexible than that used in Victoria.
The Victorians had their own idiosyncracies, where as well as the letter code, locomotive numbers were swapped around to keep superheated and saturated locomotives in separate numerical groups. At least in NSW most locomotives had only two (or maybe three) numbers. Victorian A1s in particular were progressively renumbered to keep thier running numbers below the lowest A2 number, so the number 805 appeared on five locomotives in succession as superheating advanced. At least the numbers were on cast iron plates easily moved from loco to loco.