Some locomotive subclass queries

[Western 52]

Looking through some old Ian Allan motive power books from the 1970s, a few things caught my eye, which I’d either missed when I first bought the books, or I’d just forgotten about them.

Firstly, pages 45 and 46 of the 1975 book deal with the class 45 locomotives, which at that time had not all been renumbered into the TOPS 5-digit series. On page 45, there are 22 renumbered class 45/0 and 141 class 45/1. On page 46, all the remaining locomotives are listed with their pre-TOPS numbers, under a heading which states they are to be reclassified as 45/1 or 45/2. I know there never was a 45/2 – is this headline a mistake, or was there a plan for an additional subclass for some reason? The 1976 book has them all renumbered as 45/0 or 45/1.

My second query concerns subclass numbering in general. For most classes, subclasses had a third digit in the loco number which represented the subclass such as class 47/3, numbered 47301 to 47381. However this was not always the case, and classes 24 to 26 were anomalies.

In class 24, the 24/0 variant was 24001 to 24049 and 24/1 was 24050 to 24150. Class 26 were similar – 26/0 were 26001 to 26020 and 26/1 were 26021 to 26046. Class 25 were just numbered from 25001 to 25327: 25/0 – 25001 to 25025, 25/1 – 25026 to 25082, 25/2 – 25083 to 25245 and 25/3 – 25248 to 25327. Why were these classes numbered without regard to the subclasses?

Additionally – what was the difference between the locos in the class 24 and 26 subclasses? The 24/1 and 26/1 variants appear to have been 7 tons lighter than 24/0 and 26/0, with a consequent lower RA number, but what were the technical differences that made them lighter? After all they had the same engines, etc. as far as I can tell.

 

[Bill57p9]

You are absolutely right that the subclass usually (but not always) indicates the "hundreds" digit. Another example is 37/5 which included 37667-699 whilst 37601-612 are 37/6. There were also some 373xx machines that are 37/0 and others were 37/3.
Equally some 089xx are 08/0 and others 08/9.

Pretty sure 45/2 never happened.

I would hazard a guess that 24/1 & 26/1 lacked steam heat boilers but I may be wrong.

 

[hexagon789]

Additionally – what was the difference between the locos in the class 24 and 26 subclasses? The 24/1 and 26/1 variants appear to have been 7 tons lighter than 24/0 and 26/0, with a consequent lower RA number, but what were the technical differences that made them lighter? After all they had the same engines, etc. as far as I can tell.

I would hazard a guess that 24/1 & 26/1 lacked steam heat boilers but I may be wrong.

Yes, steam heat boilers removed (though some 24s never had them anyway to start with, so really more denoting "no heat" arguably). Also according to the diagram book, the locos with boilers removed were 2 tons lighter rather than 7.

 

[Gloster]

I have a very vague feeling that 45/2 was intended for 138 to 193, but the decision was altered at an early stage and they became class 46.

EDIT: 26/1 may have been the original prototype batch and 26/2 the production one. Presumably it was decided that it wasn’t worth differentiating between them.

 

[Razorblades]

Later 24s and 26s retained steam heat boilers into their later lives; 24115-131 for example, were steaming away at Inverness until their migration south to Haymarket at the start of the 1975 winter timetable, while their Class 26 stablemates continued to generate therms until the arrival of Class 37s in the early eighties.

 

[Western 52]

Later 24s and 26s retained steam heat boilers into their later lives; 24115-131 for example, were steaming away at Inverness until their migration south to Haymarket at the start of the 1975 winter timetable, while their Class 26 stablemates continued to generate therms until the arrival of Class 37s in the early eighties.

Interesting - despite having boilers 26/1 were lighter than 26/0. The Ian Allan book has a difference of 7 tons between them. What made 26/0 so heavy? Same for the 24s, but was it the case that only 24/1 had boilers?

 

[Razorblades]

I recall reading that the BR and BRCW Type 2s were 'weight engineered' or their designs re-evaluated to save weight after production had been underway for a while; presumably to save on operating costs across the board. Hence the weight reduction at D5051 and D5320 in the respective fleets. As built, all the early 50XX and 53XX were boiler equipped.

 

[randyrippley]

The current TOPS class scheme is the third attempt
The first was never used publicly, the second briefly but it was quickly realised to be confusing.
Take the 33s.

	standard body	TC-fitted	narrow body
TOPS number range	33 0xx	33 1xx	33 2xx
first class scheme	33	34	32
second class scheme	33/1	33/2	33/3
third class scheme	33/0	33/1	33/2

the change to the third scheme was to match the class number to the number scheme, as these didn't originally match the class numbers

Similarly the 45s were orginally 45/1 (steam heat) and 45/2 (eth) though numbered 45 0xx and 45 1xx.

The 31s and 47s were also affected though I can't remember how.

Regarding the Sulzer type 2 variants, I read somewhere that with four production plants building them, each with it's own subvariants that trying to give each type a unique number sequence would have been too difficult and wasteful of numbers
Different body designs, several different cab designs, at least two different traction motors, series vs parallel

 

[D6975]

Interesting - despite having boilers 26/1 were lighter than 26/0. The Ian Allan book has a difference of 7 tons between them. What made 26/0 so heavy? Same for the 24s, but was it the case that only 24/1 had boilers?

No. As 'razorblades' said, all class 24s were built with boilers. Some of the first batch spent some time on the Southern for precisely this reason, 33s were EH only and the Southern had loads of stock that wasn't. When it was realised that they were overweight locos started to be given smaller tanks to reduce the axle loading.

As for the TOPS sequences mentioned by randyrippley, there was another classification before the one quoted as the first, but this was rapidly disposed of when they realised it didn't have enough series.

 

[hexagon789]

As 'razorblades' said, all class 24s were built with boilers.

I thought 10 of them didn't as the space was needed for a compressor and air brake equipment for use on Consett iron ore trains? Or was that a subsequent modification?

 

[Harvester]

I thought 10 of them didn't as the space was needed for a compressor and air brake equipment for use on Consett iron ore trains? Or was that a subsequent modification?

The ten (D5102-D5111) were allocated to Gateshead from new, and worked from there until around 1966 with train heat boilers. They then moved to Tyne Dock to replace the 9Fs, after modifications at Crewe/Derby Works.

 

[Snow1964]

Regarding the steam heat boilers, in addition to the boiler there was a water tank which add a few tons when full.

I am sure in later life, some class 37s (and maybe others) had their former water tanks replaced by additional fuel tanks to increase their range between refuels, which increased the working order weight.

 

[Magdalia]

The original TOPS renumbering scheme was set out in detail in autumn 1973. Railway Magazine published it in its October 1973 issue, though with quite a few proof reading errors.

In this classification there were no /0 subclasses, the subclasses within each class were numbered sequentially starting at /1. So for class 47 the steam heat locos were class 47/1, the no heat locos were class 47/2 and the ETH locos were class 47/3.

Once renumbering got going the clash between the loco numbers and the subclass numbers became evident. The subclass numbers were revised so that they matched the third digit of the number of the first loco in the subclass. In the class 47 example class 47/1 became class 47/0, class 47/2 became class 47/3 and class 47/3 became class 47/4, with no class 47/1 or class 47/2. This was reported in the April 1974 Railway Magazine, so the original subclass numbers only lasted for a few months.

The subclasses of class 24 and class 26 were based on route availability. Classes 24/0 and 26/0 (originally 24/1 and 26/1) were RA6 and Classes 24/1 and 26/1 (originally 24/2 and 26/2) were RA5. The RA5 locos had smaller boilers (L4610 instead of OK4616) and smaller water tanks (450 gallons instead of 600 gallons) to reduce axle load.

And loco weight changes when modifications are made: new equipment does not weigh nothing! For example, dual braking usually increases weight by at least a ton because of the weight of the compressor.

 

[CW2]

Regarding the steam heat boilers, in addition to the boiler there was a water tank which add a few tons when full.

I am sure in later life, some class 37s (and maybe others) had their former water tanks replaced by additional fuel tanks to increase their range between refuels, which increased the working order weight.

The working order weight of the boiler-fitted 37s included allowance for a full water tank. When the water tanks were re-purposed as long range fuel tanks, the boilers were also replaced by blocks of concrete, the weight of which was arranged to ensure no overall difference to the loco weight / individual axle loads

 

[Wyrleybart]

The original TOPS renumbering scheme was set out in detail in autumn 1973. Railway Magazine published it in its October 1973 issue, though with quite a few proof reading errors.

In this classification there were no /0 subclasses, the subclasses within each class were numbered sequentially starting at /1. So for class 47 the steam heat locos were class 47/1, the no heat locos were class 47/2 and the ETH locos were class 47/3.

Once renumbering got going the clash between the loco numbers and the subclass numbers became evident. The subclass numbers were revised so that they matched the third digit of the number of the first loco in the subclass. In the class 47 example class 47/1 became class 47/0, class 47/2 became class 47/3 and class 47/3 became class 47/4, with no class 47/1 or class 47/2. This was reported in the April 1974 Railway Magazine, so the original subclass numbers only lasted for a few months.

Don't forget that the class 47/3 only came about as a result of TOPS numbers - which sounds obvious anyway. But don't forget that what we know of as a 47/3 - IE a freight loco with slow speed control and useful for operating merry go round trains, was actually just another "Brush 4" without a bpiler. The TOPS renumbering put those 81 locos into their own series.

The subclasses of class 24 and class 26 were based on route availability. Classes 24/0 and 26/0 (originally 24/1 and 26/1) were RA6 and Classes 24/1 and 26/1 (originally 24/2 and 26/2) were RA5. The RA5 locos had smaller boilers (L4610 instead of OK4616) and smaller water tanks (450 gallons instead of 600 gallons) to reduce axle load.

And loco weight changes when modifications are made: new equipment does not weigh nothing! For example, dual braking usually increases weight by at least a ton because of the weight of the compressor.

The class 24/0 and class 24/1 were regarded differently and technically class 24/0 were banned from the Cambrian beyond Dovey Junction because they were too heavy. Brfitish Railways had quite a battle to reduce the axleload of the Sulzer twos, particularly the 24s and 26s, and if you study them closely you will see differences. Even moreso when you compare the much lighter class 25 to it's earlier and heavier cousin. Inside the cab you will see lots of internal trim paneling missing inside the 25 cabs.

What surprises me is the difference between the dual braked 26s and the class 27s. When the 26s were fitted for dual braking every one of them lost the train heating boilers, and underframe water tanks to make room for the air compressors and reservoirs. However, the class 27s retained their boilers when dual braked, possibly as a result of suspending the air reservoirs in the cab ceilings.

Class 25s generally received dual braking without issue apart from 25242 (D7592) which I suspect was the prototype for modification and lost it's boiler and water tanks. Just adding to this, the boilered class 25s that were dual braked, had a modification to the bodyside air grilles on one side, hinged so they could awing out and have the filters changed externally due to the lack of space inside the engine room on that side. Not sure if all those also received a second triangular panel at the same time.

 

[Richard Scott]

I believe 25s are lighter due to smaller traction motors but this made the motors more highly stressed and prone to failure. 26s having Crompton Parkinson electrical are pretty bullet proof but these are large and consequently heavy! The 26 sub classes also had slightly different motors, I believe, but this made little if any difference to performance.

 

[Magdalia]

What surprises me is the difference between the dual braked 26s and the class 27s. When the 26s were fitted for dual braking every one of them lost the train heating boilers, and underframe water tanks to make room for the air compressors and reservoirs. However, the class 27s retained their boilers when dual braked, possibly as a result of suspending the air reservoirs in the cab ceilings.

The relationship between boiler removal and changes to overall weight is a complicated one. Boilers, and boiler water tanks, were usually as one end of the loco, and the original design would have to take account of the variation in weight distribution as the amount of water in the tank varied.

Once the boiler and the boiler water tanks are removed, it became customary to rebalance the weight distribution with a concrete block in the boiler compartment. This tended to be a bit heavier than the boiler it replaced, to also simulate the effect of there being some water in the water tank. Don't forget that water is heavy (try picking up a full bucket of it!) and 600 gallons of water in a full tank weighs about 3 tons (the density of water varies with temperature).

Fuel is also heavy but fuel tanks are usually in the middle of the loco, between the bogies, so variations in the amount of fuel have less impact on the weight distribution.

Don't forget that the class 47/3 only came about as a result of TOPS numbers - which sounds obvious anyway. But don't forget that what we know of as a 47/3 - IE a freight loco with slow speed control and useful for operating merry go round trains, was actually just another "Brush 4" without a bpiler. The TOPS renumbering put those 81 locos into their own series.

Class 25s generally received dual braking without issue apart from 25242 (D7592) which I suspect was the prototype for modification and lost it's boiler and water tanks. Just adding to this, the boilered class 25s that were dual braked, had a modification to the bodyside air grilles on one side, hinged so they could awing out and have the filters changed externally due to the lack of space inside the engine room on that side. Not sure if all those also received a second triangular panel at the same time.

Classes 25 and 47 are interesting in that the original design was for a loco with a boiler, but some were built without boilers. Class 27 also comes into this category. Did the locos without boilers have a concrete balance weight from the start or did they have other design changes to achieve a reasonably even weight distribution without the boiler?

 

[CW2]

I believe 25s are lighter due to smaller traction motors but this made the motors more highly stressed and prone to failure. 26s having Crompton Parkinson electrical are pretty bullet proof but these are large and consequently heavy! The 26 sub classes also had slightly different motors, I believe, but this made little if any difference to performance.

When it was necessary to choose locos for MGR work at Millerhill, it was the 26 which was chosen over 25 and 27. 25s were always a liability in service - it was just a case of when and where they would incinerate themselves. Anybody who sampled Summer Saturdays on the Cambrian will have tales of smoking 25s to tell.

 

[norbitonflyer]

The 31s and 47s were also affected though I can't remember how.

Similar to the other variants. The 31s were originally classified 31/1 (pilot scheme locos with different coupling code), 31/2 (standard) and 31/3 (ETH), later 31/0, 31/1 and 31/2 respectively

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The current TOPS class scheme is the third attempt
The first was never used publicly, the second briefly but it was quickly realised to be confusing.
Take the 33s.

	standard body	TC-fitted	narrow body
TOPS number range	33 0xx	33 1xx	33 2xx
first class scheme	33	34	32
second class scheme	33/1	33/2	33/3
third class scheme	33/0	33/1	33/2

I'm sure I'm not alone in wanting to see the first scheme in full. As well as classes 32 and 34, does it explain the other "missing" classes: 18, 19, 36, 38, 39, 49, 51, 54, and 72.

(Wikipedia claims the LMS "twins" (nos 10000 and 10001 were allocated to class 34, and I have seen suggestions elsewhere that they were allocated to class 36, but since both had been scrapped by 1968 this seems unlikely. If the classification really was drawn up that early, then Class 53 must have been a late addition to the list as the "Falcon" was not taken into BR stock until 1970)

I have wondered whether classes 17, 37, 47 and 73 were originally intended to be more than one class each. After all, there seems no reason why the relatively minor differences between class 24 and 25, or between classes 26 and 27, or between classes 44, 45 and 46, merited different class numbers but similar differences in other classes did not...........

 

[43096]

Similar to the other variants. The 31s were originally classified 31/1 (pilot scheme locos with different coupling code), 31/2 (standard) and 31/3 (ETH), later 31/0, 31/1 and 31/2 respectively

Presumably you mean 31/0, 31/1 and 31/4?

 

[Magdalia]

Similar to the other variants. The 31s were originally classified 31/1 (pilot scheme locos with different coupling code), 31/2 (standard) and 31/3 (ETH), later 31/0, 31/1 and 31/2 respectively

The ETH class 31s became class 31/4.

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I have wondered whether classes 17, 37, 47 and 73 were originally intended to be more than one class each.

D1702-06 were originally class 48. I agree that there are significant differences to suggest that the Claytons should have been more than one class.

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After all, there seems no reason why the relatively minor differences between class 24 and 25, or between classes 26 and 27, or between classes 44, 45 and 46, merited different class numbers but similar differences in other classes did not...........

I would not describe different main generators as "relatively minor differences".

 

[Richard Scott]

The ETH class 31s became class 31/4.

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D1702-06 were originally class 48. I agree that there are significant differences to suggest that the Claytons should have been more than one class.

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I would not describe different main generators as "relatively minor differences".

There were quite significant differences between 24s, 25s, 26s and 27s. 44s and 45s less so but again 46s may look like a 45 but there are quite a number of differences; significant enough to warrant withdrawal of the 46s long before the 45s. 45 a vastly superior machine to the 46.

 

[Taunton]

The TOPS computer system (on an IBM 360 I believe, and the programs bought from the USA Southern Pacific company, who had pioneered it) seemed to have a technical issue with numbers ending in zero. Where locos were renumbered synchronised with their old numbers, the class leader commonly starting with 00 would get renumbered to the end, or to a convenient break point. Always struck me as not required, as Southern Pacific themselves always had groups of loco numbers all over the place.

It was apparent that different staff members devised the TOPS numbers different ways. The class 03, for example, was renumbered fully in accordance with their previous, so the little higher numbered group of 2371 etc became 03 371. But others were done differently, although with 5 digits there were plenty of numbers available.

When dmus were added the 50xxx and 56xxx cars were changed to 53xxx and 54xxx respectively "because there are already class 50 and 56 locomotives". Yet the 55xxx single cars were not done and seemed to quite happily coexist with the Deltics, resulting in me seeing two 55015s side by side at Edinburgh Waverley east end, Deltic ready to depart and the single unit sat in a bay. Notably both were allocated to Haymarket, seemingly without issue.

Classes 45 and 46 were done differently because of different electrical gear, yet other classes with multiple versions of the same were not so split.

 

[D6975]

The subclass numbers were revised so that they matched the third digit of the number of the first loco in the subclass. In the class 47 example class 47/1 became class 47/0, class 47/2 became class 47/3 and class 47/3 became class 47/4, with no class 47/1 or class 47/2. This was reported in the April 1974 Railway Magazine, so the original subclass numbers only lasted for a few months.

not true. Subclasses 24/1, 25/1, 25/2, 25/3 and 26/1 all have first subclass members that do not have the third digit matching the subclass.

 

[Magdalia]

not true. Subclasses 24/1, 25/1, 25/2, 25/3 and 26/1 all have first subclass members that do not have the third digit matching the subclass.

It was the truth, but not the whole truth. I didn't have time for that because it was past my bedtime!

There is a "hierarchy of difference" in the subclasses.

At the top are subclasses with different codes and new number sequences: classes 27/31/33/45/47 are examples. These don't have clear boundaries between all of the subclasses in the original number sequence. That's what I referred to in #13.

Then there are subclasses with different codes but no breaks in the number sequences: classes 24/25/26 are examples. Here there was a clear boundary in the old number sequence between each subclass. You have referred to those in #24.

There's also subclasses that are implicit in the renumbering scheme but without having separate subclass codes: classes 20 and 37 are examples here.

 

[norbitonflyer]

The ETH class 31s became class 31/4.

31/4 indeed, my error.

I would not describe different main generators as "relatively minor differences".

Different main generators may be a significant difference between Classes 45 and 46, but not as significant as the different engines fitted to, for example, some members of Class 17 (and one member of Class 42).

As to the apparent anomaly that later subclasses of classes 24,25 and 26 did not start xx x01, in all other cases (except class 73) the members of the individual subclasses were randomly distributed over the fleet, and renumbering in separate blocks made it possible to group them together. The subclasses of these three classes were already in separate blocks, albeit they did not start at x01 (respectively D5000/D5050, D5151/D5176/D5183 -5299 and D7500-7597/D7598-D7677 and D5300/D5320.

 

[Richard Scott]

Different main generators may be a significant difference between Classes 45 and 46, but not as significant as the different engines fitted to, for example, some members of Class 17 (and one member of Class 42).

45s and 46s are significantly different from each other in more ways than just the generator. Whole control system is different as are traction motors and cooling system.

 

[norbitonflyer]

When dmus were added the 50xxx and 56xxx cars were changed to 53xxx and 54xxx respectively "because there are already class 50 and 56 locomotives". Yet the 55xxx single cars were not done and seemed to quite happily coexist with the Deltics, resulting in me seeing two 55015s side by side at Edinburgh Waverley east end, Deltic ready to depart and the single unit sat in a bay. Notably both were allocated to Haymarket, seemingly without issue.

The DMUs were not renumbered until 1983, by which time the single cars had the 55xxx series to themselves. Given there were only 50 class 50s and 135 class 56s, renumbering nearly 2000 DMU cars seemed a bit of an over-reaction. In 1983 there was still plenty of headroom beyond the 50000-52105 and 56000-56504 blocks to renumber only the vehicles that duplicated locomotives. (e.g 52151/52200 and 56601-56735), and it would have left the entire 53000-54999 block free for new DMUs

Two DMU trailers 59101 and 59105 were renumbered (to 59110 and 59111) in 1990, and a few surviving SR DEMU cars 60014/15/16/18/100/101 (to 60152/53/16/18/54/55) around the same time.

 

[Wyrleybart]

45s and 46s are significantly different from each other in more ways than just the generator. Whole control system is different as are traction motors and cooling system.

Am I right in thinking the 45s were 220V whereas the 46s were "standard" 110V ? I think the 45s had converters to transform the voltage for at least some of the electrical machinery

 

[Richard Scott]

Am I right in thinking the 45s were 220V whereas the 46s were "standard" 110V ? I think the 45s had converters to transform the voltage for at least some of the electrical machinery

That's correct, the 45/1s lost the converters for a separate winding on the auxiliary alternator. The control circuits were still 110V on 45s although auxiliary machines ran off 220V.