Class 24, 25, 26, 27 ("Sulzer Type 2s")

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Inversnecky

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These diesels hold a special place in my affections, because the 26s and 27s (along with 47s) headed the passenger services on my local line (Inverness to Aberdeen) in the early/mid 1980s when I first took a youthful interest in railways.

As I recall there were more 26s than 27s on that line - 24s were already gone, but unlike the 25s they did venture to the northern parts of Scotland with allocations at Inverness, though I do believe some 25s were in Glasgow (the experts here will set me straight on this).

Considering that only 47 were made, the Class 26 certainly seems to have made a significant impact, being among the earliest made and outlasting the other Sulzer powered Type 2s (when other low production classes have often become more of a footnote in the history of diesel traction). Similarly with the 69 Class 27s - the BRCW classes seem indeed to have had a more successful career than their much more numerous BR manufactured "siblings".

Can someone explain the timeline behind these various Type 2s - I believe the 25 was based on the initial 24s (going by the later TOPS classification for convenience), but the 26s and 27s were made by BRCW. It seems that the 25s were built longer than the others, yet didn't last as long in use.

The Class 25 had cab windows of the same height; the 25 and 27 had a roof headcode box

Class 24 - 1958-1961 (BR) - 151 made - 1,160 hp - last withdrawn 1980
Class 25 - 1961-1967 (BR) - 327 made - 1,250 hp - last withdrawn 1987
Class 26 - 1958-59 (BRCW) - 47 made - 1,160 hp - last withdrawn 1993
Class 27 - 1961-62 (BRCW) - 69 made - 1,250 hp - last withdrawn 1987









 

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D6130

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These diesels hold a special place in my affections, because the 26s and 27s (along with 47s) headed the passenger services on my local line (Inverness to Aberdeen) in the early/mid 1980s when I first took a youthful interest in railways.

As I recall there were more 26s than 27s on that line - 24s were already gone, but unlike the 25s they did venture to the northern parts of Scotland with allocations at Inverness, though I do believe some 25s were in Glasgow (the experts here will set me straight on this).

Considering that only 47 were made, the Class 26 certainly seems to have made a significant impact, being among the earliest made and outlasting the other Sulzer powered Type 2s (when other low production classes have often become more of a footnote in the history of diesel traction). Similarly with the 69 Class 27s - the BRCW classes seem indeed to have had a more successful career than their much more numerous BR manufactured "siblings".

Can someone explain the timeline behind these various Type 2s - I believe the 25 was based on the initial 24s (going by the later TOPS classification for convenience), but the 26s and 27s were made by BRCW. It seems that the 25s were built longer than the others, yet didn't last as long in use.

The Class 25 had cab windows of the same height; the 25 and 27 had a roof headcode box

Class 24 - 1958-1961 (BR) - 151 made - 1,160 hp - last withdrawn 1980
Class 25 - 1961-1967 (BR) - 327 made - 1,250 hp - last withdrawn 1987
Class 26 - 1958-59 (BRCW) - 47 made - 1,160 hp - last withdrawn 1993
Class 27 - 1961-62 (BRCW) - 69 made - 1,250 hp - last withdrawn 1987









Not all of the class 25s has windscreens the same height. D5151-5232 (25 001-082) and D7568-97 (25 218-247) were originally built with corridor connections, resulting in a smaller central windscreen similar to that on classes 24, 26 and 27).

Also the later class 24s, D5114-5149 (24 114-149) had headcode boxes instead of the disc indicators used on the earlier locos. The original Inverness allocation (D5114-32) also originally had mechanical token exchangers fitted on the driver's side of the cabs.
 

randyrippley

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As no-one else better placed has answered...........here goes
Class 24 and 26 were both modernisation plan prototype type 2 locos, both using the Sulzer 6LDA28 diesel. The 24 were a BR design, the 26 a competing BRCW design. 24 used AEI electricals, the 26 Crompton Parkinson.
20 of each were ordered, but before they were delivered BR panicked over eliminating steam and ordered more, untested and unproved. There were detail differences between the initial 20 of each class and the follow-on batches
While these were being built, Sulzer came up with an uprated 6 cylinder engine, the 6LDA28-B and future orders used these, with machines so fitted becoming classes 25 and 27. Class 33 was essentially the same BRCW body with an 8-cylinder engine. One difference in the 27 was that electricals from GEC were used, seemingly because Crompton Parkinson were unable to deliver quickly enough to satisfy both simultaneous 27 and 33 production. In use the Crompton equipment proved more reliable.
Class 25 became the BR standard type 2, class 27 became a second source - possibly as a threat in case the BR trade unions played up. Cosmetic details existed between 26/27, and between and within 24/25. The 25 was built at three different BR workshops and also at Beyer Peacock, each site having its own build (and batch) differences, even to the point of some machines using a completely different bodyshell. Different sites also used different models of AEI electricals, and over the seven year production there was major evolution of equipment, to the point where different production batches were unable to work in multiple.
For details of the differences read the Derbysulzers site - its too much to post here.

One curiosity was the late survival of some of the 26s. They appear to have been selected for retention due to the superiority of the Crompton Parkinson electricals. The ones that lasted all received a mid-life upgrade/extension with reconditioned 6LDA28-B engines transplanted from scrapped 25s, though downrated to match the original 6LDA28 power settings for reliability
 
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GRALISTAIR

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The series 26001-007 were hard to get for haulage of course as they were fitted with Slow Speed Control for Merry go round working to power station. I did get them all for haulage but only because of railtours.
 

randyrippley

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One other point - the 26 and 27 weren't originally based in Scotland. From new they went to the Eastern and Midland regions, from where they were supplanted by later batches of 25s. They were eventually consolidated in Scotland to replace the self-destructing class 17 and 21 fleets. Notionally the 17s were replaced by a late build of 20s, but on the ground it didn't work that way.
 

Richard Scott

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One curiosity was the late survival of some of the 26s. They appear to have been selected for retention due to the superiority of the Crompton Parkinson electricals. The ones that lasted all received a mid-life upgrade/extension with reconditioned 6LDA28-B engines transplanted from scrapped 25s, though downrated to match the original 6LDA28 power settings for reliability
If they did they certainly lost the intercooler so would have been the lower 1160hp output as stated. Think Crompton Parkinson electricals took some beating. The 26, 33 and 45 designs seemed pretty bullet proof as far as electrical machines were concerned.
 

david1212

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I've also heard 27s referred to as 'Lawnmowers'

I've never heard that one ....


Do correct me if wrong but I'm sure I read somewhere that the BRCW price for the 26's & 27's was less than the actual cost price, not necessarily the estimated price, for the 24's and 25's but government policy dictated that BR workshops should be given orders over private suppliers.

Various comments on the 27's in the Highlands thread in this section state that despite the 26's having less power than the 27's they were actually the better performing locomotives on the West Highland line.
 

D6130

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One other point - the 26 and 27 weren't originally based in Scotland. From new they went to the Eastern and Midland regions, from where they were supplanted by later batches of 25s. They were eventually consolidated in Scotland to replace the self-destructing class 17 and 21 fleets. Notionally the 17s were replaced by a late build of 20s, but on the ground it didn't work that way.
Class 26 nos. D5320-46 and class 27 nos. D5347-69 were originally based in Scotland (at Inverness and Eastfield respectively) and spent all their working lives there. The others wandered up to join them at various times between 1960 and 1970.
 

Gloster

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Without doing an exhaustive check, it seems that D5300-5319 went new to Hornsey: a few went to Scotland in spring 1960, but most went to Finsbury Park at the same time until they moved to Scotland in the autumn. D5330-5335 went to new to Scotland but very soon were reallocated to Hornsey for the briefest period before returning. (It is questionable whether all, or even any, of these six actually went south. Or maybe they never came north in the first place.) Source: Shed by Shed, Part Seven.

D5370-5379 went new to Thornaby (possibly on loan from Leicester) and the rest went new to Cricklewood; the Thornaby locos went (back) to Leicester in 1965 and all remained at Midland main line depots until they went to Scotland around 1968. (There may be exceptions, but I am not going to go through the whole of Shed by Shed.)
 
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Not all of the class 25s has windscreens the same height. D5151-5232 (25 001-082) and D7568-97 (25 218-247) were originally built with corridor connections, resulting in a smaller central windscreen similar to that on classes 24, 26 and 27).
Really? I've never seen a photo of one with corridor connectors?
 

xotGD

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Without doing an exhaustive check, it seems that D5300-5319 went new to Hornsey: a few went to Scotland in spring 1960, but most went to Finsbury Park at the same time until they moved to Scotland in the autumn. D5330-5335 went to new to Scotland but very soon were reallocated to Hornsey for the briefest period before returning. (It is questionable whether all, or even any, of these six actually went south. Or maybe they never came north in the first place.) Source: Shed by Shed, Part Seven.

D5370-5379 went new to Thornaby (possibly on loan from Leicester) and the rest went new to Cricklewood; the Thornaby locos went (back) to Leicester in 1965 and all remained at Midland main line depots until they went to Scotland around 1968. (There may be exceptions, but I am not going to go through the whole of Shed by Shed.)
I never knew that Thornaby had an allocation. Has anyone seen any photos of them working in the north east?
 

ac6000cw

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Various comments on the 27's in the Highlands thread in this section state that despite the 26's having less power than the 27's they were actually the better performing locomotives on the West Highland line.
The 26's had different electrical equipment (Crompton Parkinson versus GEC for the 27s) and were probably lower geared (80mph top speed versus 90mph for the 27's), which may well have given them better lower speed acceleration - much more useful on the West Highland lines.
 

Western 52

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The 26s were competent with up to 9 coaches on the Far North line. Not bad for locos with only 1160hp! Their lower gearing would have helped of course and no need for speed on that line!
 

D6130

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The 26's had different electrical equipment (Crompton Parkinson versus GEC for the 27s) and were probably lower geared (80mph top speed versus 90mph for the 27's), which may well have given them better lower speed acceleration - much more useful on the West Highland lines.
In fact the 26s were originally restricted to 75 mph, but their maximum was tweaked up to 80 in the mid-'seventies, following withdrawal of the Inverness 24s - IIRC, primarily to aid timekeeping on the double-headed Glasgow/Edinburgh-Inverness services.
 

Richard Scott

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I've never heard that one ....


Do correct me if wrong but I'm sure I read somewhere that the BRCW price for the 26's & 27's was less than the actual cost price, not nec
Various comments on the 27's in the Highlands thread in this section state that despite the 26's having less power than the 27's they were actually the better performing locomotives on the West Highland line.

The 26's had different electrical equipment (Crompton Parkinson versus GEC for the 27s) and were probably lower geared (80mph top speed versus 90mph for the 27's), which may well have given them better lower speed acceleration - much more useful on the West Highland lines.
The power at rail for a 26 is 900hp and a 27 933hp so not enough in it to make it swing in favour of the 27. The lower gearing of the 26 will inevitably swing performance in its favour.
 

delt1c

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The 26's had different electrical equipment (Crompton Parkinson versus GEC for the 27s) and were probably lower geared (80mph top speed versus 90mph for the 27's), which may well have given them better lower speed acceleration - much more useful on the West Highland lines.
But the 26’s weren’t used regularly on the West Highland line that was a mainstay of the 27’s
 

Cheshire Scot

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Various comments on the 27's in the Highlands thread in this section state that despite the 26's having less power than the 27's they were actually the better performing locomotives on the West Highland line.
I think those comments were more of a generalisation and not WHL specific, and as noted, class 26 visits to the West Highland were very rare which would make any comparison of actual performance very difficult.

One thing which did puzzle me, particularly in view of the respective gearing and tractive effort, was that on freight on the West Highland class 27s were permitted a heavier trailing load than class 26 (or class 25) for which the same load as a class 20 or class 24 applied, around 60 tonnes less than the 27. Equally puzzling was class 37 only being permitted loads around 40 tonnes (trailing) heavier than class 27, although in practice class 37s with (or close to) maximum load achieved slightly faster actual running times than the class 27 with a full load, with both being severely constrained by the line speeds as well as the gradients.

Respective loads for the Crianlarich to Corpach timber train were 13 wagons for cl20,24,25,26, for cl27 16 wagons and for 37 17 wagons. The load for a pair of class 20s was constrained to 20 wagons by the length limit even with a modest derogation permitting an additional 3 SLU.

I recall once checking what loads were permitted on the Highland Main Line and my memory is that each class moved up one level i.e. cl 26 load on HML was the same as 27 on WHL and cl27 load on HML was the same as cl 37 on WHL. The most severe gradients on HML are slightly less severe than those on WHL and when combined with the tighter curvature on the WHL where the sharp curves caused significant 'drag' on the back end of the train e.g. when the loco was on the final leg of an S bend the rear flanges would still be exerting force in the opposite direction. Maybe somebody has the load tables from the late 70's/early 80's to give some actual figures and comparisons, mine are long gone.
 

Inversnecky

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I think those comments were more of a generalisation and not WHL specific, and as noted, class 26 visits to the West Highland were very rare which would make any comparison of actual performance very difficult.

So 26s and 27s were based at Inverness, but 27s were more on the line to the west and north, and 26s more to the east.
 

D6130

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So 26s and 27s were based at Inverness, but 27s were more on the line to the west and north, and 26s more to the east.
No.....generally speaking - pre 1980 - the 26s and 24s were used (mainly singly, but not always) on the Kyle and Far North lines and (usually double-headed) on the Inverness-Glasgow/Edinburgh services, while the Inverness-Aberdeen line was the stronghold of the Swindon class 120 cross-country DMUs. From the late 'seventies, class 47s started to appear at Inverness in ever greater numbers and began to supplant the 26s on the Glasgow and Edinburgh trains. From the May 1980 timetable the Inverness-Aberdeen services went over to loco-hauled mark 1 stock (most of which was older than the DMUs it replaced) and the first small tranche of 27s were transferred from Eastfield to Inverness to work those trains. In practice, they were worked by a mixture of 26s, 27s and 47s, depending on what was available, as the 27s which moved North were not in the best condition (Eastfield obviously wanted rid of them!).
 

randyrippley

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One of the more curious 26 workings was toward the end of their lives. There was a daily early evening northbound parcels through Lancaster, can't remember if it started at Crewe or Preston.
Always seemed to be an oddball rostering
 
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