Why were the class 27 built?

[randyrippley]

Building the class 27 fleet has always seemed a strange decision to me.
When the first ones were delivered, class 33 production was winding down and the superiority of type 3 power and ETH must have been obvious. Equally obvious was that the class 25, built in BR's own workshops was destined to be the standard type 2.
It seems to me that building the 27s as 33s would have given a more powerful and more usable (and incidentally more reliable) fleet. Its not as if the 27s were needed for a specific task: when new they were scattered around the Midland and Eastern regions on freight work, only going to Scotland to replace the class 21. And its not as if the boilers were needed: their work in England was mainly freight, while the fact that many 25s were delivered without boilers shows the 27s weren't needed for steam heat duties.
Besides which building them as 33 would have saved the cost of a set of tooling. There would have been a larger fleet of 33, and one fewer class to worry about for spares logistics.
If BR really felt they needed those type 2 locos, why not simply build them as more-standard class 25?

Anyone got an answer?

 

[alistairlees]

Building the class 27 fleet has always seemed a strange decision to me.
When the first ones were delivered, class 33 production was winding down and the superiority of type 3 power and ETH must have been obvious. Equally obvious was that the class 25, built in BR's own workshops was destined to be the standard type 2.
It seems to me that building the 27s as 33s would have given a more powerful and more usable (and incidentally more reliable) fleet. Its not as if the 27s were needed for a specific task: when new they were scattered around the Midland and Eastern regions on freight work, only going to Scotland to replace the class 21. And its not as if the boilers were needed: their work in England was mainly freight, while the fact that many 25s were delivered without boilers shows the 27s weren't needed for steam heat duties.
Besides which building them as 33 would have saved the cost of a set of tooling. There would have been a larger fleet of 33, and one fewer class to worry about for spares logistics.
If BR really felt they needed those type 2 locos, why not simply build them as more-standard class 25?

Anyone got an answer?

I think it was to provide entertainment for enthusiasts in the 1970s and 1980s

 

[xotGD]

I think it was to provide entertainment for enthusiasts in the 1970s and 1980s

And work for Scottish fire fighters!

 

[alistairlees]

And work for Scottish fire fighters!

Indeed. At one point there were so many ‘singed’ examples that it’s difficult to know how the fire service has anything to do these days...

 

[pdeaves]

When the first ones were delivered, class 33 production was winding down

Is that correct? 27s had gangway doors while 33s didn't. As doors fell out of favour I would have thought the 27 came first. I'm not a traction history expert, though!

 

[CW2]

With hindsight, the question "Why did they build any / so many of class xx" is one which could be posed of many of the various BR Diesel locos. Given that BR wanted to deliver the locos in a pretty short timescale, it was important to have several production lines open simultaneously. Arguably if the Modernisation Plan could have been carried out over a longer period then a more rational diesel building programme could have been devised. In this specific instance, building more class 33s would have been no help as their SR voltage electric train heating was incompatible with anything north of the Thames. A boiler-fitted 33 might have been too tight a squeeze within the weight / gauge limits. 27s were marginally more powerful than 25s, which were mostly restricted to running round in pairs. Certainly BR got its money's worth out of the push-pull 27s. They were thrashed into the ground.

 

[Journeyman]

In this specific instance, building more class 33s would have been no help as their SR voltage electric train heating was incompatible with anything north of the Thames. A boiler-fitted 33 might have been too tight a squeeze within the weight / gauge limits.

Yeah, the 33's more powerful engine only fits in the bodyshell because there's no boiler.

 

[Taunton]

The stated (at the time) reason why the 33s had the larger engine was because there was space for it by the elimination of the boiler, them being ETH-only. This was a Southern Region initiative, nobody else foresaw the end of steam heating, and even on the Southern at first it caused difficulties, and Class 24 had to be loaned for a while in winter to be coupled inside a 33 to steam heat the train.

BR did not even have the capacity to build all the Class 25s, a later batch had to be subcontracted out to Beyer Peacock, and building the 27s by BRCW used the same standard parts as the 33s. This can be readily seen by their longevity despite BRCW going out of business pretty much when they were completed, but unlike North British they had used all standard components instead of making them in house.

The 27s did prove to be very reliable locos, the Scottish Region particularly took to them of course, they had both (also the 24/26 versions as well) and always favoured the BRCW locos. They were thrashed for some 20 years on the gradients of the West Highland line with very substantial loads, passenger and freight, and an Eastfield crew I spoke to described how you drove them mainly on the ammeter, just keeping under the red line, and they would run for hours like that. Later they became the 1970s power on the Edinburgh high-speed push-pull of course, and ran well on that, if you discount frippery like the Deutz auxiliary diesel put in the 27/2 engine room to provide ETH (unusually, on this service the coaching stock gave more trouble than the locos). They were driven the same way on the gauge, but at very different speeds, commonly getting up to 100mph by the end of the run.

If there's one line in Britain you didn't put unreliable boiler locos on, it was the West Highland in winter, the coldest and the furthest from support, where they were the preferred power for two decades, steam heat to the end. The Eastfield and Fort William firemen were boiler experts.

I wrote more about the 27s on the push-pull here

ScotRail Express in the 1980s

I'm wondering what the service frequency/stopping patterns of the 47/7 push-pull ScotRail Express services were in the 1980s? If I remember correctly from the logo used on window stickers, the ScotRail Express routes were considered as Glasgow Queen Street - Edinburgh Waverley and Glasgow Queen...

www.railforums.co.uk

 

[edwin_m]

Is that correct? 27s had gangway doors while 33s didn't. As doors fell out of favour I would have thought the 27 came first. I'm not a traction history expert, though!

The two classes seem to have been pretty much contemporary according to the dates on Wikipedia (yes I know). If end doors were of any use anywhere, they certainly weren't on the relatively short runs on the Southern. I'd take a guess that someone on the Southern got a fleet built to their own specific requirements, but at least they were a variation on designs used elsewhere rather than being totally different like what the Western wanted!

 

[Richard Scott]

Would have thought the Crompton electrical equipment was vastly superior and more reliable than the GEC used in the 27? Would've made more sense just to build more 26s with uprated engine and re-geared bogies, I'm fairly sure the electrical equipment was easily capable of dealing with an extra 90hp? I expect there was some thing to doing with using more than one supplier though? Seems BR ended up with a huge mix of classes with associated costs of various spares. Similar thing with the 45 and 46, where the later build (46) used inferior electrical equipment.

 

[randyrippley]

.............. building more class 33s would have been no help as their SR voltage electric train heating was incompatible with anything north of the Thames. .................

Surely that's incorrect? They were used with mk1 and mk2 stock with standard ETH gear. When the 33s were built there was already an ETH conversion program running on the mk1 fleet, and the mk2 was in the process of design

 

[Richard Scott]

Surely that's incorrect? They were used with mk1 and mk2 stock with standard ETH gear. When the 33s were built there was already an ETH conversion program running on the mk1 fleet, and the mk2 was in the process of design

33s could heat any mark 1 or 2a/b/c. They were incompatible with air con stock at MA sets didn't like the 750V feed, needing at least 800V.

 

[CW2]

It was mooted at one point that the 33s (or some of them at least) would migrate to Scotland to replace the 27s on various passenger and West Highland freight services. The issue of the incompatible ETH system (with the sleepers going over to Mk3s) led first to the constructio of ETHELs (converyed from class 25s) and subsequently the 37/4 conversions. The class 33's 85mph maximum speed also rendered them unsuitable for some class 1 passenger work (though not the West Highland Line).
A 100mph 800v ETH class 33 would have been an ideal loco, but presumably the higher maximum speed would have meant lower initial acceleration.

 

[Taunton]

Is that correct? 27s had gangway doors while 33s didn't. As doors fell out of favour I would have thought the 27 came first. I'm not a traction history expert, though!

Diesel loco gangway doors, only for use between locos and not into the coaches, were provided principally so when locos were working in multiple the fireman on the front loco could go back and attend to the train heating boiler in the rear loco. Because of the design of the pipework only the boiler nearest the train could be used. Something the 33s didn't need.

 

[delt1c]

If I am not mistaken the 33,s had a higher RA than the 27’s

 

[pdeaves]

The two classes seem to have been pretty much contemporary according to the dates on Wikipedia (yes I know). If end doors were of any use anywhere, they certainly weren't on the relatively short runs on the Southern. I'd take a guess that someone on the Southern got a fleet built to their own specific requirements, but at least they were a variation on designs used elsewhere rather than being totally different like what the Western wanted!

Diesel loco gangway doors, only for use between locos and not into the coaches, were provided principally so when locos were working in multiple the fireman on the front loco could go back and attend to the train heating boiler in the rear loco. Because of the design of the pipework only the boiler nearest the train could be used. Something the 33s didn't need.

I see, a 27 is a 33 with added doors, rather than a 33 is a 27 with doors removed.

 

[Helvellyn]

Would have thought the Crompton electrical equipment was vastly superior and more reliable than the GEC used in the 27? Would've made more sense just to build more 26s with uprated engine and re-geared bogies, I'm fairly sure the electrical equipment was easily capable of dealing with an extra 90hp? I expect there was some thing to doing with using more than one supplier though? Seems BR ended up with a huge mix of classes with associated costs of various spares. Similar thing with the 45 and 46, where the later build (46) used inferior electrical equipment.

I believe Crompton Parkinson were struggling to keep up supply, which is why the Class 27s switched to GEC electrical equipment and the Class 46s to Brush.

The Class 33s were a bespoke design for the Southern, which ended up being one of only three Type 3s which weren't part of the original Modernisation plan power types. (The other two being the Class 35 Hymek for the Western Region and what ended up as the go anywhere Class 37, originally ordered for the Eastern Region).

As others have said, eliminating steam heat was something the Southern could do due to so few loco hauled services compared to other regions. A true ETH fitted mixed traffic loco worked well, but it is only hindsight that says they could have gone elsewhere. The Class 27 was more an extension of Class 26 (even the numbering followed straight on - first Class 27 being D5347, just as the first Class 46 was D138).

Could some have been transferred to Scotland in the mid-1980s? Possibly, but by that time the Class 37s had migrated North in not insignificant numbers and the benefit of converting the Class 37/4s was that a Driver could also drive a non-ETH example rather than have to learn two distinct types.