Type 2 withdrawals - why were 20's retained over class 25s?

[norbitonflyer]

Given a large number of 47s were ultimately built at Crewe Works it might be that BR was already considering a Type 4 that could be built in house as well as by a third party. I wonder if BRCW and EE maybe didn't make the right noises if any unofficial soundings took place?

EE's offering as a "Type 4 and a half" prototype had the by-then unfashionable bonneted arrangement, bacuase they already had the tooling, but it would (and did) need some internal rearrangement to make the flat-fronted design thatn became the Class 50.

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(this had in fact been done in Germany where they had encountered the same problem, but the smaller British loading gauge would have called for a steeper angle and the engineers were not happy about the possible effects on the oil circulation).

I understand the smaller British loading gauge led to other compromises as well. The German V200s, on which the Class 42 and 43 were based, were designed so that they could be fitted with either Maybach or Mercedes engines*, and either Voith or Mekydro transmissions, and all permutations were possible (even two different engines in the same locomotive). The more restrictive loading gauge in the UK meant that such there was not room to accomodate such interchangeability, so an MAN engine could not be swapped for a Maybach, and so they became two distinct TOPS classes. Given the success of the combination in the Westerns, it seems a shame there was no opportunity to try a Maybach/Voith combination in a Warship.

*Five V200s were fitted with MAN engines but replaced early on, making it even more strange that BR ordered so many locos with that make of engine - not only the thirty-eight Class 41 and 43 Warships, but also the Class 21s and 22s (fifty-eight of each), and the Blue Pullmans (five units). The fact that they couold be built in the UK, as the North British Company had a licence from MAN, probably swung it.

 

[43096]

310 by Brush and 202 by BR at Crewe.

Class 86s were built by BR at Doncaster (40) and English Electric at Newton-le-Willows (60), but they were ordered a few years after the 47s so if EE had been keen on fully building Type 4s in house they maybe eased off that.

The 86s were originally ordered as 60 Doncaster build and 40 EE, but 20 locos (E3141-60) were switched to Vulcan Foundry.

 

[Pigeon]

I understand the smaller British loading gauge led to other compromises as well. The German V200s, on which the Class 42 and 43 were based, were designed so that they could be fitted with either Maybach or Mercedes engines*, and either Voith or Mekydro transmissions, and all permutations were possible (even two different engines in the same locomotive). The more restrictive loading gauge in the UK meant that such there was not room to accomodate such interchangeability, so an MAN engine could not be swapped for a Maybach, and so they became two distinct TOPS classes. Given the success of the combination in the Westerns, it seems a shame there was no opportunity to try a Maybach/Voith combination in a Warship.

That wasn't the loading gauge; the Warship was designed to have that same interchangeability, but NBL got themselves into a mess putting their batch together and asked for various modifications to the drawings to be allowed, which was granted in order to avoid wasting any more time. So the mountings in NBL's batch weren't in the same place as in Swindon's batch and the interchangeability didn't happen. It apparently wouldn't have been tremendously difficult to modify the NBL machines so as to make it possible, but they were having enough difficulty trying to get the repairs system for the Warships working as it was supposed to already, and didn't need the extra complication.

*Five V200s were fitted with MAN engines but replaced early on, making it even more strange that BR ordered so many locos with that make of engine - not only the thirty-eight Class 41 and 43 Warships, but also the Class 21s and 22s (fifty-eight of each), and the Blue Pullmans (five units). The fact that they couold be built in the UK, as the North British Company had a licence from MAN, probably swung it.

It was what made the WR diesel-hydraulic project possible in the first place - that NBL happened to already have a licence from MAN which happened to cover that engine, combined with NBL being in a depressed area which the government wanted to allocate work to, got around the political objections to "German engines" and so removed what was at that point the critical obstacle.

 

[s491]

DP2 was effectively a Class 50 in a Deltic like body shell

Ignoring the bodyshell, DP2 was close to a Class 50 but somewhat simpler. Had EE been allowed to just transplant DP2 into the 50's body add ETS and then go "job well done", then the 50 would have been a much more reliable animal off the blocks. But BR had a wish list as long as your arm of things it wanted adding......only for that stuff to be removed during refurbishment as it was a pain in the backside.

 

[Richard Scott]

Ignoring the bodyshell, DP2 was close to a Class 50 but somewhat simpler. Had EE been allowed to just transplant DP2 into the 50's body add ETS and then go "job well done", then the 50 would have been a much more reliable animal off the blocks. But BR had a wish list as long as your arm of things it wanted adding......only for that stuff to be removed during refurbishment as it was a pain in the backside.

I know we're drifting massively here (do we need a thread split along lines of 'with hindsight what diesels should BR have ordered'?) but Achilles heel of a 50 was the generator, I believe same as used in DP2, was it a problem in DP2 or not? If not why not?

 

[35B]

I know we're drifting massively here (do we need a thread split along lines of 'with hindsight what diesels should BR have ordered'?) but Achilles heel of a 50 was the generator, I believe same as used in DP2, was it a problem in DP2 or not? If not why not?

I think there were two separate items. The additional complexity of the design, removed at refurbishment, was about the basic design. The generator was an issue, but I believe less so - hence the decision to retain them rather than replace them with alternators.

I'd be curious to know if DP2 lasted long enough to trigger that kind of issue - not to mention that it was given special treatment as a prototype for much of its life

 

[Harpo]

Handling technique was clearly a factor for class 50 generators judging by the instruction on preserved 50s to only move the power controller to off after the amps have run right back. Many Waterloo-Exeter runs felt particularly as though the power controller had become an on/off switch.

 

[s491]

I think there were two separate items. The additional complexity of the design, removed at refurbishment, was about the basic design. The generator was an issue, but I believe less so - hence the decision to retain them rather than replace them with alternators.

I'd be curious to know if DP2 lasted long enough to trigger that kind of issue - not to mention that it was given special treatment as a prototype for much of its life

1966-68 we were right on the cusp of having the tech for alternator on locos. Kestrel was the first in the UK in 1967 and that was the bleeding edge of tech for locos. DP2 had a generator as no one was brave enough to fit an alternator, let alone with the 50s. However, when it came to refurbishment you may ask why they didn't install an alternator then - a class 56 alternator would probably have fitted a treat. But when BR did the numbers they couldn't warrant the money spend.....so it never happened.

 

[43096]

1966-68 we were right on the cusp of having the tech for alternator on locos. Kestrel was the first in the UK in 1967 and that was the bleeding edge of tech for locos. DP2 had a generator as no one was brave enough to fit an alternator, let alone with the 50s. However, when it came to refurbishment you may ask why they didn't install an alternator then - a class 56 alternator would probably have fitted a treat. But when BR did the numbers they couldn't warrant the money spend.....so it never happened.

BR could and should have gone with alternators on the 50s from new - GM built its first SD40s and GE the first U30Cs in 1966, both were 3000hp locos featuring alternators. If BR was throwing the technology "kitchen sink" at the 50s, it seems odd they didn't go the whole way and go for alternators.

 

[35B]

1966-68 we were right on the cusp of having the tech for alternator on locos. Kestrel was the first in the UK in 1967 and that was the bleeding edge of tech for locos. DP2 had a generator as no one was brave enough to fit an alternator, let alone with the 50s. However, when it came to refurbishment you may ask why they didn't install an alternator then - a class 56 alternator would probably have fitted a treat. But when BR did the numbers they couldn't warrant the money spend.....so it never happened.

That’s really interesting - I knew that alternators were new technology, but not how new. However, what was interesting me was whether DP2 had suffered generator issues

 

[Acathater]

I know we're drifting massively here (do we need a thread split along lines of 'with hindsight what diesels should BR have ordered'?) but Achilles heel of a 50 was the generator, I believe same as used in DP2, was it a problem in DP2 or not? If not why not?

And the rheostatic brakes......and the hydrocyclone air filters....

 

[Richard Scott]

And the rheostatic brakes......and the hydrocyclone air filters....

I should have added these were addressed at refurbishment but generator was not, which I would gave thought was the biggest issue?

 

[s491]

That’s really interesting - I knew that alternators were new technology, but not how new. However, what was interesting me was whether DP2 had suffered generator issues

Sorry, I was a bit brief with the explanation. Alternators as a thing go back to the late 19th / early 20th century. The problem was mainly that of waiting for high power silicon rectifiers to become reliable enough, which happened around the mid 60's.

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I should have added these were addressed at refurbishment but generator was not, which I would gave thought was the biggest issue?

Correct - but again, it was down to cost. An alternator of that size is not cheap! And when you look at the likely lifespan and maintenance required to keep the generator going vs buying 50 new alternators, it came down on just keeping the generators.

My understanding is that as long as they are well maintained - ie the brush boxes are regularly cleaned out - and you don't suddenly shut off power (unless you have to of course) the generator they will just keep on going.

 

[Harpo]

Also, as I understand it, the 50s auxilliary generator not only provides ETH but also powers other kit such as the cooling fan so is also a potential loco failure cause?

 

[s491]

Also, as I understand it, the 50s auxilliary generator not only provides ETH but also powers other kit such as the cooling fan so is also a potential loco failure cause?

There are 3 generators on a Class 50. Main, ETS and Aux. The ETS does run the engine cooling fan as well as the ETS itself.

If you were changing the main generator to an alternator then you'd change all 3 to alternators.

 

[Magdalia]

Sorry, I was a bit brief with the explanation. Alternators as a thing go back to the late 19th / early 20th century. The problem was mainly that of waiting for high power silicon rectifiers to become reliable enough, which happened around the mid 60's.

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Correct - but again, it was down to cost. An alternator of that size is not cheap! And when you look at the likely lifespan and maintenance required to keep the generator going vs buying 50 new alternators, it came down on just keeping the generators.

Another development around the mid 1960s was Brush using a dual wound alternator for auxiliaries and ETH, pioneered in D1960 and D1961, which were the last two Brush type 4s built at Loughborough and fitted from new. Replacing the auxiliary generator with the Brush dual wound alternator then became the standard way of doing ETH conversions on classes 47/4, 45/1 and 31/4.

Replacing the main generator with an alternator came much later, would the class 37/4s have been the first?

 

[s491]

Another development around the mid 1960s was Brush using a dual wound alternator for auxiliaries and ETH, pioneered in D1960 and D1961, which were the last two Brush type 4s built at Loughborough and fitted from new. Replacing the auxiliary generator with the Brush dual wound alternator then became the standard way of doing ETH conversions on classes 47/4, 45/1 and 31/4.

Replacing the main generator with an alternator came much later, would the class 37/4s have been the first?

Not quite. 41001 and 41002 were the first anything traction wise to get a split wound aux/ETS alternator on the back of a main alternator.

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BR could and should have gone with alternators on the 50s from new - GM built its first SD40s and GE the first U30Cs in 1966, both were 3000hp locos featuring alternators. If BR was throwing the technology "kitchen sink" at the 50s, it seems odd they didn't go the whole way and go for alternators.

Agreed

 

[norbitonflyer]

The first twenty Brush Type 4s (D1500-1519, later 47401-47420) were known as "generators". If alternators were not common at that time, what did D1520 onwards have?

 

[ac6000cw]

BR could and should have gone with alternators on the 50s from new - GM built its first SD40s and GE the first U30Cs in 1966, both were 3000hp locos featuring alternators. If BR was throwing the technology "kitchen sink" at the 50s, it seems odd they didn't go the whole way and go for alternators.

Nine prototype versions of the SD40 were built even earlier, in 1964-65.

(...and of course the last 10 class 85 and all the cl. 86 electrics were built with silicon diode rectifiers in the 1964-66 timeframe).

Maybe the cl.50 problem was EE not having a suitable traction alternator available at the time, or not enough space to accommodate the rectifier cabinets along with the other stuff BR wanted on the loco, like rheostatic braking?

The slightly later CP 1800 class, derived from the cl 50, I think had DC generators too.

== Doublepost prevention - post automatically merged: 15 Jan 2026 ==

The first twenty Brush Type 4s (D1500-1519, later 47401-47420) were known as "generators". If alternators were not common at that time, what did D1520 onwards have?

AFAIK, the 'generator' name was a reference to being equipped from new with an ETH generator. All class 47s were built with DC main generators. Later ETH equipped 47s were all conversions of existing locos.

 

[s491]

Nine prototype versions of the SD40 were built even earlier, in 1964-65.

(...and of course the last 10 class 85 and all the cl. 86 electrics were built with silicon diode rectifiers in the 1964-66 timeframe).

Maybe the cl.50 problem was EE not having a suitable traction alternator available at the time, or not enough space to accommodate the rectifier cabinets along with the other stuff BR wanted on the loco, like rheostatic braking?

The slightly later CP 1800 class, derived from the cl 50, I think had DC generators too.

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AFAIK, the 'generator' name was a reference to being equipped from new with an ETH generator. All class 47s were built with DC main generators. Later ETH equipped 47s were all conversions of existing locos.

Oh the 47's are a fantastic mess of options! It has long been said that there were 512 built and 512 different wiring diagrams.......

The generators had DC main, ETS and aux generators. And were quite different from the remaining production build as not withstanding the dc ETS genny, also had Westinghouse brakes plus the compressors and rad fans ran off the ETS genny!! Production 47's were D&M brakes and Serck hydrostatic rad fans.

The production lot had DC main and aux generators as built, but then when they got ETS fitted to avoid having to find space for another alternator, used a split wound alternator and junked the aux generator. There were also two different types of main generator for series-parallel and parallel wired traction motored machines. And so it goes on.....almost endlessly. Although the 512 for 512 is said with tongue in cheek, as an example MT222 (Class 47 wiring schematics) ran out of letters in the alphabet for different version of the auxiliary circuit systems!!!

 

[Magdalia]

The first twenty Brush Type 4s (D1500-1519, later 47401-47420) were known as "generators". If alternators were not common at that time, what did D1520 onwards have?

D1520 onwards had no ETH when they were built, apart from D1960 and D1961. All of the others were conversions with the dual wound alternator replacing the auxiliary generator.

 

[Helvellyn]

The generators had DC main, ETS and aux generators. And were quite different from the remaining production build as not withstanding the dc ETS genny, also had Westinghouse brakes plus the compressors and rad fans ran off the ETS genny!! Production 47's were D&M brakes and Serck hydrostatic rad fans.

Always surprised me that when TOPS renumbering happened they weren't their own sub-class, or became Class 48 given that class had been freed up by the re-engining of D1702-D1706 with standard Class 47 engines (which was strange in itself that apart from the engine these 5 probably had more in common with the 487 production 47s than the 20 Generators).

 

[Acathater]

Always surprised me that when TOPS renumbering happened they weren't their own sub-class, or became Class 48 given that class had been freed up by the re-engining of D1702-D1706 with standard Class 47 engines (which was strange in itself that apart from the engine these 5 probably had more in common with the 487 production 47s than the 20 Generators).

The rules said there had to be a minimum wait period before a class number was reused - and that the old class had to be totally extinct.
In the case of the 48s the actual locos still existed even if rebuilt so weren't extinct, and the requisite time (I can't remember if 10 or 20 years) hadn't passed anyway

 

[Taunton]

BR could and should have gone with alternators on the 50s from new - GM built its first SD40s and GE the first U30Cs in 1966, both were 3000hp locos featuring alternators. If BR was throwing the technology "kitchen sink" at the 50s, it seems odd they didn't go the whole way and go for alternators.

Actually the first GM alternator loco was a GM trial unit in 1960, that they built in a traded-in F7 unit. They then did some more in an SD35 variation, sometimes mistakenly described as loco number GM 434, in fact it was 6 locos 434A to 434F. GM designed and built the alternators themselves.

USA diesel loco expert Louis A Marre wrote that the main driver for alternators was, as loco power progressively rose, the physical space required for an associated DC generator became too much for the confines of the loco body. The SD35 was 2,500 hp, with 3,000 hp coming in the SD40 they had to overcome this, which the reduced size of an equivalent alternator did. Notably the automotive side of GM was doing the same thing, at the same time, for car and truck auxiliary electrics, substituting engine-driven generators with alternators. For the "baby" GM loco, the GP38, 2,000 hp, where this wasn't an issue, they continued with generators for a while, and in 1971 only offered alternators as an option

 

[matchmaker]

Ignoring the bodyshell, DP2 was close to a Class 50 but somewhat simpler. Had EE been allowed to just transplant DP2 into the 50's body add ETS and then go "job well done", then the 50 would have been a much more reliable animal off the blocks. But BR had a wish list as long as your arm of things it wanted adding......only for that stuff to be removed during refurbishment as it was a pain in the backside.

And the thing that EE wanted but BR didn't was an alternator instead of a DC generator!