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

[Helvellyn]

Being fair (and I'm a cl.33 fan!), the 33 is shorter, has simpler bogies with fewer axles and traction motors, and no steam-heat boiler plus water tank. I suspect those differences would account for a lot of the weight difference.

It came up in another thread recently that in fact the Southern Region actually wanted to buy 'their' Type-3 loco from EE (who came up with suitable design), but it was decided 'higher up' in BR/BTC to award the contract to BRCW.


AFAIK, BRCW saw which way the wind was blowing in terms of potential orders from a monopoly, state-owned railway with its own 'new build capable' workshops to keep open for political reasons and sensibly decided to exit the railway business.

Of course if Lion had been taken further things might have worked out a bit differently.

 

[Acathater]

Being fair (and I'm a cl.33 fan!), the 33 is shorter, has simpler bogies with fewer axles and traction motors, and no steam-heat boiler plus water tank. I suspect those differences would account for a lot of the weight difference.

It came up in another thread recently that in fact the Southern Region actually wanted to buy 'their' Type-3 loco from EE (who came up with suitable design), but it was decided 'higher up' in BR/BTC to award the contract to BRCW.


AFAIK, BRCW saw which way the wind was blowing in terms of potential orders from a monopoly, state-owned railway with its own 'new build capable' workshops to keep open for political reasons and sensibly decided to exit the railway business.

It's my belief that BRCW only got the main type 2 orders as a kind of threat to the BR workshop staff - a kind of "if you go on strike we can outsource production to this design rather than the 24/25s"

 

[Trainman40083]

Reworked 46s, not 45s. 45 a totally different machine and vastly superior for many reasons.

Indeed, the 47401 batch were originally intended to be more 46s.

 

[Acathater]

Of course if Lion had been taken further things might have worked out a bit differently.

It seems that by the time Lion came into service BRCW had already decided to pull the plug, and the decision had already been made within BR to use the Sulzer/ Brush combination. And if Lion had been developed - you'd have ended up with a Sulzer/AEI combination which based on the reliability of the 27s may have been worse than the Sulzer/Brush 47s

 

[Richard Scott]

Indeed, the 47401 batch were originally intended to be more 46s.

Oddly, though, 47401-420 had electric fans (like 45s) rather than hydrostatic of all other 47s (like 46s).
We drifting off original topic here?!!

 

[Magdalia]

The 33 & 47 came about ten years after the pilot designs

The Birmingham RCW Type 3 first order was placed in late 1957, in association with the Kent Coast electrification. It was reported in Trains Illustrated in January 1958 and Railway Observer in February 1958. Birmingham RCW got the order because they could meet the Southern Region specification for a 1300-1600hp loco with 18 tons axle load, air brakes and ETH.

It came up in another thread recently that in fact the Southern Region actually wanted to buy 'their' Type-3 loco from EE (who came up with suitable design), but it was decided 'higher up' in BR/BTC to award the contract to BRCW.

In autumn 1957 English Electric did not have a design that met the Southern Region specification. Having missed out on the order they went away and designed their Type 3 that became class 37, getting their first orders early in 1959.

Indeed, the 47401 batch were originally intended to be more 46s.

The BR Type 4 order was originally 137 locos with Crompton Parkinson Electricals and 66 with Brush electricals. But Crompton Parkinson delivered late so 10 locos were switched to Brush in 1961. Around that time Brush were acquired by Hawker Siddeley and they borrowed aeroplane technology to design the Brush Type 4 as a hybrid of the BR Type 4 and the prototype Falcon on Co-Co bogies. Contemporary sources sometimes refer to the Brush Type 4s as Hawker Siddeleys. The bit I have not been able to work out is how there got to be 20 Brush Type 4s not just the 10 switched from Crompton Parkinson.


.

 

[Richard Scott]

The BR Type 4 order was originally 137 locos with Crompton Parkinson Electricals and 66 with Brush electricals. But Crompton Parkinson delivered late so 10 locos were switched to Brush in 1961. Around that time Brush were acquired by Hawker Siddeley and they borrowed aeroplane technology to design the Brush Type 4 as a hybrid of the BR Type 4 and the prototype Falcon on Co-Co bogies. Contemporary sources sometimes refer to the Brush Type 4s as Hawker Siddeleys. The bit I have not been able to work out is how there got to be 20 Brush Type 4s not just the 10 switched from Crompton Parkinson.


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There were then supposed to be 127 45s and 76 46s (as they became) but last 20 were switched to 47s hence ended up with 127 45s, 56 46s and 20 47s.

 

[Acathater]

There were then supposed to be 127 45s and 76 46s (as they became) but last 20 were switched to 47s hence ended up with 127 45s, 56 46s and 20 47s.

Is that definite? Statements I've seen elsewhere are that the whole lot were intended to be 45s, the 46s were only ordered when it was realised that Crompton-Parkinson couldn't keep up with deliveries. Furthermore that the "last 20" were an extra 20 that were switched prior to build

 

[The Crab]

Hindsight would dictate 500 EE Type 4s but with alternators rather than generators. If must be Sulzer then a reworked 45 would be the best bet.

Surely 2000hp wasn't enough?

 

[35B]

Surely 2000hp wasn't enough?

The 45s were 2,500hp

 

[The Crab]

The 45s were 2,500hp

But the "40s" weren't. 40s were EE4, 45s were Peaks.

 

[Acathater]

Surely 2000hp wasn't enough?

that seems to be a key point in the decision making - BR appears to have believed that EE couldn't build a 2500hp diesel, so went with Sulzer as first preference

 

[35B]

But the "40s" weren't. 40s were EE4, 45s were Peaks.

Yes, but uprated EE engines were already being toyed with at this time - engine development was moving rapidly.

The role of manufacturing capacity and cost also need thinking about.

 

[GRALISTAIR]

Reliability , reliability and reliability. I never got excited over Rats but 20s (type 1s) I did.

 

[Harpo]

that seems to be a key point in the decision making - BR appears to have believed that EE couldn't build a 2500hp diesel, so went with Sulzer as first preference

DP2 and 47s are very close contemporaries.

 

[Sir Felix Pole]

that seems to be a key point in the decision making - BR appears to have believed that EE couldn't build a 2500hp diesel, so went with Sulzer as first preference

J.F. Harrison , CME of the LMR, disliked EE after the disappointing performance of Cl. 40s on the WCML, barely being able to beat steam timings. He was one of the main instigators of the Sulzer relationship.

 

[Trainman40083]

DP2 and 47s are very close contemporaries.

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

 

[The exile]

BR should have built more 33s and not bothered with the type 2s. Only 4 classes of mainline diesels were really needed. 20s, 33s, 37s and 47s would have been enough.

Isn’t hindsight a wonderful thing?!

== Doublepost prevention - post automatically merged: 13 Jan 2026 ==

Polmadie 2x20 sets in Scotland were extensively used on MGR from the Ayrshire coalfield to Longannet power station in Fife. I have written here before about seeing them in the 1970s hammering up the about 1 in 50 through Alexandra Parade and Springburn flat out at walking pace. Prominent railway author Derek Cross did a footplate ride on this working leading to a Railway Magazine article about it around this time. It may have been in that article that it was described that 2x20 was preferred over a Class 47 because they gave better adhesion on undulating colliery tracks. I can believe that even so they might sometimes need a banker - the MGR trains were notably heavy for such haulage over steep gradients like this one.

Some Polmadie Class 20 were also air braked very early on, as they were used to haul (via the same route) empty Blue Trains between the two long-unconnected electrified networks, north and south of Glasgow, a task which at the beginning had been given to the last remaining Caledonian Railway steam locos in Glasgow, which were still fitted with Westinghouse brakes.

A pair of 20s accelerating up what I understand was the steepest gradient on the ECML was a treat to the ears. Didn’t last long, though.

 

[Gloster]

BR should have built more 33s and not bothered with the type 2s. Only 4 classes of mainline diesels were really needed. 20s, 33s, 37s and 47s would have been enough.

BR’s original plan was, broadly, to buy small batches of each design, try them out and then come back with a handful of large orders based on the best designs. However, the loco builders lobbied on the lines of, ‘How can we win export orders if our own national railway does not display confidence in our designs‘. And lo, pressure was brought to bear on BR and we ended up with the mess that resulted. (Needless to say, it is more complicated than that, but that came from someone who was a member of one of the relevant departments at the time.)

 

[Taunton]

It seems that by the time Lion came into service BRCW had already decided to pull the plug, and the decision had already been made within BR to use the Sulzer/ Brush combination. And if Lion had been developed - you'd have ended up with a Sulzer/AEI combination which based on the reliability of the 27s may have been worse than the Sulzer/Brush 47s

BRCW had done a lot more than locomotives, they were one of the principal dmu builders, did a lot of Mk1 hauled carriages, Underground car orders at the same time, and quite a bit of subcontracting work. It was notable that all these fell off at the same time, and presumably their management strategists could see this coming.

Strange how many orders for electric mus were shared, almost equally, between BRCW and Met Cam, as if they had some sort of financial relationship across Birmingham. The prewar Wirral electric unit cars in 1938 for the LMS were shared 50-50 between the two. When BR came back for a second large batch of these in the mid-1950s exactly the same division took place again. London Underground orders were likewise divided equally between them more than once.

 

[Harvester]

A pair of 20s accelerating up what I understand was the steepest gradient on the ECML was a treat to the ears. Didn’t last long, though.

From Portobello Junction, north through Waverley station?

 

[Richard Scott]

Is that definite? Statements I've seen elsewhere are that the whole lot were intended to be 45s, the 46s were only ordered when it was realised that Crompton-Parkinson couldn't keep up with deliveries. Furthermore that the "last 20" were an extra 20 that were switched prior to build

Yes, you are correct that 76 were transferred to Brush machines, with 20 subsequently used for 47s.

== Doublepost prevention - post automatically merged: 13 Jan 2026 ==

Surely 2000hp wasn't enough?

The 2700hp version!

 

[norbitonflyer]

that seems to be a key point in the decision making - BR appears to have believed that EE couldn't build a 2500hp diesel, so went with Sulzer as first preference

Which is odd, as Lion and DP2 were built at the same time (along with Falcon), and had essentially the same prime movers as, respectively, the class 47, the class 50 and the class 52 - albeit with different transmissions, the Class 47 being in essence Lion's engine and Falcon's transmission, and the 52 being Falcons engines mated to Voith hydraulic transmissions (a three-axle version of those fitted to the NBL Class 41/43 Warships)

Which may seeem an odd choice, given the superior performance of the Class 42 (with Mekydro tranmsisions) over the Class 43, but Class 43's Achilles heel was the MAN engines, not the Voith transmission - Classes 35 and 42 had Mekydro transmisions, but a three axle version was apparently not available.

 

[Pigeon]

Which is odd, as Lion and DP2 were built at the same time (along with Falcon), and had essentially the same prime movers as, respectively, the class 47, the class 50 and the class 52 - albeit with different transmissions, the Class 47 being in essence Lion's engine and Falcon's transmission, and the 52 being Falcons engines mated to Voith hydraulic transmissions (a three-axle version of those fitted to the NBL Class 41/43 Warships)

Which may seeem an odd choice, given the superior performance of the Class 42 (with Mekydro tranmsisions) over the Class 43, but Class 43's Achilles heel was the MAN engines, not the Voith transmission - Classes 35 and 42 had Mekydro transmisions, but a three axle version was apparently not available.

Two or three axles isn't down to the transmission. The output flanges of the transmission (either type) are on a projection of the housing that sticks down underneath, into the central well of the Warship bogie; then cardan shafts on either side take the drive from the transmission to the final drive gearboxes mounted on the axles.

On the Hymek there are longer cardan shafts leading from the transmission output to the bogies, where they connect to the rear final drive box, then a further shaft takes the drive from the other side of the rear box forward to the front one.

The Western bogie is derived from the Warship one and works on the same principle, but it is necessarily asymmetrical. The transmission output sticks down in between the rear axle and the centre one is connected by a cardan to a distributor gearbox in between the centre and front axles, with further cardan shafts either side to the final drives on those two axles as in the Warship, then a fourth cardan connects the centre and front rear final drives similarly to the Hymek.

The problem with the Mekydro transmission and the Westerns was that the appropriate model in terms of ratings was too big physically, and would have needed to be mounted tilted over at an angle in order for the resulting loco to have fitted within the loading gauge (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). So instead they designed it to use a Voith transmission then under development that would have been ideal; however Voith then changed their plans and didn't produce it, so the nearest model that was available was substituted, with the result that the Westerns ended up being overgeared in top.

[Edit: correction to Western bogie layout]

 

[Acathater]

Which is odd, as Lion and DP2 were built at the same time (along with Falcon), and had essentially the same prime movers as, respectively, the class 47, the class 50 and the class 52 - albeit with different transmissions, the Class 47 being in essence Lion's engine and Falcon's transmission, and the 52 being Falcons engines mated to Voith hydraulic transmissions (a three-axle version of those fitted to the NBL Class 41/43 Warships)

The problem with that logic is that it seems BR had already placed the converted class 46 order for the initial 20x 47s before the three tech demonstrators were released to traffic. Or if not actually ordered, certainly decided on. Something to keep the trade unions at Barrow happy. Could have been what made BRCW finally pull the plug

 

[Harlequinuk]

LMS 10000 (D 16/1) was officially launched into traffic December 1947; which the D 16/2 (Bulleid diesel) was ordered first, Ivatt pushed his team hard to get his loco built first and into service , in LMS black before nationalisation. Small addon - the 3rd Bulleid diesel should have been D 20/3 based upon naming convention of motive type, power and version number and as the 3rd Bulleid model ahd the full monty 2000 bhp 16 SVT, it would have been a 20 series not a 16 series.

 

[Helvellyn]

The problem with that logic is that it seems BR had already placed the converted class 46 order for the initial 20x 47s before the three tech demonstrators were released to traffic. Or if not actually ordered, certainly decided on. Something to keep the trade unions at Barrow happy. Could have been what made BRCW finally pull the plug

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?

 

[Trainman40083]

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?

I wonder what the split was with 47s. X built at Crewe, X at Brush.. Some of the Brush built ones came to Derby for painting.

 

[Helvellyn]

I wonder what the split was with 47s. X built at Crewe, X at Brush.. Some of the Brush built ones came to Derby for painting.

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.

 

[Trainman40083]

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.

Reminded me of Class 25 overhauls at Derby Loco. I can't recall which batch it was, between BR Darlington or Beyer Peacock ones), but the standard Derby cab was slightly different