Why 'bonneted diesels', and why the end of them?

[A0]

I wondered if I should put this in 'Railway history and nostalgia', but there are still some of these things in service. Basically, as we all know, the larger diesel electric designs of the late 50s and early 60s often had noticeable 'bonnets' at both ends ahead of the cabs. This is a distinct feature of English Electric designs, but was also found on the very early LMS 'twins' and the 'peaks'. By the mid-60s, this feature had fallen out of favour on new locomotives, and never came back in this country. It was never seen on our electric locomotives, and almost never on lower powered type IIs, apart from the very rare 'baby deltics'.

Now, I know that these bonnets always contained the traction motor blowers, but what was the specific reason for putting these and some other features ahead of the cab, rather than in the main body? And why did it fall out of favour by the end of the 60s?

But what is interesting is none of the post war electric locos had anything other than flat fronts - be it the Woodhead 76/77s, the Bullied 3rd rail locos or the later Class 73, 74s or the AC electrics 81 onwards, yet their speeds were comparable with the diesels of the time.

 

[RichJF]

It also provides some protection for the crew. It wouldn't do much in a high speed collision with another train but might make the difference if, say, striking a truck at a grade crossing.

The US also have vastly higher number of open/unprotected grade crossings, so adds into the safety when hititng an articulated truck, which happens fairly regularly.

 

[OVS Flatbottom]

On the topic of crew protection there have been numerous accidents involving bonneted locos, how many have resulted in serious injuries or deaths with the crew? 45147 not included in this one as don't think that was survivable with any design. Would be interesting to compare with similar accidents in flat fronted designs.

I've been thinking about this; to the best of my knowledge, the list of accidents where there were fatalities in diesel or electric loco cabs (serious injuries would, I suspect, be a considerably longer list) is:

Class 20: Nottingham (Lenton S Jcn) 1971, Worksop 1989 (the only evidence for the latter accident is an unreferenced statement on Wikipedia)

Class 24: Castlecary 1968, Kidsgrove 1973

Class 25: Middlesbrough 1971, Nottingham (Lenton S Jcn) 1971, Newton-on-Ayr 1976

Class 27: East Langton 1965

Class 31: Hatfield 1968, Corby 1975, Chinley 1986

Class 33: Itchingfield Jcn 1964, Hilsea-Fratton 1979, Holton Heath 1989

Class 40: Acton Grange Jcn 1966, Copy Pit (Cornholme) 1967

Class 43 (HST): Ladbroke Grove 1999, Ufton Nervet 2004, Carmont 2020

Class 45: Stanton Gate 1963, Peterborough N 1968, Bridgwater 1974, Eccles 1984 (this is 45147, the one Richard mentioned).

Class 46: Naas (near Lydney) 1979

Class 47: Bridgend 1965 (also mentioned in this thread), Monmore Green 1969, Cheadle Jcn-Northenden 1971, Eltham Well Hall 1972, Leicester (Humberstone Rd Jcn) 1972, Carstairs 1975, Eastriggs 1976 (collision with lorry that came off overbridge), Farnley Jcn 1977, Invergowrie 1979, Crewe 1980, Micheldever 1986, West Brompton 1989

Class 50: Beattock 1969

Class 52: Knowle & Dorridge 1963, Worcester Tunnel Jcn 1976

Class 56: Morpeth 1992

Class 66: Great Heck 2001

Class 81: Hixon 1968, Linslade 1982

Class 83: Watford Jcn 1975

Class 85: Warrington 1989

Class 86: Wigan North Western 1984, Colwich 1986


This list may not be 100% complete as regards collisions not on running lines. Almost all of the accidents have reports on the Railways Archive. I don't know whether the numbers are susceptible to any kind of meaningful analysis - I'm sure they're affected by, among other things, the prevailing standards of rail safety in the era when the locos in question were active and the types of traffic that they worked. That said, the number of class 47 accidents stands out, but the Peaks actually seem to perform worse relative to numbers built. On the other hand, the lack of fatalities involving the class 37 seems notable.

 

[bassmike]

You have to put the chemical toilet somewhere........

This could increase the unpleasantness resulting from a collision.

 

[edwin_m]

But what is interesting is none of the post war electric locos had anything other than flat fronts - be it the Woodhead 76/77s, the Bullied 3rd rail locos or the later Class 73, 74s or the AC electrics 81 onwards, yet their speeds were comparable with the diesels of the time.

In the case of the 81s onwards, considerably faster on average than most diesels.

Could it be simply that electrics followed European design practice and diesels followed American?

 

[37114]

As far as I'm aware because it didn't have the flat front, and, had a bonnet.

Pretty certain that I read about it in one of the railway magazines articles on the history of the class 37. I can't remember which magazine, sorry.

I think it was in an early issue of Traction. EE basically made the class 37 as a bit of a parts bin special and hence re used the class 40 cab pressings/designs to keep the cost down. There was a senior person in BR who also supported the nose design and had some sway hence the 37s looked like they did. It was such a shame that BR insisted on no nose for the class 50 as it would have been a lovely looking loco if they had just built 50 DP2s.

 

[Bornin1980s]

Why did BR insist on a flat front for the 50?

 

[pieguyrob]

I thought the design of the 50, came from the drawings of dp3 the super deltic. As well as being influenced by BR's design board.

 

[TheBeard]

I think the bonnet would cover collisions upto about 40mph. It was dropped for visibilty, but compare DP2 and the Western Pullman that killed all crew at 25mph.

 

[Bornin1980s]

The Western Pullman?

 

[david1212]

Back in the 1950's & 1960's safety was far less of a consideration than now.

OT but one factor that will be a consideration in the analysis of the Carmont incident will be the shape of the HST power car front and strength of the cab.

 

[Elecman]

The Western Pullman?

The 1963 crash at Dorridge where a Class 52 and a standby set of Pullman coaches collided with a freight train killing all the footplate crew. ( the driver was the same guy who featured on the on the Let’s go to Birmingham film)

 

[Deepgreen]

I read of it being described as "flicker". But it could, like many things on the railway, be known by different names to different people.

However, if that is the case and it was important enough to design accordingly why didn't early MUs have a similar mini-bonnet? Admittedly, when coupled, space would be wasted, but safety is safety...

Interestingly, the original 'Warships' (D600 series - class 41) had (smaller) bonnets but their smaller, shorter derivatives, the NBL type 2s (classes 21 and 29), didn't.

 

[edwin_m]

However, if that is the case and it was important enough to design accordingly why didn't early MUs have a similar mini-bonnet? Admittedly, when coupled, space would be wasted, but safety is safety...

Interestingly, the original 'Warships' (D600 series - class 41) had (smaller) bonnets but their smaller, shorter derivatives, the NBL type 2s (classes 21 and 29), didn't.

Indeed, the sleeper flicker thing never really made sense, and sounds like someone being unwilling to learn a lesson from another part of the same organisation.

 

[Inversnecky]

Not sure how much truth there is in this, but, when BR realised they needed a type 3 mixed traffic loco, English Electric responded with a shortened class 40 body shell, sitting on Deltic bogies. Apparently none of the other manufacturers could respond as quickly. BR weren't happy with the design, but, the class 37 has now been around longer than BR was.

I always wondered about the 37 and the 40. So the 37 was a refined version of the 40?

And despite the bonnet similarity, the Peaks (44, 45 and 46) had an altogether different pedigree?

 

[37114]

I always wondered and the 37 and the 40. So the 37 was a refined version of the 40?

And despite the bonnet similarity, the Peaks (44, 45 and 46) had an altogether different pedigree?

Yes and yes. The 44/45/46 had Sulzer power unit and Electrics and were completely separate designs from the 37/40.

 

[Inversnecky]

Yes and yes. The 44/45/46 had Sulzer power unit and Electrics and were completely separate designs from the 37/40.

So the Class 40 was first on the scene, and the 37 was a lighter, improved version?

 

[Cowley]

So the Class 40 was first on the scene, and the 37 was a lighter, improved version?

The class 40 was an original type 4 design (2000hp) whereas the class 37 was a type 3 (1750hp).
The class 37s were a newer design but also designed for lighter work. I don’t think there was much in it as far as pulling a train was concerned although due to its weight a class 40 had more brake force which meant they were quite useful on unfitted freight work in the 1960s/70s.

 

[Richard Scott]

The class 40 was an original type 4 design (2000hp) whereas the class 37 was a type 3 (1750hp).
The class 37s were a newer design but also designed for lighter work. I don’t think there was much in it as far as pulling a train was concerned although due to its weight a class 40 had more brake force which meant they were quite useful on unfitted freight work in the 1960s/70s.

The engine in the 37 was derated from 2000hp, allegedly for reliability. Not sure if it wasn't so wouldn't embarrass the 40s! To be honest can't believe they didn't change the order to more 37s and cancel remaining 40s once 37 was on the scene?

 

[randyrippley]

Why did BR come to favour flat fronts?

The Design Pnnel thought they looked better, and they advised BR what to purchase.
There was little or no styling done on the looks of the modernisation plan diesels, and most were plain ugly. BR created the design panel to improve things, and they set the lead.
The Westerns were what you got when the panel reworked the Warships
They Hymeks, Falcon, Lion and the 47s all came from the same design brief (which was actually contracted out)
Class 81-86 all came from another styling exercise.
While they also had a had in the class 25 cleanup of the body grilles

One they didn't have hand in was the 37, built on a budget using bits from theEE standard parts kit. Cost and expediency overrode design

The engine in the 37 was derated from 2000hp, allegedly for reliability. Not sure if it wasn't so wouldn't embarrass the 40s! To be honest can't believe they didn't change the order to more 37s and cancel remaining 40s once 37 was on the scene?

Not sure they overlapped in production?

But the only reason so many 40s were purchased was because EE could deliver a type 4 design reliably and on time, while the BR workshops found it impossible to hit delivery schedules with the Peaks, even when a second assembly line was opened

 

[Richard Scott]

Not sure they overlapped in production?

But the only reason so many 40s were purchased was because EE could deliver a type 4 design reliably and on time, while the BR workshops found it impossible to hit delivery schedules with the Peaks, even when a second assembly line was opened

They did, 37s built from 1960 onwards and 40s until 1962. I know that was the reason for so many 40s but diesel technology was moving on quickly then hence I don't understand why some uprated 37s weren't ordered instead of 40s, which could have been cancelled. Manufacturer wasn't losing out as the same one. BR could have had a loco some 30tons lighter without the cumbersome 1Co-Co1 bogies.

 

[Cowley]

They did, 37s built from 1960 onwards and 40s until 1962. I know that was the reason for so many 40s but diesel technology was moving on quickly then hence I don't understand why some uprated 37s weren't ordered instead of 40s, which could have been cancelled. Manufacturer wasn't losing out as the same one. BR could have had a loco some 30tons lighter without the cumbersome 1Co-Co1 bogies.

Or could EE have offered a charge-cooled version of the power unit in the later batch with centre headcodes, not to the full fat 2700hp class 50 spec, but maybe as a decent competitor to the class 46 at 2500hp perhaps?

 

[Inversnecky]

An interesting fact about the Class 40 I just learned: due to its length, its buffers were mounted on its bogies rather than its body. But I’m sure you guys already knew that

 

[Journeyman]

Whatever the flaws of the 37, it has to be said that it hit a sweet spot of performance, reliability, flexibility and weight. It may look a little ungainly and be bit of a mashup of other parts, but I challenge anyone to find a more successful British diesel.

 

[Inversnecky]

I challenge anyone to find a more successful British diesel.

The 47?

 

[Irascible]

The 47?

Had to be derated to stay reliable, so disputable. A 2500bhp 37 ( 49? ) might have KOd it if there was room for all the gubbins that ended up in 47s.

Not sure how EE would have managed to build another 500 of them though! the electrics would have been getting pretty ancient by the end of the run too.

 

[43096]

The 47?

Nah. 37s weren’t permanently de-rated like the 47s. The 47s were effectively tolerated by BR, largely because there were so many/too many of them and they couldn’t afford replacement.

 

[norbitonflyer]

The engine in the 37 was derated from 2000hp, allegedly for reliability.

On the contrary: whilst the class 40 engine had 16 cylinders, the class 37 had the same 12-cylinder engine that was retrofitted to the Brush Type 2, although it was able to be uprated as the Class 37 had six powered axles and the Class 31 only had four.
The 16 cylinder version went through several upratings, first appearing in 1947 in the LMS twins (1,600 hp) and the Southern railway's trio (1700-2000hp), then in Class 40 (2000hp), Class 50 (2700hp) and finally, in the late 1970s, class 56 (3250hp)

An interesting fact about the Class 40 I just learned: due to its length, its buffers were mounted on its bogies rather than its body. But I’m sure you guys already knew that

Not only that, but the idler axle was mounted to move relative to the bogie itself with, so the bogie was essentially a 2-6-0.

Bogie-mounted buffers were also a feature of the "Peaks" and class 76 (but not the otherwise very similar looking class 77)

 

[Western Lord]

On the contrary: whilst the class 40 engine had 16 cylinders, the class 37 had the same 12-cylinder engine that was retrofitted to the Brush Type 2, although it was able to be uprated as the Class 37 had six powered axles and the Class 31 only had four.
The 16 cylinder version went through several upratings, first appearing in 1947 in the LMS twins (1,600 hp) and the Southern railway's trio (1700-2000hp), then in Class 40 (2000hp), Class 50 (2700hp) and finally, in the late 1970s, class 56 (3250hp)

The number of cylinders is irrelevant. The ratings applied to all variants, V-8, V-12 or V-16, thus the 1,000hp 8CSVT in a Class 20 is (appropriately) half of the 2,000hp 16CSVT in a Class 40. All cylinder configurations were available in uprated form. The engine in the Class 31 was not the same as it was not charge air cooled. The 1,750hp rating of the Class 37 was to conform to the arbitrary Type 3 limit decided on by BR. For the same reason the Hymek was rated at 1,740hp (for some reason almost always quoted as 1,700hp), whereas the metric rating of the Maybach MD870 was 2,000hp.

 

[Journeyman]

The 47?

Nah. The 37s have lasted longer, have been far more reliable, found more useful niches for which no other locos are suitable, and there's far more of them still operating, despite there being 200 less 37s than 47s.