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

[Bornin1980s]

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?

 

[DustyBin]

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?

I believe (and this could be one of those myths!) that it was to prevent drivers being affected by the sight of sleepers flashing immediately beneath them. I also believe it provided a level of protection in the event of an accident.

 

[John Webb]

According to "British Rail 1948-78 - A Journey by Design" by Brian Haresnape (Ian Allan, 1979) many of the early diesels were designed by their makers who tended to follow North American practices in their design. A Design Panel was set up in 1956 to bring a degree of conformity and best appearance to the increasing locomotive fleet, but it was not always heeded and was also constrained by BRs financial problems. Their first efforts resulted in the Pullman diesel sets run on the LMR and WR lines. Various electric and diesel units, including 'Warships' and the 'Hymeks' were strongly influenced by the Design Panel, but their suggestions for the production 'Deltics' was resisted by the makers, hence the retention on those of the front 'nose'.

I was unable to find a reference in the book to concerns about drivers' vision and sleepers - after all many drivers on suburban electrics had been driving from the front of their trains for many years!

 

[Snow1964]

The story I heard was about weight distribution.
It is a long while since I read a book on development of 1950s mainline diesels, but from vague memory, the diesel and alternator were heavy and had to be fairly central, and there was the train heating steam generator as well

But this doesn’t really explain why some of the other parts, radiators, fuel tanks etc could go between the cabs, but others like motor blowers were sometimes forward of the cab.

I am guessing continuity of design explains some of the later ones like that from same manufacture.

 

[Trackman]

The story I heard (or read) it was a safety feature in case of a collision or whatever.

 

[pieguyrob]

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.

 

[a_c_skinner]

I too have heard the sleeper "flutter" story as I believe it was called.

 

[Gloster]

I am another one to have heard the sleeper story, in this case the twist was that at night it could have a hypnotic or sleep-inducing effect. Again, I don’t know if it is true.

 

[edwin_m]

I too have heard the sleeper "flutter" story as I believe it was called.

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.

 

[Bletchleyite]

I too have heard the sleeper "flutter" story as I believe it was called.

That story I've also heard in terms of explaining why the Mk3 coach windows are so high up (indeed I'm almost certain it's mentioned in Two Miles a Minute which is definitely a reputable source). It was, like many things on the railway, proven to be a bit of a myth, because pretty much all subsequent high-speed stock has had lower windows.

 

[DarloRich]

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

 

[Bletchleyite]

The Dutch of course have carried on with "big nose" designs - does anyone know the rationale they have used?

 

[Wyrleybart]

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?

I understand you are talking about UK or European railways. The US still build diesel locos with noses for their freight railroads, and these tend to have the toilet for the crew in it.

 

[edwin_m]

I understand you are talking about UK or European railways. The US still build diesel locos with noses for their freight railroads, and these tend to have the toilet for the crew in it.

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.

 

[Cowley]

I’ve always thought the ‘Sleeper flutter effect’ to be a bit of a strange one bearing in mind that there were plenty of other early diesel and electric locos (plus multiple units) being built that were flat fronted.
Was it more a case that the class 40 style cab was carried over to the 37 because that was the cab design that they had at the time, and the 40 partly had a nose due to the length of the loco and the styling fashion at the time?
It’s also worth bearing in mind that one of the forerunners of the class 40 - the Bulleid D16/2 had a flat front and I don’t recall the crews ever complaining about them?

Interesting subject anyway.

 

[Richard Scott]

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.

 

[Cowley]

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.

Certainly the crew of DP2 that hit the cement train at Thirsk felt that they would have faired much worse (and I have to agree in that particular accident) if they’d been in flat fronted loco like a Brush type 4 for instance.
I was just trying to find some details on the crash that wrote off D1677 ‘THOR’ because I think that hit a class 37 and possibly the crew on the 37 survived. Does anyone know?

 

[Gloster]

Regarding #17: a quick wander around the internet suggests that in the accident at Bridgend the two crew of the 47 were killed and the two on the 37 were injured. I found a press photo, which I am not going to buy at £375 (or even the bargain £340), that shows how the nose of the 37 absorbed some of the impact, despite it travelling at line-speed when it hit the derailed 47.

 

[Cowley]

Regarding #17: a quick wander around the internet suggests that in the accident at Bridgend the two crew of the 47 were killed and the two on the 37 were injured. I found a press photo, which I am not going to buy at £375 (or even the bargain £340), that shows how the nose of the 37 absorbed some of the impact, despite it travelling at line-speed when it hit the derailed 47.

Thanks for that @Gloster.

 

[alangla]

I am another one to have heard the sleeper story, in this case the twist was that at night it could have a hypnotic or sleep-inducing effect. Again, I don’t know if it is true.

Was it not something similar (flicker from the rings lining the tunnel) that led to the tiny windscreens on the Eurostars? Strangely the shuttle locos seem to have full-size windscreens.

 

[a_c_skinner]

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.

Flicker. That was the word. Blast. Rats. I worry my next word with be Alzheimer's.

 

[TheEdge]

Was it not something similar (flicker from the rings lining the tunnel) that led to the tiny windscreens on the Eurostars? Strangely the shuttle locos seem to have full-size windscreens.

Yea there was a fear that 20 minutes of hypnotic lights passing by the window would mess up the drivers eyesight. Often quoted when a vehicle tunnel is suggested.

 

[D365]

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.

What aspects of the design was BR unhappy with?

 

[edwin_m]

Regarding #17: a quick wander around the internet suggests that in the accident at Bridgend the two crew of the 47 were killed and the two on the 37 were injured. I found a press photo, which I am not going to buy at £375 (or even the bargain £340), that shows how the nose of the 37 absorbed some of the impact, despite it travelling at line-speed when it hit the derailed 47.

The photo on Railways Archive (the only information they have on this accident) confirms this.

Accident at Bridgend on 17th December 1965 :: The Railways Archive

Archive of UK railways documents

www.railwaysarchive.co.uk

 

[pieguyrob]

What aspects of the design was BR unhappy with?

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.

 

[Bornin1980s]

Why did BR come to favour flat fronts?

 

[edwin_m]

Possible explanation (but I've no idea if it's true): With a flat front the driver can probably see down to the buffers and coupling by leaning over the desk, but this would be impossible with a bonneted loco.

 

[Astro_Orbiter]

Yea there was a fear that 20 minutes of hypnotic lights passing by the window would mess up the drivers eyesight. Often quoted when a vehicle tunnel is suggested.

Iirc this is known as "segment flicker"? More to do with there being no/tiny/set back cab side windows I think, but not 100% sure.

 

[pieguyrob]

Why did BR come to favour flat fronts?

The BR design board, wanted some standardisation to their locomotives. There were several design houses in the day that worked to achieving it, I can't remember their names.

The prototype class 50 had a deltic body shell, DP2, the production run class 50's used the bodyshell from DP3, the super deltic, which was never built. But, it's design was influenced by the BR board.

If you look at a class 86 and 87, they share the same body shell. The class 56 is a 47 body shell, with a class 50 engine.

Even a class 35 hymek has similarities to a 47 in appearance. You can also include lion, falcon, and to an extent, even kesterel.

 

[OVS Flatbottom]

Possible explanation (but I've no idea if it's true): With a flat front the driver can probably see down to the buffers and coupling by leaning over the desk, but this would be impossible with a bonneted loco.

At the time when the class 60s were being designed, I remember reading that the French "nez cassé" design (like SNCF CC 72000 etc. - see Wikipedia) was suggested for them, but that BR turned it down on precisely these grounds.