Stepped noses on diesel locos

[frobisher]

Just lately I've been thinking about this. Beyond asthetics, what purposes are served by the stepped noses on diesel locos, and why have designs moved away from there? I'm thinking particularly for UK prototypes.

 

You can clearly see this change happening with the the transition from DP2 to the Class 50 so what influenced it? I can see, perhaps that the thought originally might have been in regards crash worthiness and putting a bit more structure between the driver and the front of the loco, but actual crash reports perhaps bearing out there being no advantage in reality.

 

 

 

[The Stationmaster]

Just lately I've been thinking about this. Beyond asthetics, what purposes are served by the stepped noses on diesel locos, and why have designs moved away from there? I'm thinking particularly for UK prototypes.

 

You can clearly see this change happening with the the transition from DP2 to the Class 50 so what influenced it? I can see, perhaps that the thought originally might have been in regards crash worthiness and putting a bit more structure between the driver and the front of the loco, but actual crash reports perhaps bearing out there being no advantage in reality.

 

BR turned against 'nose end' diesels in order to improve the Driver's view - especially of Shunters etc on the ground and of ground signals.

 

On earlier designs the nose ends had been used partly for equipment and also to make it easier to fit gangway connections and sometimes as somewhere out of the way to put the toilet.

[Edwin_m]

Diesel noses seem to have originated the US and been picked up by the early British diesels which mostly adopted a similar appearance. I read many years ago that there was concern about something called "sleeper flicker" distracting the driver if the track was too visible close up, but that by the 60s they had either decided this wasn't a problem or developed cab designs which prevented it being visible when seated normally. Presumably when coupling up a flat-fronted diesel the driver could lean forward to see the track close in front.

[The Stationmaster]

Diesel noses seem to have originated the US and been picked up by the early British diesels which mostly adopted a similar appearance. I read many years ago that there was concern about something called "sleeper flicker" distracting the driver if the track was too visible close up, but that by the 60s they had either decided this wasn't a problem or developed cab designs which prevented it being visible when seated normally. Presumably when coupling up a flat-fronted diesel the driver could lean forward to see the track close in front.

 

 

As far as I can remember being told the design standard was based on what the Driver could see when seated, as that is the working position and hence the nose obscures low level stuff for quite a distance in front of the loco. I've an idea (could be wrong of course) that there was a design standard specifying how far the Driver would be able to see at a certain angle of downward view, I can remember something like that being talked about on a course I was on a long time ago.

 

Even without a nose end on the loco the Driver can't see the track immediately in front but he has no need to - provided he can see signals and persons controlling the move he is making.

[pete_mcfarlane]

I always thought that US diesels had a lengthy "nose" in front of the cab to act as a crumple zone in the event of a collision, as these are fairly common on ungated level crossings in the US.

 

Some of the early UK diesels had noses (mainly EE designs), but plenty didn't (Bulleid 10201-3, Class 30/31, electric classes 70/76/77, GWR gas turbines).

[jon attwood]

I don't know how many loco designs it affected, but on some locos there were 'clean' and 'dirty' compartments which were kept seperate to avoid oil etc getting into the electrical sections, the class 07 and class 14 shunters were arranged in this way, with the cab separating the engine from the electrical gear. As diesel engine design progressed the incidence of leaks and fumes would presumably have decreased, making such arrangements less crucial.

So could some of the stepped nosed diesels been designed in this manner so as to keep the electrical control gear in the nose section entirely seperate from the oily bits? It may explain why the majority of the early designs for large locos without stepped fronts were electric rather than diesel locos.

 

Jon

[Dagworth]

In all the british mainline diesels the control gear was in the main body rather than the noses. Clean air compartments were generally a later development in UK locos, when the 37s were refurbished one of the changes was to divide the body internally to keep the electrical gear seperate from the engine room.

 

About all that was in the noses of EE locos was equipment like traction motor blowers (a right pain as all that happened was they dragged the warm air out of the cab - draughty cabs was a real problem on 37s) and compressors/exhausters etc.

 

Andi

[asmay2002]

I read many years ago that there was concern about something called "sleeper flicker" distracting the driver if the track was too visible close up

 

HCB Rogers in his book "Transition from Steam" p52 says that Bond insisted upon the nose end on all larger locos when he was "CME" but when Harrison took over he insisted on Flat fronts. Bond though that sleeper flicker was a problem but Harrison didn't see any merit in nose ends.

[iploffy]

From what I have read in the Production type 1-3 diesel electrics by Brian Haresnape there was a quote that the production lines were tooled for class 40's nose ends and EE were able to quote an attractive price for it's later class 37's, what the original idea was I do not know. Hence the proliferation of nose ends

 

Ian

[Russ (mines a pint)]

I've read about a few incidents on the Derby sulzers site of railway men being killed in cabs of class 24/25 collisions, quite possibly the crumple zone arguments holds water, but by the time of the later loco's crash-worthiness had improved to an extent that the increased forward visibility was an advantage.

Its all speculation though, wrong way round class 20's and of course the old steam loco's ever boiler or tender-first would suggest that being able to see where you are going is a luxury rather than necessity.

 

I'd put more money on the preferences of the designer of the time, there was alot of effort made (so I've read) to make the new diesels look more modern, smooth and sophisticated. The noses obviously go back to the E/F units (US started diesels on a big scale before UK), but this style of loco had already been superseded by the time of mass dieselisation of the UK. The designers and the various companies would want the stuff to look good, as this would be more likely to sell (Class 17 anybody? -vs. the large no. of 20's of antiquated design commissioned instead?)

 

Think how much more like 'an American loco' the prototype deltic looks. To how things were looking that were pilot scheme or production scheme produced? I reckon a lot might boil down to contemporary fashion, compare 50's and 60's road vehicles and the differences?