Sir Nigel Gresley - The L.N.E.R.’s First C.M.E.

The other Brown (FAS) mentions Dalby and wind tunnel tests on 10,000.

 

Wasn’t the purpose of wedge shaped cabs that they allowed a bigger front window area within a given (constrained) cab width, or did I imagine that?

Tom

 

I vaguely remember having heard this but I’d need a primary source to believe it was the reason for their initial introduction rather than a consequence of their introduction.

 

Actually, having reviewed the primary evidence myself from the NRM, this is one of the few areas I disagree with William Brown on and I make that point as much in my book.

With my apologies to Tim Hillier-Graves, but it's right there Steve.

Photographic evidence in his book.

Page 155.

Gresley and His Locomotives.



And again, draughting was the primary intention, but by virtue of the scientific process followed, the locomotive was in fact streamlined.

This is confirmed both by the evidence the late Bert Spencer has provided by way of Tim's book and that held in the NRM's own file on the W1.

This is the trouble with secondary evidence that hasn’t done the research. Time and time again with LNER matters things need to be corrected…

 

The caption to that photo says "tests" - which isn't the same as saying it was about streamlining (drag reduction) per se. I believe Maunsell had some locos tested in a wind tunnel when the SR was trying to understand problems around drifting smoke and come up with a design for smoke deflectors. So the cautionary note would be that evidence a loco was tested in a wind tunnel is not evidence that the intention was about "streamlining"; there are other things that could be tested at that time to be properly understood. The issue of smoke clearance was one that I believe affected all of the Big 4 in the 1920s as boilers got larger and chimneys got progressively smaller in height.

On the W1: the gross shape of the boiler cladding is clearly just following the underlying boiler. I think if the LNER has been really interested in streamlining (in the sense of reducing the drag coefficient) they cannot fail to have noticed how "dirty" the front of the loco is, with the raised hand rail across the front and large cut outs in the front. The clutter of lubricators etc. on the running plates also tend to suggest that aerodynamics wasn't a priority: had it been so, it would have been trivially simple to flare the boiler cladding out to clean that area up aerodynamically, rather than sweep the cladding round tightly following the underlying boiler (which makes servicing on shed easier, but at the expense of aerodynamic efficiency).

So I tend to the view that unless you have primary evidence that the explicit intention of wind tunnel tests was to reduce the drag, it seems much more likely that such tests were to achieve other ends; notably smoke dispersal and, as stated, create "ram air" to the grate to improve combustion. Evidence that a model went in the wind tunnel is not in itself evidence that the intention was reducing the drag.

Tom

 

Yes, the shape of the W1 was primarily for the draughting factor. I have said this on two separate pages now.

Yes, we do have primary evidence stating that the overall shape of the W1 reduced drag, as a consequence. That's why I am challenging the pre-conceived notions on the locomotive. It was streamlined by virtue of what it was required to do.

Scientific principles of aerodynamics and fluid mechanics were followed in the development of the outer casing as a whole. That's the point here.

The shape of the locomotive at the front end was multi-functional. It allowed for air to be pushed through the scoops and into the casing, following channels, and air to be directed up and around the chimney, meaning that smoke would be lifted away from the driver's line of sight. Drag reduction is key for both of these aims and as a result, the locomotive itself as a whole is an exercise in drag reduction.

Arguing that the aim of the exercise was not streamlining as the main aim ignores the results of the exercise.

And, with respect Tom, if we are saying that the GWR locomotive is streamlined because it was "designed to be streamlined" (but it ended up anything but - and we can prove this) and the W1 isn't, because streamlining wasn't the primary aim (but it was a consequence of what was being done via scieintific principles and even commented on as a consequence of the work), then maybe we have lost sight of engineering development.

In particular, I would encourage you to overlay the W1's shape over the A4 shape. You will be surprised at what you find!

 

Its an interesting theory Tom, but cannot be so.

The window size on an A4 and an A3 are quite similar (I know this by virtue of measuring them!) the shape of the cab was intended to be streamlined.

Note that the W1 does not, in fact, have a streamlined cab: it has a very short flat fronted cab. This is down to the outer casing shape on the W1's boiler, ultimately, but even this was modified from the original intention, and you can see that it has an outside slope on its sides.

The P2 Cock O The North was, I think, the first of the Gresley locos with the V shaped cab. I need to check that. However it was dictated by the front end and boiler shape of that locomotive, again primarily for draughting purposes, but as a result reduced drag on the overall locomotive.

This cab design became standard on V2, A4, and was used on B17 and W1 thereafter. A version of this was used on the Thompson A2/1s (being developed from the V2 design), and the rebuilt P2s retained theirs. Peppercorn's Pacifics had their own version, which was derived from the possibility of streamlined versions of these locomotives appearing.

 

On the wedge-fronted cabs, Norman McKillop commented that they also had the benefit of cutting out unwanted reflections in the front windows when running at night, so the driver didn't have a reflection of his own face every time the firebox door was opened. This is the sort of thing that I'm sure wasn't part of the original intent but probably made them very popular in practice.

 

If you are designing the exterior shape of a steam loco (primarily the boiler cladding, cab, valences, tender design etc), you have roughly the following considerations:

1. To fit inside the loading gauge
2. To encase all the functional parts of the loco (boiler etc) - i.e. self evidently the cladding can't be smaller than the parts it encloses, but ideally shouldn't be much larger either.
3. To allow the crew sufficient visibility fore and aft
4. To provide physical protection to the crew from the elements
5. To enable access to key parts of the loco for servicing (running plates, hand rails, access hatches etc. designed to allow access for lubrication, visual inspection, washouts and so on with minimal disassembly)
6. To ensure adequate dispersal of smoke and steam
7. To be buildable within the capabilities of the workshop using normal metal forming techniques
8. To enable specific characteristics desired by the designer (ram air provision in the case of 10000; reduction in drag in some locos)
9. To meet the demands of the publicity department for aesthetics (which varied over time of course)

I don't agree that drag reduction is "key for lifting smoke away from the driver’s line of sight". Studies at the time indicated that the prime cause of drifting smoke was creation of a low pressure area either side of the smoke box that tended to suck smoke and steam down, the problem exacerbated by short chimneys meaning the smoke emerged close to that low pressure area. The solution generally adopted to that (smoke deflectors) was to induce turbulence in that low pressure area: turbulence generally increases drag but the increase was small in total resistance terms and more than outweighed by the benefit. It's possible of course that there are other solutions, such as the A4 shape nose, but it doesn't follow from that that smoke dispersal inevitably reduces drag; they are separate problems.

I'd be interested to see the primary evidence that the W1 shape as built reduced drag: what was the control experiment? (i.e. what did they compare it with?)

The reason I focus on the intention is that all locos are draggy to a greater or lesser degree, but if you are going to claim a loco is streamlined - especially if you are going to claim it was in some way the first such loco - then I think you need to show that it was the explicit objective of the design to reduce drag. There seems to me plenty of evidence in design decisions on the W1 that drag reduction wasn't really much of a concern in the design process. Which is actually entirely logical from Gresley's point of view. Of all the whole-train resistances of a typical large train designed to run at speeds found in the UK, wind resistance is a rather small part (and such as it exists, cleaning up the whole train, as was done with the Coronation carriages, is of far more significance than the shape of the front of the engine). From a locomotive point of view, the W1 had so many significant deviations from conventional practice (primarily the boiler; and the compounding) that there was more than enough experimental complexity to get to an efficient locomotive, without worrying about the nuances of drag that were going to be marginal at best to the performance.

As for the GWR locos, I haven't expressed any view on them. I suspect that they were probably built that way to meet a publicity demand from the GWR marketing department who saw "streamlining" on the LNER and LMS, and didn't wish to be seen as not in the forefront of design. The answer was really to do the minimum for the publicity gain - they seem very out of character for Collett who was much more focused on making incremental design changes to improve reliability and increase time between overhauls. The SR simply didn't play the game at all.

Tom

 

I do think it would be interesting to see wind tunnel results for the various streamlining options. Much is asserted, but little evidence gets supplied.

Another possibility is that the GWR exercise was mainly to test the effect on fuel consumption. I've seen that stated in a GWR publication. "Next Station", the 1947 GWR book looking forward, states streamlining was found worthwhile on sixty-two foot railcars, but not on thousand foot trains. Of course that was written after the event.

 

Pretty much said what I was going to say there, Tom. Anyone who thinks that loco had any tendency towards streamlining knows little about the subject.

 

Ooof, I felt that Steve.

With respect, I disagree. It’s pretty clear that it became streamlined as a result of the wind tunnel tests.

Nobody has claimed that it was originally intended to be streamlined.

However, it is clear by way of the results that the scientific method followed produced a streamlined locomotive, and yes, you can claim quite cogently that it is the first truly streamlined British locomotive design.

It’s definitely first by way of results, and it definitely is the first to follow scientific experimentation to become so. Whether intentional from the outset or not, it definitely ended up “streamlined”. Not the most efficient at this stage, but more efficient than anything before it and not a million miles away from the optimum that Gresley was to find later by way of the A4.

Nothing to disagree with here, this is standard affair and I am not disagreeing with you.

Not what I was saying Tom, so for clarity, let me point this out:

The W1’s wind tunnel testing affected the locomotive’s shape. That includes the overall shape of the cladding, which initially is dictated by the shape of the boiler.

The primary aims for the wind tunnel tests were draughting and smoke deflection. Nobody is arguing against that.

The result of the experimentation was to produce a shape that pushes air into the air ducts, down and into the grate area, and also to channel air UP, and over the boiler.

In order to channel the air up and over the locomotive in an efficient manner, you need to change the shape of the front end substantially.

In the W1’s case, it was initially not to have anything approaching streamlining - at all - on the early drawings it has an A1 smoke box - as a result of the wind tunnel tests, it gets this new shape. The profile of the W1’s shape over and around the smoke box door and chimney is designed for this purpose.

Part of this draughting effect that, frankly, the A4 design perfected, was in realising that covering the wheels was as important as the front end and the sides of the boiler. The W1 doesn’t have these, this is where it is poor at drag reduction. But it does have the all important front end development, and the shape of the cladding of the boiler does help with this too.

Since it appears to be the first British locomotive design to have been put into a wind tunnel for such experimentation, how do you compare it with something that doesn’t exist Tom? The W1 is effectively the control locomotive for that to follow.

Gresley was ALL about the scientific method and had been on about wind tunnels, test centres, better dynamometers cars, etc, for decades. The W1 was his first big bold overall experiment and everything that the file at the NRM is showing is just how carefully developed it was.

The primary evidence is in the NRM’s file at York, and includes letters, diagrams, and more. Tim Hillier-Graves in his book on Gresley has provided his view, and I agree with his view on the W1.

How does that follow though Tom? Are you saying that something designed for specific purposes can’t also, by way of method and development, become streamlined?

That’s certainly how it started, but it didn’t end that way, and that’s the point.

Do we understand what the point of the wind tunnel testing was?

They put chalk into the air to test the shape and then altered the models to then improve the air flow through the ducts, over the front of the locomotive, around the chimney of the locomotive at the front end and in its overall shape behind the chimney.

By its very nature, you have to reduce drag on the locomotive to improve the air flow going over it. That’s exactly what happened with the W1.

No, it’s not perfect at this. But it is undoubtedly the start of Gresley’s journey in development of a streamlined locomotive and later train.

I will politely defer to the GWR enthusiasts around us, but they absolutely weren’t streamlined; they were definitely publicity driven, and it’s probably best left in the “bandwagon” category.

 

I think, gentlemen, you are somewhat talking past each other using slightly different shades of meaning, and making distinctions that perhaps the evidence is sketchy for. Whilst the strict dictionary definition of streamlining is to design for lowered drag, in the 20s and 30s the aesthetic was everywhere. We may note that as at least a follower, and perhaps a leader in the Streamline Moderne style that developed from Art Deco the Southern streamlined their buildings, if not their rolling stock. I think we can safely assume that lowered aerodynamic drag was not a major consideration in the design of the new Woking signal box for instance.


(Photo:Gaugemaster)

Did the Hush Hush have a "streamlined" design in the sense of the contemporary aesthetic? Undoubtedly yes. But we may note that it would be hard to make a sensible casing for that boiler that was not somewhat slab sided and featured flat planes. Following the actual components of the boiler would be a fabrication nightmare and even worse to maintain and keep clean. The primary motive for the wind tunnel testing seems to have been smoke lifting, I don't think we can argue about that, but once you have the models in the wind tunnel why would you not measure drag if it were straightforward to do? And if you had a choice between a lower and higher drag model that were equally effective in smoke lifting then why wouldn't you pick the lower drag one? Its very easy for we enthusiasts to pick on one aspect of the design and say "That must have been the reason". In practice though we know every design is a compromise and the draughtsmen are balancing a host of factors, their own aesthetic sense being among them.

When it comes to the GWR locomotives its clearly a design for lowered drag, and demonstrates quite a number of the principles as understood at the time. Its interesting because unlike other streamlining treatments it seeks to minimise the lateral cross section, which has an influence in cross winds. Was it purely a publicity exercise? Well maybe, but the GWR certainly measured the effects on coal consumption. But then if the directors impose a design fad on you then you are certainly going to measure the effects, if only so you can say "Look, we told you there was no point and here's the evidence". One thing's for sure: is anyone going to argue that the aesthetics were a high priority?

Its very hard to pick up motivation. I don't know about the rest of you, but when I put together design proposals to senior management I emphasised the things I reckoned they wanted to hear, and which I thought would influence them to make what I considered to be the right decision. I certainly didn't say "and I'm going to spend a couple of days of coding time building in some hooks which will make it easier in two years time to do this next stuff I haven't told you about but I reckon we're going to need, even though it won't help things at all now." So if you're interested in studying the history of identity management at ***** County Council my emails and reports won't tell you the whole story - indeed nothing will because I reckon most of what was only ever in my head has pretty much been overwritten!

Was the Hush Hush streamlined in an aesthetic sense. Surely. Does that make it the first streamlined locomotive in the UK. Well, we're into semantics. Most UK locomotives were already far more streamlined than European and American ones because they tended to hide all the draggy lumps bumps, gadgets and pipes rather than have them out in the air stream. If it was only streamlined in appearance because all the other design factors sent it that way, rather than a distinct design for low drag does that make it the first streamlined locomotive or not... I reckon we can argue about that until the cows come home and not get a definitive answer.

And besides, I think if we are honest, and with the benefit of hindsight, streamlining steam locomotives for low drag was pretty much a red herring anyway, so arguing about who was first to do something that didn't actually need doing... Well...

 

If the shape was in the wind tunnel for streamlining then are the reports available that mention drag forces (Cd)?

The GWR attempts might appear laughable but shows understanding of basic aerodynamic principles, although practicalities ended up with bits getting removed bit by bit, i think overheating issues played a part, the picture you shared is after the valance around the front end was removed.

If you look up people who modify their cars for hypermiling they typically look like the GWR streamlining, because it's taking an existing design and improving it, as opposed to being made aerodynamic when it was designed. As an experiment, it is perfectly acceptable.

 

It's interesting to see a signalbox presented as evidence for the streamlining or not of a steam locomotive, that is for certain Jim!

I disagree that we're talking semantics though. Gresley's W1 is, by virtue of its development:

• The first steam locomotive in tested in a wind tunnel. No doubt of this. Photographic and report evidence confirms this.
• The primary aims are improved draughting and smoke deflection. No doubt of this. It's stated in the records throughout.
• Both of these above result in a design that is "streamlined" (aerodynamically better, perhaps, if "streamlined" as a word is an issue?) and this is commented on throughout the projects development and both primary and secondary sources of the time confirm that it is considered to be streamlined.
• It is the first to follow scientific principles where aerodynamics are concerned in terms of design. Unless there is evidence that another locomotive design was taken for wind tunnel testing prior to 1926, I don't think this can be argued with.

I take issue with the idea that the W1 (actually designed around genuine scientific principles in aerodynamics to improve its shape) is being labelled as "not streamlined" or not recognised as such, where the GWR locomotives (designed on a whim for the publicity department and very clearly unscientific) is somehow "understanding basic aerodynamic principles" (they're not. At all. In fact there's areas on the GWR locos that increase drag by way of the casing, not decrease it).

Fundamentally though, aerodynamics was really starting to get into vogue in the 20th century and the W1 represents Britain's Railway's first serious attempt at utilising these scientific principles. It should be recognised for this, as should Gresley and his design team.

Yes, because the whole point of the exercise was to reduce drag and maximise the air flow up and over the casing, and into the air ducts. You can only do both of these functions by reducing drag through shaping the front end and the sides of the casing to encourage the air flow over it. That's a really basic aerodynamic principle.

That it was for draughting and smoke deflection actually only gives you one outcome: a design which fundamentally has to minimise drag at some level. How well it does it, is part of the overall design development of Gresley's express passenger locomotives, because by removing the deflectors and reshaping the side profile around the smokebox, we get the superior A4 shape from the starting point that is the W1.

I find it difficult to reconcile that we are seriously suggesting the GWR efforts (no wind tunnel experimentation, no true understanding of aerodynamics applied, cross section and shapes not encouraging air flow but actually creating more vortices at different parts of the casing) are "streamlined" but the W1 isn't.

 

As you say, Semantics matter here.

Streamlined = "having a form that presents very little resistance to a flow of air or water."

Was the shape of the W1 to reduce aerodynamic resistance, or was it to funnel the air to the inlet and lift the smoke, (it can of course be all of that though.)

It WAS however shaped it'd seem for airflow and tested as such, so clearly was shaped through aerodynamic testing, although the Reynolds numbers for the pictured model could prove interesting.

 

Nevertheless its possible that's the case. If the W1 shaping was purely designed for smoke lifting with no intent to reduce drag then by the dictionary definition it was no more streamlining than the installation of smoke deflectors on an A1 or A3 was. To streamline is an action, but its defined by the intention, not the result! One may streamline badly! But personally I've never seen a proper analysis of the various streamlining implementations of the period to compare how well they worked compared to a bare locomotive.

 

I have it deep in my memory bank that the streamlining of an A4 saved about 300 hp at 75 mph over a conventional loco (i.e. an A1) but I can't cite that source and it may be total rubbish.

 

So what I’m getting from this is:

If something is intended to be streamlined, and is streamlined badly, then it’s streamlined.

If something that isn’t initially intended to be streamlined, but ends up so as part of a scientific process… then it’s not streamlined, despite the result physically and scientifically being streamlined.

Got to be honest Jim - that sounds like an absurdity to me.

And to be brutally honest I’m not buying it.

Yes, I think that’s true actually but I need to check for the source.

Any form of streamlining that makes something overall less draggy is a gain at all speeds. That it was measured specifically on the A4s in comparison to the A3s is something we need to take seriously.

The point I’ve been trying to make in a roundabout way is that the W1 was Gresleys first in depth experiment into a variety of different methods and developments of a scientific process for locomotive design. I am in no doubt of the importance of the wind tunnel experiments on the W1: it appears to have been the first so tested and modified as a result of such testing. The result speaks for itself.

I note that the wording of virtually everything that is released by the LNER to the press at the time of its development and then entry into service mentions “streamlined” - I think if the LNER thought this and sold it as such, and its gone through a process to meet with a more efficient shape aerodynamically, then it surely must be streamlined.

If it sounds like a duck, quacks like a duck…!

 

Interesting they claim "the first locomotive fitted with a water tube boiler to run in this country" - they must have missed this one from nearly 30 years earlier



(Drummond K10 from 1901).

Tom