Did this improve performance? Streamlined King + Castle

Added a couple of photos of the GWR Streamlined King and Castle
Did it actually improve the running or not?

6014 King Henry VII in streamlined form
https://railway-photography.smugmug.com/GWRSteam-1/Collett-Locomotives/Collett-460-designs/Collett-King-Class-60006029/60006029-Pre-1968/60136019/i-ZJ762Cz
5005 Manorbier Castle
https://railway-photography.smugmug.com/GWRSteam-1/Collett-Locomotives/Collett-460-designs/Collett-Castle-Class/Collett-Castles/5000-5012-4073-5012-Built-June/i-mg4nQ9D

Neil

 

Probably not, since the design was not continued.

 

I have read (in an O.S. Nock book if I recall correctly) that the streamlining was a token gesture by Collett to appease the PR side of the GW who thought they should do something when Gresley introduced the streamlined A4. It wasn't a serious attempt to streamline the locos and it has been rumoured that he picked up a lump of clay, roughly moulded it to the front of a model and said something along the lines of "there you go"

 

How much credit to put in those Nock stories is unclear. The clay thing seems very unlikely. Why would he have bothered to send someone out to find modelling clay and locate a model he wanted to abuse when all that was needed was a tracing of a weight diagram and a pencil?

Its an interesting exercise to compare the Collett streamlining to the streamlining of the 5AT project.

http://upload.wikimedia.org/wikiped...inal_form_(2011_painting_by_Robin_Barnes).jpg

http://c1.staticflickr.com/3/2782/4416925836_24ff9a1346_b.jpg

The other thing that might be interesting would be to model all the different streamlining approaches properly, including the effects of crosswind. It wouldn't altogether surprise me if Collett had managed a Pareto, achieving 80% of the benefit for 20% of the effort.

However as most authorities seem to agree that the typical GWR 'express' train, after making a fast start, could maintain the timetable by lolloping along gently at 55mph or so then the benefits of streamlining on all but a handful of trains would probably have been minimal.

 

Internal streamlining was as important as external streamlining and that's where the A4 won hands down.

 

I read somewhere that the external streamlining on the A4s was not really effective under about 90mph so I assume that was similar for the Duchesses. If this is so the rudimentary GW streamlining would have been no use at all. I'm sure the fitters and disposal staff found it a real pain. I remember being at New England when an A4 came over the pit ( I think it was 60029 Woodcock) and no one could locate a key for opening the cods mouth so proceedings had to be suspended while a search was organised to find one. It was good for me as one trespassing 15 year old was not the priority.

 

And yet we see similar treatments round the world on various European, US and Australian locomotives, and, as mentioned above, even on Wardale's 5AT. That's a lot of people making the same error. I would be interested to see a real study done on the aerodynamics, because all I've ever seen are people making, frankly, emotional judgements with no evidence behind them.
The 90mph figure emanates, AIUI from some testing Bulleid had done, and which I have seen questioned. If it had said 60mph I would believe it more easily, but I haven't done any tests either. However in "Master Builder's of Steam" there's a table of HP required to overcome head on air resistance for both the A4 streamlining and a standard LNER Pacific, which includes:
60mph
Std - 97HP
A4 - 56HP

70mph
Std - 154HP
A4 - 89HP

80mph
Std - 231HP
A4 - 134HP

90mph
Std - 328HP
A4 - 190HP

So clearly there's still a pretty big percentage saving at 60mph, but also at that speed aero drag is nothing like as important as it is in the 90mph range
However its clear that by 1948 no British CMEs had much confidence in the value of the big dustbin treatment, since they'd all dropped it. It seems clear everyone had decided they were more trouble than they were worth.

 

Apart from certain very Major routes ( I suppose ecml being one) its very difficult to run one train at 90mph + if all the other trains are generally scheduled at or about even time. So no lack of confidence in the big Dustbin treatment, just not practical to run everything at Dustbin enhancing speed

 

One of the key advantages of the A4 streamlining was the wedge nose proved to be an excellent exhaust lifter. The streamlining would have earned its keep on the pre war streamliners but less so on less illustrious trains.

 

Except Doncaster as they kept the casings on the A4s right to the end.

 

Bear in mind a Class 8 pacific can sustain somewhere in the region of 1500hp for long periods, and shorter bursts up to 2000hp or more. So a saving due to streamlining of 40hp at 60mph is negligible, whereas a saving of 140hp at 90mph starts to look more significant: it's getting towards 8 - 10% of the available sustained power. So the statement about streamlining only really starting to make a difference above 90mph rings true.

In general, all else being equal, the power required to overcome drag scales with the cube of the speed (which those figures show). Equally, I wonder whether on the LNER trains, cleaning up the underframes and intra-carriage gaps was not at least as significant a factor in reducing power requirement as what was done at the front end.

Tom

 

I believe the streamliners were designed as a complete package with quite a bit of effort going in to reducing drag of both loco and rolling stock.

 

Peter Townend in his book "East Coast Pacifics at Work" mentions that the Post-War A1 class were to have streamlined front-end casings the same as the A4s, but this was vetoed prior to the final building of the engines.

Cheers,

Alan

 

Though they did dispense with the side skirting.

 

It should also be noted that still air conditions are seldom encountered which is why the H.P. required to overcome head on air resistance was calculated for speeds far higher than 90mph for the A4, running into a 30mph headwind at 60 mph is the same as running at 90mph. And so on.
The A4s were a remarkable compromise the streamlining was good enough for the times when it was built and the exhaust clearing of the design was a serious, though originally unintended, safety feature.
If you can obtain access to Michael Harris' book on LNER coaches you can read of the care taken to attend to the air smoothing of the rolling stock that was built for the streamlined trains. Add in the speed at which these trains were built and the whole package produced by this impoverished company was a truly magnificent achievement.
Did the GWR have to make an attempt at streamlining? I suppose that you have to understand the times. They felt that they had to but in truth did not need to when the nature of their operations are considered.

 

To improve access to some of the mechanical gubbins but the basic streamlining remained.

 

I recall a figure somewhere between the two being cited for the benefits of streamlining with reference to London Underground's 1935 streamlined stock prototypes. Even in the tunnels, they didn't offer a benefit.

The result was the 1938 stock that is still in service.

 

It would be very easy to do the tests - grab a few old Hornby models and find a friendly graduate student...
In my own wind tunnel days, we tested various Airfix kits between "official" experiments, and a few model birds (duck, kestrel, seagull) but sadly not any locos.
The LMS did wind tunnel tests on the Duchess shrouding, and I am pretty sure the LNER did on the A4s (or the shovel-nosed P2 perhaps?)

 

LNER did test A4 models in a wind tunnel.

 

As a publicity move it was entirely logical to go for the bullet type streamlining as an alternative approach to the bathtub type, particularly as Castles and Kings were already built close to the weight limits (I assume Manorbier Castle remained classified red).

But the disappointment lay in the detail, the front shrouding wasn't as smooth as it could have been, the steam pipe casing could have been run back to join the splashers and why, oh why, did the copper chimney cap and brass safety valve casing have to remain? A bit more care and enthusiasm in the execution could have resulted in an appearance that was admired rather than ridiculed! Though a tender more along the lines of the later Hawksworth design would have been more appropriate too.

Never mind, at least they also had the streamlined railcars!