Why

[Tom Quayle]

If only the NRM had relised this sunner because any enthusiast can see that as it was before over haul it is wrong so a coat of BR green and 60103 on the cabside is the best idea for it

[Matt]

Not at all, most people think of Scotsman as LNER, Apple Green. They won't notice a double chimney, and as for the smoke deflectors although they shouldn't be there in that livery, they are there for a reason, plus they look good. Alot more people would complain if it turned up in BR Green, than keep it as it is and just get the odd purist with nothing better to do winging about it's accuracy. Remember 4472 is a British Institution, not just your average engine. Be thankful it is going to be running for at least another 7 years, and not stuffed and mounted.

[x568wcn]

The reasons are simple really, the double chimney, is not just the bit on the top, it's the blastpipe underneath, and needs to be done during the overhaul, if they have one. With a double chimney, lots more smoke comes out of the chimney, and without the deflectors it would get in to the cab, and be a danger.

Mark t

[richard]

I hadn't really thought the logic of Kylchap -> greater smoke problems before (although I knew they existed).
The A1s and A3s had smoke problems - as did most express engines of the era - hence the appearance of smoke deflectors on many British express designs.

I think the logic goes like this (if anyone knows better - go ahead and correct me, this is partly my own reasoning here...)...

- Kylchap increases the flow of the exhaust steam from the cylinders (think of a performance exhaust or air intake on a car)

- As well as improving the efficiency of the cylinders, this increases the blastpipe draught over the fire. Hence better burning => better heat output from the fire & greater burning efficiency.

Increased burning would give more smoke.
Increased burning efficiency would reduce soot (or the size of the soot particles).
Greater blast might push the smoke out of the chimney at a higher velocity?

-------
re. 4472's livery: Whatever the NRM does, it will be criticised by some. It seems like there are lots of enthusiasts arguing for only genuine (pre-1968) livery/engine variants (also see the fuss about "Royal Scot"); but there's also a lot of aguement against all the "boring BR liveries" around at the moment. Well you can't have both!!!


Me? I think liveries should be varied. Eg. Did the B12s ever wear GER Royal Blue? That would be good to see again!
But also we should recognise that all working steam locomotives have been modified from their pre-1968 days. Authenticity should be balanced with modern running issues (in cab equipment, Tornado's boiler & tender, 4472's ears, etc).


Richard

[Colombo]

Richard has got it nearly right.

In the conventional single blast pipe, the products of condition in the firebox are drawn through the fire tubes by a vacuum in the smokebox. This vacuum is created by a blast of exhaust steam up the chimney from the blast pipe. The exhaust steam is accelerated at the nozzle of the blast pipe by the restricted cross sectional area of the nozzle. The smaller the nozzle the sharper the blast. This creates a back pressure on the exhaust steam passages and reduces the pressure drop available across the cylinders and so the use of steam becomes less efficient.

Locomotive designers had to optimise between a soft blast and poor steaming, but with more efficient cylinders on the one hand, and a better steaming boiler, but a less efficient steam engine on the other.

Kylela and Chapelon invented the Kylchap blast pipe and double blast pipe. By using multiple steam nozzles venting into a double chimney they were able to generate sufficient vacuum in the smoke box with less steam pressure drop across the multiple nozzles than with the conventional single chimney.

This enabled the locomotive to use its steam more efficiently and increase the steam output of the boiler by increasing the suction of air into the firebox, hence burning more fuel, which enables the locomotive to be worked harder.

The softer blast at the outlet of the chimney results in the smoke not being thrown high into the air and it sticks close to the boiler, thus obscuring the view forward from the cab. The sloping front of an A4 or the use of smoke deflectors pushes the flow of air over the chimney upwards when the loco is moving forward fast enough.

Colombo

[cooperajn]

Ole to Richard on liveries - remember how magnificent the Ivatt 4 Tank looked in Caledonian blue.
If you take the purist approach to its logical conclusion, any loco with electric warning flashes should be in 60s BR liveries - perhaps with a yellow diagonal on the cab side!

Incidentally, whatever happened to that particular piece of logic?
Duchesses, A4s, etc were not allowed under the wires because of their height - i am not aware that are any lower now.

TonyC

[richard]

Tony: Perhaps they're now allowed because they're running a bit slower, and they're also surrounded by babysitters and inspectors?

During regular running (1960s BR), each engine would have only had a crew of three including a guard.


Colombo: Thanks: So increased draught over the fire, but a reduced blast out of the chimney due to the Kylchap design. I assumed a straight through - what goes in must come out at the same speed
Makes sense as to why the A3s finally had smoke deflectors fitted even though their original smoke problems were known about in the 1920s/30s.


Richard

[cooperajn]

I think the point was that a double chimney of any design had a greater exhaust area and therefore reduced velocity; hence the exhaust was not forced clear of the boiler.
Ironic though that for all the experiments on Humorist and on Royal Scots, it was the Southern which introduced the basic deflector shape that was universal in the UK until the German design on the A3s.

TonyC

[x568wcn]

On the subject of the Duchesses, Duchess of Hamilton is being restreamlined, but not to the height it was originally, but to the modern day loading height, and as for engines under the wires? was it not down the the deforming of the wires from the heat and soot? but now they find the soot makes the electric pass better

And they used the German style deflectors on the A3s as they found them suficiant!

Mark t

[Tom Quayle]

But theres one thing we must remember about what is going to happern not what people want to happern and the truth is that a vote by steam railway readers means it will be in BR green. Only one problem and that is that 60800 is going to go back to LNER green. Why canrt thay be in the same livery to make double heading a better posibility. As for 4472 being an insitution as far as I can see I can name a few locos that desreve the title of Worlds most Famous engine as much or more. For example 4468 Mallard 100mph compared to 126.5 is no contest in my book and on looks I still think gresleys best works were the A4 and V2. Although not LNER we have to admit that 3440 was actually the 1st to do 100mph and I think the American Big Boys and Challengers are more imposing than scotsman.
Not being Picky just my opinion

[Matt]

and the truth is that a vote by steam railway readers means it will be in BR green

Nope, it will be LNER Green as 4472.

[LNERandBR]

The problem the NRM has is that the Usual Members of the public will not recognise Flying Scotsman in BR Livery. Also there is the 4472 Brand.

The only problem is that its got the Double Chimany and Smoke Deflectors of the 60's and the NRM's goal is to preserve its engines in original condition. Therefore the only way Flying Scotsman can be concidered original at the moment is to paint it BR Green.

Also Flying Scotsman hasnt got Vacume Breaks meaing that it is restricted to Mainline operation or a peserved railway which has air breaked stock.

The only way the NRM can have Scotsman in LNER livery without cousing conterversy is to bite the bullit and remove the Double Chimney and smoke deflectors and put a single chimney on it.

[Matt]

Which isn't going to happen, does anyone else not think it looks good in its current guise?

[Tom Quayle]

I think the oposite I think its hidious I think BR green site very nicely on Gresley locos just look at 60009 and 60800 (not for long). BR blue looks good but is even less prototypical than the mess it is in now

[x568wcn]

It's not a mess, LNER green is a much nicer colour to see running through the country side, I've never seen it in BR Green, and don't wish to either, so it's staying the way it is IT WILL BE LNER/APPLE/DONCASTER GREEN AGAIN!


Mark t