Draughting arrangements for Bulleid Pacifics including the Giesl ejector

I am quite hesitant to comment on this as a pure outsider, but isn't this a monopolist view? In a competitive market
the customer would go for the most economical locomotive. I understand your point though!
Kind regards
Jos Koopmans

 

The suggestion on the table, however, is a whip round to provide the cash, not that either the loco owner or the railway is expected to pay. If either or both of those parties benefit as expected (respectively by reduced coal consumption and possibly by reduced maintenance) that will provide an incentive for similar modifications of other locos.

 

Imagine a typical railtour loco, burning - say - 50lb per mile on a 200 mile day. That's 10,000lbs of coal, say 5 tons allowing for lighting up etc - under £1,000 at today's prices. A 10% efficiency improvement saves you £100 per day, set against gross income of perhaps £40k - £50k for a train of 400 passengers. Even if I am out by a factor of two in the coal consumption, the savings to be obtained, as a proportion of the total money, look to be within the margin - about equivalent to one extra ticket sale.

Maybe Bulleid had a point after all...

If I were a rail tour promoter working on tight margins, I'd be looking at the efficiency of the catering and other areas well before worrying about coal costs. If I were a locomotive owner, I'd be wondering how I could pay for the modifications when I'd be passing on what savings there were, and those savings look to be tiny in cash terms relative to the totality of gross cash within the industry.

Tom

 

I suspect the suggestion of Bulleid locomotives for such modifications will also be extremely controversial.

The rebuilding of these locomotives is still enough to provoke heated debates on here regarding improvements v. 'Unnecessary vandalism' arguments around 50+ years after the event, the suggestion that the original design was deficient in a further area will only flame these fires I fear.

 

Finally some exploitation figures! However imho there is more to it, the test report shows that 1 lbs of coal evaporated between 6-8 lbs of water. Is there a sufficient amount of water in the tender for 200 miles? And what about the improved views if less steam is ejected?
As for the opinions on original design, it is poorly engineered anyway, look here what it says about the taper chimney entrance:
https://neutrium.net/fluid_flow/pressure-loss-from-pipe-entrances-and-exits/
Engineering should be left to the engineers and not to the public opinion!
Kind regards
Jos Koopmans

 

All our preserved locomotives are deficient. None represent the best that could have been achieved at the time of their design and construction and they are even more deficient when compared and contrasted with what can be achieved today.

The question is: Does it matter?

If the issue is one of the exhaust system being changed it is not as though such a change is irreversible. In a number of cases where the system has received the benefit of a more scientific approach there is no outwardly visible indication of such a modification being carried out. Further, if you are responsible for a working locomotive as opposed to a static museum piece you will come to a point where there is next to no original material left in the working machine. So as exhaust systems wear out and need replacing what is the point in not, when the time comes, taking advantage of the best that is on offer? We are talking about steam locomotives here and if you can improve the ability of a locomotive to make steam, reduce fuel consumption for a given power output and obtain a valuable increase in the maximum power achievable why not do it?

The extra performance insurance offered by a fully optimised exhaust is probably of more value on the mainline but which preserved railway would not want to make appreciable savings on its annual fuel bill? Though enthusiasts in general may be impressed by the products of a poor combustion system - recent "Tangmere"thread for example - there are those who are far less favourably disposed and it might not be in the best long term interest of the movement to give them ammunition.

There are other changes that can be made to locomotives that the onlooker would never be aware of. These would offer savings in efficiency, mechanical durability and naturally as an extension of these financial savings.

Bulleid did not get the point. His designs offer low power to weight ratios. But he was not alone. If you are only using a locomotive occasionally a simple saving in fuel use may not seem that important. use it for thousands of miles a week and it is another matter. The combined benefits of the exhaust system package, on the other hand, are well worth having.

 

there is considerable evidence available of occasions where 'minor' adjustments to loco draughting resulted in huge improvements.

those of us lucky enough to read the BR test reports of the 1950s are very well aware of such things. a friend of mine related how Sam Ell of the ex-GWR swindon test plant held a lighted cigarette to the top of a chimney of a loco under test, and the cigarette smoke was sucked INTO the chimney due to the cone of exhaust steam and gases of combustion not filling the top of the chimney! Sam Ell perfected the ordinary chimney with single jet and then double chimneys, but Jos Koopmans has shown that Sam Ell wasnt up to dealing with the multiple jet nozzles of the Bulleid pacifics.

a very simple and relatively cheap amendment to the Bulleid Lemaitre exhaust arrangement will, as shown by Jos, produce a much better exhaust also with reduced back pressure. such a modification deserves very careful consideration.

because of the cost of the BR test reports they are not generally well known. they transformed all manner of locos from the LNER V2s to the Ivatt class 2 and 4s etc.

there is quite a lot of evidence that the 'one size fits all' Lemaitre arrangement used by Bulleid was defective. see the SR Schools so modified.

because of the way the Bullied pacifics were made the change to Jos's modification should be very easy and inexpensive, and can only have significant benefits. coal consumption/cost is but one factor. Jos has already referred to stress and wear on the boiler. i would also suggest that all the MN and BB and WC pacifics could have their troublesome thermic syphons removed (one of the MN class tested by BR had none fitted and showed no difference from those tested with them fitted).

cheers,
julian

 

Generaly, arranging a water stop every 50 - 100 miles isn't too problematic. Coaling during a journey rather more so, though it should be possible to arrange at a long layover, i.e. at the destination.

Read the "diesels on the back thread"! I suspect many paying passengers rather like the wisps of steam coming past the carriage windows to remind them of what is up front! Certainly I've never known "the views were obscured by steam" to be a complaint ("obscured because the windows were dirty" - that's a different matter!)

Surely a key part of engineering is knowing which problems are worth solving though, and I'm not convinced that there is enough financial gain to be had trying to optimise what is essentially a Victorian technology. Negotiating a bigger discount from the wine supplier will have a greater impact on the tour operator's bottom line, for a lot less effort and risk, than trying to redesign the front ends of a large number of mainline locos of different types.

I think that there is an interesting academic thesis for an engineering-minded historian (or a historically-minded engineer) to look at what Bulleid knew about the physics and thermodynamics of front end design; why the MN, WC and Nelson all have a basically similar arrangement despite being different size etc. Such a study would no doubt be struck by the exigencies of trying to get designs out in the pressured atmosphere of wartime, and on a railway that didn't have static-testing plant of its own. An interesting historical study - but I can't see that there is a financial justification for carrying out modifications to what are, in the end, historical objects. You might as well stick a jet engine in a Spitfire and then wonder why - despite it being the fastest Spitfire in history - no airshow promoter wants to book you to appear.

Tom

 

Whilst this "armchair expertise" is all very interesting, those who propose these changes need to come up with a definite plan and sell it to loco owners and/or heritage railways. Some locos have had modifications of course - Giesl on 34092 and, for a while, 78022. A few have had Lempor exhausts fitted. Thus there is some data for the classes of locos involved but to involve different classes of loco and/or modifications different to those I've mentioned, someone has got to be the guinea pig to see if theory is borne out in practice.

 

A bit like fitting a Spitfire with silencers.

 

I suspect 242A1 would consider it an improvement

Tom

 

We jest but the Bristol Mercury engines in the Gladiator, Blenheim and Lysander were fully silenced. After all, we wouldn't want to disturb the Hun while we're bombing/strafing him now would we? Oops, off topic.

 

Straffed by a Lysander - eek!

Regarding modified/optimised exhausts, I think the benefits are only clear cut on the mainline. If you can get say a class 6 to steam both better and more reliably, you can add an coach or two, and that's where all the profit is, to fund that next overhaul. Just be sure not to overload, or else that overhaul might come round more quickly than you'd want.

Other than that, on a heritage line it makes sense if you've got a perennially shy steamer.

 

You remind me of something I read about the MSWJR 4-4-4 Tank engines, no 17 and 18. Supposedly they were spectacularly poor steamers, but the crews figured out if you wedged an iron bar (they say in the MSWJR book a jimmy so it presumably was a crow bar) across the blast pipe it spread the exhaust and thereby aided steam raising. Unfortunately it also significantly raised coal consumption so it didnt meet with official company approval.

Makes you wonder how many inpromptu mods were made by small companies down the years that just were not recorded.

 

Jimmys were often used according to various footplate tales, everything from bucket handles to custom made screwed expanding bars that could be moved from one loco to another. By splitting the blast you're creating a very crude twin nozzle blast pipe and increasing the surface area of the exhaust for entrainment of the gases - but how the split blast interfaced with the chimney is anybody's guess! There was also the danger of the jimmy falling down the blast pipe and causing havoc.

 

And there's the $64,000 question. How much real benefit is gained if you use the extra performance to pull heavier trains?

 

It shouldn't normally be a problem unless you start 'doing a Scotsman' and push up the boiler pressure and/or cylinder size so increasing power output. All you should aim for in most cases it to keep the needle on the mark in high steam demand or below average fuel quality situations.

 

How many times recently has lack of steam caused significant delays to other services? Thinking about recent high-profile mainline steam incidents: 34067 at Winchfield was due to poor maintenance. The Hall that caused a steam ban at York had at its heart a faulty ashpan screen. The Black 5 that failed on Parkestone Bank was simply overloaded - it couldn't move the train even though it was blowing off, so no shortage of steam there. Tornado failed at Chester(?) with a faulty air pump. The Castle trip was cancelled because the loco failed an FTR well before it got out onto the mainline. I'd be interested to see counter-examples, but how many trips recently have seen a loco fail, or run below required performance, on account of lack of steam?

I'd be interested to see someone from the industry - heritage line or mainline - set out a list of what they see as the major strategic challenges to the continued operation of steam engines, and how many of those challenges would be solved by improved draughting. Not many, I suspect.

Tom

 

Please forget "surface area" it has nothing to do with the jet entrainment. The dimensionless ratios that can be deducted for front-end comparisons do not use any surface area. It is the difference in momentum that is leading.
The flow passes the jimmy and connects again and the advantage is the obstruction of the orifice, so velocity goes up!
Kind regards
Jos Koopmans