Improving loco performance - re-rebuilt Merchant Navy?

In the thread "The engine I want to see for the first time is...", 242A1 raises the interesting question of applying the practices of Chapelon and da Porta to British locos. Rather than hijack that thread, I thought I'd start a new one.

Here's the scenario: one of the unrestored Merchant Navy locos changes hands. The new owners have an interest in engineering, access to good workshop facilities and a small team of enthusiastic volunteers with good general engineering experience and skills. Any specialist work will have to be sub-contracted at commercial rates. The budget is £500,000, and let's say that the boiler and firebox will cost £250,000. Instead of restoring the loco to "authentic" condition, the new owners want to advance steam locomotive design. They wish to reduce running costs, increase availability and increase usable power.

What would you do, given the chance? Roller bearings? LemPor exhaust? Caprotti valve gear? Could you reduce the coal consumption and increase the power output, or would it be one or the other? And what could be done to improve the adhesion, to use any extra power?

 

Fascinating idea. Roller bearings, capracotti valve gear, streamlined exhaust ways, triple compounding, increased boiler pressure, bogie tender with condenser, oil firing, water pre-heater to name but a few things.

Even with all that you will have a couple of numpties squwarking over the paint!

 

I like the suggestions above, except oil firing (purely because I like shovelling coal!) but would also add a steam coal pusher to the tender to make life easier on the firemen. Do Merchant Navy's have slack dampening gear built into the rear of the tender's front wall like some of the standards do? If not, I'd include this too!

Bigger water tank for greater range. (possibly a tender tank re-shape - why not?!) Dependant on steaming - nice big double chimney with suitable blast pipe - possibly a new design.

Having not worked on a Merchant Navy to date, I don't know what type of injector controls there are in the cab, but I would definatly go for something similar to Lord Nelson's if possible - fantastic to use, great pick up, very straight forward! I would almost call it gorgeous! :-$

Modernised cab fittings (if your going down the route of updating things) such as can be found on modern traction, including comms gear, lighting, etc. electrical connections for lamps, etc a-la Tornado?!

Front cab window wipers just for a laugh!

 

I think you may have lost sight of the budget along the way there. You've only 250k to spend - remember what Tornado cost. So we need to optimize the shopping list for maximum benefit I think?

As you've already got one of the best steaming boilers ever made, I'd go for anything that improves combustion efficiency. Have a look on the 5AT site for ideas. eg air-preheaters. Better steam passage ways and blast pipe/chimney design are also high on my list, and if the budget allowed then improved valve arrangements - maybe caprotti or else leave as is but with twin piston valves per cylinder (not easy on the inside one though I imagine. Roller bearings are worthwhile too.

Just remember to leave enough money for several different coats of paint to please the rivet counters.

 

Good point, I did forget about the budget here. Your definatly right with pre-heating and airways though, but how much will research into this cost? Can it all be done in house? Would be nice to try!

 

Would there be sufficient scope within the UK loading gauge to apply triple compounding in a meaningful fashion?

 

250k is the budget for the inital restoration, but hopefully if that's successful, more money will be available for steady development, as has happened with 71000, IIRC. So our imaginary team would need to do the things that require major modifications to frames or cylinders first, and things that can be done during or between intermediate overhauls can be added or enhanced later.

IIRC, Ian Riley has already proposed an 8-wheel tender with increased water and coal capacity for his MN. I imagine something the length of Lord Nelson's tender, and the height of a normal MN or even an A4 tender, riding on a pair of 2-axle bogies. What capacity would that give? 7,500 gallons and 6 - 7 tons coal? I'm sure I've seen Bulleid tenders with water sprinkler pipes around the coal space, though I don't know whether that's original or a modern addition.

OVSB was very keen on improving conditions for the crew. He put both injectors on the fireman's side, electric lights on the guages, steam-powered Ajax fire doors, and provided seats both sides. Don't know how the injectors compare to those fitted to Nellie, though. Obviously, any improvements in that respect would help.

How much modification would be needed to the firebox for gas-producing combustion? Do you have to have mechanical stoking to make it work?

IIRC, the 9Fs that had mechanical stokers fitted were much harder to fire manually, because the mechanism intruded into the cab floor and required the fire doors to be higher and smaller than normal. And of course, they often had to be fired manually because the damn thing kept jamming, because of ungraded coal and poor maintenance. Not saying it's not worth doing, and I can see that it would really help sustained power output, but how much does it improve the efficiency?

I imagine that replacing the MN's Walschaerts valve gear with Caprotti or similar would not be worthwhile unless the original was damaged or large parts were missing. Likewise, replacing the existing single values with pairs would require new cylinder castings and so not something you'd do unless you had to replace damaged cylinders anyway.

Bulleids already have a fairly soft draft and low-ish back-pressure thanks to the Lemaitre exhaust. That can certainly be improved, using Porta and Wardale's developments. Not sure, though whether a double-chimney arrangement is necessarily better than a large single chimney? The down side of improved drafting always seems to be drifting exhaust, especially when running at short cut-off. Is that necessarily the case? And if so, what can be done about that? I suppose the radical approach is to turn the loco around, like an American "cab forward", but that probably only works with oil-firing, and would need a rather different bogie design. The pony truck under the firbox was designed to trail, not to lead. Instead, some aerodynamic work is needed around the smokebox and chimney. I wonder if a formula one team would like to do some unusual work on their fluid dynamics simulators, now that they're not supposed to use them as much during the season? BR never added a wind tunnel to the Rugby testing plant, did they?

 

i think the reason rugby never had a wind tunnel is that the aerodynamic effects on locomotives aren't as major a component of drag as they are for cars or planes. while the effects of windflow over the locomotive will play a part, remember that carriages aren't very aerodynamic either- the tiny additions such as open windows, latches, and the gaps between carriages mean that for a train of mk1's (newer carriages are much better) i reckon the aerodynamic drag of the carriages might make up as much as 2/3 of the overall drag. so to build a wind tunnel capable of holding a 12 carriage train would require also getting a fan capable of providing a flow of air over that distance, which would greatly reduce any accuracy.

i think if i was going to rebuild a bulleid, a merchant would be better as there is the larger platform for improving the boiler. the first thing i would do is computerize most of the running- a computer could easily work out when to ignite all or half of the burners, when to inject water into the boiler, calculate the range accurately based on oil and water consumption, whilst intergrating all the electric boxes needed to make steam legal on the big railway. a computer could do things that no fireman could do, like accurately gauge the temperature of the fire, operate injectors, determine which burners to use etc. it could even have an intergrated cctv setup to alert the driver of objects on the line or people sticking their heads out of carriages. i suspect that on the mainline a 'digital locomotive' would still have a second man.

the boiler would need several thermic siphons and several oil burners, which would effectively make the boiler half air tube and half water tube. then better cladding- curved ceramic plates ideally- would reduce heat loss through the boiler barrel and cab drastically. to improve water quality, a reverse osmosis plant could be designed into the tender. the fuel would have to be oil, it is much more easily moved and requires much less effort to burn.

 

With all the talk of improved/faster stoking and aerodynamics it sounds as if this engine would be allowed to run prolonged above 75mph. As it will most likely not run above that speed on NR, I doubt you'd actually need to drastically modify the standard MN, the benifits would never be seen.

If a mechanical stoker were introduced without causing problems with the cab floor and firehole door and assuming the grade of coal used was perfect and the stoker never jammed, it means you can get the coal in faster and make more steam, but assuming the MN's can make enough steam for 75mph running without wearing the fireman out, would all this be a bit pointless?

Ceramic cladding would add weight that would counter the heat loss saving. Foil sheets under the cladding to trap radiating heat would be more appropriate, again such as used on Tornado.

 

A stoker was fitted to a MN on a trial basis - 35005 was the loco IIRC and under trial conditions it consumed around 25% more fuel. No idea whether there was a commensurate increase in steam output, but I would doubt it - probably more clag though.

 

If I recall correctly, the trials of the mechanical stokers ( at least one 9F was also fitted) had more to do with burning lower grade coal than obtaining greater output.
The increase in consumption of 25% was not unexpected however the volume of ash was more than expected and showed that additional modifications would be needed..

 

I still think it's not going to show true potential.

This is an old engine with old parts and a mix of new bits... what point a new boiler if the cylinders going ala 73096.

I say build a new one to new standards, but consider building a similar class member to original specs...

Yes it costs more.. but at the end of day are we teaching old dogs new tricks or restoring historical locomotives, neither is improving locomotive performance with new technology... who knows if it the new one has carbon capture technology, Gordon will pay for it

 

just put it back as original. And put right the lack of attention to detail that OVSB inflicted on them.
And you will have the finest steam locomotive ever.
Yes, with a huge 8 wheel tender.

 

Aren't some of you discussing some methods that are already being set out here? http://www.5at.co.uk/
And with the Automatic stokers, this had been, tried and tested and failed? Plus the Giesel Exhaust as applied to 34092?
Air Conditioning would be a must on a Merchant Navy though - Be it the summer months or winter...
But I like the idea of the tender with more capacity.
Also as for Aerodynamics - Unless it looks like the front of an A4 that wouldn't be Bulleid now, would it?

 

How much air-conditioning do you want on a Bulleid?

You have the side windows, and air circulating between loco and the tender. That was enough for us in the Steam Days doing 90 mph

 

On a Merchant loads! On a WC, not so bad - But a difference between doing 25mph on a preserved line to 90mph or the limit of 75mph as it is set at now-a-days...Free Air-Conditioning at that speed..

 

For the speed of 25 mph, and a 10 mile run; a piece of cake.

Back corners, and under the door; and fire accordingly. The job is done on prep.

 

"The Position of the Locomotive in Mechanical Engineering" - I.MechE. Presidential Address by W.A. Stanier, 1941. Published in full within the IMechE Proceedings and can be found in most University Libraries: -

He begins by explain the most British compounding attempts suffered from condensation losses and lack of understanding of the principles of steam flow. He then goes on to say the only British locomotive to apply superheating to the compound was the Midland Compound and within the limits of size good work was done by the class, but its cylinders and valve gear has never been modernised so its actual efficiency is below that of present day simple engines. He also explains that the De Glenn locomotives of the GWR did not meet expectations and following chapelon's work it is now known these locomotives were strangled by the effects of restrictions in the ports and passages.

Then comes the interesting bit: -
"Now that modern French investigation has so expanded our knowledge of how a compound locomotive should be designed, the question naturally arises, why we should not in this country abandon simple for compound expansion? The answer is that the thermal gain would be more than counteracted by a mechanical loss. Figure 10 (a diagram titled "Cylinders of representative Four-cylinder compound locomotive applied to London Midland and Scottish Coronation Type") shows it is incompatible to combine within within the British Loading Gauge both the large low-pressure cylinders which are required and the bearing and crank dimesions shown by experiance to be essential for freedom from heated bearings and for high mileage repairs."

As for tripple compounding Stanier explains the mechanical and space disadvantages are even greater and there were only two attempts - Webb's 1895 attempt with a 2-2-2 and the Delaware & Hudson RR 4-8-0 L.F. Lorree in 1933 which was withdrawn shortly afterwards.

I found this an intersting insight into his view on the topic and shows that the Derby drawing office did have a serious go at trying to making it fit. The diagram is a plan view of the engine and shows with the compounding cylinders to the dimesions required by Chapelon's work. The external HP cylinders would foul the loading gauge by two inches either side and the cranks of the inside LP cylinders would only allow 7 inches between the back of the driving wheels and the sides of the cranks for the axle boxes (Coronation axleboxes were 10"x10"). It also could not work the otherway around (as per 242A1 etc) with the LPs on the outside and the smaller HP inside again because of the loading gauge.
I am not sure why the cylinder centre lines had to correspond with the centre-line of the driving wheels unless it was a pay off of loosing space to the boiler/smolebox or there was a fluid dymanic reason against haveing inclined compound cylinders.The diagram is a good indication of the limitations in bearing and crank axle sizes caused by the British Loading Gauge. The cannon boxes required to fit roller bearings would not have helped this situation either.