Design of boilers

If one was to present an accepted design of copper loco boiler to a club and the only deviation from spec was that it had been professionally TIG welded, with relavent certificates would it be accepted for test ? And if not why ?

Yet if it was built by an amatuer and silver soldered it would be ok !

With current costs for copper and silver will there be a movement towards small welded steel boilers ? I seem to remember in ME that someone did tests on the reative conduction of copper and steel and found that in REAL terms there was no significant difference, especially if one then used expanded copper tubes..

Any thoughts ? Noel.

Edited By noel shelley on 03/03/2021 21:45:28

Thank-you. yes, I did discover the sorts of fields in which matrices are used, including graphics programming; but only much later. The course taught only their internal manipulations, no definitions, no purposes, no examples.

We would not have been what a "transform matrix" is or does, only how to transform it, perhaps.

I think computers like matrices because they suit the physical nature of the circuits.

'

My work-place sometimes took on work-experience students who then found the company's stock-in-trade unit, the decibel, hard to grasp because schools had no idea why anyone uses logarithms, so don't teach them.

The worst example of educated ignorance, though was told me by a scientist who asked a student to determine the real wind-speed and direction from its measurements on a survey-ship cruising obliquely to it. She thought it should be fairly straightforward for him, but he had to admit knowing nothing about trigonometry as he had never been taught it!

'

I recall my nephew once stating you don't need to learn much maths because you have calculators. I asked him, "How would you know what you are trying to calculate and how to do it, and so know what to enter in the calculator?" He could not answer that one.

Best not ask him to calculate a boiler shell strength then....

The Inspector may want to see some evidence of weld design eg type of weld prep to give a sufficiently strong joint. Also stay spacing may need to be looked at, I know from the Aussie code that the "flat" area is taken from where any radius from flanging ends so having no flange for a welded joint would give a larger "flat" area requiring staying.

As the Welding is almost certainly going to have to be done by a pro then labour cost is likely to be higher than a few sticks of silver solder so I doubt it would work out cheaper than home building but should offer a saving over the cost of a professional boiler that is flanged and soldered.

One of my copper boilers was TIG welded, with the stays adjusted accordingly. The tubes were silver soldered as TIG welding here is a little more difficult and I doubt the results would be satisfactory on copper. That boiler is still going strong with many, many steaming days under her belt.

I am not a fan of any requirements for professional or welder certification for the smaller boilers. If the club boiler inspector is any good he would pick up welding problems just by visual inspection, especially if TIG is used. Whether intended or not, requirements like these just make the hobby exclusive. We actually had a professionally built steel boiler imported by one of our members from the UK. I was asked by our boiler inspector to have a look at the dissimilar welding techniques used on the tubes. Not something I would recommend on a boiler, but I said it would not result in catastrophic failure so the boiler was allowed to steam. Not 6 months later the boiler failed on the fire door ring due to poor root penetration. The member told me later that the only subsequent service from that “professional” supplier was lip service!

Personally, all my boiler designs are run past our boiler inspector. Weld root design, photos, material certificates etc. all become part of the data pack and this should be done even for the smallest boilers. My view is if he finds something he’s not happy with, he’s helping me in the long run. You most certainly don’t have to be a professional to do a good job…

In the UK a non-coded welder needs to submit recent weld samples to professional inspection to comply with the current boiler code in addition to the inspection by a club inspector. This applies to all welded boilers and the material (welded steel or TIG welded copper) is not specified.

See paragraph 6.2 here **LINK**

Thanks for the link, I've downloaded it and I'll go through it. Standard test samples are welded and tested to destruction for our club inspector as well. This is just good practice.

I'm curious, if you shake a cola can does the professional inspection authorities come running

How I empathise with Nigel's problem with Matrices, which is just one example why maths is difficult to learn and teach! Although interested in theory, I have a practical mind that sees little value in learning complicated stuff with no obvious application. I get bored.

The problem is that a great deal of mid-range mathematical techniques are building blocks, not obviously useful in themselves. Textbooks illustrate matrices with simple examples, which seem to complicate sums for no particular reason. I remember thinking at at school quadratic equations were an interesting puzzle with no application, and switching off. More fool me.

You have to accept mathematical building blocks pay off when advanced problems are tackled later. As one of my books casually mentions: Many equations are apparently not quadratics are reducable to quadratics by a suitable substitution. Suddenly the advanced student, having been taught to solve apparently useless quadratics, discovers they help solve difficult problems like finding the radius of a large pipe with two small rollers and a pile of slip gauges.

Likewise matrices don't make much sense manually, but become super-powerful whenever a calculation involves manipulating tables of data and/or tables of formula. For example a 2D CAD object defined as a series of X,Y coordinates can be transformed, rotated and mirrored with ordinary methods, but by a quirk of mathematics, it turns out the 2D calculation is done more efficiently by a computer in matrix form. And another major advantage appears when the CAD package has to transform X,Y, and Z coordinates in 3D. In matrix form, the 3D calculation is similar to 2D, whilst conventional formula applied to 3D transformations become downright clumsy and inefficient. Then, if a 3D object is moved in time, i.e it exists in 4 dimensions, the conventional approach suffers another painful explosion of complexity, which the matrix form doesn't. And best of all, matrix calculations can be parallelised in hardware, making matrix calculations super-fast. Note that most of these advantages are low value to a chap using paper and pencil methods.

As most home engineering doesn't involve much calculation of any sort, it's not obvious why matrices are a jolly good thing. We're like a canal bargemen: they have no need for advanced navigational aids such as compass, radar, GPS, chronometer, sextant, and a nautical almanac. Learning to use them is a waste of his time. A blue water sailor does need advanced methods, and anyone planning to land a probe on Venus is obliged to do even harder sums! Engineering is the same: building to a plan or assembling components requires practical skills; the need for theory and advanced maths kicks in when original design is required. Not many of us do original design because we copy existing practice. Bob's thread is interesting because he challenges that: I think he's on to something in that a thoroughly well-optimised design should perform better than approximations, but it's likely the approximations in existing boiler design aren't far wrong. The improvement might be tiny, or like Tornado, the modern implementation could be noticeably better than the prototype. (Partly achieved by improved dynamic balance, achieved by number crunching with a computer. Arthur Peppercorn would have done it in 1948 but he didn't have a computer to do the huge number of calculations.)

Dave

There's nothing in the MELG rules to say you can't present a professionally-welded boiler, in copper or steel, with its paperwork, to a familiar design, to a club boiler tester.

The difficulty is that the welder might insist on the copper being "phosphorous de-oxidised" - I don't know the metallurgy in detail but this is the grade for welding. It does not matter for silver-soldering. Consequently it may well be easier and perhaps not significantly more expensive to have the whole thing supplied professionally, and indeed there is at least one manufacturer in Britain, of welded copper boilers.

However, there are also anecdotes of club boiler-testers declining boilers needlessly, and it would not surprise me if one refused to test a boiler made in the way you say, merely for it not matching his misunderstanding of the rules. (One is said to have rejected a boiler because its builder had increased the firebox wall thickness! I think another objected because the feed clack bushes were in better and more prototypical locations than drawn. )

Whilst moving to steel boilers may give sizeable material cost savings, I think in the UK at least much of that saving would be wiped out by the bureaucracy. The regulators and insurers between them have basically made it impossible for any but professional boiler-smiths to supply and build completely, to costly certification schemes for material, fabricator and assembly.

I think it is time we in the UK started to look at alternative (not necessarily replacement) materials. Cost apart, I cannot see a convincing reason not to use stainless-steel or silicon-bronze of their appropriate grades for the application - but whilst the bronzes are stronger than but can be formed and silver-solder in the same way as pure copper, I think the selection and welding of stainless-steel very much for the professionals. The real objection is the greater cost of these more exotic materials.

Going back to the roots of this thread, the Wahya boiler is a 4.2l stainless boiler designed using modern materials and modern heat transfer design techniques. The cost of the boiler was 170GBP (just converted the receipts). What is of particular interest is the grate size (which is small) relative to the cylinder swept volume, and yet it’s an incredible steamer on our poor quality coal. I TIG welded the boiler myself and am by no means a professional (I don’t do it for money) or qualified (no papers) welder. My personal view is anyone capable of a fine model has the ability to master welding with little effort. It’s sad that bureaucracy is limiting development in the hobby (in the UK).

Better still is to have the actual boiler welds no destructively tested for a modest fee which should be accepted, thread on here where that was done.

This boiler was home welded steel and cost less than £200 for materials and ND testing, insured via usual club insurance so Nigel has it a bit wrong about the red tape preventing it from being done, it is more down to how few home builders can do a good welding job

Edited By JasonB on 04/03/2021 13:05:02

Luker -

I agree with your sentiments entirely but unfortunately our hobby became swept up in the European Union's 'Pressure Equipment Regulations', and the legal definition of 'work'.

The PER, in its English-law manifestation, seem written by and for lawyers who have heard of 'welding' and think all pressure-vessels are of aluminium or stainless-steel. The legal requirements are mainly trade-controls and to keep 'Notified Bodies' (test laboratories) rich, but include "...is, in fact, safe" - at the end of the list!

The PER apply only to boilers made and "placed on the market by way of trade". So the professional boiler-makers have to obey the rigmarole of certificates, Notified Bodies and CE mark (being replaced in the UK by a new, non-EU, one). Implicitly, we amateurs can still make our own boilers as we wish from the materials we think appropriate, according to the PER, as long they are, in fact. safe! And we can sell them, as privately-owned property, but not as traders.

A trade-built boiler pre-dating the PER is still legal. It has only to pass normal boiler-tests.

'

Now , we are also victims of precedent.

A few years previously the Health & Safety Executive (HSE) decided that clubs offering miniature-railway rides to the public are "fairground attractions" needing to be under professional show-trade equipment rules on design, construction, testing, maintenance and use of said equipment. This could have crippled or even destroyed the hobby.

Naturally, we expressed collective dismay. I attended for my society a meeting between clubs and Her Majesty's Principal Inspector of Fairgrounds (for the HSE).

Fortunately HMPIF was a reasonable chap who understood our predicament.

He explained the legal point that by inviting the public we are "at work", despite no-one being paid in cash or kind, we are under a 'legal duty of care' (DOC); and need to be able to show we are discharging that responsibility "as far as reasonably practicable". It means as well as engineering precautions, preparing Risk Assessments and records of operation and maintenance of society equipment... and taking the recommendations those show up.

He said something very important: "You are not building nuclear power stations!"

In other words, use common-sense, don't stifle yourselves with self-generated paperwork.

'

Hence the umbrella committee, the Model Engineering Liaison Group (MELG), representing from the various society federations, insurers and HSE.

MELG created the boiler test regime so engine-owners and club boiler-testers can follow the DOC and PER; keep the insurance-business happy - and be safe! (The Book of Procedures, bed-time reading only for insomniacs, could be better arranged.)

So, the DOC includes that our engine boilers are safe and can be shown as such, as far as practicable.

As stressed at Northern Federation of Model Engineers meetings I have attended, if your club can show it has done its best to protect members and visitors, then it is far less likely to be a victim of a spurious insurance claim (some try but are rebuffed); and if the worst happens the "man in the curly wig " is much more likely to be sympathetic in Court.

'

PER does not say who may or may not design and make welded boilers, but they lay down material, fabrication-inspection and skill requirements too stringent for most but fully-trained, coded welders to follow; and the insurers can only insist on the rules.

'

I say the MELG boiler test book is not easy to follow. It and the certificates seem designed as confusing as possible. This has led to tales of nervous society boiler-testers ( volunteers free to decline to test a boiler unfamiliar to them) "failing" perfectly good boilers through not understanding the rules properly. That though is their, and their clubs', fault. They are not supposed to fail equipment without good reason.

Finally I did not say the rules ban a home builder welding a boiler, just that the requirements make it nearly impossible.

'

I own a 7.25"g version of LBSC's Juliet . Its boiler is its second, is of copper; the last built by Reg Chambers. The loco was built originally as a club project, with a steel boiler made by a professional welder with no steam-loco knowledge, using ordinary seamless tube and hot-rolled mild-steel plate of unknown provenance.

The steel boiler had expired in service after 20+ years' hard use, quietly extinguishing the fire by a corrosion hole in the (unstayed!) firebox. I cut it open. The firebox was badly corroded, not helped by the gauge-glass bottom nut being below the crown. The rest was in fair condition. That was before material certificates etc,, but the boiler was tested annually under a simpler though effective system.

I wonder what has been achieved by the red-tape...

Yet I have also been involved in failing a brand-new copper boiler of LNER pattern, built by a retired, professional copper-smith, faithfully to an anonymous drawing - oddly, he would not reveal its source. Lacking stays, the inner firebox had partially collapsed under the builder's hydraulic test to working-pressure. A very sad evening, and I think to his fledgling hobby.

Nigel-

Thanks for that background; it gives me a little insight into how the hobby is managed in the UK. All that red tape is bound to stifle innovation. Safety and common sense is incredibly difficult to regulate.

Thankfully our club has a spirit of helping the builders get the best loco onto the track, this includes the boiler. On the rare occasion a boiler is deemed not fit there are normally a number of club members offering to help fix the problem, especially if they see the boiler was self-built.

Nigel, your right I was the victim of a boiler inspectors lack of understanding of the rules ! It cost me over £300. see post no6 in this thread. The only good thing was that I bought a beautifully built commercial boiler with every conceivable add on you could think of. It is still unused and to buy the add ons NOW would cost almost what I paid for it.

It was built in 84 so no CE mark It was based on a design good for 70 psi and OD 5". The whole thing was enlarged to 6" and heavily built. The original test was 2X Wp = 160psi Wp80psi Doing some calculations it would be good for 120psi even with a saftey factor of 8. The club ticket it was given was wp100psi INTERESTING ? Noel.

Indeed. When I was suffering O-level maths in the seventies, there was no hint of any practical application for matrices, or anything else; pointlessness was regarded as a virtue - hence the fetishizing of Latin, that most useless of subjects (academic linguists are free to differ).

The reason that matrices are used in CGI is that a common construct in computer programming is the array, and a matrix is, essentially, an array, and can be manipulated using simple rules.

Human-friendly controls in the program's user interface essentially manipulate vectors which conceptually aren't as easy to represent in the computer's world. It has to convert them into lower level arrays to actually work on them.

To comment on the thread, from which we've drifted, I think its interesting to consider whether boiler design can be improved, even if the practical answer is that there's no point/it's as good as it gets already, or whatever.

I agree!

I wonder what an engine specifically engineered to win IMLEC would look like. An engine with no obligation to resemble a full-size locomotive, or to be practical beyond winning IMLEC, and run in conditions that don't require the boiler to be certified.

I suggest:

• A tall vertical boiler balanced by outriggers
• Draught created by a tall chimney, not steam blast
• Waste steam used to pre-heat air intake and tender water
• Scale prevented by only running on distilled water
• High pressure, possibly from a water-tube boiler, with efficient superheat. (Isn't a water-tube boiler the logical conclusion to Bob's idea? It's all done with radiant heat.)
• If a fire-tube boiler is used, corrugate the firebox
• Oil burner to maximise heat and remove ash issues.
• Only burns one oil of known heat value so that combustion and heat transfer can be optimised.
• Grate area, firebox volume, and heating surfaces, calculated and proportioned to match the fuel and to optimise IMLEC performance.
• Large diameter steam pipes and a big steam chest
• Valve gear simplified to minimise friction
• Large aperture poppet valves, precision made to minimise leaks, possibly from exotic materials.
• Everything thoroughly insulated without regard to appearance!
• Optimum speed and load determined by experiment with a Dynamometer Car, and observed during trial
• Maximum automation allowing the boiler to control input and output to eliminate the possibility of a heavy handed driver wasting steam with excessive acceleration, or otherwise running the engine outside it's sweet-spot. Also manages combustion to best effect, neither underheating or overheating the boiler. Remote control and automatic shut-down
• Ideally driverless and without human passengers because they wobble, shift and raise the centre of gravity. Also, removing people means bigger risks can be taken with the boiler, speed, and balance.
• Thermal proportions, weight, adhesion, static and dynamic balance and other design features to be computer modelled to optimise performance
• Only run the engine under ideal track conditions - level, stiff track in good condition, few points, and large curve radii etc. And only run on dry, windless days.

Slight problem with all this! Lots of expensive development and build work, resulting in a zero romance, plug-ugly locomotive only run on very special occasions. Just a bit dangerous too, with a risk it might not significantly outperform an ordinarily good IMLEC contender. And if it fails to win the builder will be hideously embarrassed...

Dave

Go on, build one!

Actually does sound like a great challenge or a new category!

FC

Wonderful!

It's that last criterium that will prove the hardest to meet....

I like the contradiction between fitting a high boiler and even higher chimney balanced by out-riggers (on rails or with counterweights?), and hauling no passengers with their raised c.of g.

BTW... We read IMLEC report comments like "Fred stopped to drop off 3 passengers ... " . Never mind the few ounces of coal consumed by the 1/8-scale loco, what of the weight of the 1/1-scale passengers? I've not read of discreet weigh-ins!.

More power to your elbow SOD. Jim Ewins made a loco to win IMLEC, called Jimmy's Riddle. It incorporated several of his pet theories, and didn't win. I think the lesson from recent IMLECs is build it big and drive it hard.

Many moons ago there was a competition for hot air engines run at the ME exhibition (when there only was one). A good start on SOD's trail would be a similar competition for stationary steam engines, it's a lot easier to build and develop a single cylinder engine than a loco, and easier to instrument as it's not moving round a track. Steam at set pressure supplied by the exhibition management, probably electric heating.

SMEE used to have a rolling road for locos which could exert some load (shades of Swindon/Rugby) not just having it running free on rollers

I'm three parts of the way there ! Got the the verticle boiler with tall chimney, Stuart No1, just need 2 sprockets and a bit of chain + the wheels. A bit of applied science and fine tuning and That's it ? Victor Ludorum !