Flash boilers

[MikeWilliams]

I was asked a few weeks ago now, whether I knew anything about flash boilers.  The answer was (and is) "no", but I hope somebody on here does.

Carson, the well known pre-WW1 maker of quality live steam locos in several scales, made their LNWR Experiment engine in Gauge 3, Gauge 1, and other scales.  The Gauge 1 version had a flash boiler and my acquaintance has the chance to buy one, which he hopes to get running again.

Has anyone done this?  Has anyone even seen any model railway engine with a flash boiler actually working?

I know they are not uncommon in toy boats, but that's a bit different and he wants to retain originality wherever possible, including the 100 year old boiler!

For those who know even less than I do about these things, I understand that a flash boiler basically runs dry, is heated, and a small amount of water is then let in, making instant steam.  The fast expansion and exit of the steam sucks in more water, and the process repeats, giving power in pulses.  Now, I guess most forms of propulsion are in pulses - pistons for steam or i.c. or commutators for electric, but I believe the flash boiler pulses are bigger and slower, which one would have thought was just what a model railway engine didn't want.

Any experiences would be interesting.

Mike

[454]

Would this mean that if the steam is produced instantaneously then it is not stored in a pressure vessel like a boiler?

[MikeWilliams]

That is correct Dave, and for that reason, using a 100 year old boiler is not so daft as it sounds because if a joint gave way there's hardly any volume of steam to do any damage.  Whether the boiler inspector would agree is another matter!

Mike

[Andy B]

To explain a bit more about flash steam, and in particular how Carson applied it to their model locos,  here is an extract from the catalogue of James Carson & Co Ltd, London, dated October 1911:


"Flash Boilers on Model Locomotives

A few years ago one of our customers wished to increase the speed of his model locomotives and consulted us. We suggested a flash boiler. He was a little doubtful, and wrote to a well-known and much advertised firm of model makers asking if they considered the scheme practicable. They replied, that having consulted their "engineer," that they were of the opinion that it was quite impossible to fit such as system within the limits of a 3 1/4" gauge locomotive.
Notwithstanding this, our customer had sufficient confidence in us to allow us to design and fit the system we proposed, and the results were eminently satisfactory. After the engine had attained the speed of 13 miles per hour, he was so satisfied with it that he placed another engine (built by the same celebrated firm), which took 35 minutes to raise steam, in our hands for conversion to the new system.
Some time ago we turned our attention to the 1 3/4" gauge locomotives, and while the model produced was eminently an advance on anything offered before we felt there was still room for improvement, especially as regards the length of time which such a small boiler will run for on one filling of the boiler. While we supplied ready means of refilling the boiler while under steam, the introduction of cold water necessitated a wait till steam again got up.
We therefore have, after much experimental work, perfected a flash steam boiler for these small engines.
With this system, the boiler becomes a coil of steel tube, coiled in a particular way and enclosed in an outer case or shell, so that externally it presents no difference in appearance to any other boiler.
The flame from a specially designed lamp blows on to this coil and incidentally the realism of the model is much enhanced by the view through the fire door, as the asbestos lining of the boiler shell, under the action of the flame, resembles a real fire.
One end of the coil is coupled up to a water vessel carried in the tender, while the other goes to the regulator which is in the orthodox position.
The water vessel in the tender is of ample size and should not be filled more that about half full. It is fitted with a pressure gauge and an air valve, which takes an ordinary bicycle pump.
The procedure is as follows:- Having got the blow lamp going, place it in position in the engine. As soon as the end of the coil, viewed through the fire door, begins to get red hot, air is forced into the water vessel by a bicycle inflator, till the gauge shows about 30 to 35 lbs.
The engine is then ready to start and will run continuously for 40 minutes if required.
The pressure in the water vessel falls slowly, of course, as the water is used up, but a stroke or two of the bicycle pump will restore this, and moreover the engine is to a certain extent self compensating, as the hotter the cylinders, et., become the less pressure is required.
Unless actually seen it is difficult to believe the enormously increased efficiency obtained by the use of very hot dry steam. The consumption of water is reduced to about one-third and the speed and liveliness of the engines are phenomenal."


The "well-known" firm was, of course, Bassett-Lowke, and their "engineer", Henry Greenly.

[David_V]

Hello Everyone and apologies for reviving such an old thread for my first post! However, I do have a reason...

I am the 'acquaintance' referred to my Mike in the Original Post back in 2012. I did eventually acquire the Carson Loco that he referred to. Here it is: (OK, I know this is not G3, so please humour me!)

As mentioned in the thread, James Carson & Co. were one of the best of the pre-war (Pre 1914) model locomotive manufacturers. While most other brands could be considered semi-scale, Carson took great pains to get his models more or less spot on.

Carson made locos in G1, G2, G3 and other scales. Today, perhaps the most common survivor is his LNWR 'Experiment' in G3 (So you see the post has some relevance!). Almost all surviving Carson locos have been re-boilered and I'm very fortunate to own two original Smithies boilered examples - a G1 'Experiment' and a G2 'Precursor'. Both of these have been brought to working order, the G2 model running on a special track created for the purpose.

Carson's 'Piece de Resistance' was the flash steam 'Experiment'. Carson built quite a few of these in G1 starting in about 1908 and they were highly thought of at the time. One owner called his "a demon of a goer". Since the Smithies locos were always somewhat anaemic (by our standards, anyway) there was clearly a demand for something more powerful and longer running. Carson claimed the G1 model would pull 10 tinplate bogie coaches and run for 40 mins, all with better efficiency than comparable 'internally fired' models.  However, today, very few survive. LBSC ('Curly' Lawrence, famous writer in 'Model Engineer') wondered in the 1920's "where they had all gone" and answered his own question by observing that the examples that he'd seen were thoroughly worn out.

I've known about these locos for a very long time and set out to discover if they really did work, and if so how well. My G1 Smithies boilered 'Experiment' came to me complete with the original burner and in good condition. It took little more than a new safety valve spring to have it running around an improvised track of G scale rail, the only thing coarse enough! The G2 Precursor needed many repairs and the backhead cleaning of soft solder and reflowing for original style fittings. This process showed how well made the Carson boilers were, and bodes well for G3 Carson owners like Mike, complying easily with modern model engineering standards. The completed Precedent runs very nicely for about 10-15 minutes on a boiler fill.

I first saw the flash steam 'Experiment' that I now own many years ago when even then it was far outside my pocket. I heard tell of it from time to time and when finally it became available again I knew fate was involved somewhere! But would it run?

The model is unique in still having the original blowlamp. As LBSC had said so long ago, these models were thoroughly worn out, mine being no exception, so quite a bit of remedial work was needed even to get it to turn over. Fortunately the running gear in the flash and Smithies versions is identical, including the beautifully engineered Hackworth valve gear, so at least I had a pattern to follow. The flash boiler and it's lamp is another matter, and there's still so much to learn..

Despite all this, I finally got it to run for long enough this week to capture the evidence on camera, and here it is:

Link to video clip > https://www.dropbox.com/s/fnzcvhuaeicoi0m/Video%2021-09-2020%2C%2015%2057%2050.mov?dl=0

A Gauge 1 flash steam Carson 'Experiment' simmering quietly on the evening of it's first successful run in modern times, 15 September 2020.

If any of you know of any other flash steamers out there, I'd be very interested to know. Already, through Mike, another more or less complete G1 example has come to light. And what about G3 flash steamers? They were built in a variety of gauges, and one time SMEE chairman Jim Crebbin said that a 3 1/4" Caledonian 'Dunalastair' "was the fastest he'd ever seen".

[MikeWilliams]

Welcome David.

I never thought I'd see a flash boiler engine in motion, so hats off to you.  I look forward to reading more about your exploits and having migrated from Gauge 1 to Gauge 2 I am sure we can convince you to make the obvious leap to the senior scale.

Like you, I would love to hear of a flash boiler in Gauge 3: running, derelict remains or even a mention in historical magazines.

Mike