firing the boiler

[Eric Moffat 1Participant @ericmoffat1]

I have looked at Fred Graham's photo of his centre-flue boiler with considerable envy.

I built a similar boiler (nowhere close to the quality of work in his photo) mine has a capacity of approx. 500ml. and a flue diam. of 22mm.

I have been firing it with an adapted gas blow torch (scharnberger make) as this is the only adequate source I could find. The torch must be located 12mm back from the mouth of the flue. I now wish to put this boiler into a model of Mr. Harley's Miranda (yet to be built). I plan to present the complete model to my grandson, but as he is not yet old enough to appreciate the danger of an open flame gas torch, I have made a number of unsuccessful attempts to make a closed burner along a similar style to Mr Grahams,but, like Mr Price, I cannot get one to burn hot enough to generate anywhere near th BTU's generated by the blowtorch.

Can Mr Graham, or anyone else advise me how I can make a CLOSED heat source to fire a boiler of this size? I have made about 8 or 10 proto-types 2 of the closed type but without success, I must now admit an inadequate amount of knowledge/expertise to complete this project without the assistance of the members of this forum.

I thought if I completed enough proto-types I would sooner or later stumble on success, but I am not so optimistic.

thank you in anticipation

[Eric Moffat 1Participant @ericmoffat1]

[Paul TParticipant @pault84577]

Hello Eric

Can you post some photos of your work so far and some basic dimensions of the engine / boiler combination.

Paul

[martin ranson 1Participant @martinranson1]

Eric

Are there any cross-tubes down the length of the main flue? if it is an empty length of tube it may be possible to fit a piece of rectangular stainless steel gauze about 30 or 40 mm. wide, bend it into a long vee shape and slide it down the length of the main flue. This would generate a lot of radiant heat inside the main flue, it may boost the effective heat output of your burner. Is the burner a noisy ( or roarer ) type or is it silent? If you want some info. on other peoples ideas then try looking at MODEL BOATS for June 2005 or July 2008. These are of various sizes and are all the silent type of burner. The silent type of burner still sucks in air but is probably easier to hang onto the end of the main flue. You could also find MODEL ENGINEER for 03 August 2007, 19 June 2009 or 09 April 2010. Each of these articles is the start of a series. I would ask the same question as Paul in the reply above, this also leads onto the old,old question of whether the gas tank is starting to go cold as the gas is being used. If the tank goes cold it loses pressure rapidly.

martin ranson

[Eric Moffat 1Participant @ericmoffat1]

G'day Paul,

I have posted some photos on the photo place, I don't know how to show them here. I must emphasize, the complete engine,boiler system is a project in hand yet.

The boiler is 125mm long & 100mm in diam. with 4 cross tubes the flue is 22mm in diam.

The "V" 4 engine is Mr Arnott's design with only a slight modification, as is the boiler.

Mr Arnott's heat source was based on a "Taymar" gas torch, which they do not now manufacture.

I will attempt to produce photos of my own unsatisfactory burners very shortly (flat camera battery).

Thanks for your interest

Eric

[Eric Moffat 1Participant @ericmoffat1]

G'day Martin,

The aforementioned details may assist your diagnosis as applied to the boiler.

I will post photos of the unsuccessful burners shortly, I am sure, however the temperature of the tank is not a problem as the flame is inadequate as soon as it is lit & even when the gas is supplied from the source.(disposable can.)

Regards

Eric

[Paul TParticipant @pault84577]

Hello Eric

A few questions:

What pressure is your boiler intended to operate at and is the water supplied by pump or gravity fed.

What is the fuel gas and what pressure is the supply both in the storage vessel and at the jets? Can you also confirm the internal diameter of the feed pipe between the gas storage and jets.

What size and how many gas jets do you intend to use.

Looking forward to seeing the burners.

All the best

Paul

[martin ranson 1Participant @martinranson1]

Hello Eric

Looking at your photos, it seems the main flue travels along the boiler barrel and then up vertically through the top of the barrel. Is there a 90 degree plumbing bend to turn the corner ? Peters design was, I think, from quite a few years ago, did it use 22mm pipe please? or is the design from Fred Graham? the taymar burner you mention was either called a 2900 or a 3500 ? I think I saw it in Model Boats. Is that what you are working from ? I do not know if it used 22mm pipe but if I was building to your size ( 5inch length and 4inch diameter, that proves I am a dinosaur&nbsp I would have used 28mm pipe and squeezed in 12 cross-tubes with a diameter of 3/16 inch or 5mm using a Calor jet size 8. I look at the set-up and think it is a large boiler, large engine, but only a small burner with possibly not enough flame capability. Maybe Paul is thinking along similar lines? the gas pipe is, I hope at least 1/8 inch diameter. If the flame is instantly inadequate, then is the jet or the gas pipe partly blocked? Paul has asked what the pressure is supplied to the jet assembly. A pressure gauge on the piping near the jet is incredibly useful. Does the boat you are building actually need a 4 cylinder engine? Four cylinders, double-acting take quite a lot of steam.

hope it can be sorted out … Martin Ranson

[Eric Moffat 1Participant @ericmoffat1]

G'day Paul,

the boiler has been taken up to 50psi as that is about double the requirement of the engine.

the water is supplied by yours truly via the plug between the safety valve & steam supply valve.

the gas used id lpg/butane from a disposable can (see photo) via 3.5mm pipe internal diam app.1.75mm.

I am assuming a closed gas burner will have one jet. I have tried both no.5 & 12 without success.

the burners & other photo details are on my album. I have no idea how to show them here!

regards

Eric

[Eric Moffat 1Participant @ericmoffat1]

Gday Martin,

Peter designed the boiler with a 25mm flue using a 90 degree bend to the top. He only specified 4 cross tubes. Mine is slightly longer but slightly less in diam. so I estimate capacity to be very close to design.

Mr Harley's "Miranda" was powered by his own design 11mm bore twin cylinder engine (see album photo) I found this to be very "steam hungry" so I decided the "V"4 smoother running and not so "hungry", it purrs along very sweetly! running for 35mins on a full boiler.

the photos on my album may supply more info

By 3mm diam pipe, were you suggesting the inside dam. or outside?

Regards

Eric

[Paul TParticipant @pault84577]

Hello Eric

The photo of your burner shows a very slow and yellow flame which is systematic of a lack of gas pressure and/or oxygen.

The feed pipe between the gas storage vessel and the burner has many slight bends and offset soldered joints, it is possible that the feed pipe has become constricted either at a bend or with solder ingress which would result in a loss of pressure.

Before further experiments with burners I would suggest a pressure and flow rate test on the existing feed pipe or replacing the pipe with a larger 3mm or 5mm I/D pipe.

Can you tell me what you have soldered the joints with specifically those joints on the boiler and live steam pipes.

Have you any photos of the boiler before the lagging was fitted, if not can you tell me how the boiler was constructed and how the constituent parts are joined together.

Paul

[martin ranson 1Participant @martinranson1]

Eric

I wish the steam plant was sat on my bench so I could test out so many variables. However I realise that is not very practical. It would be so simple to investigate causes of pressure dropping, even swopping my burners for yours. looking at Pauls answers and mine I still think we are both heading in the same direction. I think that maybe it could take quite a long time before one of us hits on the right answer. We could easily be 400 miles apart and that is awkward….. All my systems have used 1/8 inch O.D. pipe which is usually about 1. 7 mm bore, I have happily run calor gas jets up to size 12 with this size of pipe. Incidentally when I wrote "calor size 8" I meant to type in size 5 … sorry about that.

If you want the layout of a burner for 22mm pipe I would still suggest you read model Boats for July 2008, page 51… the running pressure of the gas jet is typically 15 PSI ( about 1 bar )

P.S. I did not type in the smiling face halfway down my answer…. any offers how it got there ??

Keep trying … martin

[Eric Moffat 1Participant @ericmoffat1]

G'day Martin, I wish you could examine my steam plant too, but as we are much more tha just 400 miles apart, this is not possible. I am in the other side of the world in South Australia!!

I have twice bathed my gas jets in dilute sulphuric acid to lean any obstruction.

I find it more confusing when the gas torch burner produces precisely the flame I need, but my burner is not on the same page, both operating from the same fuel source!.

Thank you for you advice, I will obtain a back copy of July 2008 and wwork from there.

Regards

Eric

[Eric Moffat 1Participant @ericmoffat1]

G'day Paul,

It is not evident in the photos, but both the torch burner with the sought flame and the other, are operating direct from the disposable gas can shown in the other photo. I normally use that system to recharge my copper gas tank, but I wanted to demonstrate with the direct pressure from the source.

The boiler was constructed using a suitable length of 1.5guage copper pipe and same guage ends. The ends being further reinforced by 2 6mm s/steel rods running through the boiler and the rods also serve as mounting points for the completed boiler. All boiler joints and bronze bushes being silver soldered.

I always soft solder the supply pipes so that should the boiler run dry or the safety valve malfunction, then the system will fail at the weakest point and not explode. That is the theory at any rate. It has actually been tested once when I accidently let the boiler run dry and the heat then melted the soft solder and released the pressure with only damage to the stem pipe line. Similar to the sacrificial wire in you car electrical system which will burn out before your entire electrical system is destroyed.

As you can see, Martin has recommended I seek info. from july 2008 issue so I will continue to make more burners and who knows, I may yet stumble over the correct unit. I cannot recall the Latin phrase, but in English "bash on".

I have struck a number of problems during the construction of this steam engine system. Probably all due to inexperience, but using trial and error I have reached this stage and I refuse to be beaten by the final problem. There is an answer somewhere.

Thank you very much for your assistance and advice

Kind Regards

Eric

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