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[MOG8]

Hello,
Does anybody know:
1) which glue is used on ceramic burners to seal the ceramic material to the burner casing?
2) how to machine the ceramic material to obtain a perfect round ceramic disk?
3) how much space (if any) should there be left between the ceramic material and the bottom of the burner?
Could you give any suggestion about:
4) the correct dimension of the burner diameter for a  vertical multi-tubular boiler ( 4" E.T. Westbury test boiler).
5) the free space to be left between thew top of the burner and the boiler lower end-plate.
Thank you all,
Giovanni

[kiwimodeller]

Hi Giovanni, I have not tried working with pot boilers so can only help with questions 1 &n 2. I have tried hi temp silicone and a fire clay to seal the ceramic in burners I have made. Neither was successful so now I just make the ceramic a tight fit in the casing. If it comes loose I simply fit a piece of stainless wire across two of the secondary airholes to make sure the ceramic cannot come out. As for cutting the ceramic material I simply mark mine out with pencil and cut it in the Dremel scroll saw. It can be filed if a little oversize. Hope this helps, Ian.

[MOG8]

Hello Ian,
thank you for your reply and helpful suggestions.
Now I know definitely something more about ceramic burners.

[Brooks]

I discussed my ceramic burner construction on this thread:
http://www.rcgroups.com/forums/showthread.php?t=1153159

If you use "soft brick" for the ceramic, the burners are, dare I say, pathetically easy to make. Soft brick is used as insulation in pottery kilns, and may be purchased at pottery supply stores (or if they don't have it, they will be able to direct you to a local source). The brick can be scratched by your fingernail, and cuts as easily as cutting blackboard chalk.

To get a perfectly round disk with this brick, you can simply rotate your round metal brick holder/container on the brick - it will cut the brick to a perfect friction fit, no glue needed. If you use this method, be sure to drill your holes in the brick  and install your gas line first, as the brick will be difficult to pry out of the container. Or, you may do as I did, rotate the container to mark the brick, then finish the cut with hand saw of your choice, and files or sandpaper. Probably better to avoid breathing the dust, just as you would when cutting any ceramic.

The flame space needed between ceramic and boiler bottom for a ceramic burner is smaller than that needed for a "regular" gas burner. You can experiment to find the right height, or you can just go with 3/8-1/2 inch spacing. Details are given in the above url.

Burner size - I like big burners, so I'd say make the burner the diameter of the boiler. This will maximize the heating surface of the boiler, always a good idea. However, the flames will lick the sides of the boiler, unless there is a metal skirt to contain them; if you don't want to add the skirt, then make the burner diameter smaller than the boiler diameter. Maccsteam boilers insert the burner from the side, rather than placing it at the bottom of the vertical boilers. Here, the burner size will be set by the size of the insert tube, of course.

Hope this helps, ask more questions if anything is not clear.

[MOG8]

Thank you Brooks for your reply.
I do not think to be able to find  what you call soft brick material, but I know that Polly models sells ceramic material to make burners.
Your detailed answers (and the description of the burner  construction in your thread)  have cleared a lot of doubts to me and to all the readers.

[Neil]

Hi, MOG8,
I use an old hacksaw blade to cut my ceramic materiel, which I purchase from a gas heating company nearby. (I could send some your way if you wish). I'm not sure what Polly Model Engineering sell, but, I'll bet it's the same as in most English burners, ala, Macsteam and others, so you don't need mine  Except, the local one has about a million more little peaks to glow red hot, and produce more heat for less gas. I have made a lot of different shapes, and there doesn't seem to be much difference in performance, except quite long burners, compared to the width. I use a fireproof cement to seal the edges, if I have been slack with the finer points, else, a really good fit is good enough, I find.
I have found, on a round burner, to get it close in size, then push it down whilst rotating the ceramic and you get a really good fit. You must be sure that what's underneath is right by then of course.
As to the distance above the mixing tube/fire tube (I'm not sure of the correct terms here), I use a stainless tube of 10mm, and drill it a fraction to fit the gas jet and holder, and the air inlets of course. Therefore the ceramic has to be at least 10mm from the bottom of your container. In my experience, I like the gas tube (Sometimes this is not necessary in a round burner),( but the mixing tube is, of course. I digress). There must be a "spreader" of some kind, though, I find, you may not. The gas tube I like at least 1-2mm from the bottom of the container, and the ceramic at least 1mm above the tube. That makes 13mm from the bottom of the container, and, in my case, as the ceramic is 12mm, 24mm wall height. I like the ceramic to be just a little proud of the walls of the burner, that way the casing of the burner does not get roasting hot immediately. Of course it will after a long time in a confined space.
Oh, I forgot the gas outlets in the tube beneath the ceramic. I have seen so many variations, and, most seem to work well, but, I prefer (depending on the length of the burner) quite a lot of 1.5mm holes, in 4 staggered rows. These rows will be facing the bottom of the container of course. I have also used, on a burner 100mm long, just 3 holes of 5mm diameter, and that works ok too.
UI have had great success with the above, but, I hasten to add, I am not an engineer, or a gas expert, just an inveterate tinkerer. ?If you tinker long enough, you will usually get it right.

Cheers. Neil.

[MOG8]

Hi Neil,
thank you for the time taken for your reply.
I was just hoping to find some other replies, as things are never as simple as they seem to be.
I have drawn as CAD sketch of what I have understood from your reply, for my benefit and for those who are interested in the subject.
One new question was ready while drawing the sketch: Is the end of the gas tube plugged? (far left of the drawing)

You mention: "There must be a "spreader" of some kind".
I guess that you are referring to the gas tube with the staggered holes. Is it so?
I have never had a chance of dismantling a ceramic burner.
I thought that the gas tube just ended on the outer casing and that the left space would do as a "spreader".
Things are never as simple as they seem to be.
Thank you very much Neil.
Cheers,
Giovanni

[Brooks]

I've seen them both with and w/o a spreader. Mine has one, end plugged, simply because I used an Accucraft Ruby loco poker burner as my gasjet holder and spreader, not troubling to make one from scratch. The steam tramp's burner (url below) has no spreader, and generates steam very well.

Getting an even spread of gas, even with a multi-hole spreader, is not simple (nor necessary for ceramic burners, in my experience). To get an even spread of gas along the outlets, you need to equalize the pressure throughout the inside of the tube. This can be approximated by putting a screw of wire in the tube. This turbulator you've inserted converts the  high speed-low pressure gas&air mix entering the tube into low speed high-pressure gas&air. W/o this insert, the gas will preferentially flow out the last holes in the tube; this behaviour is due to the Bernoulli effect, and the opposite of what one might first expect. A fancier way of achieving the same equalization is to make the tube cone-shaped; this is generally the method used by commercially-made gas appliances.

Burner w/o spreader, post#8 has description and photos:
http://www.rcgroups.com/forums/showthread.php?t=717385

[Neil]

MOG8,
Do as I did, gut a brand new burner to have a look. What will it cost you? A bit of ceramic, (and, at worst, fire cement), at about AU$10 locally.
Yes, there is a plug in the end of the tube, I forgot to say, sorry.
You will be astonished what you will find in the burner, or, (on the other hand), what you may not find.
You could strip the lagging off the boiler too, and learn what I did. NOTHING extra, besides what you would expect to find.
ALWAYS KNOWLEDGE COSTS, whether it's fees at a Tech School, or pulling something to bits to learn what's inside. It's not a million dollars, after all.

Jump in, both feet, Giovani, JUMP!

Neil.

[mogogear]

Giovanni-

I am making a ceramic burner as you are describing--I have made only the burner cup or base and the radiant It is here in a thread on RC groups as well (also on Mamod and Other steam)

See if there is any thing there that can assist--I too am working out the gas delivery tube- So I will monitor your thread as well.

Ciao

http://www.rcgroups.com/forums/showthread.php?t=1219427&page=3


BTW- I have successfully incorporated input from Brooks' straight ahead and simple designs myself, as well as admired Giovannis's steam collection and design work and products == the piped gas burner you made for your Elliot Bay was masterful

[MOG8]

Thank you all for clearing all my doubts with your experience on this matter.
I don't think I can find soft brick material here in Italy, but I have ordered a piece of ceramic material to make a burner.
This will be built with the help of all of you.
Thank again,
Giovanni

[Neil]

Giovani,

You must have people who make factory heaters. The ones standing on a pole, over a 45kg LPG (gas) cylinder?
Surely you must? Most places in the world do.

There are the others too, who make gas wall heaters, be they the tall ones, or the consoles. They have the same things.
That's where you get the Ceramic from, and, (in Australia, at least), not $27.50, per piece, but a mere $5.00, or less..

Goodness, send me your address and I'll send you a piece for free. (Skinnyfish727@yahoo.com)

Regards.
Neil.

[steamboatmodel]

Try places that sell kiln supplies for the ceramic bricks.
Regards,
Gerald.