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Copper boiler scratch build project.

I started a boiler project several months ago by accumulating some raw materials, and then starting the actual build. I have not worked on it for nearly two months because of life changes and minor illness. I expect to be working on it again soon, and I wanted to get a thread going and bring it up to date.

I built a Graham TVR1A engine and I need a boiler to run it. The commercially available units cost an enormous amount of money. So, I decided to build one. I have never built a boiler before, but it did not look very difficult to me.

I purchased a 3" diameter length of copper pipe from a local plumbing supply store. 12" long it was, and I cut it in half to make two 6" pieces.

I purchased a 12" square sheet of copper to use for the end plates. I cut the sheet into four squares. I made end cap formers from oak wood. I read about this in a book titled "Making Simple Model Steam Engines".

I annealed the end plates on top of my kitchen stove, and supplemented the burners with a propane torch.

I used a 1 Ton arbor press to form the end caps, annealing after each press and then trimming the excess with a band saw and belt sander.

Once the two end caps were made I measured where I wanted the burner tube holes to be and then drilled them out. I did this before soldering, otherwise the pressure inside from the heating would have been a problem.


Next I made the burner tube housing from brass bar. I turned it on my 9x20 lathe.

Then I rigged it up to my mini mill and drilled the side air ports, and a set screw hole.

Next I machined a burner tube end cap from bronze bar.

I used a small chop saw to cut slits into the stainless steel burner tube.


I made a small hearth from fireplace brick and then silver soldered (brazed, technically) the end cap onto the burner tube, and then the burner tube into the burner tube housing. These small bits I was able ti use my propane torch for the heat.

And, it worked!


Since the propane torch did such an easy job of brazing the burner tube I thought I could use it to braze the end caps on the boiler. Wrong! All it did was turn it all black.

After cleaning the parts again, I used my welding outfit to get it hot enough to braze. Worked a treat, obviously.

Afterwards, I brazed in the burner tube.


Next job was to drill holes for the various bushings. I drew a line in the center of the boiler and used the drilling chuck in my mini mill.

I then made several bushings from bronze bar, and drilled and threaded them in various model engineer thread sizes.

And then just for fun I mocked it all up next to the Graham.


I wanted to have a fancy smokestack bellmouth so I made one. I learned a couple of new steps on the lathe doing this as I had never turned a taper before. It didn't exactly go easy, but in the end it turned out satisfactory.

And this is where I left off last December.

To be continued...............

Very well done, that's gonna be a nice boiler.
You obviously didn't have any problem brazing the burner tube into the boiler without any holes in the boiler??

Fantastic looks great well done!!

Great work and when do we start putting OUR orders in  

Wonderful job mate!  



For never building a boiler before, you are certainly doing a professional job of it. Very well done.

Thanks fella's.

BK: When I brazed the end caps I used the burner tube as an alignment tool. There was enough of a gap to let any pressure buildup  to escape. The end cap brazing takes an enormous amount of heat and about a minute to complete.

When I brazed the burner tube on the first side, the opposite end was still open for any pressure to escape. As I brazed the second side, well yes there was no way for any pressure to escape. However, the burner tubes are very small in comparison, 3/4" vs 3", and also they only required a few seconds of heat to finish the job.

a professional looking job there well done

wow that is brilliant i'd like to build a boiler but don't think i could.

Good work on that , and nice heavy guage copper   but there is noway you used that little heating torch on that !  
Will be interesting to see how the guage glass mounts up .
Lookin forward to see it in steam .  
Swift Fox

You have done a great job on that boiler, well done.

Thanks again fella's for all the nice compliments, it is very encouraging.

I intend this boiler to be used along with the Graham engine in a model boat. So it is being built as a "marine boiler", however, I will need to build a boat from scratch. 1) To save money, and 2) because I have not been able to locate a commercially made hull that meets my exact requirements.

I realize that this message board is mostly about static "steam plants". And I find I like them a lot, the more I read about them. So in that vein, I decided it would be neat to make a steam plant in the interim while I wait to build a boat. So I have been playing around with the idea and cut myself a board to mount the bits on. Here is a mock up of what it may end up looking like.

I hope to be feeling better soon and be able to get back to work on the boiler. I need to braze the bushings into it and I won't mess about with the oxy/acetylene outfit unless I am at 100%.

Dean W

That's looking great, Tom!  
I like this way of making end caps.  The shape looks nice, not to mention the structural aspect.
Sure looks like a good size for that engine, too.  What pressure do you plan on for the boiler?

Hope you get to feeling well soon!

Tony Bird

Hi Tom,
Just picked up this thread you have done a great job for a first boiler. Is the burner a copy of a prooven design? It looks a little long with a lot of slots for its diameter.
Regards Tony.

Dean, the TVR1A engine is designed to run on 35 PSI. My safety valve blows at 60 PSI. I will pressure test the boiler to 120 PSI.

Tony, the boiler and burner design is from a good friend who is a master model engineer who does loco's as well as boats. He drew up a plan for a "basic boiler" for me.

I did make it a slight bit too long I suppose, but the slots end at the end of the boiler.
Dean W

Sounds like a useful pressure range, Tom.  You'll end up with an engine that can use 60 psi one day,
and will have a boiler handy.  

I had a chance to do a little bit of work today, so at least some progress has been made.

I brazed in the two end cap bushings. Now it is sitting in the pickle, and next I will try to braze in all the bushings along the top at one time. If it gets too oxided up before I get them all finished I will stop and pickle it again and then move on to the rest of the bushings.

I had to figure a way to hold the boiler vertical, and a small drill press vise came in handy for the job.

H2o vapour

Cracking work, nice design and looks the part.

Enjoy & thanks for listing


Yeah !  

and when you`ve finished sweating over a hot brazing hearth , you can cool off with a dip in the pool .  

Thanks fella's.

Cool off is right, the pool water is a balmy 53°F today.  

I removed the boiler from the pickle and cleaned up the slop around the bushes. It turned out nicely. Tomorrow I will tackle the bushes along the top.

After clean up, it is all ready for the next series of bushings:

I could not have gotten a better alignment for the siphon!

Dean W

It looks good, Tom.  You're right, the siphon bush puts the gauge in just the right position.  
Can you tell me, how far do the end cap flanges go into the boiler shell?  Just curious.



Well, about this far Dean.  


It went well today. I brazed in all four of the bushings on the top in one go. And then without pickling I cleaned the area on the side for the last bushing and brazed it in.

Now the boiler shall sit in the pickle overnight to get it spic and span after which time I will dress up the slop around the bushings. Then it can be pressure tested.

These are the top row bushes to be brazed in one go.

And here they are after.

Side bushing ready for silver brazing:

Job done:

Five bushes done today:


What recipe are you using for the pickle?


Great job...GREAT JOB...Great Job!!!!

And nice weather to do it in!

Looks like you are heading for  Hemmens type of water gage

The details of wrapping the at "poker" burner style burner in stainless mesh so it acts as a radiant may really kick up its efficiency is posted around here some where.... But what ever y you do --- you are off to a roaring start ...

Your end cap bashing is first rate

Also sorry to hear you are stubbornly ill-- get better my friend!

Thanks Mo.

Alan, straight 5% distilled white vinegar.

Wow, that is an absolute beauty of a boiler. The endcaps are perfect. It is just so nice, I'm speechless.   I wish I could do that.
Dean W

Your brazing steps are going well.  Looks like it's getting close, Tom.  
Steam Models

Gee! you've done a wonderful job on that.
And it's a nice compact design as well.  ...   You should be very happy with that?

Thanks for the comments fella's.

Well, it seems I got some work done just in the nick of time as it is raining today and it's expected to continue through this coming weekend. So I will have to set up 'shop' temporarily under the backyard patio cover so that I can do the grinding/filing/sanding of the brazing slop around the bushings.

What a wonderful build of a fantastic boiler!

Well done Tom!!!

Thats going to be a fine looking boiler when completed  
Lots of pictures and details, what a great thread, thankyou!

awersome!!! Well done! My congratulations!!!! Great job!!! Keep going!!!  

The weatherman decided to give us a break today and so I scampered out to the shed and took the boiler out of the pickle and dressed up the bushings.  

Here it is fresh out of the overnight pickle bath.

Here are the various tools and abrasives needed.

After the first go 'round with a Dremel and green stone:

Next with an 80 grit flap wheel:

And then some needle file work:

And then I had to take a break when my granddaughter arrived with a hot fudge sundae in hand!    

And then I took some 80 grit cloth sandpaper roll and scrubbed the entire boiler. I finished one end cap that will be exposed with up to 240 grit cloth roll, for the time being.

That's all for now folks!

Well done!

Keep giong! I'll follow the post!  

That does look good.  

Thanks fella's, I appreciate it.

I pressure tested the boiler today. The test went well. I can now work on the finishing details.
Dean W

Kmot wrote: I used compressed air. I know there are some who will squawk at that, but so be it.

Tom, the reason some will "squawk" at it is that it's a dangerous method.  If we are going to show something
that flaunts safety precautions and just say "so be it", wouldn't it be good of us to admit or explain the hazard
for those who are less informed?

I apologize for creating a controversy.

As one who realizes that the scars of some very testy and chiding members on another forum effect many ..( Tom and I both - but we are only a few) Deans concern is true and you are very much among friends- I lead that line!!

I have to say that the reasons can be explained more fully in available literature and basic physics principles Tom.

You hit on one of  them in your last post..

This is a layman's brief over view- but for these purposes - you are correct- water doesn't compress ( at least to any appreciable degree) and so..cannot store energy. Potential energy.

Air can compress to a great degree. Thus having enormous stored energy.

If a boiler was to leak under even great hydraulic pressure - it will first just spring a leak. No danger there- LEAK found!!! A good thing. ( same original volume - just under pressure- which is being lessened by the leak)

If under great compressed air pressure ( now there is a great deal of volume wanting out- under a great deal of pressure) and if a weakness is found- it all wants out now and will exploit the weakness to rupture.

Balloons POP- Water balloons just SPLAT - probably a bad example

I am no engineer - and I am sure my explanation is lacking in detail- But Dean comment I am sure was given in good heart and is in true concern.

I hope a learned member can point to a good source of information for Tom to reference. Tom- you have built a fine boiler-Nothing taken away from that...Lets see what else surfaces here in the spirit of a broader understanding for all members to use.

I apologize for creating a controversy.

Mo, I am now confused. Is the complaint registered because I have not proven my boiler is safe to use? Or is the complaint registered because using compressed air is a more dangerous "test" than using water?

I apologize for creating a controversy.

Kmot wrote:
Mo, I am now confused. Is the complaint registered because I have not proven my boiler is safe to use? Or is the complaint registered because using compressed air is a more dangerous "test" than using water?

In short - the latter.  I think you proved your boiler withstood the pressure.

Interestingly I think that to perform the hydraulic version - all you would have needed to do ( to have been in safer) would have been to fill you boiler completely with water and then apply your compressor air pressure.

I have seen nice hand lever pump that apply hand stroked pressures t o  water filled boiler-And I do not have something like that either.

Once again _ I will see if I can find the information or hopefully some one else has a book mark and can post a helpful link for all. Not to direct it solely at you - but to the broader membership. We gain new members all the time and these things are good to vet out and not to dismiss as mere "common knowledge"

Since the forum has a great resource area and such support in formation should be placed there as a matter for future reference.

Cheers to you Tom--You have produced a finer boiler than I have ever built..
Dean W

Oops!  I went to reply to your questions of the last several posts, Tom, but they've disappeared.

Anyway, I wasn't talking about your boiler being unsafe at all, which was one of the things you had asked
about.  I meant, to use air for a high pressure test poses a serious threat in the event of a failure.  As Greg
said, there is so much air, even in the small boiler shell, that if there is a fault the boiler can very well burst
and send pieces flying.  With water it cannot burst.  If there is a failure it will simply be a squirt of water,
and no one gets hurt.  

There is a lot of info on hydro testing in books by Kozo and K.N. Harris, along with a lot of other authors
that don't come to mind at the moment.   Either author puts out some good reading for any of us interested
in model boiler building.

Kmot wrote:
I apologize for creating a controversy.

Tom- No need to and you did no such were asking questions.

All is well.

FWIW, I used to work daily on CNG buses that had 10 fiberglass gas cylinders under the floor and above the roof, each 5' x 2', tens of feet of line and fittings, and filled to 3500 PSI. A pin hole leak at that pressure can slice the flesh right off your face. And I have seen the result of a single one of those cylinders exploding. 100 PSI doesn't seem like much to me anymore. That, and I am quite confident in my skills so I was not worried about a failure. I have also been given the impression from other forums that others thought a boiler test was not valid unless it had been a hydrostatic test, as though the medium made a difference. I initially thought I was being questioned on that. I know now that the concern is because of the possibility of a blowout with compressed air if someone has poor assembly skills.

So, DO NOT TRY THIS AT HOME!. This test was performed by a professional under controlled conditions!
Dean W

Kmot wrote:
All is well.
I know now that the concern is because of the possibility of a blowout with compressed air if someone has poor assembly skills.

Wouldn't necessarily be assembly skills, Tom.  It could be a materials failure, which would pop regardless of your good work.

So, how close are you to firing your boiler?  It looks like it's about ready!

Performed a second test today. Built steam pressure up to 100 PSI and checked for leaks. Only one plug I made was leaking. Nothing on the boiler itself leaked under the heat and steam pressure.

Dean W

Looks like it wants to run an engine, Tom.  
Does this one get a full firebox around it, or the type that goes up the sides about half way?  

Thanks for the vid.

Like a Mamod or Wilesco? No, neither of those, it will have a burner inside a flue and an exhaust stack at the opposite end. Sort of like the typical marine boiler. Because it's destined for a boat.  

I can not wait to see her push an engine and then a prop or two and then the hull around the water Tom

Building a burner or buying one?

When you get to that part I have found a cheap source for a tap, valve and gas line to attach to any burner - Commercially made for about $13. Then you could use a  disposable back packing gas canister.

Nice work!!

I have built the burner already, pictures are posted earlier in this thread.

It wants to run an engine, Tom!

Well done! Only 1 valve is leaking!    

Well, a setback today.  

I tried heating up the boiler with my burner today, and I could not get a good flame. No matter what I tried, including modifying the burner several times all I got was a rich flame out the top of the stack instead of a hot flame inside the flue.

Back to the drawing board!  

Great boiler. The mini gauge adds a nice touch! I look forward to seeing it run an engine...

Bad luck mate , but there is an easy fix , get youself a burner designed for a Centreflue Boiler , there are a number of Ceramic ones on the market , and i have seen one made by a model engineer that has a big stainless head with 4 or 5 Large holes in it that work like a flame thrower to Blast Max heat in there .

Thanks Ben.

I fooled around with it more. I tried every which way, and it just won't support the flame inside the flue.

I don't think the design is flawed, just my execution. Apparently, burners are tough to do!

I will get it working though!

That might be an option down the road, thanks Geoff.
Dean W

I don't think anyone wanted to discourage you with the burner you built, Tom, but some of us noticed that
it is an open firebox design that you used.  I think you can put a nozzle on the jet end to get the result you need.
Something similar in appearance to a Bernzomatic torch end, if you know what I mean.

You'll figure it out.

Thats right , absolutely no discouragement intended .
My comments were regarding steamproduction , pressure recovery and maintaining working pressure under load .
But trial and error are a great way to learn , so good luck , and i hope to see it in steam soon .

Kmot wrote:
Well, a setback today.  

I tried heating up the boiler with my burner today, and I could not get a good flame. No matter what I tried, including modifying the burner several times all I got was a rich flame out the top of the stack instead of a hot flame inside the flue.

Back to the drawing board!  

I have read much and the rich flame tells you important stuff...I=On my stock Cheddar boiler and burner which was jetted at a #8 was dropped to a #5 after reading that that may be required. I could still light a flame at the top when it was fired up????

Too much unburned fuel for sure..but go to a #3??? Surely not? Yes indeed and get a lot more time out of my small fuel tank and a hotter flame to boot.

Burners are more fiddly for me than many here but I have not worked out the formula yet. I am getting better. I sure copy and measure the burners I have bought and there is a lot of variance in those as well. The magic number are eluding me or I sure would share.

With no cross water tubes - a low pressure flame would seem better so you just do not shoot the heat out the flue.

Tom do you remember reading about using some twisted heavy gauge copper wire run down the center of the flue to create a spiral vortex or at least a baffled flow so that the heat has more time to transfer?

I know that is not the point you are working on but more burner food for thought.

Also if you have need of some  ceramic fire brick to drill for that type of radiant - I would be happy to throw you some for experimentation

Thanks for the comments guys.

I think a Bernzomatic type tip would be blowing hot flame straight out the stack, no?

The issue I have is that the burner tube, does not burn inside the flue. All the gas stays unburnt until it reaches the end of the flue where there is enough air to ignite it. The air ports drilled into the housing are supposed to mix with the fuel so that it will remain lit inside the flue. The idea was to have flame heat rising straight up. And no flame coming out the stack.

A ceramic burner might do the trick. I am still going to work with the burner tube for awhile however. I just need to figure a way to get more air into the flue.

Ahhh more information--- IMHO More air is needed Tom..If it won't burn til it is out through the top- it is starved for air.

Can you hold the tip of the torch back from the boiler flue so there is a bit of a space like a Saito burner? Does that help?

NO crosstubes ! , of course ! ......... this aint the kinda boiler for the burner i was thinking about , sometimes i get excited when trying to help , sorry for messin up your thread .  
Dean W

Tom, the Saito burner that Greg mentions is what I had in mind when I referred to a nozzle like a Bernzomatic
torch.  Whether the heat all goes out the back end of the flue would be easy to check and cost no money/time
in further development.  See what happens if you hold your plumbers torch about an inch from the flue inlet with it
burning full blast.  Worth a try.

Check out some pictures of the Saito setup, too.  Probably some good ideas in those pics for you.  Many
boilers like yours have water tubes criss-cross in the flue for heat collection, but the nozzle type burner
may still work for you.

EDIT:  (I see Geoff mentioned cross tubes in his post while I was typing.  Didn't mean to be repetitive.) end edit.

For your current burner, you may try a smaller jet and larger air inlet holes in the jet housing.  The thing is, with
your burner in the flue, I think it can't help but make a draft, drawing fuel up the chimney.  I'm not sure of that!
Just thinking it.

a last bit..You also may need your "stack" in place. The "L" bend to divert the exiting heat etc upwards - Just in case you are still testing with both ends of the flue open and basically horizontal.

This may really help slow the flow from the burner and change the dynamics and characteristics of how your burner performs.

Just random thoughts, cause I have free from  brain storms all the time..not my line but it applies

non impediti ratione cogitationis

Keep brainstorming guys!

More info:

The gas jet housing had two 1/4" holes. Now it has four.

The burner tube ran the entire length of the flue. Now it runs 3/4 of the way because I shortened it.

I tried covering most of the slits, and having about 1/4 as many open as originally.

I moved the gas jet nozzle in and out of the housing. All the way out, in fact.

I tried with the stack on, and off. With the elbow only, on and off.

I lit the burner tube outside the boiler, adjusted the gas jet nozzle for a perfect blue flame, and then inserted it into the flue. It went full rich and only soft yellow flame came out the end of the flue.

I removed the burner tube while the flame was burning out the opposite end, and none of the slits were lit as I pulled it out.

In every situation and adjustment, a flame inside the flue doesn't exist. Even after inserting a perfect burning tube, it goes out inside the flue and only stays lit at the end.

I tried dozens of times and adjustments trying to light the gas from the stack and have the flame sucked back into the burner tube. It just would go out most of the time or turn into a soft yellow flame.

I'm using a #5 jet.

I tried the gas valve from barely open to full open and all points in between and with all adjustments as listed above.

I spent two hours steady trying to get it to burn right.

I need more air inside the flue, I think is the problem. I don't know if opening two more air ports helped or hurt. Possibly it hurt by slowing down the velocity of air.

The burner tube works fantastic, with a very hot blue flame, outside the flue tube, and quickly turns the stainless steel tube red hot. Inside the flue tube, it goes out.

Keith S

I don't know much on the subject, but I'd be interested to see what happens if you shorten the poker even more, down to say 1/3 or even 1/4 the length of the flue. I'm having difficulty thinking of how to explain why this sounds right to me. I think there might be a relationship between the length of the poker and the diameter of the flue. Your flue seems to have similar dimensions to commercially available boilers, but your burner is much longer than I've seen in my limited experience. I think there is probably a certain spot along the length of your burner where the exhaust gases are trying to get by, only to be thwarted by more flames. The result is that the entire fire gets snuffed out.

I'm willing to wager that there is some magic relationship between flue diameter and burner length, and if you shorten that thing, you'll get fire where it belongs. You need to leave room for combustion gasses to expand and head out the chimney.
Dean W


You're sure covering all the bases, Tom.  Some folks seem to hit the right combo straight away, and sometimes
it's a situation like yours.  The way you go at it, I'm sure you'll get it.

What Keith said makes sense to me about the exhaust gasses.
Hope you'll give the plumbers torch a shot, too.

mogogear wrote:

Just random thoughts, cause I have free from  brain storms all the time..not my line but it applies

non impediti ratione cogitationis

Braccae tuae aperiuntur

Made you look!


Yeah, this is driving me buggy! I will either succeed at making a working burner, or burning my shed down!  

I was just out there again. I enlarged the air port holes. Couldn't keep the burner lit inside the flue, although I did get more blue flame coming out the end.

I tried my propane torch also, Dean. Rip roaring flame blasting out the stack like a jet engine. But the few seconds I held it there, it did warm up the boiler some.  

Keith, you may be on to something. I've got nothing to lose, and I can always make another burner tube so I am going to go whack a chunk off the end and see what happens!
Dean W

Tom, I was just reading a Cracker thread on another forum.  The fellow made a burner like yours, but it
appears to only go into the flue about 1/4 of the full flue length, (just has five slots, too).  He also made the burner
pipe off set from the center of the jet housing, so the bottom of the slotted pipe would sit in the bottom of the flue.  I
suppose that gives it more room to make fire.

Don't go loony yet.  You'll get it.


Check out this thread from Tony. it starts out on ceramic radiant types and then has some ideas on the poker burner style you are wrestling with

I didn't recall when you joined us- so you may have already seen some of this

Gotta go- it is sunny and I have a hobby day - so I need to get the next coat of epoxy on the Cushing hull!!

Greg, those various burners all look great. Even mine looked great, out of the flue tube. Nice, hot, blue flame. But once inside the flue tube, nada.

I tried cutting mine down today. In stages. I eventually milled away about half of the jet nozzle housing to get more air inside the flue. I was able to finally get it to burn inside the flue but only a tiny bit of gas. Any more and it went rich again, went out inside the flue, and only burned when it reached the air at the end of the flue.

I was able to get a modicum of success today. In order to get it to make a flame inside the flue, with the tube now cut down to 1/4 the length of the flue, I had the housing half out of the flue to get more air inside. This allowed it to actually heat up the water and make steam. But it took over an hour. Entirely unsatisfactory performance.

The radiant type is starting to interest me.

Attached is a before, and after picture, of my now decimated burner tube.


So, I am going to start over again, with another burner like I had already made before but with a couple of slight changes. It will get resolved!  
Keith S

Try using a narrower blade to cut the slots in the poker. They look a little wide to me. Hey, there  must be something wrong. Also, maybe when you make the base part, make it so the poker is not coming out of the centre, but is instead offset so that it is closer to the top of the flue, with the slots facing downward.

That's what I would do. I encountered one burner being built on another site that emphasized the narrowness of the slots, and as for the other thing, I looked at the excellent burner in my Roundhouse locomotive, and that's how it looks.

I almost wish I was down there to help with this. One of these days you're going to hit upon the right formula, and I would like to share the credit. Also, it's nice and warm where you live.
Dean W

Tom, I know you'll get it!

Check out this pic from a Cracker type build on HMEM.  That engine has a similar flue setup to yours.  
Note how he put the tube down at the bottom of the mounting flange.  He mentions that this was
important to get this burner to fire inside a horizontal flue.

Photo credit:  Bob Sorenson.

The build thread is here, and the burner part starts around middle of page eight:

Another similar build on the same forum shows the same type of burner for the horiz flue.  Maybe
you can modify your current burner to work in that manner.
Tony Bird

Hi Tom,
I am not an expert but have made a few gas poker burners. The burner will need to be offset as far as possible in its boss to give maximum combustion space. This is possibly why your burner doesn't ignite in the tube
Before starting on a new burner you might try the following. The gas/ air mix can be altered in two ways. The size of the air holes and the position of the gas jet relative to them. With the burner out of the boiler cover all the air holes, sticky tape will do and light the gas, you should get a very soft flame as all the air is being supplied from outside the burner. Turn the gas off and expose one hole and light the gas, the flame should now start to look more like a flame on a gas cooker. It needs to be blue with as little yellow as possible.  If it is OK try varing the gas pressure and if the flame increases in height and visible stays the same the gas /air mix in about right. If not try exposing another hole or part of it. When the flame seems OK try fitting the burner while lit into the boiler if it stays alight then it is about right.
Another way to have a play is to move the gas jet back and fore altering its relative position to the holes.
Looking at your photograph the jet might be a little far back relative to the holes and the thickness of the tube where the air holes are is a bit thick. I have to make some burners today for some 'Cracker' locomotives. I will take some photographs that might help your design.
Regards Tony.
Tony Bird

A sketch of one of the types of gas poker burner that I make. Signed copies available for a small fee.

Components. The K&S tube used for this small burner is 1/4" and the next size up 9/32".

It is uses K&S brass tube and the design allows the poker part to be changed. At the moment I am using large slots covered with mesh which seems to be more controlable. Models previously made have had slots or drilled holes. The design allows various designs to be tried out. The poker part was made as follows;

The end of the tube is slightly deformed by using a 3 jaw chuck as a press to make it a push fit in the plug. Burner without mesh works but not that controlable and will easily blow itself out.

With mesh low.

With mesh high.

Test lighting in test flue. For Crackers the burners run inverted as there is not always water on top of the flue in the small boiler.

Fitted with a larger poker.

Boiler test Video.

Not very clear but steam has been raised.

Usually larger burners are more tolerant regarding gas/air mix and poker design. If anything isn't clear please ask.
Regards Tony.

Hi Tony,

Thank you very kindly for your most informative post. I appreciate it very much.

Yes, my poker was in the center of the flue, but the gas slots were inverted. I had thought this would allow good combustion. I was given this design by a friend, who said it is pretty much an exact copy of the poker burner in several of his locomotives.

I think the problems all stem from my execution of the building of it. The tip about the thick walls of the air ports is interesting. I can make them thinner on the next housing. Also I am going to try different gas jet sizes.

Tony, I have a question after watching your video.

The poker is offset, and you have it situated at the top of the flue with the gas slots inverted?

Is the hole in the face of the housing just a "peep hole" or is it calibrated to be part of the air/fuel mix?

Tony Bird

Hi Tom,
Just started on a gas tank for the locomotive back from the shed.
Your questions:
These burners shouldn't care which way they point being off set it doesn't seem to matter. On the Cracker locomotive with a standard parallel boiler which only has 50ml of useable water the burner is inverted so it heats the part of the flue which has water against it all the time unless it runs dry. This locomotive has a 'T' boiler which holds a lot more water but I will still fit the burner inverted.
The hole is a 'peep hole' this type of burner shouldn't need secondary air to work.
As I have mentioned I am not an expert on burner technology, I have just try things sometimes they work often don't.
Gas jet sizes her in the UK model gas boilers seem to use numbers 3, 5, 6, & 8 which I have one of each of. When making a new design of burner I start with the smallest (3) and work up. Any further help please ask.
Regards Tony.

Thank you again Tony.
Dean W

Tony, thanks a lot for putting this up here.  Tom has got some good tips, but he's not the only one!

Do you know the orifice size of the jets you mentioned?  I've built some burners, but mostly use proven
designs, as from a book or prints I may be using.  When I've built my own, I end up hunting for an unknown
orifice size and have to go the trial and error method.  If you know the hole sizes in the 3, 5, 6, & 8 jets
you use, would sure appreciate it.
(I use watch bushings when I make my own jets.)

Thanks again,

Tony Bird

Hi Dean,
Sorry I don't. But I do have a jewelling set gauge and broaches which will fit the holes so I will try measuring them. Yes bouchons work well as jets and I have used jewel holes for making small gas torch jets for fine work using oxy/act as gasses. Alas with the advent of quartz watches the size range of these bearings is much reduced.
Will get back to you.
Regards Tony.

Dean W wrote:
Tony, thanks a lot for putting this up here.  Tom has got some good tips, but he's not the only one!

Do you know the orifice size of the jets you mentioned?  I've built some burners, but mostly use proven
designs, as from a book or prints I may be using.  When I've built my own, I end up hunting for an unknown
orifice size and have to go the trial and error method.  If you know the hole sizes in the 3, 5, 6, & 8 jets
you use, would sure appreciate it.
(I use watch bushings when I make my own jets.)

Thanks again,



sizes commonly available are: -

Number 3 which has a 0.15mm dia jet bore

Number 5 which has a 0.2mm dia jet bore

Number 8 which has a 0.25mm dia jet bore

Number 12 which has a 0.3mm dia jet bore

Number 16 which has a 0.35mm dia jet bore

Confirmed by Nick Monahan in another forum..sorry as they are in metric and that may not work for your drill index
Tony Bird

Thanks Greg. That saved me some time and I have made a note of them.
Regards Tony.

Wow, only .05mm difference between my #5 and the next smallest jet.  

I have finished the machining of parts for a new poker burner. Differences are a much shorter tube than before, 4" versus about 7". Greater spacing between the gas slots. Less gas slots. Longer neck for the gas nozzle so that it can nearly close off the air ports. This is basically the design that is already used in some simple locos, according to my friend.

Next up, I will make an offset version like Tony has shown. That will require some different techniques and parts.

I concurrently machined a bushing and am in the process of making a copy of the Ministeam ceramic burner as used in their center flue boilers.

Dean W

Greg, thanks for the numbers!
Tony, we have a good supplier for small watch bushings here.  If you need some, let me know.

I cross referenced the numbers from Greg using my standard watch bushing chart.
Here are the standard KWM bushing numbers for the jet sizes Greg put up, in case someone would like to know.

#3 jet, 0.15 mm hole, same as KWM L56 bushing
#5 jet, 0.2 mm hole, same as KWM L01 bushing
#8 jet, 0.25 mm hole, same as KWM L57 bushing
#12 jet, 0.3 mm hole, same as KWM L02 bushing
#16 jet, 0.35 mm hole, same as KWM L58 bushing

The KWM numbers are for that German company, but American makers use the same numbering system.

Tom, sorry to crowd your thread.  Thought this may be pertinent for people interested in jetting.

No worries Dean, it's all pertinent info as far as I am concerned.

I just tried the new poker burner and it actually worked!  

It supported combustion while fully inserted into the flue tube. I was able to open the gas valve slightly more than before. It took about 30 minutes to build up to 50 PSI, which is better than the hour it took before with the old burner hanging out the flue.

So, I am headed in the right direction. I think playing with some different jets will help get it dialed in.  

A short video of my small success.

fire3 from Kmot on Vimeo.


Great perseverance Tom...See how fast it raises steam when you fill it with almost boiling water - then shoot the burner to her! I bet you get up and running in less than half the time!

Congratulations Dance!  Dance!
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