Poker burner

[Gordon]

I am starting to think that I am just stupid. I have been building a Cracker Locomotive which is supposed to be simple but I just cannot get a burner to work. I have tried the one shown on the Glaser plans and cannot get it to work. I have looked at threads about others building a poker burner and have tried to build the same thing. The burner flue is 1/2" copper tube which is about 5/8" OD. The burner tube is 1/4" OD copper. I have tried burner tubes 1 1/2" long and 3" long. I have cut slots and tried burner holes from 1/16 dia to 3/16 dia. I have tried 2 holes to 10 holes. I have tried air inlet holes at the nozzle from 1/16 dia to 3/16" dia. I have tried putting stainless screen around the burner. I can get a relatively blue flame outside of the flue but as soon as I insert it into the flue I just get yellow flame out of the end with no burning at the burner tube. I am sure that I am missing something but I am running out of things to try.
I also just noticed that the butane tank I have built does not seem to hold much butane. It is 5/8 OD x 1 1/2" long with a Ronson fill valve. It only seems to burn less than a minute before it runs out of butane. I am not sure if that is another problem or part of the burner problem.

Gordon

 

[BaronJ]

Hi Gordon,

I'm no expert but from your description if you can get a suitable flame outside and it turns yellow inside that suggests a lack of oxygen/air. Are the air holes big enough are they far enough back from the jet. Have you too much or too high a gas pressure.

The air to gas ratio must be correct to get good combustion.

As I said I'm no expert but think bunson burner. HTH.

 

[rklopp]

I would first solve the butane fill problem, because you may have too little butane to maintain pressure as butane leaves the tank. During filling, is your Ronson valve venting gas while liquid goes into the tank? If not, that explains why little fuel makes it into the tank. There is a vent path around the side of the valve that may be obscured by a threaded tank bushing that is too long.

I have a Cracker with a similar-sized tank. It lasts about 15 minutes, which is about half again as long as the water lasts. My burner is per the original plans, and works well. It takes a couple of re-lights and burns at the top of the stack for a minute or so before everything warms up and the filled tank drains enough to be flowing gas instead of liquid through the jet.

 

[Gordon]

I am not venting off any gas while filling. The Ronson valve came from a broken Harbor Freight torch and I still use one just like it and the torch does not vent off gas while filling. The valve has a screw driver slot with the fill stem coming up the center. There is an O ring at the bottom to seal it into the tank. I will take a look at it again.

 

[Gordon]

OK I sent a message to Tony Bird who has experience with this type of thing. He asked for photos but apparently attachments are not permitted in private messages but are permitted in the forum so here are the pictures. Anyone else with input is welcome to respond.
Gordon

 

[BaronJ]

Hi Gordon,

I have three refillable butane gas devices, a Ronson Lighter, a Cooks Torch and a Gas Soldering Iron, non of them seem to vent any gas whilst being refilled from a 120Gm cylinder. However I do agree with the suggestion that the gas pressure from the tank could be too low to drag enough air into the burner to get the blue flame.

What is the size of the jet ? Your photographs don't show too much detail. If you have access to a bunson burner the tube should unscrew and you will be able to see the jet, air holes and its construction. It will be almost the same as your burner but the jet size might be a little different.

 

[Tony Bird]

Hi Gordon,

The flue tube in your boiler is about 1/16" smaller than the ones I used in the Crackers I built, but I hope it will not make any difference.

The important dimension is the combustion space i.e. the different between the sizes of the burner tube and the ID of the flue. In your boiler it is 1/4", so the flame height must as a maximum be not much more than this, otherwise the flame travels down the flue which becomes a blow torch.

So you need a flame having complete combustion which is low so the heat travels as slow as possible down the flue. To achieve this it helps to have a small jet, here in the UK I use a No.3 also a very sensitive gas valve is needed. The mesh I use is 40 denier Nichrome.

To get as much space as possible the burner tube should be touching or nearly touching the flue wall and the mesh go only about 3/4 the way around the burner tube.

If the above is right the length of the burner and the number and shape of the holes doesn't seem to matter.

Attached is a drawing and photograph of the burner I use. The later ones have two round holes instead of the slots. Works as well and quicker to make.

I hope this helps.

Regards Tony.

View attachment Drg 06 Arrangement and Detailsof Gas Burner.pdf

 

[Tony Bird]

Hi Gordon,

While looking for the burner drawings I came across a video taken while playing trains in the Low Countries a couple of years ago. It shows several Crackers that have been made the Americanised one has twin single acting cylinders, the 'T' boiler one with its extra water capacity runs a lot longer than a standard one. The Cracker being used as a load is to the original Ernst Glaser design complete with blow lamp burner the rest are of my modified design with poker burners and the gas tank under the footplate which makes them and their boiler about 1/2" longer.




Regards Tony.

 

[Gordon]

Thank you. It is too late to change the flue size without starting over. I have done pretty much the same except that I can move the burner down a little further. I did not realize that the distance was that important. I was trying to use standard US sizes. Metric pieces are not very available. Dumb USA. I was not able to find jets in the US so I drilled them. Tricky even with a CNC mill. I have a couple of things to try now.
Gordon

 

[Gordon]

Tony:
I have tried everything per your suggestions. I made a new burner which goes all of the way to bottom of the flue so I have close to .300 over the top of the burner. The ID of the flue is .550 and the burner is .250. I can get a small blue flame burning on the face of the burner but as soon as I insert it into the flue the flame goes out at the burner face and comes out of the end. I have tried different nozzles with not much difference. I tried drilling a larger hole where you have drilled the .2 mm site hole thinking that air would come in there. I even made a new shut off valve for the tank using a sewing needle which gives a much more sensitive adjustment. Blue flame at the burner until I insert it in the flue at which time it goes out. I am running out of ideas again.

 

[BaronJ]

Hi Gordon,

Where can I find the drawings that you used to build this engine and did it come with dimensions for a suitable burner. I really struggling to understand why you seem unable to get this working properly.

Sufficient gas pressure and the right gas air mixture are needed. I've never built a poker burner but I have made several Bunsen style burners running from household gas, propane and butane without any difficulties.

Also since its very difficult to drill very fine diameter holes I have used jets from carburettors in mine.

 

[Gordon]

Baron:
The drawings are at http://www.john-tom.com/html/SteamPlans2.html. The plans are for Cracker.
The jets are far smaller than any carburetor jets that I am aware of. The hole is .2 mm which is .008". The one Tony is using is a #3 which is .15 mm which is .006. I am using butane for fuel and I have tried from the tank I have made and also directly form the butane cylinder. I cannot understand why I can get a blue flame when the burner is just in the open and then the flame goes out a soon as it is inserted. It would seem that within reason once it is burning at the burner it should be pretty much independent of outside air in the flue unless the flue is so close that it extinguishes the flame. I am sure that there is some simple explanation for this. Many others have built this same burner without this many problems.

 

[BaronJ]

OK Gordon,

Thanks for the link. Give me chance to go and have a look at the drawings and I'll get back ASAP.

RE: The carburettor jets. The last one I used was for a moped engine carb. I recall it was around 10 or twelve thou. It was actually marked with a letter, "C" I think. But it was a while back. The burner is in a box somewhere. If I can find it I'll dig it out.

 

[BaronJ]

Hi Gordon,

Daft question the flue pipe is open at the far end isn't it ?

 

[fcheslop]

The air for combustion is drawn in from the two holes drilled across the tube and make sure the jet is not to far forward covering the holes.
cheers

 

[Gordon]

Baron: I tried burner shown on the original drawing with no luck so I have been using Tony's design show in post #7.

Yes, I know that the combustion/fuel mix is mixed at the end of the nozzle at the air intake holes. That is why I do not understand why the flame goes out when it is inserted in the tube.

 

[BaronJ]

Hi Gordon,

Daft question the flue pipe is open at the far end isn't it ?

You didn't answer this question. The pipe that the burner is inserted into,
is it open at the chimney end ? Can waste gases escape up the chimney into the air ?

 

[Gordon]

Yes. End is open. I have actually been trying to get it to work by putting the burner in a tube the same size as the flue. See the picture I posted earlier.

 

[BaronJ]

Hi Gordon,
Interesting web site that you linked to. I found the plans and downloaded them.
They are quite straight forward with nothing to suggest that something special should be done with regard to the burner assembly. In fact apart from a few small differences in tube diameters they are the same as I've used for Bunsen burners. The flow control valve was interesting but I had hoped that I would learn something new ! Alas not.

When you fill your gas tank, I wonder if you can hear any liquid sloshing about inside if you shake it ?

 

[fcheslop]

The point I was trying to make is What is the position of the jet in relation to the air holes is it as per the drawing?
cheers