Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hi Maurice,

It looks as if if your boiler/burner combinations produces more than enough steam for your engine and excellent result. Well done!

Some nice boilers you got there, I especially like the look of the horizontal boiler.

I hope in the next week or so to be able to fire the boiler for the first time, the chassis has been test on the track using a test boiler mounted on a truck and the ceramic burner is one of my well proven designs. The pot boiler has about 30 heat exchanging staple shaped pins similar to the ones to be used in the vertical boiler, again a design I have used before.

Interesting concept with those heat exchanger pins on the boiler plate, does this not give more resistance and turbulence in the flue gas channels?

Yes, but the slowing down of the exhaust gases allows more heat to be absorbed by the boiler and in a centre flue boiler doesn't seem to effect the combustion and I have used a similar design before.  These boilers are quite small 55 mm in diameter or less and trying to keep the water capacity as large as possible and producing enough heat can be a challenge. Some years ago I boilers with plain flues and similar boilers with different types of heat exchanging pins, there was a much larger steam production with pins that without, not easily quantifiable but the engines used to test them could be run at a much higher speed continuously using the boilers with heat exchangers.

Optimal flue gas stream depends mainly on the density difference between the hot gas from the burner and the cold surrounding air supplied to the to the fire box. If there is no cold air due to a closed fire box then there will be limited flue gas flow, independent from the combustion air supplied through the burner. Excessive flue gas in the firebox will cause poor combustion of the gas. Could the lack of cold air supply cause some of the issues you are experiencing?

Yes, that is the case and was cured on my boilers by using a blower to suck the gases though the tubes. I think the difference is probably caused by the different types of heat produces by our different ceramics.  It is seemingly general in the model steam locomotive world to pretty much seal the burner be they ceramic or poker into the boiler using the air mixed with the gas for combustion.  In this video which I have just posted in the model boat section the holes that used to supply air to the original meths burner have been sealed when convert to a ceramic burner.  The burner is lit by a flame applied to the top of the chimney and turning the gas on. The covered holes can be seen on the still photograph below



Take care Tony.