Radiant Heaters

[Eddie Price 1Participant @eddieprice1]

[Eddie Price 1Participant @eddieprice1]

I have recently completed the 16mm gauge loco ‘Eric’ from Brian Wilson’s book “Steam Trains in Your Garden”, but have had problems with the gas burner. The burner is a 9.5 mm diameter brass tube with 0.5 mm slits cut in it, and it fits into a 3/4-in diameter firetube in the single flue boiler. I had great difficulty in controlling the burn. Too little gas and it went out, too much and the flame came out of the chimney. When it managed to stay alight it took a long time to reach working pressure and then when the throttle was opened the pressure fell away. No amount of fiddling with the gas supply or the position of the burner in the firetube had any effect. So I did some searching on the web for some ideas and came across an entry for Radiant Poker Burners at Southern Steam Trains for Gauge 1 Astor locomotives. I thought I would give it a try.

The radiant burner is formed by wrapping two separate layers of stainless steel mesh around the poker burner tube. I obtained some pieces of stainless steel mesh and chose a #60 mesh. I think this refers to the number of openings per inch. The first layer was wrapped around the firetube and held in place with 0.2 mm stainless wire. I think this layer is intended to act as a sort of diffuser and this is a photo of the flame.

The next step is to attach a second layer of mesh, but in a loop above the burner so that there is a space of 3 or 4 mm above the first layer. This proved to be quite difficult, but I eventually managed it with lengths of stainless wire holding it in place. The result of lighting the gas is quite startling. The gas starts to burn with a blue flame as before, but then quite suddenly the gauze glows red and you have a radiant heater. This is what it looks like.

 

This was with a No. 5 jet. As you can see it is glowing brightly – too brightly. So I put in a No. 3 jet and this is the result.

I think this would be more acceptable. It is not so intense a glow and is probably using less gas. However, these images are for burns in the open. When placed in a fire tube the results were not so encouraging. With the No. 5 jet the whole poker tube started to glow red. As it is only thin-wall brass I quickly turned it off. With the No. 3 jet the results were a little inconclusive. Certainly the poker tube did not glow red, but neither did the gauze. I suspect the problem lies with the limited diameter of the firetube. Perhaps Gauge 1 Astors have a larger diameter firetube. So not entirely successful, but I had noted that there was far greater control of the flame with the single layer of mesh than without it, so I decided to use this in the boiler. The results were excellent. It was far easier to light the gas in the first place, and there was a greater degree of control with the gas regulator valve, from a low flame to a high flame. Working pressure was reached in about 4-5 mins, and there was no loss of pressure when the throttle was opened. This was with the No. 5 jet.

So I haven’t managed to produce a proper working radiant heater, but I have managed to improve the control of the burner by wrapping one layer of ss mesh around the burner. The Southern Steam Train writer produced a number of different burners with one and two pokers per burner and achieved greatly improved gas duration. Some more research is obviously required for the smaller diameter firetubes.

Eddie Price

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