You do loose a bit of the radiant heat that you get from a coal fire as you are mostly relying on the hot gasses in the tubes to provide heat.

Cut the ceramic block to fill most of the firebox area and have the flame going upwards, Ideally the boiler would be designed from the outset for gas firing if you wanted the most efficient firing.

J

Sorry Bazyle…

Fire risks of coal?

Do they want stuff that doesn't burn?

And gas is safer is it?

Andy

Coal fires tend to drop embers through the grate and sparks up the chimney.

Gas doesn't have those problems so yes, in effect, safer.

Lofty

As I said in an ideal situation teh boiler would be desined for gas firing, probably one big firetube down the middle with a spiral of cross tubes that would come into contact with teh hot gasses as they travel along the boiler.

If you angle the flame sideways in a boiler designed for solid fuel then its just going to hit the smokebox tubeplate and risk overheating it, with teh flame going up it has a bit more room before it hits the crown and you can always add a couple of baffles.

The smaller engines are never easy to fire needing constant attension, you may find it easier on charcoal rather than steamcoal

What's all this about a fire risk from traction engines