Sometimes information derived from a failed experiment is just as useful as a successful experiment. Several readers predicted that burning coal would not not work in my dredger engine boiler, but I had to be convinced.
So, I removed the gas burner.
I have 3 types of coal. One is Welsh steaming coal in 25-30mm lumps. It has an attractive shiny appearance. The other is coal lumps which were picked up next to a local railway line and are probably from Newcastle NSW. I also have some brown coal, but it is in the form of briquettes, and I did not attempt to use them.
Both black coal types were too big for the ~60x40mm diameter firebox in the dredger engine. How to make them smaller?
Smash them up with a hammer and pass them through a sieve? That would leave a lot of unusable tiny fragments as well as bigger bits. And be very messy. And require making a sieve. If my experiment was successful that is what I would do in future. Did not happen.
Meanwhile, I tried a hammer with a splitter edge. The Welsh coal had definite layers, and split fairly predictably, with not too much dust or tiny fragments. The Australian coal crumbled unpredictably into many fragments with a much lower usability fraction.
I started the fire with newspaper, then pine and hardwood kindling. I should have paid more attention to the wood sizing, because it was problematic getting the wood alight. Also, I had not set up a blower for the chimney. I was relying on a really long chimney extension to provide enough draught.
Got the fire going with the assistance of a gas torch. When the fire got going the draught seemed adequate.
Tried to add coal lumps, but they would not fit the firebox while the wood lengths were in place. Firebox is just too small. So I persisted with wood. Soaked some in mineral turps.
I was not impressed with the appearance of the fire, but surprisingly, eventually, steam was produced, but never enough pressure to run the engine. And the fire did require constant attention. The front of the boiler was quite dirty after all of this. I am glad that I have not yet painted it.
I will give the wood + coal fire another attempt, but size the pieces better (smaller). The Sievert type burner is looking more likely.
Later in the day…..
…after a further discussion with Stuart I have decided to try the Sievert burner. Made some steel rings which are a press fit on the burner, and an easy sliding fit inside the firebox.
This is the new burner inside the firebox. Not exactly @Trevithick, but I bet that he would have used it if it had been an option.
I still need to make a fitting to hook up a valve and the propane hose. And try it out maybe tomorrow. Another experiment. I hope to not see flames shooting out of the chimney.