One other thing you mentioned the other day was that you are going to raise the bottom of the whole boiler, how will you control the much increased amount of air getting in as that will make a coal fire burn even faster?
Now that I have the materials to make a base I've been thinking a bit more about this.
My boiler dia is 5" so the surface area of my fire grate is 20sq" approx (assuming the fire hole door is closed all the air needed for combustion passes through this 20sq"). At the moment using my boiler as I have been using it without a base the only air intake (apart from the fire hole) is a cut away slot on the botton of the boiler front - I estimate this to be about 3sq". (Looking at my earlier photo may help)
The idea is to blank off the front cut away slot and have all the air needed to enter a 'box' that the boiler will sit on with a 5" dia hole under the grate - in other words instead of having a 3sq" of air intake going to a 20sq" grate I can substantially increase that but control it via a 'air door'
I'm really not sure how much air a boiler of this size and design needs so I'm kind of guessing here but I dont think it would be difficult to get nearly 20sq" of air holes in the 'box'.
I guess what I'm kind of getting at is does it sound right to have the same amount of air intake surface area in the base as the fire grate area of 20sq" ?
In practice the area of the grate exposed to air is probably closer to 15sq" than 20sq" allowing for fire bars but you see what I'm getting at.
Anyone got any thoughts before I start cutting and soldering ?
Thanks
Peter.