internal heat riser length to barrel?

Heat rise length barrel? I have welded two smaller oil barrels together- 53 1/2 inches- My heat riser is 50 inches, so I currently have a 3 1/2 inch gap from the internal heat riser to the barrel. Seems to pull well, but unit is not installed, been firing outside. I know how important the pull is, I need to get this right, looking for other opinions on heat riser lengths.

Thank you

Tahj; I don't have practical experience with sizing the gap between the top of the heater throat and the steel heat diverter. I would assume several factors come into play, not the least being the size of your firebox door opening, flue run and chimney cross-sectional size, and how much heat you wish to extract from the flue stream via the barrel top. One video I watched recently suggested 1 1/2" would put the majority of the heat dump directly at the top of the barrel, while increasing the gap to three inches might create a hot-spot torus half-way down the outside of the inner throat.

My question is, if one does not wish to extract immediate heat, but rather send all the heat produced to thermal storage, why bother with the throat?

Here's a link to an article that appeared in Fine Homebuilding, Jan. 87, explaining a stove I built in Missoula.

http://www.finehomebuilding.com/how-to-articles/kang-masonry-stove.aspx?ac=ts&ra=fp

-rockpicker

Thank you, very informative.... I think I will get another heat riser tube to give the 1 1/2 inch gap between riser and barrel. I am gonna run tests on both.....

Keep ya posted, wanna complete this project and move to others....LOL...\

G. Karl Marcus wrote:One video I watched recently suggested 1 1/2" would put the majority of the heat dump directly at the top of the barrel, while increasing the gap to three inches might create a hot-spot torus half-way down the outside of the inner throat.

Which video?

C. J., In answer to your question, "which video?", it's this one:

http://www.youtube.com/watch?v=qtFvdMk3eLM&feature=player_embedded#!

in an 8 inch system you will want a gap of 2 inches. please dont fiddle with the gap till you have built one to the standard. after you build it then adjust the gap to get the results you would like. you only have a half inch to play with so it pays to start with the optimum and adjust from there.