Cindy Mathieu wrote:If you are building a rocket heater on a wood floor, you need to incorporate an air gap between the wood and your burn tunnel. The layers might be the wood floor, stone, bricks to create air gap, another piece of stone, then, the burn tunnel. A detailed recommendation for this is found in the 3rd edition of Rocket Mass Heaters on page 68.
The burn tunnels do get very hot and because the fire is usually down lower than in a cast iron stove, the wood floor is subject to spontaneous combustion without proper precautions.
Jay C. White Cloud wrote:O.K. Paul, if you don't mind, I am going to "dissect" your post and see if I can break some of it down and perhaps alter a few points for clarity and correction.
I will take that you mean "jointed" the post when you write "cut."
In this picture you can see that I cut out the post
Well the "cross timber" is the "bent girt" or "bent beam" those between the different bents (primarily European modalities but also in Middle Eastern and Asian as well as in other timber framing cultures) are called "connecting girts" or "or connecting beams."
where the cross timber seats to for a shelf of sorts.
The "seat" that forms a "shelf" is the joints "bearing point" and is generally, in its entirety, called a "housing."
That is neither traditional, nor good practice. The "bearing point" of the "housing" should take all the primary load that is subjected to the joint from gravity and all tectonic loads. That part you have correct. In in many designs, the peg is only there for getting the frame together, and could be remove latter, as it is not really needed at all. Better yet, do not design joints that need pegs, but instead relies on a "draw or compression" wedge, or gravity to make the joint work over time. "Draw pinning" is the method of keeping joints tight both in general format and to the beary surface and this is done by "offsetting" the "trunnel" or "peg" hole in the receiving (mortised) member, not by elongating the hole in the tenon which is not traditional or necessary. I would also not that oblique braces are often not peg at all (nor should they be as they work in compression load only,) nor is there enough "relish" in the long grain of the brace tenon to make the pegs functional, often making the joint weaker and failing as oblique braces do in general the smaller they get in length, as they react to tectonics within the frame making them a fulcrum on the nearest joint. Most (almost the majority) of timber frames built through history (other than in Europe and the last 400 years by Europeans in North America) do not use oblique bracing, but instead use "horizontal" bracing modalities. The Middle East through to Japan, has relied on "horizontal" bracing and tying systems more successful against tectonic load than anywhere else in the world, and still do. This is why they have the oldest frames and the oldest sustained timber framing cultures (other than some small pockets in the Swiss Alps and Carpathian mountains.)
As a green timber dries it will shrink so if the peg hole in the tenon is a tight round fit ,the peg will end up bearing all the load . The shrinkage will lift the cross timber off the shelf.By elongating the tenon hole vertically the cross beam can settle back down on the shelf as it dries.
Sorry that got long winded, but it was warranted. Thanks for making it possible and good luck with your timber faming. Let me know if I can help (or confuse ) you more than I have thus far.