Paul was asked the question about front bottom access air intake ports. The question posted here at this time:
The question was about the front bottom access port. I can not speak for others that have not tried this front access build, but I can tell you from experience that it is the best part about the front of my RMH.
The advantages included but not all inclusive:
* easier start with no need for large amounts of paper or heat riser priming.
* easier access to bottom of feed and burn chamber.
* easier clean.... can i say that again... its much much easier than scooping out of the top with some custom tool or your hands out of a narrow feed tube. much easier.
* direct cross air intake seems in my experience allow the wood to burn all the way down and better than top down air intake.
* less smoke back puffs when starting and operation if air intake is at the bottom.
* direct better view of burn tunnel and bottom of feed area when you are examining your system with out kinking your neck or use of mirrors.
You can see my front access ports and build of my rocket mag stove in my signature links
I have designed and tested 3 of my own rocket stove mass heaters and all 3 of them have front access. When it comes to cleaning them out, I couldn't imagine any other way. I can only guess how difficult it might be to clean out a conventional J-Tube without a front access. Ash clean outs are a must on this type of wood burning appliance, and most of it seems to be in the burn chamber, so a front port just makes good sense. External air intakes are also great ideas for airtight buildings or energy efficient buildings, because of the huge amounts of air and displacement of such said air required
I have found that it is easy to clean out a 6" J-tube by hand (note that mine has a back sweep so that the flat floor is a few inches shorter than the whole unit; for a squared-off core you might need a sardine can), and I can easily reach all the way to the back of my 8" J-tube with a sardine can with an 8" or so handle attached. Also note that these are built to specs, with the 6" feed tube being 12" tall and the 8" being 16" tall.
A front cleanout door can be useful, but is definitely not necessary unless you are a gorilla with huge hands and forearms. It is also not even desirable to clean every bit of ash from the burn tunnel floor, as a thin layer helps insulate it and can cushion the surface if you have castable or other softer materials in the burn tunnel.