John Casey

allen, thanks for the warning...it's good that I asked before diving in, I guess.

Is there any way to overcome the laminar flow problem, maybe by increasing the number of pipes in the outflow well above the equivalent area of the 6" stack? Say, up to 12" or even 18" of total area? Or, is the division into separate channels going to cause problems too?

I've read that wood has a lot more BTUs to offer than, say, propane. My current roaster (propane) tops out each time I use it, and it's basically useless in a Kansas winter (never reaches 475F). I think I can get partway there using decent insulation, but was really hoping to find a way to use wood instead of propane. And the rocket stove seemed to offer the most in terms of quick warm up and limited wood use.

Well, even if it won't work, playing with these prototypes has definitely got the gears turning in my head!

Maybe the answer is to try to run the drum vertically with an auger inside...that's a much more complicated build though, in terms of bearings (that will be in the heat stream) and the auger design.

Hey everyone,

This is my first post, but I've been lurking on and off for some time now. It's a GREAT resource, and I find that I lose hours at a time reading up on this stuff. Thanks for all the information.

I'm starting to build some prototype rocket stoves (not RMH yet), with the end goal of replacing the old tired propane grill body that supplies the heat to my coffee roaster. I'm currently playing around with a 20-gallon galvanized trash can, some 6" black stove pipe (it's the only size I can find readily around here, at least so far), and a bunch of perlite I grabbed from the local nursery. I've already measured temps > 1000F at the top of my very short stack (20" from the bend) and I can see that I need a taller stack already.

1000F seems like it's plenty enough for coffee roasting, IF I can translate into bean temp with reasonable efficiency. I need to end my roast around 470F, hopefully with up to 4 lbs of beans. I'm using a rotisserie-style drum with vanes to stir the beans, but I digress. I'm looking at a taller stack to try to make it burn cleaner. I figure I can always vent in some cooler air using a different duct and fan to get to the temp I need. But, I digress...

My main questions are:

1. I need to channel the flue gases into more of a rectangular shape to hit more of the spinning drum. Will it work for me to split the exhaust into, say, 9 1-inch pipes and create a sort of manifold that I could reshape into a line?

2. Looking over the setup above, am I taking any wrong turns, or missing something important? I'm still learning how all of this stuff works, and how to make it work optimally...

3. I'm looking around for something that will hold up better than stove pipe, assuming this thin-walled stuff may not have a long lifetime in such a harsh environment. I'm currently checking out refractory supplies for when I get the prototype stove working and I'm ready to create something more permanent...is there a really GOOD material that I should be checking out?