Math As Easy As 1 – 2 – 3
The math that drives the physics of the “Rocket” is fairly straight forward. The length of the roof of the Burn Tunnel must be at least two times (2x) the diameter of the cross section. So, for a 200mm / 8in system, the roof of the Burn Tunnel must be 400mm or 16in, at least.
The height of the Heat Riser, measured from the roof of the Burn Tunnel, must be the three times (3x) the diameter of the cross section. So, for a 200mm / 8in system, the height of the Heat Riser, measured from the roof of the Burn Tunnel, must be 600mm or 24in, at least.
There are some “math reasons” why you should not exceed 3x the cross section for the roof of the Burn Tunnel. In my design, I aimed for a Burn Tunnel roof length of 2.2x and it works well.
If you want to “go big” somewhere, the place to do that is the height of the Heat Riser. The taller it is, the faster and hotter the Rocket will run. Just keep in mind that you will need to find something to put over it, one way or another, as the Barrel Cover.
The chart below provides a fast, simple look-up for the measurements of your system:
Woof. Ok, this post is waaaaaay longer than I had expected it to be. Hopefully you are still with me, and better yet, some of this was valuable to you.
In my next post, I’ll talk about my first and subsequent testing burns that I have done with the “Version 2” system and a few surprises I have learned along the way.
After that, I will talk about how I run my Rocket Mass Heater system in my greenhouse, including lighting, feeding and cleaning.
If that doesn’t prove to be another TL;DR bait, I’ll finish up with a review of what I’m coming to recognize as “normal behaviours” in temperature and a bit of a snark about Rocket Mass Heater systems are and are not.
If you have any constructive comments, questions or suggestions, please leave them in the comments section below this post. I would absolutely love to hear from you! I hope this series of posts helps someone else get into this fascinating technology.