Reluctant to rocket

I have a strong wish to support having this reach folks in the UK, I'm not enough of an expert to add much technically but happy to offer moral support.  

My two cents would be compromise on the aesthetics of the barrel if you can establish proof of concept.  For England! or wherever you are!

I would also say that feeling is believing, feeling the heat, and so your example will be of value to people far beyond a hundred youtube videos.  I am in a similar attempt where I am in the USA, and I have to let go of some ideal ways of doing things because I'm trying to mimic what my townspeople would tend to do or find easiest.  I hope that helps with motivation a little, and I will be watching this thread and hope to catch up on pages 2-4 soon.  

Also another person in the UK has just said he's going to build one, I can put you two in touch if that's all right with you.  Might be some quirks about your context that are in common, I don't know.  Climate, regulations, dimensions of materials, etc.

Good luck!!!

Hello Nick,

I cast my vote with those that say, essentially, go to the basics.
Use the proper size barrel, and double check all your math, and physical distances in your build. Double check the riser ratio and quality of insulation installation. That sort of thing.
When the geometry is right, the riser is well designed and constructed, and it can breathe, it should burn very, very hot.

I've built several rocket stoves, and they've all done well so far, but I also found that when I cut corners, or "experimented" I tended to get poor results.
My case was the chimney, which I initially did for cheaps (low cost) and therefore too short (and putting it at a decided disadvantage). Very finicky burner that was, because the draft was so iffy.
When I think about my inner spacing, and see yours, I think it looks very "cramped" and cast my vote to a choke point. The dragon must breathe!

An 8 inch rocket is truly a monster! My 6 inch is able to cook me out of my living room, breaking over 100*F in the room, and raise the temps to comfortable levels several rooms over, with a bit of electrical fan assist (1,384 sq. ft. total, and NOT designed for good airflow throughout, being built around 1950, with the idea of cheap fuel).

Good luck, and keep trying!
Erik

I use my own RMH to heat a poorly insulated space, but these are the impressions I got from using spaces around Wheaton Labs and watching Paul use his in the FPH. You don't run it at partial throttle unless you are trying to keep the aesthetics of the rocket roar going. Burn at 100% until you have generated enough heat to charge the mass, then let it burn out and cover the feed. This gives the most efficient burn and lets you change focus away to other tasks.

I'd say this would be filling the feed 80-100% with wrist sized sticks every 25-40 minutes. The system can be turned up to 11 by using matchstick sized wood or straightening out sticks as they burn down and fall if you care to. I run mine lighter like it looks like you are, but am trying to keep constant heat radiating from the barrel and the mass is just to extract some more heat before exit. Using larger chunks of wood is good for throttling down the burn also, but wrist sized is a good average size for a quick, hot burn since smaller is much more finicky.

As for design issues, I concur with what has been posted about the barrel. 50mm top gap was the minimum mentioned by Ernie and Erica in the book, but ongoing experimentation has shown the 80mm provides consistent results while still allowing enough heat on the surface of the barrel to use it in a stove fashion. If you don't want to cook or heat drinks on it, it sounds like it can be as high as you wish.

Pushing the minimums here seems the likely source of poor performance. Given the emphasis of Ernie and Erica and their mentor Ianto on affordability of construction, I'm guessing minimums in the book are based around common, thinner barrels. Stainless steel is thicker and does not conduct heat from inner gases to the radiant surface as readily from my understanding, so running on minimum CSA there could hamper your thermal pump's 'push'. Also, did you use the actual measured inner diameter of the barrel to calculate that CSA? The picture of the new riser just looks like it has next to no space to where the barrel sits.

Finally, I was going to mention the cleanout Ts. The length of the dead ends seems to be about twice normal, even more for the one by the chimney. I was thinking in terms of diminishing pressure to guide gas through the turn, but Scott sounds like he has some experience with such phenomena so maybe turbulence from 'bounce' is a more accurate description. Intuitively a closer flat surface at the turn would seem likely to produce greater bounce to me. It would be an interesting experiment if fabricating plugs to try a 45* angle one that would fill the space like the wall of a regular outside of the 90* bend's duct...

One more note, didn't you say you were going to remove the constriction at the end of the riser?

The secondary burn in a J tube occurs as the heated gases coming off of the fuel make the turn from horizontal to vertical at the base of the riser. As I've heard it explained at Paul's Jamborees, the 90* turn there serves to create some turbulence and mix remaining potential creosote and ash to where it combusts. I'm not sure exactly what this square thing is without a picture, but seems like it would pose much less of a problem at the bottom of the riser around that turbulence than at the top where the gases are trying to slip over the edge of the cylinder through your tight tolerances...