Randy Me

Hey folks, thanks for the advice so far! Out test run outdoor was successful, starting the build indoors. We're laying out the exit flue and wondering, what to use for a clean out plug. We have an 8" exit flue and have two Tees for cleanouts (placed so we can access all parts of the whole run for cleaning). I have a metal CAP made for the Tee but it's not a tight fit. I'm worried about noxious gases leaking out. I also saw a metal PLUG is available for the 8" pipe, which is different than the end cap that I have, and might be a tighter fit, I don't know. What do people use to plug the clean out?? I saw a video clip with Ernie and Erica and they pointed out their clean out plug which they said was only $12 and seemed to fit tight. Anybody know what that item is exactly and where can we get one? Or have any other suggestions?

3.5 inches. Would a half inch make a difference? I still don't understand the the dynamics. Why is the spacing of that gap so critical??

We put together a test system using firebrick, 8" I.D. round insulated heat riser, 55 gal steel drum, 8" exhaust pipe (16' w/ three 90's), following Ianto's book pretty closely. We have slow flow through the system with some worrisome backsmoke.

We want to understand the dynamics better. What makes the rocket force? How can we tweak the system to get a stronger flow?

The only deviations we made from a traditional design is using the barrel right side up with a removable lid, and cutting holes in the bottom for the heat riser and 8" outflow directly connected to the bottom of the barrel. The heat riser has about 1.5 inches of rock wool blanket insulation. We dry stacked the blocks and sealed joints with clay/sand mortar. The burn tunnel is about 6" high x about 7.25" wide. It's not extra long either.

Don't get me wrong, we DID get a positive flow through the system, but it was weak, not as rockety as I would want to pull more fire and smoke in that direction. It was too easy for fire and smoke to go vertically up the feed area. And we still have more exit flue to add to go up and out a wall in the building.

So, what makes the rocket power?

Photo: http://www.flickr.com/photos/9867280@N07/8178815692/in/photostream

Allen, thank you kindly for the reply. I have the book and have read most of it, but somehow I missed that page, I guess I better read it again more carefully. The description of the mortar work is good, I think it provides sufficient detail. It suggested mixing the mortar a bit wetter, "about the consistency of guacomole or custard" so it can be applied thin, just enough for leveling and filling tiny gaps, about 1/8 inch if possible (3 or 4 mm). --Randy

Whether 'tis Nobler in the mind to MORTAR
The CRACKS and GAPS of outrageous FIRE,
Or to take Arms against a Sea of CO2...

but seriously... I see mostly dry stacked fire brick. I like the idea of mortar to help level and seal. I'm wondering how an adobe-like mixture will perform, whether it would hold up. I'm talking clay / sand at about 1/3 clay to 2/3 sand ratio. It's local clay. I'm nervous about experimenting like this on the first one. I'd feel safer following a recipe. Is there a reason most people dry stack? Anybody tried building one with clay/sand mortar between the bricks, like traditional mortar but with clay/sand?

Another question... for the thermal mass, will recycled concrete rocks work? Someone told me certain types of rocks will crack or pop or sort of explode when heated. Is this an issue with the mass part of the system? I think not, but I wanted to ask.

Thanks guys!

Rando