rocket retrofit

[s2man]

I hate incomplete burns. I burn all of my fires hot - no banking and smoldering for me. But my standard wood stove still sends some smoke up the flue.

I've become intrigued with the rocket stoves and read everything I can find online, and I plan to get the RMH book. But we just bought the homestead last summer and I've already got too many projects lined up to start a RMH this summer.

I was looking for your thoughts on the following retrofit to my existing stove. It seems like an easy experiment, and can easily be backed out if it does not work. I'll be tearing out my flue this summer to upgrade from snap-link to welded pipe, so that may be a good time to move the stove outside and play, I mean experiment, with it.



Not to scale.

Oops. I meant to draw a Tee instead of an Ell, for clean out.

[s2man]

Hmmm. I just reread the "MH mechanism, the drive behind the drive" and see where too large of a chamber beneath the riser makes the rocket lose its drive. So that will probably shoot this idea down.

OTOH, I've got 16' of vertical flue and will not be cooling the gases in a masonry bed. So as long as I can get the riser warm enough to support secondary combustion, I'm not really concerned with the rocket driving the exhaust.

[canyon]

What you describe and show in your drawing is pretty much what I have going in my tester rocket (being a self contained woodstove rocket makes it somewhat portable for testing/firing benches). It works great and can charge a bench with 24' of 6" horizontal flue without draft problems although I try to use a bypass for lighting/preheating. If you can at all add some mass after the stove you will be glad you did.

[Donkey]

Canyon,
Did you modify the firebox or air intake?

[canyon]

I modified the firebox by welding a cover over the old upper horizontal exhaust exit and then cutting a 6" hole in the top and welding on a length of 6" schedule 40 pipe which I insulated with kaowool (shielded with a wrap of scrap stainless corny keg sides) for a heatriser. Then I covered that by welding down a stainless 1/2 bbl beer keg (with another welded on top of it for hot water) and welded in a 6" side outlet at the bottom. Then finally I lined the inside of the horizontal fire box with firebrick. I think there is a picture of it from maybe two years ago that you did the fancy work for me on. I forget the thread name, maybe "water heater by canyon" ?

[s2man]

Thanks for the feedback, canyon. Good to know I'm on the right track.

Feb 23, 2011 19:18:12 GMT -8 canyon said:

If you can at all add some mass after the stove you will be glad you did.

I'm contemplating a mass bench or shelf, but we haven't finalized the basement layout, yet. So not sure where to put it right now. And definitely too busy on the homestead this spring to build one now. Perhaps it will come together before fall.

We do have a lot of mass in the concrete basement and log walls. It takes a couple of hours to warm up one end of the house in the morning. Once I get the thermostat-controlled fans installed to move warm air from the L/R to the B/R's, I'll have an even larger heat sink.

[canyon]

Your mass doesn't work for you the way it does when you couple it to your rocket. When I first built mine, I laid out some urbanite and then set the flues on top and then as I built the bench slowly with clay/sand mortar and rock/urbanite/cob over weeks I temporarily loosely stacked all of my urbanite and rocks that I was working with on top of the flue that I was already firing and it didn't really do much. Until I actually packed the mass into a more monolithic conductive unit with mortar I almost didn't feel like the mass was helping (of course it must of helped in theory but I couldn't "feel" it until I packed it in). The difference is mind blowing. You really need to directly couple the mass to the flue for it to work for you meaningfully.