Smoking problem with Rocket Stove

We are attempting our first rocket stove (and mass heater) this weekend and have tried many variations but still have trouble with smoke (and flame) coming from the feed. Initial paper start fire is really rocket sounding, but as the sticks are added, the sound isn't there, and eventually flames and smoke start coming up the feed side.

Here is what we have:
6" x 33" double insulated pipe that has been filled with vermiculite and clay
firebricks, clay, sand, regular bricks found in alley.
pre-burned 20 gallon barrel

Questions: 1) is there an ideal burn chamber length? too short, long, or tall? (ratio to the size of the pipe?)
2) is there a limit as to how high the feed chamber can be?
3) is there an ideal ratio of the size of the feed chamber to the upright pipe (6")

Dale Schlehuber wrote:We are attempting our first rocket stove (and mass heater) this weekend and have tried many variations but still have trouble with smoke (and flame) coming from the feed. Initial paper start fire is really rocket sounding, but as the sticks are added, the sound isn't there, and eventually flames and smoke start coming up the feed side.

Here is what we have:
6" x 33" double insulated pipe that has been filled with vermiculite and clay
firebricks, clay, sand, regular bricks found in alley.
pre-burned 20 gallon barrel

Questions: 1) is there an ideal burn chamber length? too short, long, or tall? (ratio to the size of the pipe?)
2) is there a limit as to how high the feed chamber can be?
3) is there an ideal ratio of the size of the feed chamber to the upright pipe (6")

Hi Dale,

Yes, those are all critical measurements. The burn chamber csa, (cross section area) is the choke point. The top gap on the barrel, the exhuast manifold, and the exhaust pipe all needs csas larger that the burn chamber. Feed chamber should not have higher csa than burn chamber. Ratio of feed to heat riser is 1:2, I believe. Make sure that your connection between feed chamber and heat riser is not leaking; that will cause the smokeback after lighting.

Mike

Hi Mike,

Have you seen this diagram? As far as dimensional ratios, this image has it all in a nutshell.
NOTE: for some reason, the "D" dimension that is mentioned in the formulas, is missing or obscured in the drawing-- it represents the length of the burn tunnel.

I have seen the drawing, but unfortuneately I am unable to enlarge it to see what dimensions and writings there are. Thanks for the idea. We have got the stove part working great once I found erica and eric's formula under the engineering section.

right around 24 inches due to the brick sizes. a 20 gal barrel would let you make it around 18 inches. CSA needs to be uniform throughout, heat riser needs to be about twice the inside measurement of the burn tunnel preferred= more.