Rocket Bell dimensions

[josephcrawley]

I was talking to a friend who builds masonry stoves for a living about the amazing peterburg stove I saw on this site and I was expressing my interest in building a small (5'x6'x2') downdraft(rocket stove) all brick stove using the bell principles. He mentioned that he thought there were particular proportional rules to bell design. Does anyone know what those might be?

thanks

[peterberg]

Nov 12, 2009 9:25:00 GMT -8 josephcrawley said:

He mentioned that he thought there were particular proportional rules to bell design. Does anyone know what those might be?

Virtually any shape can be used as a bell. Some shapes do have its own advantages. For example a narrow and high bell delivers a very good heat distribution with relatively low heat stress at the top.

Wider and lower bells take up more heat because they have a wider ceiling. The ceiling is the hottest part, make that wider and it will take up more heat. So some shallow bells in a row, beside each other, will become a very efficient heat exchanger.

The above are all the rules I could think of. Keep the rules in mind and you're reasonably safe. You don't mention the system size by the way, and the 5'x6'x2', is that width, depth and hight? Something tells me it would fit an 8" system.

[josephcrawley]

it is an 8" system. 5' wide 6' high and 18" deep. I have about a hundred bricks and need to get about 200 more to finish my test model. I would like to use it to heat my 900sq/ft home. Would you recommend buying those double size 18" bricks for the bell roof sections or is casting the stuff with refrac cement cheaper/better?

thanks
Joseph

[peterberg]

Casting refractory concrete isn't easy. It has to be done using a vibrating table in order to get the air out. Those double size bricks sounds like a good alternative.

I presume only the riser of the rocket stove would be inside the bell. It is done before as an experiment, see heatkit.com/research/2009/lopez-rocket.htm
The best results were obtained with a proper rocket.

[canyon]

Peterberg, Thanks for that link! What a wealth!

[josephcrawley]

This link also has some neat rocket/bell heater pictures. mha-net.org/docs/v8n2/wildac09f.htm