trouble with the prototype rocket stove

so for about a month now i have researching and then building a prototype 3 Heineken keg tall rocket stove. due to the size constraints i used standard 3"duct work piping instead of the 6 or 8 inch duck work which is uninsulated including 90 degree adjustable heat riser and elbow/intake. in addition the exhaust port on the back end is also a 3" duck work in the style of a RMH as a single unit.

On the intake part it has an attachable 90 degree adjustable to create a J style RHM from a L style. i am having issues not with the exhaust but with the fire itself. it doesn't want to STAY lit as well as its difficult to 'prime'. I am unable to boil water or FULLY cook an egg as it currently is. before i had completed it i was able to get it to become hotter then it is now getting. i used rivets and JP WELL to attach everything. at at least two spots the jp well has become brittle and broken off or began to chip.

any advice. or is this stove 'cooked' to use the pun correctly.

here are some pictures of the stove.

design:

pics:

Im relatively new to the rocket stove thing, but if the heat riser is un-insulated it wont work as it should. There needs to be a differential between the gases rising in the heater riser (should be _hot_), and the temp of the descending gases in the bell, which will still be hot, but not as hot as coming up the riser. If the riser is un-insulated inside the bell, then everything is basically the same temp. Having good insulation from the beginning of the burn tube to the top of the heat riser seems to be really important.

I would also suggest insulating both the burntunnel/feed and the riser. Even an inch of welders blanket or Roxul would make a difference and still leave enough room in your barrel for exhaust. Instead of jb weld, I would use silicon seal. There is high heat stuff in the automotive dept. Its only good to 700C, but your barrel should not get that hot.

its an all metal construction it reaches equilibrium and goes out. you need a differential in heat to make it work right. insulate your burn tunnel and heat riser. and get a bunch of spare pipe cause you are going to burn the pipe out really fast.

so i went ahead and got a double wall for the thing. now i have also increased the j tube to 4 inch form 3. i would like to thank you all for your help and i will let you know how things go. also since i have to shorten the length of the straight double wall part.

Now is there a insulator like ash that i could use to fill the double wall for better insulation since i have to shorten it a bit anyway?

also anyone ever used a high tempature foam insulator for the fill of the heat riser? something like 'Isofoam' or 'SOLIMIDE' polyimide foams.

Perlite is the normal material used there, sometimes mixed with a clay slip to keep it together as the metal burns away.

Catrina Weathersett wrote:so i went ahead and got a double wall for the thing. now i have also increased the j tube to 4 inch form 3. i would like to thank you all for your help and i will let you know how things go. also since i have to shorten the length of the straight double wall part.

Now is there a insulator like ash that i could use to fill the double wall for better insulation since i have to shorten it a bit anyway?

also anyone ever used a high tempature foam insulator for the fill of the heat riser? something like 'Isofoam' or 'SOLIMIDE' polyimide foams.

Ash will work. The only problem I have heard with it is that it absorbs moisture and compacts. Also, as it gains moisture it becomes corrosive, though I don't think it eats steel as it is high PH not low. The lye can be washed out of it, but then I think it is not so fluffy and insulative after being wet. Try and see.