Basic lengths on a rocket with L style burn tube/riser

Ok, so I am going to try a rocket firepit..... Girl Scout camp..... I know that the j tube is a 1:2:4 ratio, but is there any equivalent for these L shaped outdoor cooking style tubes?

Basically I am going to make a fire brick tunnel around a form, then that will be in a 36 inch sono tube and be poured full with concrete with some added ingredients to make it play well with the heat.

I know concrete..Ick...but 5 yr olds are hard on stuff and I will be moving the first one around to our nine camp grounds all over the western side of the state, so the toughness is needed.

Any ratio or other advice would be great!

Chadwick Holmes : I think I understand what you want! This is a variation on that /////See link Below :

http://ernieanderica.blogspot.com/2011/12/oysturkey-and-tea-stump.html

For further information ////// See this second link :

ernieanderica:info

For the good of the Crafts ! Big AL

That is exactly the type I am talking about....that one in particular is beautiful!

So then my question is: is the feed tube length as critical in this design as in a j tube, and is there a ratio of feed tube to riser that has proven to be a clean burn with some visible flame?

Logically that ratio is not as important as you have no "pushing" to do and you don't have the friction of a longer system to compensate for, but I figured there would be folks here that can set me in a proven direction....

Chadwick Holmes : For this type of simple rocket stove the dimensions and ratios do not seem to be that important. There is definitely a need for some insulating material

to be part of the mix that lies next to chimney, it needs to be there to make the fire burn hot and clean !

In no special order the next most important things are The shelf that the wood sets on and provides an air passageway underneath to promote the wood fuel burning only

at the tips, The Horizontal Feed Tube ( and air supply ) can be a little bigger in diameter than the chimney, and will increase in size overtime as it gets used . And You will

need to create pot supports to hold the pot above the top of the chimney or you can ''Borrow cooking grate for a single burner from some Cooking stove !


-or the whole thing can and has been made with Tin cans and used with a wind break for ice fishing ! link below :

https://www.youtube.com/watch?v=CfCLRufKhjc&list=PL4680BB06883874B3


I hope this was timely and useful, for the Good of the Crafts ! Big AL

Thanks a ton Big Al!!!