J tube

Hi, I have been looking at the forum for a few years and I have a couple of questions…
It seems that the J tube became very popular on the forum around 10 years ago and the standard method was to use a barrel and a piped bench.
I have read hundreds of post but I dont see anything about the placement of the riser in the barrel, I mean does it have to go in the middle? Does it work best with the riser in the middle?
If so then the popular formular of 124 or on a 6” system 8” deep fire box 16 tunnel and 32” heat riser wont put the riser in the middle of a 23” barrel and still have room to feed the wood?
If I want to make sure the riser is in the middle for say cooking purposes  than you would need a 10.5” high fire box 21” long fire box and tunnel and a 42” tall riser and that wont fit in a single barrel?
Also I read that the shorter the tunnel the better!
I know the J tube has lost some popularity in recent years but as a cooking stove it still seems like the best option for me.
So I wonder if there is a way to get the riser in the middle of a single barrel, could I use a angled riser or perhaps cut out the bottom of the barrel somehow  to feed the wood ?

Hi John;
With an 8" J tube I use a 16" deep feed tube,  apx a 12.5" burn tunnel (roof) and up to a 50" riser.
Riser placement in the barrel is optional. It normally sits in the middle, but can be offset to any side.
No angle wanted or needed. Your riser should be vertical.

Hi John, I think I know what you mean, you are saying it is impossible to fit the standard 6” J tube design in to a single barrel?
There is an ‘Uncle Mud’ design  that does fit inside a barrel but it does not strictly  apply the 1-2-4 ratio.
I went though all those  thoughts a few years ago and the first one I built, I had to sink the fire box into the ground to achieve a single barrel cooking hight !
I have since built quite a few designs and I have found that a lot depends on how much mass you have or how big the bell is or how long the piped mass might be.

In my case I only have a small bell as mass and a direct chimney route, so I don't actually need a full hight riser to get the results I am happy with, I think that if you have a long way for the hot gasses to travel then you need to stick to the specs.
My latest stove only uses one barrel but the barrel is about 4” off the ground.
It burns without any visible smoke and gets extremely hot, if fact far to hot apart from cold spells in January and February !
What exactly do you want to build?

Eliminate the piped mass and go with a bell type mass or bench and you will probably find your system to be much more forgiving as most common causes of flue restrictions are eliminated.