Our first job is the make the inner sleeve which will fit between the two can bottoms. We're going to use the split cylinder we lovingly made last time. The picture below should help a little.
A/ The circumference of the inside of the can (black line in can bottom) PLUS 30mm.
B/ The height of your tallest can bottom.
The lines with cut against them will hold the sleeve together. To measure them, pop your sleeve inside the can bottom, your aiming to get the sleeve to fit snugly into the lowest point (where the black lines are on the pic below). You'll find the ends of the sleeve will overlap ... use a pen to mark 10-15mm inboard of the over lap, mark it inside and out. Transfer the marks to one side and draw the lines ... half way down from the top for one and half way up from the bottom, for the other.
Once our lines are cut we need to add 3 or 4 notches to the bottom edge. Be as accurate as you want, it wont make any difference to how well the thing works! We should now have something that looks a bit like the picture below.
Roll it up and slot the two cuts together to form a cylinder ... as below. If you've loads of excess material on the join trim a bit off if you like.
I'm hoping that you haven't drunk your last full can just yet as we're going to need it. Use a full can (remember it has to be the same size) and CAREFULLY stretch ONE on your can bottoms. Don't go too mad or you'll either get them stuck or split the can bottom.
Doing well aren't we? ...This is the part that requires a little patience. First, put your inner sleeve into the stretched can bottom, with the notches you cut at the bottom. We now have to get the other can bottom to slide into the stretched one. It will be tight, you will get it in, apart from a tiny bit that won't behave itself. If you're struggling, cut yourself a shim from your scrap cans and use it like a shoe horn ... take your time, don't swear and be gentle. Once the two cans are lined up they should slide together fairly easily. Give 'em a good old squeeze and the end result should look something like below.
You did remember which way up it goes didn't you? ... the notches in the inner sleeve must be at the bottom. The picture below shows where we're going to cut to remove the TOP. I find that if you cut the crossed lines first, then score the outer circle you can often just break the quarters off.
The picture below shows the top removed and I've also cleaned up the outer edge ... don't feel you have to though. You can go as mad as you like tarting it up, file/grind it down, polish it or paint it ... whatever you like. You should also see some black dots, these are your potential jet locations. I've played around lots with sizes and location of jets and depending what your going to be cooking in these aren't bad. The upper dots, will produce flames that point more or less upwards, very good if your pot is a small diameter one, however you'll also need some kind of pan support, otherwise the pan will smoother the flames and put the stove out. The lower jet location will produce flames from the stove sides, so are more suited to a wide pan. In this configuration you can get away without an additional pan support too ... just sit your pan on top of the stove. Use a drawing/notice board pin to make the jet holes. Twist it like a drill and be careful not to push too far, you only want holes in the outer skin remember. I find that 8-12 jets works ok. Again be as precise or slap dash as you like with marking them out.
That's it, job done. Pour 20ml or so of meths in to your new pride and joy and fire it up. It'll take a couple of minutes to bloom but once it does it should look like this. Something to note - I've put two sets of jets in the stove below to try and show how the low and high jet locations will burn. Have fun!