Or maybe its the "change" in my biking related activities that sees the benefit of hauling one of these lightweights and fire up a cuppa while at rest on long day rides...
Choosing a can...
Decided on the orange can as holes on the beer can might result in the fire angling out a lot further...thereby decreasing heating efficienc. On the orange can the holes would be pointing a little more upwards and should still leave enough of a gap to whatever its heating to keep flame alive.
|Pokka 1 : Heineken 0|
Punching holes...took a shortcut here. Just scored a line and eyeballed as the drill went around punching at ~1cm intervals.. 1.5mm drill bit.
Took note that diameter is ~5cm... kinda determines the next 2 cuttings.
(as the intended opening to height ratio is 1:1)
Removing drilled top
4.5cm height (estimated ~1 cm will be inserted into lower half later)
Lower half scored and removed in same manner. Height ~2.5cm
Remaining center strip measure and cut down ready for forming into inner surface of hollow (jacketed) wall of stove
Finished parts... Center piece formed by rolling it to the same diameter as the recessed ring in the lower section (middle). Next make markings where the piece over lap on both the inside and outside. Cut halfway from top down the marking on one side and halfway from bottom up on the other. Slot them together. This will hold everything together without using anything else.
Nip an outlet at bottom of center piece for alcohol to flow to the outside and vaporize in jacketed chamber.
Fitting.. this got me into biatch-mode.. unlike the dimple cup designs, even with the prior widening of the top part, fitting one soft aluminum piece over another with both having the same diameter had me wishing I have 10 fingers in each hand... Hardest part of the whole "manufacturing"
Do it slow so as not to maul or crush the parts. The opening at the bottom of the lip on the top piece should be just about the same diameter as the jacketing wall..Use the bits of jagged edges to close up spaces as best as possible. Doesn't have to be airtight, just minimize so that the fuel will build up enough pressure overall. Helps that some of these vapor will cross over to the other side for the burning later on.
|Opening 51mm : Height 43mm.. ok a little lower than my estimation earlier on. Theoretically the priming would be "fiercer" and use up a little bit more fuel.|
First test: Worst fuel to use-- 70% IPA (isopropyl alcohol). If this burns then more efficient fuel like 90% IPA or methylated spirit would definitely work. As suspected.. pretty big fire during priming.
Priming duration before ring of fire is lit ~30 sec. Not bad.
Flames sputter after ~1-2 mins. Sign of oxygen deficiency?
Before the entire ring is extinguished, if pot is raised slightly.. flames will recover and continue burning. Hmmm don't really fancy the idea of a separate pot stand to raise it up...
Somewhere at the back of my mind fuzzy acquired knowledge of things thermodynamic from eons ago started flickering...
*Specific Heat Capacity,*
Testing deduction of insufficient oxygen: Raise cup slightly with leftover folded alu strips
Measured 25ml of 70% IPA this time... to ~400ml water.
~1 min of priming-- probably due to the water leftover in initial testing earlier.
Room window closed. Still air...Flames moving around. Probably indication of an erratic vapor pressure from the volatile IPA inside the jacketed chamber.. Can't really be helped as the walls and all the inner edges aren't smooth and probably due some interference of the water vapor from the IPA itself.
Remainng fuel ~ 8ml.
Used 17ml but this remainder should have a higher percentage of water as it gets left behind while the alcohol burns away at ~70 deg Celcius...
Brought it to boil (~4.5 mins?). Pretty good going by all the testing I have seen on other's DIY alcohol stoves.
And--------- first cuppa. Sencha.
Time for some field testing tomorrow
.... Ok Got methylated spirit this morning... packed everything out for a ride, Extra water too, all ready to test AND... forgot the frigging tea bags! Duh
But yea, with the "legs"mod last nite and using methylated spirit this morning and a boil test- basically the stove is all good to go. Priming needs only ~15 sec compared to the longer time for 70% IPA. 400ml brought to boil ~3:45min. Yes, the flame is harder to see-- almost colorless.