Nov 9, 2013 at 7:52 am #1309634
I have sold a fair number of the pre-ALPHA phase Focus Fire 14 Esbit stoves. I am getting ready to design the next revision stove and I am looking for feedback on how I can improve the design (both good and bad) to make a better product. Tell me what you like about it, tell me what doesn't work for you. I am looking forward to hearing from you – JonNov 9, 2013 at 9:38 am #2042803
I had a Houston moment a couple days ago with mine… photo does not show how bad it got, as I had to go grab my camera… but this happened for reasons totally unknown.
You already know this, Jon, but the three things at the top of my list are:
(1) resolve the issue with warping and thus the corners lifting up off the stand/ground
(2) make the clasp not be a triangle so it stays closed
(3) if at all possible, make it be a two-piece design so it will slide into cups/pots and not take up as much room.Nov 9, 2013 at 11:20 am #2042821
I have seen this before. There are two things that can cause this.
1) the windscreen setup is too tight. Esbit can into a thermal runaway condition similar to an alcohol stove, so good ventilation is important.
2) Small burn volumes can overheat the stove. By burn volume, I mean the volume of airspace between the ground to the bottom of the pot. The stove puts out ~325 watts. In a mug size system, this volume is about 24 cubic inches. With a beer can this drops to ~15 cubic inches. When you try to pump 325 watts out through half the volume, the interior "airspace" getts hotter. So, the smaller the diameter, the more ventilation you need. Alcohol stove are even more prone to thermal runaway and this is why it is harder to build a stove for small diameter mugs/pot. Best regards – JonNov 9, 2013 at 2:53 pm #2042862
@dwambaughLocale: Pacific Northwest
Hey Jon, that is fantastic information and explains so many things I have seen happen when fiddling with alcohol and esbit stoves.
Do you have any web resources of your own or others with more jewels like these
Thanks!Nov 9, 2013 at 3:44 pm #2042871
I have designed windscreens ranging from ~6" in diamter down to one for beer cans. The beer can size windscreen is by far more difficult to design. Aditionally, all of my current stove designs use a ground to pot hieght of 1.8" and most stoves are ~2.25" to 2.5". This put extra pressure as the "burn volume" is even lower.
I also have extensive work done with dry baking and this is even more difficult than just boiling water. Thermal feedback and thermal runaway are one of the biggest issues in designing a windscreen.
One of the reasons that Caldera Cones work well is that (IMHO), the taper allows for a larger "burn volume" at the bottom but bnarrow at the top to hold the pot. CC are also designed with a 2.25" ground to pot distance.Nov 9, 2013 at 4:25 pm #2042883
@dwambaughLocale: Pacific Northwest
Not to sidetrack your thread, but I'm wondering what you have to say about Esbit wing stoves and an optimal setup with a 450ml mug.
Thanks!Nov 10, 2013 at 12:43 pm #2043059
@yon I also have extensive work done with dry baking and this is even more difficult than just boiling water. Thermal feedback and thermal runaway are one of the biggest issues in designing a windscreen.
Take note what yon said about dry baking being much more difficult than just boiling water. It's so true so we should stick to the user friendly way of just using boiling water to bake wether you use esbit or alcohol for fuel, makes no diff..Jun 7, 2014 at 1:57 pm #2109623
I now have the BETA Version of the Focus Fire 14 in Titanium. Also, I am looking for feedback on the stove and would appreciate any and all inputs. The stove is listed on the main page of our website and if you click on the link it will take you directly to PayPal. At this time, the Focus Fire 14 Titanium stove will only ship as a DIY product in the USA.
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