More Foster’s Fun

Glenn,

If you make your windscreen from SS or Ti, and put four properly spaced little notches or 1/2 hole punches in the top edge of the cone, you can fill the cone with twigs/wood, then put two SS or Ti tent stakes or rods in the notches across the top and put the pot on the stakes. With a SS or Ti groundsheet you can then burn wood with your system too.

The windscreen is actually a cone, but the angle of the picture makes it look like the sides are straight

Yep. I'll be doing a bit more fiddling with this one probably, then I'll order some Ti sheeting from Titanium Goat and play with wood. It wouldn't replace my bushbuddy, since a single wall, detached floor twig stove is still basically an open fire, but would be nice to have that capability if I ran out of fuel and didn't want to make a small rock ring.

Too bad the Ti sheeting isn't really any lighter than the aluminum flashing, at least not from the way I interpret the specs. But worth it for the added durability for the same weight.

Just about the only thing that titanium gets you here is the ability to have a wood fire within the cone. Aluminum just would not stand up to the heat.

–B.G.–

Actually, I suspect the cone does a pretty good job of focusing hot gas convection and IR radiation into the pot vs. an open fire. Haven't tested the concept yet. Probably not nearly as efficient as the bushbuddy though. Wish I had one to test and compare.

But I'll do some test burns of cone vs. open fire, and see what I come up with. I'll need to get some wood clothespins to use as standard fuel units first.

Cool! Another set of boil tests to run!

Glenn,

How tall is your windscreen? If it's shorter than your can, you can roll the windscreen and put it inside the can, along with the stove, fuel bottle, spoon and lighter. It's hard to tell from the pictures, but it looks like the windscreen would fit inside.

In this respect, SS and Ti foil may have another advantage over aluminum, besides durability. I'm sure there is a better-tempered and springier aluminum available than the flashing I use, but the flashing is so soft and malleable vs. SS or Ti foil that when I roll it up enough to fit it inside the can it deforms and doesn't spring back to it's original shape when unrolled. Both SS and Ti foil will roll and unroll and retain their springiness and shape.

Also, just wondering what kind of joint you are using to join the windscreen ends?

It's only about 5 1/2 inches high, right at the 2 cup line in the pot when on the stove. Rolling it produces a much taller dimension though, since the angle of the cone is pretty steep. Edit: My final version is only 4" high, with 3.5" top and 5" bottom diameters.

It's just a tab and slot connecter. I've been doing it for flashing material screens for a little bit now, and it seems to work prety well. Kind of goes back to the metal properties though, not sure how it would work in something like Ti, since this stuff holds its shape pretty well once you get it where you want it, then "cook" it in.

As far as boil time comparisons between twig stoves, I guess it might be fun for the sake of academics, but is kind of a moot point when fuel is basically unlimited. Not even much point in using a pot lid over a twig stove, except to keep the debris out. Speed of boil doesn't mean much if you have to gather your own fuel anyway. They are just simply two completely separate philosophies and practices IMO. To me, when it comes to wood stoves, it's only about the form factor. So then it comes down to packability and functionality. My personal preference is a bushbuddy type that you can set on a rock, a picnic table, tree stump, or pick it up and move it around. I'll take the compromise in packability by sticking it in a big ol' cookpot like a 12cm Imusa mug, which. I'd want for over a woodfire anyway.

So if anyone's looking to experiment with frustum cones but isn't sure how, since I just learned, I thought I'd do a quick demo of how I'm doing it. For all you college grads and geometry whiz's, this will seem pretty childish, but it works, and if it's easy enough for an average backwoods traveler like me to figure out, then hopefully others can benefit from it as well. This works for me in practice, so I hope I didn't butcher up the description too badly.

There are only 5 numbers needed.

T = Top hole diameter
B = Bottom hole diameter
H = Height of the finished cone
L = Length of the flat dimension cutout
A = Apex of the full cone height

The first three, T, B and H are simple dimension sizes.

L has to be calculated like this:
L = B * 3.14 + (any overlap for seams) / 4

A is calculated like this:
A = (B * H) / (B – T)

Now with all 5 parameters, a cone can be mapped out on a piece of material pretty easily.

The ready-to-cut map is pictured here for detail.
This one will have a 3.5" top hole, a 6" base and be 4.5" tall.

Start with a square piece of material. I used 12" aluminum flashing, cut to 18 inches long. Draw a horizontal base line along the bottom, leaving enough room for the radius of the cone to dip below it. I just made it one inch from the bottom edge.

Draw a vertical line straigt up the middle. If the material is 18", then measure in 9" from the edge at the top and bottom and connect the points.

Now along the baseline, mark out B, being careful to center it on the verical line.

From the baseline, measure up along the vertical line and mark off A.

Draw a line connecting A to the 2 points on the baseline at the ends of B.

You should now have a triangle depicting a side view of a full cone. Measure up from the baseline somewhere along both edges of the material and mark off T, then connect the points, drawing the line for the top of the cone. Now just to be sure things are going properly, measure the length of T between the two sides of the triangle, to verify it's the correct length.

Now for a compass, my ruler has a hole in the end, so I just stuck a thumbtack through the aluminum at A, and taped a scrap piece of material with a notch cut in it, to the ruler at the appropriate places and guided a marker around the radii.

The arcs are formed where the points from B and T intersect with the sides of the triangle formed when A was connected to B at each end of the baseline.

All that's left is figuring out how long to cut it off at, and drawing some spacer lines for punching the holes. And whatever you decide for a seam, but that's up to you. So from center of the baseline where the vertical line meets, measure out L in a straight line on either side and mark where L intersects the outer arc. Do this twice, to make a total of four segments to the total length. I then set my ruler along the tack as an edge guide and drew lines for the ends of the material and for where I wanted my holes. I just spaced lines a half inch apart, as that worked for my overall sizing.

Also, Zen Stoves has an app at the website that will do the calculations for you:

http://zenstoves.net/PotStands-Conical.htm#ConeTemplates

Editing this post out since I've found the proper modifications to wrap the cone around the pot and still fit it inside the cozy. It's all about the proper geometrical ratios I see. It's also a compact enough size now, to be cut from a roll of 6" aluminum, without having to buy a larger 12" wide roll.

Final size is a set of compromises, with a 4" height, a 3.5" top and 5" base diameter.

Some people believe in storing the cone inside the cook pot to protect it. Others feel as though they should store the cook pot inside the cone to protect it.

If your cone is tall as yours seems to be, then you can protect the edges on one end by sticking that end inside the cook pot. Then, protect the other end by sticking it inside your bowl or mug. The middle is left open, because it can't do too much damage.

I've seen lots of people who use CCF to sleep on. Just put the flattened cone metal on it and roll up the whole works.

–B.G.–

The final cone version is 4.5" high, which makes the material slightly longer. The whole cone will fit inside the can, but then what? I can't fit a water bottle in there anymore, and then I'm back to square one of it taking up proprietary pack space solely for a cook kit. My "bowl and mug" are the can and cozies, described in the original post, so no help from those candidates.

I don't understand how a cone shape can be wrapped around a cylindrical base without deformation of the annealed, malleable aluminum shape. That might work if I go to a Ti sheet however. It does still leave the fact that the corners protrude from the wrapped form, leaving pokies to worry about. I tried wrapping it cylindrically around my other 1L bottle, but was unhappy with A.) Form deformation and B.) Kit separation.

Rolling it up in a CCF would seem to hold merit, but I don't use one.

Appreciate the insight though Bob. Thanks.

Edit: Again, just editing in how I finally compromised the above dilema to achieve frustum fitting nirvana with a 4×3.5×5" geometry.

Glenn, thanks for the tutorial!

Glenn, I use a 4.5" tall cone, and it fits easily into a Foster's can when rolled up with enough room to put 500 ml water bottle in it. Looking at your pictures, even your water bottle will fit in the can with the windscreen inside.

The cone is 4" diameter at the top, and 5" diameter at the base. Rolling and placing an aluminum windscreen in the can is somewhat problematic, in that the windscreen needs to be re-formed by hand when you remove it, though it's not difficult to do. But it works like a charm with SS and Ti.

For the joint I use a flat lock seam. Pretty easy to make, no little bits to keep track of (paperclips, etc.), and bomb-proof.

I've always read about putting ground-foil under the burner when it's cold, to better warm the fuel, so I've never tested with it. I've set up my systems on cast iron skillets, inverted tin pans, concrete blocks, and a few other surfaces. My thinking was that I certainly didn't need to warm the fuel even more, since thermal feedback was my constant enemy.

I've discovered today, that under "normal" conditions (above freezing?) the exact opposite appears to be true. It would seem that the reflective nature of shiny metal (as thoroughly discussed in other threads) bounces enough heat upward and out of the burn chamber to actually allow the fuel to run COOLER, slowing down the burn time and dampening the thermal feedback. This looks to be a real game changer for me.

Even using a more cylindrical shape of cone that will actually fit in the can, rather than the more angular design I was having good luck with (but would NOT fit in the can) I have been able to get 2 cups to roll for 20 seconds on 15ml of fuel.

As I say, this is a work in progress. Not much for real answers out there, and plenty of the information is just plain wrong. Other ideas leave out vital information which result in improper function, like a cone that won't fit in a can due to improper geometry. Sorry guys, but saying "it'll go, just shove it in there" isn't helping lol

Edit: the 4" top and 5" bottom on a 4.5" high cone is cylindrical enough to fit in the can as you say Dan, but then I fight the same thermal operational problems that I do with a standard cylinder. So to maintain the functionality of the cone, and integrate the packability of a cylinder, I shrunk the height to 4", and made the top to base ratio at 3.5" to 5". Also allowing the elimination of the upper exhaust hole array.

As for the seam, I think the flat lock would work well in a springier metal, but for an aluminum sheet that wants to coil back in on itself from a stored form, I like the simpler tab/slot. Less material or bulk to store. Maybe this will better show it.

Wary as I am of reviving controversy, you might find some useful ideas on this thread:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=57714

The shorter, two-part cones fit better into pans, but the conic section required for a can cone subtends a fairly large angle, so, as you're finding, doesn't roll up very nicely.

The slot & tab joint I use on conic windshields it easy to make, easy to mate and seems robust enough, provided it's folded with care.

The PostScript generated by the zenstoves page posted above does all the split cone and joint design for you.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=88844

I new simple closure design utilized for the Conquistador can.

http://www.youtube.com/watch?v=iHe9hlMbH9g

.

So today I splurged and picked up some more sophisticated testing gear. An actual thermometer for one. Seems odd that I'd be doing all this testing without an actual thermometer, but all I've really been after is getting water to boil with 15ml in a cough medicine measuring cup. Apparently I was reading the wrong surface tension line on that too, as evidenced by the 5ml medicine dropper I picked up today. I've also taken to using a scale for measuring my water. This has lead to what appears to be some really good news on my part.

1.) I've upped the water quantity from 2 cups to 500ml, and still getting a boil.
2.) I was using a wee bit too little fuel for my measurements.
3.) I wasn't running a boil long enough to hit 212. About 900' ele boils about 211 I found out.

So after I incorporated this new measuring gear, I of course ran a few boil tests. Not many, only about 3 so far, but the results are good.

8 minutes to boil with 30 seconds to burn out is what preliminary averages seem to be.

I've also modified the cone screen to be able to fit inside the cozy and around the can, with minimal holes for maximum wind protection. I'm still utilizing the same tab/slot closure and it's still working fabulously as always. As edited into the above posts, my final cone dimensions for this system are 4H x 3.5 x 5".

The new Laboratory. Mwahahaha

Like it!! What could be better than a personal lab?

Fancy thermometer.

While I'm handing out compliments: Impressed with the details you show of the cone. Looks professional, not home-made. Strong work, my friend.

It was the only thermometer with a wire Wally World had. I found it in the BBQ section for $16. It's wireless, which leaves a little to be desired since it seems to broadcast in 2-3 second intervals, but I can live with that. Bonus is that it runs on AAA's, so rechargeables with no coin batteries to buy. And for $16? I might even use it for BBQing this summer ;)

Well far be it for me to turn down a compliment lol Thanks!

Edit: I picked up another thermometer with a hardwired sensor to compare to the wireless model. Seems they're pretty much dead on and hit boil within 2 seconds of each other. So the wireless one looks like a winner with a built in timer, backlight and 100' range. Will be great for doing some outdoor testing this coming spring.

"I new simple closure design utilized for the Conquistador can.

http://www.youtube.com/watch?v=iHe9hlMbH9g
"

Dan…I NEED one of those windscreens for my AC/BC pot!!! Send me a PM on how to order it, please.

Matt

With the acquisition of new testing gear and spreadsheet efficiency calculations, I thought I’d do some running tests. Hopefully get some long term results over the course of weeks, maybe even months. I’ll just keep editing this specific post as I acquire data. This will be as much of a log for myself, as for anyone else who might be interested now, or in the future. It won’t be so much for testing this particular setup, as it will be to see how long term variables might affect performance, versus just running a series of burns at one sitting. Not something I’ll be updating every day, but hope to do a few each week anyway. Not really sure why I’m doing this yet, but maybe some data will emerge that will provide meaning. If not, it’ll just be something fun to do to keep me out of trouble ;)

I’ve opened a fresh bottle of SmartWater to use as a constant, and will reweigh and top up with each test, leaving the original water in the covered testing can without dumping it out. 500ml of water and 15ml of Sunnyside Denatured Alcohol fuel will be used in each burn. Stove, pot, lid, windscreen and baseplate are kept constant as shown in the “laboratory” posted earlier. Primed with pot in place. Timer not started until full bloom. (30-50 second primes with 1 degree temperature rise – negated for consistancy.) Indoor environment with no wind. Initial temperature of water measured representative of all surroundings. Barometric pressure obtained from wunderground.com. Elevation of 899 feet. (Direct link to this post.)

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PERSONAL TEST RESULTS
Test date- Hum- Temp- Boil- Burn- Efficiency- Notes
03/28/14 – 21% – 63º – 8:04 – 8:28 – 61.7% – First boil on fresh bottle of SmartWater
03/29/14 – 16% – 65º – 8:15 – 8:32 – 60.0%
03/30/14 – 26% – 65º – 8:27 – 8:45 – 60.0%
03/31/14 – 25% – 63º – 8:03 – 8:14 – 60.1% – 7 ml water added for loss ea time so far
04/02/14 – 21% – 68º – 8:06 – 8:46 – 61.5%
04/05/14 – 21% – 65º – 7:25 – 7:55 – 61.2% – 210º elevation boil / noted low burn times

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> Begin using calc V.2.0
Test date- Hum- Baro- Temp- Boiled- Burn- Efficiency- Notes
04/07/14 – 25% – 29.77 – 65º – 8:20 – 9:00 – 61.8%
04/13/14 – 28% – 29.83 – 64º – 8:05 – 8:35 – 61.2%
04/22/14 – 25% – 30.06 – 67º – 8:20 – 8:50 – 60.0%

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ALCOHOL STOVE EFFICIENCY CALCULATOR
With a great deal of help from fellow BPL members, I’ve been able to piece together a spreadsheet that accounts for multiple variables involved in testing stove efficiency. The cells can be moved around to whatever format one is comfortable with, as long as the cell labels in the formulas are adjusted accordingly. The formulas (bold type) can be copied and pasted into a worksheet for ease and simplicity. For the sake of the formulas in this example, the cell locations will be:

C2 = Target Temp for Boil =((1730.63/(8.07131-LOG10(C8/.0393700791974))-233.426)-(.00104*C9))*1.8+32

C3 = Boil Time (m:ss) (user defined entry)
C4 = Burn Time (m:ss) (user defined entry)
C5 = Initial Fuel Quantity (ml) (user defined entry)
C6 = Initial Water Temp (ºf) (user defined entry)
C7 = Water Volume (ml/g) (user defined entry)
C8 = Barometric Pressure (in) (user defined entry – 29.92 default)
C9 = Elevation (ft) (user defined entry – blank = sea level)

C10 = Efficiency Rating =C7*.0042*((C2-32)/1.8-((C6-32)/1.8))/(25*C11*.789)
C11 = Fuel-to-Boil Used (ml) =C5*C3/C4

Target Temp is calculated from the user defined entries in cells C8 & C9, and is the temperature that Boil Time is recorded at. Burn Time is recorded when the stove runs out of fuel and self-extinguishes. Initial Fuel quantity is easily and accurately measured with a 5ml oral medicine dropper, or similar item. An initial water temperature reading is taken before testing is performed. Accurate water volumes are weighed on a gram scale where mm = g. Barometer readings can be had from any local online source, or a home Barometer calibrated to local conditions. Elevation is an easy look-up for your location. The Efficiency Rating cell (C10) is recommended to be formatted to display as a percentage. The Fuel-to-Boil readout is more of a curiosity to plan future burns.

This is how the above example would display with the results from 04/07/14

Revision Notes
V.1.0 – 04/07/14 – Initial Conception

V.2.0 – 04/25/14 – Altered cell C10 to replace elevation-only temp in formula, with fully adjusted barometric+elevation boil temp from cell C2.

Glenn, like you, I am interested in stove efficiency testing, and want to start putting my stove setups to the test. Now that Ben has bequeathed us the "Efficiency Calculator" SS….wouldn't it be interesting if we had a separate thread devoted to empirical stove efficiency tests. Where detailed parameters would be published and could be checked /verified by all. A sort of distributed crowd-sourced laboratory, following the sort of data that David has been publishing.

I'm sure it would become something of a competition to see who could eek out the most efficient setup, and obviously someone will eventually shade the truth to get the best numbers, but I can also imagine such a thread being very enlightening, as we learn "best practices" from each other. Look at all we've learned already from David's published data.

So I will be looking forward to your Stove Efficiency Test post, and hope to contribute at some point. (I hope you will post more data than is in your first entry!)

You're already at 62% efficiency?!

"I new simple closure design utilized for the Conquistador can.

http://www.youtube.com/watch?v=iHe9hlMbH9g
"
Dan…I NEED one of those windscreens for my AC/BC pot!!! Send me a PM on how to order it, please.
Matt

Yes, I will do that tomorrow. You can't believe how many things are going on around me.

Hey statistics guys…..I've been able to boil 3 cups of 50 degree water in 40 degree ambient air temps using the Conquistador pot and new windscreen design on 25ml of denatured alcohol. How does that come out on your charts? I used the 3cup capacity flat bottom beer can pot. The one with the cool graphics :-)

Oh, forgot to mention that the water continued to boil for 1.5min until flame out. Did 3 tests, all were approx the same results. Test were conducted in my cold garage.