More Foster’s Fun
- This topic is empty.
-
I've edited this original post to reflect my current setup. No real operational changes, but I've cut almost an ounce off, so here's the latest. Some of the thread posts refer to issues I've since resolved.
Highlights of this thread include:
*This post, with my completed kit.
*A simple method to draw a frustum cone.
*A basic alcohol stove efficiency calculator. (At end of post.)Links to other relevant threads:
*Delmar's Alcohol Efficiency Test your system, share your results here.
*Advanced Calculators Downloadable advanced and multi-fuel calculator versions.I know, I know, everyone has a Foster's thread, so bear with me while I get mine out of the way. I'm trying to achieve the usual goals; lightweight, fuel efficient, functional, and packable. David Gardner got me to embrace the frustum cone idea over on his thread, and this is my result. Of course cones are nothing new, but there's a satisfaction that comes with experimenting and building something unique yourself.
103 grams for everything shown. Dual cozies, no-prime Barbasol stove, 65ml fuel bottle, oven-liner foil components, extremely minimal pack volume.
With standard 500/15 test protocols, it gets +60% efficiency indoors, and ~55% efficiency outdoors, with 45º, 75% RH, slight breeze.
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 straightSo 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 heightThe 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) / 4A 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.
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.
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
"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.)
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
> 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%
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/C4Target 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 ConceptionV.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.
- You must be logged in to reply to this topic.
