Modifying a Trail Designs 12-10 alcohol stove ?
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Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
Preliminary testing on 01/07/2013 20:25:09 MST Print View

Well, I had a package from Zelph waiting for me when I got home from work today. I had ordered a Starlyte with a lid, and I have to wonder if he was reading this thread because he sent it without the pot stand. But he also included a second Starlyte WITH a potstand, and one of his windscreens, and a little disposable aluminum foil ashtray that I suspect is meant to be used as a priming pan but which suspiciously also makes a great 3/8" shim for the Starlyte... Hmm...

Anyway, thanks Zelph.

So I did some preliminary comparisons with the 12-10. I ran boil times on 600mL of 55F tapwater. It turns out that my wife just bought a nifty new digital meat thermometer that includes both a timer and an alarm when a set temperature is reached. Mwah-hah-hah!

Hey- she stole my digital scale, so payback is a bitch.

Anyway, I set the thermometer alarm to 200F. My house is at almost 7000 feet and it is worth noting that the water was in a rolling boil by the time the thermometer read 200F. I'm not sure if that jives with the altitude or if it is merely some systemic error, perhaps because the remote thermometer probe wasn't fully immersed (I didn't want it touching the bottom of the pot). Thus these results may be a bit premature, but I figured I'd give some rough first impressions.

pot test 1

Unfortunately I got some pretty wide variations on repeat runs. In retrospect I think I found the error- I was eyeballing 600mL by the graduation on my pot, which is clearly inaccurate. I should have used a measuring cup (not having a graduated cylinder handy). Nonetheless some things are clear:

I ran the 12-10 using the tentstakes as intended. It is worth noting that one stake got red-hot and deformed under the weight of the pot- these are the included titanium stakes. I then ran the Starlyte with the pot resting on the lip of the cone, without the stakes. As expected the boil times and fuel consumption on the latter sucked- they were both significantly worse than the 12-10.

Then I shimmed the cone and Starlyte up to allow better ventilation and run it a bit more lean (i.e. allow more air/oxygen in):

pot test 2

Doing this resulted in boil times and fuel consumption both quite significantly BETTER than the 12-10. Clearly, yes, the Starlyte needs to run more lean, as Dan had found.

I then used the ashtray to shim the Starlyte up by 3/8", which should have put it in the "sweet spot" regarding height to the pot from Dan's experiments. However, I got very similar times and fuel consumption to the previous results.

But as I mentioned I think I have identified the source of my result variability. When I get more free time (probably not until at least this weekend) I'll repeat some runs with better water volume measurements.

I know that Rand did extreme amounts of testing when developing the 12-10 to get it to perform well in the widest possible conditions- I remember it. And, having used the 12-10 in Caldera Cones quite a lot in varied conditions I have to say that they impress me, but in purposely making a generalist stove the 12-10 probably truly EXCELS nowhere. I'm thinking thus that 7000 feet may be one place where the 12-10 performs well but doesn't excel, and perhaps this altitude is the Starlyte's prime time.

Another question, of course, is "Does the 12-10 need to run more lean at this altitude, too?" I would seem to make sense that it might but I didn't test that. (But I will.)

Also, as advertised, the Starlyte is very easy to light and is spill-proof.

Anyway, more will follow.

Edited by acrosome on 01/07/2013 20:40:30 MST.

Dan Durston
(dandydan) - M

Locale: Cascadia
Stove Fun on 01/09/2013 18:16:20 MST Print View

Great to hear things are coming along. Stove testing sure is fun. Nice to see you're getting some interesting results.

Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
OK, data: on 01/13/2013 16:05:35 MST Print View

So, I measured 2 cups of water very carefully, and did two trials for each data point and averaged them- all were consistent. I called water "boiling" when the temperature rose by 120F (because that gave me target temperatures around 180F, at which point bubbles were continually breaking the surface, but not a rolling boil). I did not use a lid on my pot, since it seemed to shift around, so I removed it from the equation. My pot is an Evernew wide 0.9L. My house is at almost 7000'.

On the charts below you see a line for the Starlyte stove with varying numbers of shims under them. 0 shims means that I shimmed the cone up to allow better ventilation, but also shimmed the stove up to keep it at "ground level" relative to the cone. -1 shims means that I did NOT shim the stove up, so it actually sat a little lower than the bottom of the cone. Each positive numbered shim is one layer of cardboard used to shim the Starlyte higher and higher, closer to the pot (4 shims is about 7/16"). 4 shims should have the stove well into the "sweet spot" that Dan derived.

So, as the x-axis moves to the right, the stove gets closer to the bottom of the pot.

You also see two single-data points; both represent the TD 12-10 stove. One is with the stove used as directed with tent stakes holding the pot high, and the other is with no stakes and thus with the pot supported on its lip (i.e. closer to the stove).

Fuel Useage:
fuel use

Boil Times:
boil time

You can see that I got much different results than Dan. I don't know if this is due to the altitude or what.

The 12-10 stove used as directed (with the stakes holding the pot higher)has the best fuel consumption, and the worst boil time.

The Starlyte curve shows better boil times the FURTHER the pot is above the stove- unlike Dan's data. Altitude?

If I use the 12-10 after removing the stakes and let the pot sit on it's lip, as with a Classic Caldera Cone, it looks like fuel consumption may be similar to the Starlyte, and boil times improve significantly but are still inferior to the Starlyte.

(Just for grins, I also checked the 12-10 with the cone shimmed up for better ventilation and there was no significant difference in either boil times or fuel consumption.)

Some thoughts:

1) Really, the difference in fuel consumption across this range is very trivial, 0.34-0.41 oz. Even if we double that to allow for a higher volume of really cold water taken to a true rolling boil, we're talking 0.68-0.82 oz, a 0.14 oz range. It would take 3.5 days with two boils a day to cost you one measley ounce. Or, thinking of it another way, the difference costs you about 3 ounces over a 10-day trip. So, I think that other factors might be considered more important- burn time, packability, stove weight, etc. On these points (under my conditions) the Starlyte seems to win- it's faster and smaller, and weighs about the same as a 12-10, plus has the anti-spill capabilities.

2) I'm willing to bet that some data got scrambled on that fuel consumption curve for the Starlyte. I suspect that this function is somehow dependent on my starting and ending water temperatures, which varied from 51-172F to 64-184F. In theory it shouldn't be, but I'm trying to think of reasons to explain that double-hump. Well, really, I need to do about 20 trials at each data point to be rigorous, but that might be bordering on OCD. Anyway, I'll bet that in reality there is just an improvement in fuel consumption as boil time increases (within reasonable limits).

3) In general, given my conditions and pot choice, the Starlyte trades faster boiling times for higher fuel consumption, though lowering the pot onto the cone lips with the 12-10 stove lessens this effect.

4) With the 12-10 stove I can speed my boil times by about 1.5 minutes at the expense of 0.06 oz more fuel consumed, merely by not using the tent stakes to support the pot. That sounds like a reasonable trade. (Though for about the same fuel use, the Starlyte boils considerably faster. It just requires more ventilation.)

5) Since I'd have to punch more ventilation holes in my cone to use the Starlyte efficiently, I think I'm sticking with the 12-10 for now. The differences really aren't that large, and an 9 to 11 minute boil time doesn't annoy me. I may toy with the idea of a custom cone for the Starlyte when the fanaticism bug hits me again.

Edited by acrosome on 01/14/2013 10:13:02 MST.

Dan Durston
(dandydan) - M

Locale: Cascadia
12-10 / Starlyte on 01/14/2013 06:01:03 MST Print View

Interesting results. I think one significant difference between our setups is that my pot is tall/narrow, whereas yours is wide. So for a given pot height, you've got a lot more volume of air under the pot inside the cone. The larger cone circumference may affect airflow etc.

Upon initial glance, your graph of pot height vs. speed looks roughly similar to mine. My X axis is pot height, whereas yours is # of shims, so our graphs are flipped on the x-axis compared to each other. (ie. As you go to the right your pot height is getting lower, whereas mine was getting taller). Your -1 and 0 shim tests are the fastest ones, with seems to correlate with my observation that ~2.3" is the fastest. And then we both observe boil times taking longer as the stove is raised up, so the sweet spot seems to raise the stove up just enough to get good fuel economy.

You're fuel economy graph seems a bit funky. I wonder if maybe you happened to get a little better than normal fuel economy at 2 shims. Changing the .37oz to .39oz gives a nice graph. One interesting take away from your tests is how the fuel economy seems to vary less than mine does. I suspect this is because your wider/larger volume cone is less sensitive to height tweaks. I seem to have observed about a 20% spread in fuel economy over 1.5" - 2.3" pot height, whereas your data seems to fall within 10% or so.

Since you're fuel economy varies so little, I'd probably opt for a setup equivalent to about 1 or 2 shims.

Edited by dandydan on 01/14/2013 13:48:31 MST.

Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
Pot Width? on 01/14/2013 09:45:43 MST Print View

Yeah, clearly something is awry with that fuel consumption graph at 2 shims. I'm pretty confident that it should be smoothed, as you describe. Perhaps some day I'll get around to repeating it.

Regarding the rest:

Do you really think that the wider pot makes that much of a difference? Your "sweet spot" regarding pot height is around 4 of my shims- just when my boil times start to go to hell. My "sweet spot" seems to be with the pot suspended much further from the Starlyte.

I guess I can see how the wider pot might mean less variance in fuel consumption- as long as the flame isn't wrapping around the pot sides and going "out the chimney", I guess there would be less variance because most of the heat is washing around the pot bottom anyway.

Hmm... So, yes, I guess I see how a wider pot might be more tolerant of minor changes like this.

When I try to figure out how much extra venting I need by multiplying the circumference of the cone bottom by how high I shimmed it up I get really large numbers- almost 3 sq in. That's a lot of extra TD vent holes.

And, yes, I have considered ordering a custom cone that's 0.22" shorter and with twice as many vent holes...

Edited by acrosome on 01/14/2013 09:52:54 MST.

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Modified StarLyte on 01/14/2013 14:15:25 MST Print View

Modified StarLyte burners are now available:

http://www.woodgaz-stove.com/starlyte-burner-with-lid.php

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=72057

Edited by zelph on 01/14/2013 14:18:04 MST.

Dan Durston
(dandydan) - M

Locale: Cascadia
Stoves on 01/14/2013 14:19:09 MST Print View

My theory on air holes (with no testing to support it) - is that in real world conditions you get more airflow into the cone than you do in the "lab" because:
1) Uneven ground means that some air can sneak under the cone
2) Even light winds seem to push a little more air through the holes than perfectly calm indoor testing.
3) Outdoor air temps in the morning/evening when I'm cooking breakfast/dinner are typically colder than my 70F house. And colder air is more dense/oxygen rich.

Accordingly, you may not need all of that calculated area. Additionally, the air gap under your cone is arbitrary and it could in fact be too radical (or not radical enough). Ideally testing would be done with this variable to find the sweet amount, and then that could be replicated through additional lower perimeter holes instead.

As well, air flow is complicated stuff and it's not as simple as just area I believe. I believe one big hole won't flow the same volume of air as two smaller holes with the same total area. Velocity plays a factor, where in some cases smaller holes are good because the chimney effect sucks in air at higher velocities etc.

So airflow is complicated stuff, but my experience is that adding one hole punch between each existing hole (shown) seems to work quite well. You could easily add more, but I'd start to get worried about how it would fair in windy conditions as it may get vulnerable.

airholes

Regarding the pot shape, this is an interesting dynamic. It's widely believed that a wide pot is more efficient than a tall narrow one. I believe this is mostly because (1) less flame gets around the pot / more heat is transferred before the air escapes, but you also have the advantage that (2) all your pot is inside the cone, whereas mine is only half cone-submerged (about 400ml).

starlyte graph

Your "sweet spot" regarding pot height is around 4 of my shims- just when my boil times start to go to hell.
Keep in mind that at 1.8" pot height (equivalent to your 4 shims I believe) my boil times (9.5min) have deteriorated somewhat (vs. 2.0" = 8.5min) and 2.3" is actually my "sweet spot" for speed (~8.2min), which is basically what you found (0 shims). Direct numerical results aren't directly comparable between our tests since pot size, start temp, finish temp, elevation, water volume and maybe fuel all vary.

The real difference between our testing is the fuel economy. My graph shows a clear degradation as I raise my pot, while your graph is a bit more funky. I think pot height really affects how well air can mix in with the fuel/flame, so if yours had more air flow you might need less height to mix that in, whereas maybe I have more airflow so I can get away with a lower pot? Hard to really say.

We can see in your fuel vs height graph that -1 or 0 shims seems to be the worst, and 4 shims is actually the best if we disregard the 2 shim result as anomalous. It would be interesting to see your stats on a 5 shim test to see if you could would get a ~9.5min boil with 0.35oz fuel usage. Obviously this won't be the sweet spot, but testing over a larger range would make trends easier to spot - especially if they are somewhat linear. My lowest pot height test was 1.4", which is about 7-8 shims in your setup, and that was my best fuel economy result.

Edited by dandydan on 01/14/2013 14:29:28 MST.

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Modified StarLyte in side cone windscreen on 01/14/2013 15:16:13 MST Print View

This video was made a few years ago. It shows the modified StarLyte stove that has the burner with reduced surface area. I now have those modified burners available. I'm confident that burner will work with Caldera Cone efficiently. Time permitting, I'll try the burner with my Caldera Keg. One thing I noticed about my caldera cone is it does not sit flat on the ground which lets lots of additional air under it's base. I have not used the cone yet, got it to experiment with.

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Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Modified StarLyte in side cone windscreen on 01/14/2013 15:52:32 MST Print View

Dan must be a serious experimenter. Nobody except a serious experimenter would use a Variac so obviously.

I'm not complaining. I had one also, but that was thirty years ago. I was a tiny child.

--B.G.--

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Re: Re: Modified StarLyte in side cone windscreen on 01/14/2013 16:22:59 MST Print View

That's my small one. I have 2 more, 20 amp and 30 for when I get serious.

I'm still a chld that's likes to play. I modified my windscreen to have a mica window so I could see inside. I was able to watch the flame pattern with ease as I made my hole adjustments. I guess you can say I'm a serious experimenter. haha, I never shoot from the hip.

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Re: Re: Re: Modified StarLyte in side cone windscreen on 01/15/2013 08:09:16 MST Print View

Here are 2 videos that show how I used the burner inside a windscreen:

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