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Canister Windscreen – Quest for Quality
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Rod Braithwaite
(OddRod)

Locale: Salish Seashore
Canister Windscreen – Quest for Quality on 11/05/2012 22:21:39 MST Print View

ADVISORY – 15 photos imbedded

Background & Request

My environment is 4 season pacific rainforest, boil-in-bag cooking, often on windy and exposed shorelines. I like the Micron Ti 2.5 canister stove. I use it with a ti mini solo pot and a myog windscreen, made a few years ago from some sheeting I got from Ti Goat (see pictures below). I’ve just built a couple of smaller windscreen designs, and I’m unsure about how to compare the three systems. My request is: given that I have no instruments, limited time and skills, and no testing experience – is there a straightforward way to measure the performance of three competing windscreens?


Current Windscreen - The Adjustable OriginalAdjustable Original

with Mini Solo pot inserted

This windscreen was designed work for a variety of pot sizes, and so has an oversize reflector disk that supports an adjustable cylinder above. The cylinder is a simple rectangle, with a cut-out for handles, which is rolled to the desired diameter and set on top of the disk. The system heats all the way up the sides of my pots, the upper wall of a half filled pot gets so hot it vaporizes splashes and the front of the “pouring-out” stream. If I’m out solo I use a low flame and get a gratifying number of boils per fuel canister. If I’m out with others it gets red hot cranking out pot after pot of hot water. Paper clips suspend the lower disk and are used to hold the cylinder together. I’m still using the original paper clips from three years ago. (see pics below).

heat deflector disk

disk supports cylinder weight

stowed inside pot

I’ve been happy with this windscreen system, but feel there is room for improvement. My experience has been that when I pick a pot to pack, I almost always reach for the mini solo, so the benefit of a screen that adjusts to differing pot sizes is not being realized. The goals I have set for a new system are:

a) I’d like it simpler – fewer parts, faster setup, less overall “fuss factor”
b) I’d like it lighter - the current disk, rectangle and paper clips weigh 56 grams
c) I’d like it smaller - the adjustable windscreen is 3.6 centimeters taller than my mini solo.
d) I’d like calories/gram of fuel efficiency to stay close to current levels.


Screen Idea #1 – The Three Point Shield

I couldn’t think of anything simpler than a curved barrier facing into the wind. A paper prototype sorted out some details.

mockup

mockup with pot

ti version laid out

attachment slots at 35% of screen height

At this stage the ti was too springy to stay on the rear stove struts if I gave the stove a shake. Rolling the screen tightly gave it increasing curvature, until it was slightly compressive on the struts but still expansive in the pot. Attachment slots are at 35% of screen height

after additional shaping

top view

There is ample room to work the stove valve, with or without the pot. So far, the lower part of the windscreen has been cool to the touch during operation.

regular 3 season mount

A minor feature is that the screen can be inverted. I thought this might provide some radiant or reflective heat to help vaporize butane in colder conditions. Testing required.

inverted for cold conditions

Screen weight is 20 grams; setup is basically snap on / snap off. The screen stows in a few seconds and takes almost zero volume in my pot. The picture below is not an empty pot; there is a windscreen in there.

almost invisible

Next I made a small heat reflector disk. Slips on and off easily and weighs 4 grams.

heat reflector disk

disk is 4 grams, slips on easily

screen #1 ready for initial testing

Screen #1 ready for testing. If results show that the reflector disk is the way to go, I’ll trim the bottom 2 centimeters off the windscreen and save 3.6 grams. Adding back the 4 gram weight of the reflector means system weight would see a small increase to 20.4 grams.


Screen Idea #2 – The Ringer

During development of Idea #1 (the Three Point Shield); I used a scrap strip of ti to prototype the attachment slots. The result turned out well, so I decided to make an additional screen to compare and test against the other two systems. A couple of 3 millimeter folds fasten the ends of the strip into a circle. The Ringer weighs 9 grams and works with or without the heat reflector disk, exactly the same as Screen #1.

9 grams

with heat reflector disk

view from underneath

good storage

The picture above shows fuel canister, micron stove, folding spoon, lighter, myog ti pot lid, three point windscreen and heat reflector disk, with room for a towel. (n.b. I usually keep my spoon in my food bag)


PRE-TESTING SUMMARY

1) Adjustable Original
(cylinder and supporting disk both required)
Weight = 56 grams
Height = 15.6 centimeters
Fuss Factor = moderate (to me, at least)

2) Three Point Shield
Weight = 20 grams
Height = 11.2 centimeters (fits inside pot)
Fuss Factor = low (no paper clips to worry about or lose, “snap on” ease & speed)

3) The Ringer
Weight = 9 grams
Height = 4.5 centimeters
Fuss Factor = low

4) Heat Reflector Disk
Weight = 4 grams
Fuss Factor = low+1 (because it adds a second piece to the new windscreens)


I’d like to end this post by asking for help from the collective smarts of our myog wizards – my problem is that I have no equipment, little experience with testing, and only a few vague ideas on how to collect useful data. My goal is to determine unit weight of fuel consumed for calories transferred into water. I see comparing, in windy conditions:
a) No windscreen at all
b) Adjustable Original windscreen
c) Three Point Screen without Heat Reflector
d) Three Point Screen with Heat Reflector
e) Ringer Screen without Heat Reflector
f) Ringer Screen with Heat Reflector

Does anyone have a “close enough for horseshoes” testing technique to suggest? Should I use two reciprocating fans, on different swivel speeds, to simulate gusty winds? Can I just weight the canister after each burn, or should I buy six new canisters and rotate them during the tests? Is humidity a factor? What else don’t I know? Etc.

Thanks for any observations shared or advice offered.

P.S. - I can spend 30 or 40 bucks on thermometers and such as needed, just tell me what to buy.

Edited by OddRod on 11/06/2012 19:49:13 MST.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Canister Windscreen – Quest for Quality on 11/06/2012 00:08:40 MST Print View

If you have a new line between each picture, and between text and each picture, it makes it easier to read on the web page.

Standard experiment would be to do a number of runs with different windscreens. For each run, measure the same weight of water, same temperature change, measure weight of canister before and after to determine weight of fuel used.

Get one of those probe temperature sensors from cooking store. But then you can't easily hit the same temperature for each run. But, you can get close, stick the probe in and record the temp, and then normalize between the different runs - just multiply the weight of fuel used by the actual temperature change.

Do your 6 cases several times and see if the results are repeatable, or just random difference between runs.

Yeah, you could put up a fan to get a consistent wind.

Wipe off any condensation off the outside of the canister before you weigh it - that can effect the result.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
CO hazard on 11/06/2012 02:01:39 MST Print View

Good chance of elevated levels of carbon monoxide with the first version. Dangerous. Needs lots of air flow from underneath.

Cheers

James Arzigian
(Renais) - M
Workmanship and materials on 11/06/2012 02:23:39 MST Print View

Rod,
Those are some classy windshields! What thickness Ti are you using? How did you make the required cuts, particularly in the bottom reflector? I really like your design which allows all of the windscreen to be stored inside the pot; Ti screens stored elsewhere I have found difficult to protect.

Daryl and Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: Canister Windscreen – Quest for Quality on 11/06/2012 07:54:14 MST Print View

Rod,

What are you using on the pot handles for insulation...the pinkish stuff?

Rod Braithwaite
(OddRod)

Locale: Salish Seashore
Good advice. on 11/07/2012 00:09:17 MST Print View

Thanks for the feedback everyone.

@Jerry A – the formatting tip is appreciated. Have made changes as suggested, really helps, thanks for that and the testing setup ideas. Followed by more thanks for the excellent point about wiping condensation between tests – it would have been really annoying to learn that the hard way.

@Roger C – I’m happy to say I've never used a stove inside a tent. Your 2007 report “Stoves Tents & Carbon Monoxide – Deadly or Not?”, showed the Micron had second rate emissions (40/low, 90/high). A question if you would, please - all my screens have the heat reflector disk mounted well above the air inlets of the Micron – does that not ensure the burner is getting about the right air supply? Or does the burn need significant air in addition to what comes up the central tube? FWIW, the flame looks completely blue, I can’t see any difference with or without the screen. Much thanks.

@Jim - Thanks Jim. I used .005” thickness titanium foil from Ti Goat. They advertise the stuff as “very durable by foil standards” and that has certainly been the case for me. I used a removable hole punch and scissors to make the cut-outs.

@Daryl C – the handles are covered in Imperial Hi-Temp Silicone Sealant, rated to 316*C or 600*F. I could not find silicone tubing, unfortunately. The sealant was finicky to apply, and I made a minor mess of it, but it insulates quite well. Here is a picture of the product:

Silicone Sealant

As for simulating wind, I was wondering if two reciprocating fans, positioned maybe 15 degrees apart, might reproduce swirling/gusty wind conditions? Anyone had luck with that approach?

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Good advice. on 11/07/2012 02:29:27 MST Print View

Hi Rod

> all my screens have the heat reflector disk mounted well above the air inlets of the
> Micron – does that not ensure the burner is getting about the right air supply? Or
> does the burn need significant air in addition to what comes up the central tube?
Yeah, the flame usually does need to draw in extra air from the sides. Good to let it do so.

> FWIW, the flame looks completely blue, I can’t see any difference with or without the screen.
Ah, well that is good. Don't want any funerals.
It's just that some of your photos looked as though the flame had almost nowhere to go. Imho, there needs to be at least 10 mm or 1/2" clearance around the side of the pot.

Cheers

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Good advice. on 11/07/2012 07:58:39 MST Print View

Great! I now have the patience to look at all your pictures, nice

I don't think you need the bottom reflector. The wind doesn't blow in there. Maybe if it's really windy it would be good? But I try to find sheltered places. It would be interesting to see if you could measure a difference in fuel consumption.

If you're in cold conditions, heat down to the canister is a good thing.

Rod Braithwaite
(OddRod)

Locale: Salish Seashore
another goal to add on 11/07/2012 23:37:37 MST Print View

Looks like I missed: "e) I need it safer..."
(Thanks Roger, I'll add a few air holes)

For testing, I'm going to buy a signaling digital thermometer and then copy the approach Will Rietveld used in his BPL report "Performance Comparison Testing of Lightweight Canister Stoves: Controlled Data Evaluating Key Variables of Temperature, Wind, and Windscreen Use". I hope to calibrate my results to his.

I'm at sea level, and Will was at 6,650 feet (2,027 m) - anyone know if denser air (at the same windspeed) will have a material impact on the outcomes? I plan to avoid the lower boiling point issue by measuring gr/fuel needed to increase from 20C to 70C (68F to 158F)

The testing will likely take me some time to accomplish, it might be December before I'm done and can write up the results.

Best regards till then.
Rod.

Edited by OddRod on 11/07/2012 23:57:49 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: another goal to add on 11/08/2012 01:51:56 MST Print View

> if denser air (at the same windspeed) will have a material impact on the outcomes?
Well, yes, but I doubt it would be easily measurable without an awful lot of effort. In which case, it probably won't matter.
Measure!

Cheers

John Kays
(johnk) - M

Locale: SoCal
Reflector Disk #1 on 11/15/2012 13:21:05 MST Print View

Rod,

I have the same stove and can't tell from your photo how you get the disk over the top or bottom o the stove. Have you another pic or an explanation how? Which one of these screens do you like the most? And which the easiest to make? Nice post! Very helpful.

Edited by johnk on 11/15/2012 20:08:58 MST.

Gary Dunckel
(Zia-Grill-Guy) - MLife

Locale: Boulder
Stove wind screen on 11/15/2012 13:57:53 MST Print View

Rod, I did something similiar a couple of years ago, and I posted an MYOG thing on BPL. Here's the thread, which includes a lot of good comments from the members:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=45927&disable_pagination=1

I am thinking that you could achieve your desired goals by just sticking with your Adjustable Original, but by cutting the height down so that the screen fits your pot. I think that you don't really need the whole pot to be cloaked by the wind screen.

My design is quite similiar to yours. I did notice that the canister can get warmed up if I turn my flame up moderately high, which is a bit handy in below-freezing temperatures, but pretty dangerous when it's warm out. I don't tend to use my reflector at anything over +40* F for this reason. But I get really efficient boils with minimal flame, although it take a couple extra minutes to achieve a boil. I am impressed with how efficient my stove is during windy conditions.

I admire what you have come up with, Rod. Your setup looks a lot more professional than mine. Good luck with your quest, and please report back to this thread when you've compiled results of your tests. Oh, one more thing--don't blow yourself up by overheating your canister. Roger Caffin just hates it when that happens!

Robert Kelly
(QiWiz) - MLife

Locale: UL gear @ QiWiz.net
What a coincidence . . . on 11/16/2012 10:09:13 MST Print View

At the request of some WhiteBlaze canister stove users, I have been working on a project to develop a windscreen system that would adapt to just about all brands of canister stoves. If I am successful, it might eventually be another QiWiz UL Gear product.

Anyway, I think I have a workable concept, yet to be tested. Stay tuned. I agree with comment that the base circular plate may not be necessary if the ring of windscreen is far enough below the level of the burner. Not sure I have the answer for how to test your various models, but I look forward to your results with great anticipation.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: What a coincidence . . . on 11/16/2012 10:13:59 MST Print View

What I don't like about wood stoves is

I want to use my pot as my cup to drink coffee out of

The outside of the pot gets sooty from wood stove

This is obnoxious to drink out of - I don't want to put my lips on soot

I could bring along a seperate cup, but I hate to add weight and volume. We quickly lose any advantage to using wood stove over alcohol or canister stove

John Kays
(johnk) - M

Locale: SoCal
Danger on 11/16/2012 10:37:04 MST Print View

Won't elimination of the disk exposé the canister to overheating and possible explosive consequences?

steven franchuk
(Surf) - M
Re: Depends on the source of the heat on 11/16/2012 13:41:05 MST Print View

"Won't elimination of the disk exposé the canister to overheating and possible explosive consequences?"

Depends on how the heat reaches the canister. If it is infra red radiation yes the canister could overheat. But if it heat from the hot burner being conducted down through the metal tube to the valve and caister, no eliminating the disk would not cause overheating.

Infra red is generated mainly by the flames. Most stoves sold don't have reflectors and most don't get how due to the infra red released by the flames. So in my opinion infrared is a minor contributer to canister heating. Conduction of heat through the metal is in my opinion is the primary cause of overheating. If the burner is entirely enclosed it could get extra hot causing the valve and canister to get hoter than normal. If the wind screen also blocks flow of air around the valve and tube more heat would reach the canister.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Danger on 11/16/2012 13:42:34 MST Print View

> Won't elimination of the disk expose the canister to overheating and possible explosive consequences?
Given the hundreds of thousands of upright canister stoves which have been sold and are used in the field without explosion, this does not seem very likely.

Cheers

Franco Darioli
(Franco) - M

Locale: Melbourne
Canister Windscreen – Quest for Quality on 11/16/2012 14:20:55 MST Print View

BTW, those handles remain cool enough or cool down very fast if you keep them apart...
(without any coating)

John Kays
(johnk) - M

Locale: SoCal
Danger on 11/16/2012 15:16:58 MST Print View

Well, covering the top of the stove with a pot and surrounding it with a wind screen leaves little room for the heat to escape except down towards the canister interface where pressure from heat buildup is likely to release. These stoves usually come with warnings including one not to enclose it while in operation. I just assumed that the disk in the OP photos was there to protect against this risk just described while in operation with the windscreen? Sorry I am not understanding but it seemed obvious and thus the inquiry.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Danger on 11/16/2012 16:36:34 MST Print View

> covering the top of the stove with a pot and surrounding it with a wind screen leaves
> little room for the heat to escape except down towards the canister interface
Ah, OK. Well, you are right IF the windscreen is wrapped tightly around the pot. But that is a serious NO-NO! Yes, it could lead to serious overheat of the canister plus a high level of CO production.

You should always leave a gap between the pot and the windscreen all the way around. Say a finger width everywhere. That is enough room for convection to exhaust all the hot gas upwards, away from the canister. You should also leave a gap in the windscreen at the bottom for the air to get in. The gap is a good place to have the control valve of course.

Holes around the bottom of the windscreen? Yes, they work, but they tend to get damaged in the field - at least in my experience. I prefer a simple gap.

Cheers

Edited by rcaffin on 11/16/2012 16:37:10 MST.