R-Caffin / H-Jim style can-top stove windscreen: why not make it support pot (rather than stove)

[al b]

http://adventuresinstoving.blogspot.com/2011/08/windscreens.html

http://www.backpackinglight.com/cgi-bin/backpackinglight/exploding_gas_canisters_the_hazard_of_overheating.html
(see Real Life Field Use section)

For cannister TOP stoves (not remote), when using the above Roger Caffin / Hiking Jim style can-top stove windscreen (with heat reflector):

why not make the windscreen support the pot on 2 skewers/pegs, a bit like a caldera sidewinder, (rather than the pot resting on the stove itself). This should be more stable and may be lighter for cheap stoves whose pot supports may be heavy (I am assuming they are removable).

Different cannister sizes could be dealt with by different height skewer mounting holes.

The idea might even allow use of cheaper/lighter 185g narrow aerosol style cartridges, with a little cannister support (pegs or foil cone etc), as cartridge only supports the burner, not pot.

Re(2): Photos of RCaffinStyle windshield with additional canister ventilation on 12/17/2011 05:34:52 MST Reply Report Post Print View

Roger Caffin said "Neat,…"

Thanks, its useful to know that the vertical gap shown is all that is needed for oxygen access, however, the canister level cutouts and heat deflector are for reassuring me (by increasing margin), (and any bystanders who might appear but will see the canister is not enclosed).

I was hoping the upper heat reflector would also increase efficiency a bit…
I think the heat de/reflector(s) are also useful for counteracting the (presumably) slightly lowered wind resistance due the canister level vents.

( EDIT !! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !!
Heat deflectors now seem a bit frowned upon:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=65243&skip_to_post=558429#558429

!! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !!)

[al b]

Alternatively, perhaps a tri-pod stand from which cartridge hangs, thus making cartridge diameter irrelevant to stability, allowing
fresh air all around, with easy to make cyclindrical windshield around pot; a bit like a UL version of the following:
http://www.outdoorworld.co.uk/campingaz-bivouac-stove-kit

(narrow cylinders should be cheaper and lighter)

[al b]

I tried my first cone-ish idea in alu foil:

Am unsure if is strong enough/heat proof enough, but the photos should show what I meant. Note the highly important heat reflector/shield to protect canister.

May be the tripod idea in 2nd post is better….

[Roger Caffin]

Hi Alan

From looking at your photos, I would worry that you do not have enough clearance around the pot for the hot gases to escape fast enough. This could have 2 results:
* poor efficiency and/or heating rate
* elevated CO levels

Personally, I find the canister base plus solid pot supports to be a bit more confidence-inspiring than that very light Al foil, especially when I am stirring the pot.

The canister heat shield is probably VERY necessary in that configuration.

Cheers

[Jerry Adams]

If you are running the stove at temps below the normal level for canisters, like 32 F, then removing the canister shield will heat up the canister so it will run better.

You could go down to 20F or below.

Just put your hand on the canister and if it gets warm to the touch, then you need the canister shield

[Greg Mihalik]

"Just put your hand on the canister and if it gets warm to the touch,…"

…it might be to late for a graceful shutdown.

[Kevin Beeden]

This is essentially a Caldera Cone using a 'gas adaptor' (Alan's clearly used my clone script to create the support). Stirring is therefore no more of an issue than it is with a Caldera Cone. Well, apart from the big chunk taken out of the base…

I'd echo Roger's comment about the exhaust vents at the top; fine for a Cone with a low fuel burn rate alcohol burner, not so fine for a flat-out gas burner. Of course, flat-out gas burners aren't very efficient unless you're using an HX pan.

The latest clone script allows you to add as many rows of holes as you like, so you could make the top part look like a colander until you think you have enough exhaust holes. You'd just have the tedium of punching the holes…

I might be tempted to move the clone's lower holes up to the point above the canister reflector. On the other hand, the updraught of air past the canister might provide some cooling.

[al b]

Roger (Caffin):
Thanks.
Heatshield was definitely compulsory in above design, however, I suspect many others (who don't know of 50C test) would be unhappy on seeing it, given the dire warnings on stoves, limiting where this design can be used, and as I have fixed the stove's pot support to my liking, I may stick conventional support and other ideas, at least some of the time. On the other hand, if cone doesn't support the pan, then if could have more ephemeral section around cannistor, just like the tripod idea…

Kevin (Beeden):
Thanks.
Actually the c(l)one wasn't done from your script, just "on the fly", but I did use an old clone template for the tab joints.

Kevin and Roger:
I could cut more (triangular) exhaust vents:
The cone was meant to be more conic/wider at top for better exhaust, but the source foil tin was too small.

All:

Given their own warnings maybe manufacturers should give a foil heat deflector with each stove.

I still like the previously mentioned tripod idea, similar to the Bivoac stove above: if stove manufacturers insist on such warnings, then I think they should sell proper lightweight windshields like that, that enclose pot properly, leaving cannister protected (by heatshield) and open on all sides for cooling. And when the cannister hangs from stove, lighter,cheaper aerosol cannisters can be used: I suppose, alternatively, I could make foil conic stabiliser (from Kevin (Beeden)s clone script) to allow use of narrow cartridges with top stoves.

Or I could stick to meths, if I could get a civilised easily adjustable simmer…
(why do meths bottles fail to mention that you can extinguish it with water: seems rather useful info…?)

[al b]

Version 2: wider, more exhaust vents; a non structural foil tripod (canister open on all sides apart from the foil "struts")…

Note stove now supports pan not windshield.

May have to remake more tidily…

[Jerry Adams]

Now you're moving in the direction of my windscreen http://www.backpackinglight.com/cgi-bin/backpackinglight/myog_aluminum_windscreen.html

other windscreens in responses

[Stuart R]

The big problem with cones / windshields of this size is: how do you pack them?

Jerry has made a nice little one that looks like it will stow inside the pot

Edit – see post above, didn't know it had it's own article

[Kevin Beeden]

> The big problem with cones / windshields of this size is: how do you pack them?

The 'flissure' setting on my clone generator script will create a two-part, horizontally split cone that will usually fit inside the pan it supports, depending on pan depth, and burner height. Here's one for Alpkit's MyTiMug:

The packing issue was also part of the rationale behind the SqueezeBox Stove.

[al b]

The shown windscreen is now a cylinder, so could be rolled up into a cardboard tube (eg from kitchen roll).

However, Jerry's minimal-ist windcreen (perhaps made adjustable), a heat re/deflector and a "kitescreen" is beginning to appeal to me.

For more efficiency the Jerry style windscreen could become a hanging (from pot rim by friction) cone….

[al b]

The following is a heavy version of my tripod idea:

http://www.amazon.co.uk/Go-Systems-Base-Camp-Stove/dp/B0055T0H2C

If made lighter it might be an alternative to remote stove, whilst allowing a proper windshield around burner and pot (but not cartridge)

[al b]

I have settled on a Roger Caffin style open cylinder windshield but with cutouts around the cannister (so that it is essentially open to air for cooling). One or two heat shields are used. So like my earlier photos but with a vertical gap/opening at the control valve, like Roger Caffin's.

[Hikin’ Jim]

Hi, Alan,

Have you got any photos of your set up?

HJ
Adventures in Stoving

[Roger Caffin]

Hi Alan

Yeah, I've seen that design before, but for the life of me I cannot see what the point of the legs is – apart from increased weight and INstability. It just ecapes me.

Cheers

[Bob Gross]

"but for the life of me I cannot see what the point of the legs is"

The cook does not have to bend over so far to tend to the cook pot.

–B.G.–

[Hikin’ Jim]

Alan

Is the idea of the tripod to elevate the burner away from the canister so that the canister can remain cool?

I suppose the question that springs to mind is why not just use a remote canister stove? Am I missing something here?

HJ
Adventures in Stoving

[al b]

Roger Caffin said "but for the life of me I cannot see what the point of the legs is"

At their base the legs would be wider than a canister therefore more stable and would thus allow stable use of narrow aerosol cartridges. The windscreen could exclude the legs and canister. I had hoped that legs could be reduced to the weight of a remote hose.

HJ said "Is the idea of the tripod to elevate the burner away from the canister so that the canister can remain cool?"
Yes-ish: a windsceen could stop at top of legs leaving the canister open to air: inspiring my cutouts.

Why not a remote stove: I was initially attracted to it because it avoids the flexible, seemingly vulnerable gas hose, perhaps that was the designers idea too, (if so, he would seem to be the only other person, apart from me, thinking like that :) )

HJ no photos of my current cannister stove windscreen (yet?) but its just like the Roger Caffin cannister 3/4 windscreen but probably a bit more than 3/4 enclosure and with large cutouts at cannister level (like in the abandoned 100% enclosures above).
And same heat deflector disc(s).

[Hikin’ Jim]

Well, if you do get something rigged up, do post some photos. And do be careful.

HJ
Adventures in Stoving

[al b]

Here are the photos:

Note the cutouts all around the canister.
I still test the canister temperature.

NB Rather than relying on foil "columns" to support the functional screen around pot and burner, an alternative construction would be to use tall skewers to support a foil screen, thus leaving cannister completely open.

[Roger Caffin]

Hi Alan

Neat, but can I make a suggestion? Skip the cut-outs and holes around the bottom.

They weaken the foil for a start, and they are just not needed either. The gap on the down-wind side will let in plenty of air for a stove even at full throttle. Yep, the gap *as you show it* is more than enough.

So why are there holes around the base of a Caldera Cone? Because it goes a full 360 degrees around the burner, for strength. very different thing.

And as I have said before, I don't use a heat reflector on the stove above the canister either. Never needed it, even in the Australian summer. One less thing to worry about.

Cheers

[al b]

Roger Caffin said "Neat,…"

Thanks, its useful to know that the vertical gap shown is all that is needed for oxygen access, however, the canister level cutouts and heat deflector are for reassuring me (by increasing margin), (and any bystanders who might appear but will see the canister is not enclosed).

I was hoping the upper heat reflector would also increase efficiency a bit…
I think the heat de/reflector(s) are also useful for counteracting the (presumably) slightly lowered wind resistance due the canister level vents.

( EDIT !! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !!
Heat deflectors now seem frowned upon:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=65243&skip_to_post=558429#558429

!! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !! !!)

The canister stays cool OK, although the top is less cool, just slightly warmer, i.e the canister sides felt cold, the top just at the beginning of what is sensed as warm (i.e. not very warm): I think the brass stove body (with pre-heat loop) conducts some heat downwards.

NB The 2 smaller lower edge holes are for using a stick or similar to hold the screen open.

Your idea for holding your windscreen open with ti stakes leads me to a possible variant with completely open to air canister; 3 stakes simply hold a windshield around burner and pot:

I have not shown the heat reflector/wind deflector for clarity.
The screen height could be adjusted to suit different cannisters.
It might be lighter.
A bit more complicated to make, but I think even the stove manufacturer's lawyers would be happy with it…..

[Roger Caffin]

Hi Alan

Yeah, I tried using a 4" high windscreen propped up in the air like that a couple of times. It was a real pain: it kept falling down to the ground. I prefer 'simple' myself, but ymmv.

Cheers

[Author]

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