Hi Daren

Neat. Ti top plate? or SS?

Do you have a dome of mesh inside the burner head, maybe over the main upright tube? It looks like it.

What is the fuel line? Source? I can't find anything with a really fine bore like that, so I have to assemble my own.

Cheers

the top plate is Stainless Steel.
there is a diverter plate in the burner head. it is a 1/2" round S/S punch knockout spot welded to, and supported by, S/S woven wire mesh.
the fuel line is the Brunton stove stand line with a short piece of heat shrink tubeing on the end. i have a local source here in Canada that can supply the same hose. they are called New Line Hose and Fittings. pricey stuff.

Daren......

I was so impressed by Daren's hybrid stove I decided to make my own version for my first stove project.


Many of the parts came from a MSR Pocket Rocket and a Brunton Stove Stand. As pointed out by Daren, the Pocket Rocket mixer tube has the same thread as the Brunton base so it can be simply screwed on (with a small spacer) after cutting a thread on the stand base to take the PR jet. This is an easy and worthwhile modification on its own, saving 39g by eliminating the PR valve/base.

The heat shunt is made from aluminium with a small copper fin. Aluminium has double the thermal conductivity/density of copper, but copper is used for the fin as aluminium has a low melting point of just 660C. I actually wonder if this heat shunt is a bit too efficient, as the whole base gets quite hot after a while.

The steel legs from the Brunton stand are replaced with legs made from 1.5mm aluminium sheet. The pot supports are cut down titanium tent pegs which push fit into the legs. The size of the legs and pot supports were chosen carefully so that the folded stove fits neatly inside my preferred cooking pot (AGG 3-cup Al pot) with room to spare.


The complete stove weighs 174g (6.14oz).

Blimey - the competition is getting fierce! I am much impressed by all these pictures. The Ti pot supports are also impressive.

> I actually wonder if this heat shunt is a bit too efficient, as the
> whole base gets quite hot after a while.
Could be. The solution is very simple however - slim down the copper heat absorber and slim down the aluminium upright. You should be able to make up a couple of variants and measure their performance?

Cheers

Hi Stuart,

Very nice work especially for a first effort.

tip: you can take the so called flame wind protector off the burner, in my opinion it is useless against the wind and my tests show that if anything it possibly reduces the efficiency.

Tony

Hi Guys, thanks for the tips.
I prised off the 'windshield' and slimmed down the aluminium heatshunt to 4mm dia. This seems to be an improvement, but I would like to do better. I think performance would be improved by running a pre-heat tube through the flame and I would also like to use a fuel hose with a smaller bore, but it's a question of being able to source suitable materials in small enough quantity to be affordable.
Flame control in liquid feed mode is a bit course, but there's not much I can do about the valve.
Cheers

Hi Stuart

Small bore hose is a problem. The stuff most companies use starts at 1/4" because that's where the market is. The alternative is to make your own out of Teflon or PFA tubing and SS braid.

> performance would be improved by running a pre-heat tube through the flame
Only to the extent that it would be easier to ensure that the liquid fuel has boiled. It won't make any difference once that has happened.

> Flame control in liquid feed mode is a bit course, but there's not much I can do about the valve.
You are right - valving the liquid is very tricky. That's why mounting the whole stove on the Brunton stand has some merit: you get a valve at the gas feed. But it is extra weight. Oh yes - you NEED the valve at the canister as well, as a safety on/off.

Cheers

Hi Stuart,

>I think performance would be improved by running a pre-heat tube through the flame and I would also like to use a fuel hose with a smaller bore, but it's a question of being able to source suitable materials in small enough quantity to be affordable.

I played around with preheat tubes on my early Pocket Rocket modifications.

http://www.backpackinglight.com/cgi-bin/backpackinglight/winter_canister_stove_modifications.html

I used some small bore high pressure tube on that stove mod, now I use SS hypodermic tube which works very well and is light, I am lucky as through my work I have access to such things.

Tony

There is a company called Small Parts which sells small-bore SS tubing:
http://www.smallparts.com/
I have NOT dealt with them (and have no connection with them), but at least they sell the stuff in less than truck-loads!

Doubtless there are many others.

Cheers

Useful stuff there, thanks for that.

I'm thinking about regulating the liquid flow using a needle valve (from a RC model engine) just before a pre-heat tube. This is the arrangement on my Coleman Sportster white gas stove and works well. Any thoughts?

Turning ideas into reality is always another matter, however.

Niiiiice!

I've been using a WindPro for a while and it's been working pretty well, except that the hose doesn't swivel: I like starting it in gas-feed mode and preheating the preheat tube with no flareups, but inverting the canister tends to flip the stove upside down. It would be stupid to put a couple of o-rings in the hose-to-canister connector, right? The connector screws in, so pivoting it would result in changing the compression of the o-rings. I'm guessing that I'd re-learn what Feynman learned about the Challenger--that o-rings aren't very flexible at -20. Any other ideas?

As for this mod of yours, I'm worried about one thing: most plastics don't really like heat or thermal change. The end of the fuel hose and the connector at the preheat end have plastic bits. So:

1) How about replacing the single rubber o-ring at the preheat end with a brass washer or two? That end doesn't need to be adjustable and brass will seal quite well (easy to verify, too). I used a brass washer to change the (fixed) orientation of the canister connector in my WindPro and it tested leak-free.

2) Your thermal transfer from the fixed heat-conductive rod is uncontrolled (or at best open-loop). You get a certain amount of heat transfer, and it's fixed, so the temperature of the preheat block is a crap shoot. But you could build a closed-loop controller with just a differentially-expanding material (two metals laminated together as on a metal-strip thermometer) near the base of the heating strip. If the preheat block got too hot, the heating rod would bend away from the flame, and vice versa. Then the setpoint should be easy to calibrate so that the generator never got hot enough to damage any plastics.

3) Why a 1mm fin? Wouldn't a cylinder conduct better (higher volume, lower surface area)? Or is the area under the pot going to be warm enough anyway that heat loss down the fin is a non-issue? Given that you said "Use copper; brass doesn't conduct well enough" I'm guessing that changing the section might be another viable fix.

4) As for brass vs. copper vs. aluminium bearings: would a couple of brass washers solve the problem? Their bearing friction should be lower than that of the brass-copper or brass-aluminium interface, right?

I too wish for a titanium pot with aluminium or copper fins welded on, but that'd be a trick. BPL custom gear shop? Meanwhile, REI is currently selling the Primus EtaPower 1.7l pot with heat exchanger fins (claiming 212g; similar to the MSR 2l Ti) to $35. I have one on order (it's web only but free shipping to an REI store).

The MSR fittings are a problem, I know. More recent designs from Primus and others feature a genuine rotating connection at the canister. MSR apparently gave up.

> The end of the fuel hose and the connector at the preheat end have plastic bits.
I'm not sure I understand exactly what you mean here. I assume you are talking about the Brunton stove stand?

Ah, well, that end gets hot under any conditions, doesn't it? But the 'plastic' you are talking about (inside the hose) is actually Teflon or PFA, and they will take very high temperatures. It's not a problem under realistic conditions.

The O-rings should be Viton. That can take high operating temperatures as well - over 200 C.

Yes, you could use brass washers to adjust spacing, but I think that places a high force on the screw threads, which would worry me a bit. I would need drawings of what you propose to comment further as I am not sure I understand.

Yes, the thermal feedback is sort of fixed. But the system can tolerate a very broad range of temperature, so precise control is not needed. As long as the preheat block is over (about) +20 C everything works fine. If it gets up to 50 C ... no worries. If it gets to 100 C I would back the fin off a bit, but even so that should not cause problems. You can fine tune the feedback by adjusting the length of the fin or the angle it goes into the flame too.

One thing to remember is that a small flame might not put quite as much heat into the fin as a big flame, but a small flame does not need as big a gas flow either. There is a sort of balance here between heat flow and heat requirement.

Why a 1 mm copper fin? I found that 1 mm x 6 mm copper fine worked fine. Aluminium has half the thermal conductivity of copper, so an aluminium fin 2 mm x 6 mm might work just as well. Do remember that aluminium melts around 550 C, so don't get the tip of the fin too hot! But yes, I have used an aluminium fin on other stove designs.

> brass vs. copper vs. aluminium bearings:
Sorry, more details needed. I'm not understanding just yet.

> a titanium pot with aluminium or copper fins welded on, but that'd be a trick.
Yeah. Actually, I suspect it would be a metalurgical breakthrough! Worth $$$.

Cheers

The modified Brunton stand is a great starter project, but the end product is far from light. After a couple of iterations in which a learned a few things which are not obvious, here is the final (possibly!) version of my winter stove stand.

The stand weighs 58g, the Gnat stove weighs 47g and so the complete winter stove is 105g (3.7oz).
At this weight I'll probably use it most of the year round, with the lighter 170g canisters.

3.7 oz!! very impressive.

All I want for christmas is a .... Stuart, inverted canister stove tutorial.

Roger….Your “original design” (http://www.backpackinglight.com/cgi-bin/backpackinglight/myog_winter_stove_summer_upright_stove_brunton_stnd.html ), you stated “made the heat conductor 90 millimeter high (to match the height of the stoves I was proposing to use) and 10 millimeter wide.” You used a Snow Peak GST100 and a Vargo Jet-Ti in that design.

On 02/24/2010, Re: Preheating at the hose posting you say “I found that 1 mm x 6 mm copper fin (Heat Conductor) worked fine.”

QUESTION: Were you using the same stoves as in your “original design” with the copper fin design change from 10mm to 6mm?

James
I made this without the use of a lathe or even a drill press, so perhaps a brief tutorial is not out of the question if there is genuine interest. Almost all of the component parts are obtainable, with the exception of the SS braid - this is a Roger 'special'
cheers

Edited by Scunnered on 12/26/2010 12:28:35 MST.

Stuart,

Genuine would be putting it mildly.

James

Hi Ken

The stove used is not really relevant: what matters is the temperature of the flames and the thermal conductivity between the flame and the block at the bottom. All that is needed is for the block (and hence the fuel inside) to be warmed enough to be somewhere between 10 c and 50 C - above freezing but touchable. Great scope for fine-tuning!

The original 10 mm wide heat shunt (heat conductor) was made of brass, but that has a lower thermal conductivity than copper. By changing the brass to copper I was able to reduce the width to 6 mm and still have the same conductivity.

You can also do some fine tuning by adjusting the length of the heat shunt and how it pokes into the flame. Even more scope. :-)

Cheers

Hi James

> inverted canister stove tutorial.
Well, there's this thread and article, and all the Winter Stoves articles. So what more do you want? Perhaps we can do something.

Cheers

Selecting a Canister Stove for Cold Weather Backpacking
Part I: Stove and Fuel Fundamentals
http://www.backpackinglight.com/cgi-bin/backpackinglight/selecting_stoves_for_cold_weather_part_1.html

Selecting a Canister Stove for Cold Weather Backpacking
Part II: Commercially Available Canister Stove Systems
http://www.backpackinglight.com/cgi-bin/backpackinglight/selecting_stoves_for_cold_weather_part_2.html

http://www.backpackinglight.com/cgi-bin/backpackinglight/canister_stove_efficiency_p1.html

http://www.backpackinglight.com/cgi-bin/backpackinglight/canister_stove_efficiency_p2.html

http://www.backpackinglight.com/cgi-bin/backpackinglight/canister_stove_efficiency_p3.html

Lightweight Canister Stoves REVIEW SUMMARY and GEAR GUIDE OVERVIEW
http://www.backpackinglight.com/cgi-bin/backpackinglight/lightweight_canister_stoves_review_summary.html

You may have jumped the gun on assuming I hadn't researched this earlier...

I have been following this thread for quite awhile. And have read most of the other articles you referenced. I have even purchased a brunton stand to replicate the original MYOG stove in your article -- available time to come up with something nicer than the primus express spider stove (FYI I have also read that article) have kept me from proceding.

I had actually requested the spider for christmas -- didn't get it so was planning to purchase in the coming weeks... and then Stuart provides this update. This appears to definatly be the eloquent solutions I was looking for as far as MYO inverted cannister stoves go.

Anywho, thanks for consolidating all of those nice articles / threads and of course all of the quality info you have provided through the years re. canister stoves.

James

Edited to add "and of course..." at the end

Edited by jnklein21 on 12/26/2010 14:19:33 MST.