>:"Fair question. I was including the requirement to heat the fuel up from, say, 20 C to wherever it boils."

Got it. While for fuels gaseous at ambient temps (propane, often butane), you primarily need to provide the latent heat, for high-boiling compounds, you need to provide a lot of sensible heat as well. Yes, then diesel would need to absorb more heat to boil than white gas than butane. Also, because the deltaT is less between the burner flame and heavier fuel to be heated and because the heated fuel vapor will have more losses once it leaves the vaporizer section, you'd need an even larger convective or conductive heat exchanger to heat that fuel.

Hello all, this is my first post at BPL!

I had some thoughts on regulating the thermal feedback to the inlet tube based on temperature. Don't discard your heat shunt concept just yet.

You might be able to achieve regulation (preferably automatic regulation) by either varying the thermal conductivity of some parts of the stove, or by varying the exposure to thermal energy of some parts.

To vary the thermal conductivity of the structure, it would be nice to have a material that has a thermal conductivity with a strong and inverse dependence on temperature. As the temperature of the conducting parts rose, the conductivity would decrease, thereby reducing the thermal energy transmitted to the fuel. Unfortunately, I don't know of any such materials.

But, varying the exposure of the inlet tube and connected parts may be possible. In this case, you would want something to move as the temperature rose. What I imagine here is one of your flat metal shunts made out of bi-metal sheet. As the temperature of the shunt rose, the shunt would bend away from the flame, reducing its exposure and consequently the amount of heat conducted down to the inlet tube. The regulation would vary smoothly with temperature. Alternatively, you might find a shape memory alloy that would bend out of the way at an appropriate temperature. This deflection could potentially be much greater than with the bimetal, but all the deflection would occur over a narrow temperature range, which might be ok or even desirable. Or, you could go low-tech and just put your shunt on a hinge and manually flip it out of the way or adjust it once the stove is warmed up, at least for initial testing. You would probably want the rest of the stove to be designed to contribute relatively little heat transfer to the inlet tube, so that the moving component could have maximum control of thermal feedback.

You might think of other variations on this theme.

-Stephen

Hi Stuart

> a hole thru' the centre of a brass M5 bolt and then brazed the SS vaporiser tube
> into the hole. The bolt with tube then screws into the aluminium base
Yes, I played around with this idea too, but I had trouble getting it miniaturised and hermetic. It remains possible though.

> a little anaerobic threadlock for good measure.
That bit worried me. Most anaerobic threadlocks are based on methacrylate, which has a limited tenperature range. Maybe a silicone sealant could be used instead?

Maybe I will have another look some time.

Cheers

Stephen, that's something along the lines of what I was proposing. Great minds think alike.

Unfortunately, so do mediocre ones.

> flat metal shunts made out of bi-metal sheet.
Novel! I imagine it could work.
But sourcing the material ...

Cheers

not sure if they could be made to work in this application, but bi-metal coils are at the heart of most house thermostats, and there's probably a mature technological base that knows how to manipulate their properties.

Bi-metal sounds very interesting and it should not be hard or expansive to source.

Picture: http://www.google.se/imgres?imgurl=http://www.hilli1.de/Physik/Folien/Waerme1/Bimetall.gif&imgrefurl=http://www.hilli1.de/Physik/Folien/Waerme1/Bimetall.htm&h=660&w=514&sz=23&tbnid=oZjbVetxRYXVOM:&tbnh=89&tbnw=69&zoom=1&usg=__IAb2lOT2K7tr0ORmGJq8mXWP4rc=&docid=1VfhP_GJPe_5DM&hl=sv&sa=X&ei=FkY4Uf6QO4vesgbykYCYBA&ved=0CEAQ9QEwBQ&dur=670

Edited by tordnado on 03/07/2013 00:49:57 MST.

It doesn't even have to be bimtallic in the traditional sense of two alloys continuously bonded to each other. Simply two metal rods triangulated with a narrow base would, if allowed to pivot, bend away from the hot side. The hot rod could be either a conductor of heat to a vaporizer or the vaporizer tube itself. The cold rod could be a turnbuckle to field tune it for ambient temps or different fuel types ( butane, white gas, diesel, yak's milk, etc).

So, what is the heat of vaporization of yak's milk?

--B.G.--

>Novel! I imagine it could work.
>But sourcing the material ...

I don't usually give novel ideas away. If you make it big in the stove industry, you owe me some CNC play time...

Here's some useful info on bimetals. These guys would probably send you some samples if you tell them you are developing a product.

http://www.cladit.com/tech.html

> http://www.cladit.com/tech.html

f a s c i n a t i n g...

Cheers

Roger,

Very interesting what you've learned by experimentation (and frustration at times, no doubt). Sounds like it's all about the heat and consequent pressure within the canister although I still wonder some about the Jetboil Sol (although I suppose if I'm really curious I can do a bit of experimentation).

Interesting bit about the difficulty of sealing a pre-heat loop. The FMS-118 Volcano at least has the sealing right (although it seems they've got the diameter a bit too big).

I do notice the Kovea Moonwalker uses a shunt instead of a pre-heat loop. The one thing I don't like about this arrangement is that the whole stove gets quite hot and takes a while before I can reasonably pack it away, but the Moonwalker has a lot of metal. Smaller, UL style stoves will likely not have this problem.

It's late, and I don't have any particularly brilliant insight to add (would that I did), but I thank you for writing yet another article that very few people are in a position to write. It is such articles that make BPL such a great place to be a part of (well, and the people too of course).

HJ
Adventures In Stoving

Actually, Kevin, you apparently are a stove designer. I think you just designed a SVEA 123.

Here's our own HikinJim priming one with denatured alcohol:

http://www.youtube.com/watch?v=TfRRs4x51k8

But the alcohol used is more like 3 ml on a cool day. Maybe two such treatments ( 2 x 3 ml) in snow-camping conditions.

Roger,

I just noticed this elsewhere on BPL regarding your MYOG canister remote stove:

Works with standard screw-thread canisters, French Campingaz canisters, and Coleman Powermax canisters, all in full winter mode. This means I can use it virtually anywhere around the world.

Hi Jim

All the details, in great and gory (or glorious) depth, will be revealed soon. The connector is more like the French Campingaz one than the Superfly. I tried the Superfly and was, frankly, a bit scared of the way MSR had done it. Things flexed ... It was not an option for me.

The pin - you would not believe how much trouble that gave me! The Lindal valves are all different. Yes, a solution was found, and yes, it will be in the article to come.

Fwiiw: I have been using my winter stove for 6 - 9 months now.

Cheers
(Yes, I know I'm mean not giving all the details now ...)

IANASG (I am not a stove geek), so maybe this is a dumb question:

Given all the troubles vaporizing butane, why not make light canisters with 100% propane specifically for winter use?

Why are Coleman-style propane steel canisters the only ones on the market anywhere close to backpacking size?

(Edit) And to answer my own question:

http://www.backpackinglight.com/cgi-bin/backpackinglight/canister_stove_faq

Edited by Rex on 03/09/2013 10:56:30 MST.

As the link you added explains, pure propane is so high pressure, it requires thicker steel. About exactly the weight of the propane regardless of size (14 oz. 16 oz, 20-pound/4.5-gallon, 80-pound, etc).

There are about three people on this very gear-heady site that I'd trust to load their own lighter canisters for winter-only use and be damn sure they never got above room temperature during transit and use. Those safety margins are used for good reason as HikinJim, RogerC, and I have all proved at times.

Now if someone offered a refillable 200-gram fuel weight aluminum or titanium propane canister, I'd order a handful.

I own a Chevy Siverado that I had converted to Run on Natural Gas. It has a polymer tank that is wrapped in fiberglass and carbon fiber.
It has a fill pressure of 3600 PSI.

I just use public fill stations but there are several types of home filling stations.

It would be nice to just have a small refillable bottle to use with my stove! No more issue with low temps and no more canisters in landfills.

Maybe 3M or GE see an ultralight mini tank in there future?

> It has a polymer tank that is wrapped in fiberglass and carbon fiber.
Bring it on!!!!!

But the cost of production would likely be swamped by the cost of development and insurance and safety testing and getting approvals and ...
Sigh.

Cheers

Roger that is most definitely the problem!
It is amazing what is out there just waiting
Well my son can look forward to such high tech gear!
In 25 years who knows what possible