windshield VS heat exchanger!?

Generally, a windscreen is more important than a heat exchanger, but of course that will change with conditions. On a windy day, a windscreen can be come really critical, but on a calm day, the heat exchanger alone will do fine.

One of the reasons the Jetboil is better in lighter winds is that the heat exchanger provides some wind protection. The Jetboil isn’t so good in heavier winds.

What’s the lightest HE pot? Not sure. Maybe the Jetboil’s Ti pot? Generally, heat exchanger pots don’t “pay” for themselves in terms of weight saved unless you’re taking a longer trip (maybe a week plus).

HJ
Adventures In Stoving

This isn't what you asked for, but this weighs 0.9 oz:

nested:

Tricky measurement but this gets maybe 10% better efficiency than similar windscreen. I can tell that the water boils more on the edge right where the ridges are.

I believe that the assumption that the heat exchanger takes a long time to break even is based on a wind free comparison! Correct? I would love to see some real testing.

"This isn't what you asked for, but this weighs 0.9 oz:" Great to see! I made a very similar version but it had rounded surfaces on the contact surfaces. It works really good but I'm in love with the convenience of the jetboil and it would be very similar with a heat exchanger stove on top of an upright.

Can you put the pot down without removing the shield?
What is the wire made of and is working well? I have a tension spring, it works pretty well but I have to use 2 of them because that was the length I had at home.
Do you have problem with the sheet deforming? it does require a bit more precision then just a windshield!

MSR has made their version for years, but it is 6 ounces and $35.

They used to make corrugated aluminum for lawn edging. It is easy to fold flashing, but I thought the edging would be a cool application. If making one of these for a particular pot, you could could punch holes and use one or two light springs like the ones used on carburetor linkage. Remember carburetors?

I do remember carburetors and I would say that the heat exchanger would only work well on one size pot unless one is really lucky so that the overlap would match on the next "indent".

Lets not forget the original question, how does the heat exchanger compare to a windshield in normal (somewhat windy) conditions?

I sort of copied that MSR heat exchanger, except simpler and lighter.

I just set it on the ground with the shield on and it holds it up fine.

I use #18 gauge galvanized wire. I formed two hooks – you can see under handle in first picture. The springiness of the aluminum against the pot pushes against the wire to keep it on.

There is nothing precise about this : ) I just bent aluminum, drilled a few holes for the wire to go through, threaded the wire through, bent one hook, eyeballed where to bend the other hook.

I think this aluminum was intended for flashing. It's maybe 1/4 the thickness of the #18 wire.

I use this in the wind sometimes and it works pretty good, but I try to get into sheltered location. It's narrow enough to fit into pot, which is a compromise for wind protection – probably better if it was a bit taller. But it does extend below the level of the flame.

The exhaust fumes stay next to the pot on the sides, and some of the heat goes to the aluminum which is conducted to the pot.

Tord – pretty much any stove question has an answer here on BPL, if only you could find it. Try this for starters:

"Performance Comparison Testing of Lightweight Canister Stoves: Controlled Data Evaluating Key Variables of Temperature, Wind, and Windscreen Use"

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

/www.backpackinglight.com/cgi-bin/backpackinglight/lightweight_canister_stoves_test_report_ii.html

cheers

Unless you're using a Reactor or JetBoil, it's not a question of "HE vs. Wind Screen" with heat exchanger pots. You use them *together*.

The HE pots sit on top of the stove's pot support arms, rather than extending around and down below them. So, although the pot's base uses fins to transfer more heat from the flame to the pot, it doesn't shield the burner from wind.

The burner head, being generally below the pot supports, is still exposed to the wind when you've got an HE pot on top, and therefore can be blown out, etc… So, the same desire for a windscreen and applies to any such stove, whether you're using an HE pot, or not.

See it sitting up above the support arms, with the stove head naked to side-wind?

In terms of which are light, the Optimus HE Weekender pot above isn't bad, but the Fire Maple that's a full litre is lighter per capacity. It's still 3 ounces heavier than a .9 litre Ti Evernew, though.

Having used non-HE and HE pots quite a bit, I think the observation that the additional weight of the HE system either won't, or takes a long time to, "pay for itself" in terms of grams of fuel saved may be totally right, but that this metric misses one point: the HE pots boil a LOT faster. I like fast.

Related Thread: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=67938

In my use (and Dave's as we used his test unit together) I say HE all the way.

The Eta Express is the fastest boiling stove I have ever used and the MSR Reactor is the second fastest and the best fuel consumption. (The EtaX is second on fuel use.) Those both use an exchanger and the Eta even has a little wind block too.

I know that Roger hates the Eta but his was a preproduction unit. I have a retail one and am alive to tell the tale… (Cough, j/k;-)

I do think that windshields are great and use them as often as I can.

As far as figures? Average boil with a good stove like the Crux or Giga used around 0.35 oz (by weight) of fuel for a 2-cup boil for 3-season use. The Eta and Reactor were in the 0.18 oz range. I attribute that to the heat exchanger.

Jerry: that's pretty friggin' brilliant! 0.9 oz.; nice. And it fits inside your pot.

I bought a used caldera cone (not ti-tri) just to try as a canister stove windscreen. Not recommended, I know, but if you're careful and judicious, adjusting the opening of the screen according to conditions and testing the warmth of your canister throughout the boil, the darn thing works very well. I think that I've almost doubled the efficiency of my canister set up. I've used this approach for thirty nights or more, and feel confident that it's not going to blow up in my face, as long as I'm attentive. But any windscreen–or heat exchanger, I presume–will help enormously on fuel consumption.

I'm now confident that a 4 oz. msr canister will last for six days, probably more, at two boils a day for a single person. That's pretty good.