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Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
A faster boil on 09/26/2009 15:20:48 MDT Print View

After a season of hiking, the 4 oz two person titanium wood stove I built last winter shows the signs of ample use but is otherwise holding up well. It's been out on lots of weekend hikes and a 5 day loop hike in the Adirondacks cooking three meals a day with no sign of deterioration.

If I had a complaint, it was all those people with canister and white gas stoves cooking about twice as fast as I could. We generally boil at least a liter, sometimes 1.5 liters or even more at each meal. I was really tempted to get a canister stove, but I didn't want to carry the weight, especially on the 5 day hike. I looked at all my requirements and decided I to experiment with a forced draft.

I came up with a fan and duct that disassembles and stores inside the stove for transport. The setup added 1.9 oz. for a total weight of 5.9 oz. which is still better than a canister stove and fuel canisters. I don't include batteries because I already carry a USB power supply that recharges from a 4 oz. solar panel on my pack. Compared to my camera and PDA, the energy consumption of the fan is a negligible adder.

The forced draft reduced boil time (1 liter 20degC water) from 9.4 minutes to 5.9 minutes, besting many canister stoves See Heat Exchanger Stove Shootout: Part 2 in the BPL articles.

While it pained me to add the weight, I'm happy to have a stove that cooks as fast as a canister stove but weighs less and doesn't require me to carry any fuel.

FAN AND DUCT SECTIONSFAN AND Duct sections

FAN AND DUCT ASSEMBLEDASSEMBLED FAN AND DUCT

FAN CONNECTED TO BASE OF STOVEFAN CONNECTED TO BASE

FAN DISASSEMBLED AND PACKED IN STOVEPACKED FAN

NEW STOVE LAST JANUARYNEW STOVE LAST FEB

Edited by herman666 on 11/09/2009 06:09:31 MST.

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: A faster boil on 09/27/2009 03:55:29 MDT Print View

Good result Keith. So did 3V run the fan plenty fast, or did you need a 3rd AA battery? Or did you run it direct from the USB/solar panel at a higher voltage?

Edited by tallbloke on 09/27/2009 03:56:58 MDT.

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
Re: Re: A faster boil on 09/27/2009 09:58:30 MDT Print View

Rog, The fan uses 5 Volts. I have a boost regulator that converts the 2.2V nominal from the AA NIMH's to 5 V. I built it from a kit. If you want learn more about it, here's the link:

LadyAda Mintyboost 5V USB Power


All the electrics I carry (camera, PDA phone, mp3 player) charge from the USB connector on the boost regulator. I charge the AA's the boost uses in my solar charger:silva solar charger

Edited by herman666 on 11/10/2009 11:38:33 MST.

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: Re: Re: A faster boil on 09/27/2009 13:17:51 MDT Print View

Very nice setup Keith. I have a small 4oz panel too. It charges a cellphone ok, but it's never sunny for long in the UK it seems.

Michael Meiser
(mmeiser) - F

Locale: Michigan
alt design on 11/14/2009 14:29:17 MST Print View

Keith, interesting stove.

I'm using I think the same fan in my woodgas / forced air prototypes.

Don't know if you saw the video:
http://www.flickr.com/photos/mmeiser2/4079433096/

It's crazy hot and clean and can be used with or without the fan.

My only problem with it is it doesn't pack well and it's not durable enough to use as a heat source for extended periods.

I'm working right now on a flat pack version. Been testing a bunch of designs. Tough to translate the same brilliant wood gas characteristics from the heineken can to a square "flat pack" design.

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
Re: alt design on 11/14/2009 15:08:28 MST Print View

Yes, I did see your video and I think you've got a nice prototype there.

I agree that light weight and durability are difficult to achieve in the same design. I managed to come up with a workable solution for my setup. For light weight and heat resistance, nothing beats titanium. The 0.005in. titanium from Titanium Goat is amazing stuff. With the fan on, the whole stove glows orange. At night it's a sight to behold, but it holds it's shape pretty well and shows no sign of burnout.

There is one 0.01in. stanless steel ring in the base where the legs attach and one in the base of the windscreen where it rests on the firebox. The Ti was too flexible in these horizontal areas to support the weight of a full 2 quart pot.

I've been using it since last February and it's in great shape. The secret is in the packing. everything except the windscreen packs inside the pot. The windscreen packs around the pot. So the pot protects the stove, and supports the screen so it can't be crushed in my pack. Without the pot, the paper thin stove would have been crushed on the first outing.

The fan setup pictured above puts out too much air, and after viewing your video, I'd say you could also get away with less air movement. As I write this, the JB weld is setting up on the manifold of my new fan which is much smaller and has about a third the power of my original setup. The cardboard mock-up of the new fan and duct is pictured below.small fan duct side viewsmall fan duct front view

Michael Meiser
(mmeiser) - F

Locale: Michigan
flat pack protype wood gas is coming along well on 11/20/2009 10:54:24 MST Print View

keith, my flat pack protype is coming along well. I think I may have figured out how to make it gassify without a double wall. The key seems to be inward slopeing sides which simultaneously funnels heat over the center of the flame and reflects heat back into the center of the stove.... and a secrete weopen, a false bottom which preheats and distributes hot fresh air up along the walls supplying a constant flow of hot fresh air.

Pics should be coming soon.

Franco Darioli
(Franco) - M

Locale: Melbourne
A faster boil on 11/21/2009 18:46:41 MST Print View

You may want to look at the Inferno by Trail Design. I don't know how it works (technically) but it seem to burn the gasses as well .
Possibly the two cones concentrate the gasses and allow the secondary burn, whatever it is ,it seemed to work on my "make do" version (a TiTri cone and an aluminium (temporary...) inverted cone insert.
Franco
http://hikinginfinland.blogspot.com/2009/09/gear-talk-trail-designs-ti-tri-inferno.html

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
Re: flat pack protype wood gas is coming along well on 11/22/2009 19:21:16 MST Print View

Looking forward to seeing it.

I built my new fan setup (the one shown in mock up above) and tested it this morning. It was about halfway between the first fan and no fan in performance which makes sense because it has about half the air flow. I had hoped that the big fan was producing a surplus of air, and that the smaller fan would perform equally well in cook times, but it appears that the burn rate is proportional to air flow.

The lesson learned is if you're willing to carry the batteries, you can likely get canister stove cook times with wood. With the small fan I'm getting roughly twice the power output of a Pepsi can alcohol stove. I can boil more than 50 liters of water on a set of NIMH AA's. I think I'll live with that for now.