Double Walled Stoves

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zelph
Posts: 15746
Joined: Tue Aug 14, 2007 1:53 pm

Double Walled Stoves

Postby zelph » Thu Sep 06, 2007 2:18 pm

The double wall feature onbackpacking size stoves is worthless to the performance of the stove.

Side by side comparison of two Sierra Zzip stoves showed small difference in performance. One had the double wall removed and was tested under exact conditions as the one with two walls. These tests and comparisons were conducted in January of 2007. Here is the information as to how the comparison was conducted and what the outcome was::

I've modified my zip stove to eliminate the double wall feature. I believe the heating of the fan forced air to be insignificant in the performance of the stove. The volume of forced air being the major contributing factor for the stoves ability to consume wood and provide high heat at a very fast rate.

I will perform tests using my old stove side by side with the modified version as time and weather permits.

First photo shows stove apart before cutting beginsImage

Second photo shows cutting complete Image

Third photo shows stove re-assembled Image

Fourth photo shows stove in a bare bones state without upper rim attached. Stove has sufficient strength to be used without it in my opinion. Reduces weight by 18 grams/0.58 oz. Image

Fifth photo Image shows cutting being made with a Dremel rotory cutting tool. Blade being used is a diamond impregnated cutoff disc.

The stoves weight before modification was 326.2 grams/10.49 oz.

Modified stove(with rim) weighs 203.7 grams/6.55 oz.

Total weight reduction is 122.5 grams/3.94 oz.

The stove weights given are without fan assembly.

Fan assembly with battery weighs 110.5 grams/3.55 oz.

I've completely photographed the modification procedure and will post photos and instructions after burn tests are completed.

.007 stainless steel was used to cap off the shortend inner walls to maintain the flow of forced air through the row of holes located on the lower innermost wall as seen in one of the photos.

Enough people wanted titanium zip stoves so they made them using TI. If enough people want a single walled stove they'll make them that way, don't you think so? Less walls, less weight.


first photo shows harware http://img.photobucket.com/albums/v228/ ... ove010.jpg

second fphoto shows software http://img.photobucket.com/albums/v228/ ... ove011.jpg

I chose this type of Softerware so that each test burn can have the the same amount of fuel for each consecutive burn. I will count out the exact amount of each size fuel piece for each test.

I'm using fluffed cotton yarn for my tinder starter and the different size sticks as shown in the second photo. Yep!!!!! Clothespins all nice and kiln dried, tounge depressors, and craft sticks.

Water will be taken from the tap and test will be conducted in a calm/no breeze environment.(unheated greenhouse)

Are all of you in agreement that this is looking to be a fair way to go about testing my theory????

Any suggestions or questions?

update

--------------------------------------------------------------------------------

I found that the ss pots were not the same weight, one was 38 grams heavier, I swithced to using Kmart grease pots with outward rolled lip. Both were identical.

I attached machine screws to the body of the fan housing to create a stop for the lever that controls the volume of air going into the stove so that each test burn the air volume will be the same.

Assembled a thermometer stand to hold thermometer in pot while stove is heating. Long stemmed thermometer to keep my face away from hot stove and be able to monitor constantly.

All fuel and water has been weighed and are in individual containers ready to go

All materials are now in unheated greenhouse to be aclimated overnight in preparation for tomorrows tests. Three tests per stove will be made.

Tests will be made Saturday and results will be posted Monday

Any Comments? Anything I forgot?

machine screews to body Image

thermometer stand Image

fuel and water weighed Image

fuel in unheated greenhouse Image


Three tests for each stove have been completed.

After lighting, each stove was given one min. of time for tinder to ignite fuel and then pot of water containing two cups of water was placed onto stove. A clock was placed in a position to the rear and off to the side for photos to show min. into burn.

Temperature of water, fuel and air was at 35 degrees for the first two sets of tests. The temperature for the third set of tests had risen to 37 degrees.

No photographs were taken of the first set of tests

This first photo shows both stoves packed with same amount of fuel.http://img.photobucket.com/albums/ ... ove024.jpg

The next six photos show the progression of testing the unmodified stove during the second set of tests.

Photo one: 2 min. into burnImage
Photo two: 3 min. into burn Image


Photo three: 3 1/2 min. into burnImage


photo four: 5 min. into burn, water boils, flame starts to get smallerImage

Photo five: 6 min. into burn, steam comes out and raises lid of pot Image

Photo six: 6 1/2 min into burn shows fuel remaining Image


The next seven photos show the progression of the testing of the modified stove during the second set of tests.

Photo one: 2 min. into burn Image

Photo two: 3 min. into burn Image

Photo three: 4 min. into burn Image


Photo four: 4 1/2 min. into burn, boiling water pushes lid off pot Image

Photo five: 4 3/4 min. into burn shows boiling water and flame pattern Image

Photo six: shows remaining fuel Image

Photo seven: shows remaining fuel 1/2 min. later Image


The next eight photos show the progression of the third test done on the unmodified stove. Also shows how the fuel was packed into the burn chamber. The fuel was stacked around a clothespin in the center and later removed before lighting the tinder located at the base of the clothespin. The clothespin formed a hole that was used to put the butane lighter into to start the tinder as shown in one of the photos.

Photo one: shows lay of fuel and clothespin in center Image


Photo two: filled with fuel with clothespin in middle Image

Photo three: shows butane lighter in center hole to show how stoves were llit Image

Photo four: 3 3/4 min. into burn Image

Photo five: 4 min. 10 sec. into burn, temp at 150+ degrees Image

Photo six: 4 min. 20 sec. into burn Image

Photo seven: 5 min. into burn, temp. at 200 deg. Image

Photo eight: 6 min. into boil water boils Image


The next three photos show the progression of the third test done on the modified stove. Water boiled at 4 1/2 min.

Photo one: 2 min into burnImage

Photo two: 2 min. 36 sec. into burn shows flame pattern Image

Photo three: 3 min. into burn Image



The next two photos show cleanliness of stoves before and after test.

Photo one: before tests http://img.photobucket.com/albums/v228/ ... ove009.jpg

Photo two: after tests http://img.photobucket.com/albums/v228/ ... ove049.jpg




Boil times for each stove:

Unmodified: Test one: 5 1/2 min.
Test two: 5 min.
Test three: 6 min

Modified: Test one:4 1/2 min.
Test two: 4 min.
Test three: 4 1/2 min.

The Results: The Modified stove outperformed the Unmodified.
"Nothing Ventured Nothing Gained" stove store = http://www.woodgaz-stove.com/

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ConnieD
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Location: Montana
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Re: Double Walled Stoves

Postby ConnieD » Thu Apr 22, 2010 11:11 pm

I thought their double wall design is supposed to make the fire burn hotter and reduce the wood completely to ash? No?

Does chafing fuel clean the soot and creasote from the wood fire?

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Ridgerunner
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Location: SW, Ohio
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Re: Double Walled Stoves

Postby Ridgerunner » Fri Apr 23, 2010 10:58 am

Nice test Zelph but I will disagree with you statement:
The double wall feature onbackpacking size stoves is worthless to the performance of the stove.

I would think that a doubled wall stove with wicking material in between would perform differently than without. Remember, a fast burn is not better than a slower controlled burn. That said, your test on the zip stoves shows a marked difference when comparing a hollowed double walled stove to single walled stove. ;) I like your vacated clothespin lighting cavitiy :idea: :D
"Many of lifes failures are people who did not realize how close they were to success when they gave up".....Thomas Edison

"Live Life....Love Life....Ask More !

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zelph
Posts: 15746
Joined: Tue Aug 14, 2007 1:53 pm

Re: Double Walled Stoves

Postby zelph » Fri Apr 23, 2010 1:05 pm

Ridgerunner wrote:Nice test Zelph but I will disagree with you statement:
The double wall feature onbackpacking size stoves is worthless to the performance of the stove.

I would think that a doubled wall stove with wicking material in between would perform differently than without. Remember, a fast burn is not better than a slower controlled burn. That said, your test on the zip stoves shows a marked difference when comparing a hollowed double walled stove to single walled stove. ;) I like your vacated clothespin lighting cavitiy :idea: :D


We agree that we can disagree..... :D

I made another comparison of a double walled wood burner that was super insulated with fiberglass cloth that gave the same results. No difference in performance. Link: viewtopic.php?f=60&t=1120

The clothespin cavity was cool :ugeek: :P

Boil times for each stove:

Unmodified: Test one: 5 1/2 min.
Test two: 5 min.
Test three: 6 min

Modified: Test one:4 1/2 min.
Test two: 4 min.
Test three: 4 1/2 min.

The Results: The Modified stove outperformed the Unmodified.
"Nothing Ventured Nothing Gained" stove store = http://www.woodgaz-stove.com/


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