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Archive for June, 2011

Following on from the hanging stoves I fired up the test bench on the weekend and ran some wind tests on the JetBoil stove that I have modified for the hanging stove.

Testing setup

 

Test procedure.

 

Part of the design of my JB hanging stove is that it does not have to be hung, it can be used as a normal remote canister stove, for these test I used the stove as a remote canister stove.

JB hanging stove used as remote canister stove

 

The stove was placed on my test bench with a small pedestal fan placed a meter away,  I placed my old Vane Anemometer on the bench and tested wind speed which was measured at around 12kph (note, the wind speed feels faster that 12kph but I could be wrong) I then attached the stove to the canister and took note of weight, measured 500g of water in pot, replaced lid.

Test with MSR windshield

 

I then placed stove on test bench, placed thermistor in pot at 1 cm from bottom, started data logging program and at 10 second started stove and adjusted to a high flame setting, when water temperature reached 95º stopped stove, removed pot and re-weighed canister, noting the new weight. From logged data start temp was noted and fuel used was normalized to grams of fuel used per 80º (g/80C)

Using Caldera cone windshield

 

 

The tests

 

The first test was with no windshield and no wind, this is used a base line figure.

 

Results, fuel per 80ºC = 6.1 g

 

The second test was with the fan on but no windshields.

 

Results, fuel per 80ºC = 8.2 g

 

The third test was with fan on and using an old MSR wind screen which was placed completely around and secured together with a clip.

 

Results, fuel per 80ºC = 7.4 g

 

The fourth test was using a Trail designs Caldera Cone windscreen, this windscreen is designed for a BPL Ti 550 pot and was too small to fit over the JB pot with the cozy on it, so I placed the windscreen as best as I could around the pot with the gap opposite the fan, the fuel line came out this gap.

 

Results, fuel per 80ºC = 6.9 g

 

Below is the heating rate graph, the fastest boil (pink line) is the test with no wind the slowest is the test with wind but no windshield.

Wind tests

 

Discussion of results.

 

First I wish to point out that these tests are not what I would call scientific, I only did one run per test and with canister gas stoves they are very hard to adjust to repeat runs, but there is a trend that fits in with what I was expecting.

 

The result clearly show that there is a reduction of efficiency with the introduction of wind, and that a windshield does make a difference, I am surprised how little loss of efficiency the JB system has with no windshield., from past tests with a normal upright stove with no windscreen there was a much high loss, I am also surprised with this system what little difference a windshield made to the efficiency and these test the CC windshield was only marginally better that the MSR windshield.

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I am not a climber and probably will never be, I enjoy fiddling with stove design.

Concept prototype

I got interested in hanging stoves a few weeks ago after reading a comment about hanging stoves on an Australian Bushwalking forum, the comment reminded me of liquid feed stove system I started working on about five years ago, as can be seen from the photo I put a Pocket Rocket stove on the base of an upside down canister, part of the idea in doing this is in very cold conditions there is an option to put some of the reflected heat back into the canister, for some reason I shelved this idea until now. While I do not climb I can see some advantages of  hanging stoves in some cases in backcountry snow camping.

A hanging stove idea prototype

I started my recent hanging stove project by making a simple hanging stove bracket to hold the canister upside down, I then made some legs and a pre-heat tube modification for a Gnat Ti stove (called Kathmandu Backpacker Stove Titanium here in OZ), the legs have been made to clip on the base of the canister. This worked well except the Gnat stove has something wrong with it and I have difficulties with simmering in both the upright canister configuration and liquid feed configuration., I have since replaced the Gnat with my favorite a Kovea Supalte Ti stove and all is working well.

Hanging a Chinese remote canister stove

My cheap remote canister stove then turned up and with the current hanging plate the new stove fitted very nicely on the base of the canister, but I will point out that at the moment this is just playing with design and I realize that with this system would be difficult to fit a wind shield and pack away.

liquid feed JB PCS stove

The next part of my hanging stove project was to use a JetBoil Personal Cooking System (PCS) with a liquid feed modification that I had done a number of years ago will before JetBoil came out with the Helios I have used my modified JB stove in winter in Australia a few times so I know that it works in cold conditions.

Pre-heat tube

I needed to hang the canister on the base, so I machined up a bracket that screwed onto the plastic shroud, the bracket takes the std JB 100g canister, I did the machining so the canister clips in so it does not fall out while it is still easy to put in, and that it would still fit into the JB PCS pot.

All packed away

I then needed some way to hang the JB stove, I did not want to buy a JB hanging kit as they are expensive here in OZ, so I got a some spare tent poles and some SS wire form the local fishing store and made a rough copy, while the hanging kit is OK for display purposes I would not like to assemble it on the side of a cliff at -20ºC, some more design thoughts needed here.

 

Where to next, as I am not a climber I have been doing some research on hanging stoves to try and understand what is needed, I have also been in contact with a leading British Climber to try and get an understanding of what is needed. So far I have found a few ideas, one is using a larger pot as the windshield, his seems to be very popular and I have seen this done with backpacking stoves, I have also found that my idea of hanging the canister upside down under the stove is not a new, it was done very nicely to a WindPro stove by Longshanks in Denver and the idea posted on a climbing forum last year. http://students.washington.edu/climb/forum/viewtopic.php?f=19&t=5759&start=0

I am combining this project with one that I have been thinking about doing for a while and that is windscreen design.

This project will continue.

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