Bushwalk Australia

I have been playing around doing some stove testing in my shed again, this time I am doing a series of tests on the effectiveness of different windshields, and I have just tested a Trangia 27-1 windshield and I thought as a few BA members use Trangia, and some have the gas stove conversions they might be interested in theses results.


These wind tests were done with my Trangia 27-1 using a Kovea Ti Supalite stove that has been modified by adding a pre-heat tube and stand, this allows the stove to be used in a remote canister configuration with the Trangia windscreen and base, the holes in the base were positioned away from the wind. The pot used was the 1 liter 27-1 Trangia pot.

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-15kph (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.


The tests were done with the canister in an upright position, to get consistency I put a valve on the canister and ran the stove until the flame was at a fairly high stable level I then only used the valve on the canister to turn the stove on and off.

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


Results

Test 1, no wind, windscreen

Fuel used in grams per 80ºC = 7.5g

Test 2, wind with windscreen, stove was lit, then fan turned on.

Fuel used in grams per 80ºC = 7.3g

Test 3, wind, no windscreen, During this test it was obvious that it this system is greatly effected by wind and to raise the water to 95ºC was going to take some considerable time and fuel, I stopped the tests at the same time as the no wind test and as the heating rate is usually linear I extrapolate the results.

Fuel used in grams per 80ºC = 53.0g

Test 4, the holes in base are placed into wind.

Fuel used in grams per 80ºC = 8.2g

Discussion of results.

As can be seen from the fuel used in the wind/no windscreen test the Kovea stove efficiency was affected quite a lot by wind but the use of the Trangia windscreen does improve the efficiency to the point where if used correctly, wind may have a very small affect on efficiency, the difference between the results of the no wind and wind/windscreen tests is very small the difference could be considered in normal testing error.

Conclusion.

The Trangia stove system with its inbuilt windscreen is very good in windy conditions but it is preferable to place the holes away from the direction of the wind.

Tony

Hi Tony
I do think that many underestimate the advantages of a well designed windscreen as well as the importance of matching burner/screen and pot for the expected conditions
(water temperature and wind)
There are lots of examples of windscreens that are too open or at times even too sealed or close to the flame to be efficient.
A 10% or so increase in fuel usage just by having a few holes in the wrong place would indicated a much more substantial increase with larger holes or gaps.
Multiply that by a few burns a day and it adds up.
Finding the exact balance is a bit of a science and that is one of the reasons why I like my TiTri Caldera Cone.
(the work is already done for me)
One of the problems I found with the typical loose screen around the pot is that in the wind it ,of course, moves around so it is hard to keep a set gap between it and the pot.
With the Trangia all of that is taken care of.

Thanks for the report
Franco

I am working on a wind shield for my Trangia, something that supply the air directly to the flame, rather than it taking air from everywhere it will take air from specific areas, so it has to draw the air from the outside with more force, pressure to the flame with more.

I am thinking pipes from the outside to the flame, maybe 4 of them will do maybe more.

Also will try to close the pot in so the only air coming in is from below, I am just tinkering to see if anything makes any real difference, I just like to tinker and gives me a reason to us e my dremel

Might have to put a pressure hole on the top of the windsheild so it don't blow

I am just a wannabe mad Scientist.


Cheers.

I once made a windshield stand for a spirit stove that worked pretty well. Much faster to heat a meal than any butane stove used in the canoe club at the time. It is here along with images of a standard mini trangia.

http://www.flickr.com/photos/16440739@N ... 110821727/

Anyway my shield was pretty basic but I took some trouble over the intake and exhaust areas and perhaps I can offer some tips.

We have to ensure that the wind does not change the air pressure at the intake and exhaust of the combustion chamber. This despite gusts and direction changes. If a surface is parallel to the airflow then it or a hole in it experiences ambient pressure. Therefore the wind must be across the hole but it gets trickier if the air is diverted around an object and turbulence is always an issue.

I suggest a stand with intake holes all around the base. A horizontal diffuser plate above these holes to separate the intake chamber from the combustion chamber. This plate should have a number of holes, to feed just enough air to the flame. So we have an intake chamber below the plate and the combustion chamber above. We want to keep the flow in the intake chamber as smooth as possible and parallel to the plate. Perhaps we could press the base intake holes to form a hole and baffle that directs the flow to swirl. Now we should have a pretty well controlled pressure and therefore flow into the combustion chamber. In any case, the inlet chamber serves to slow the wind and allow variations in local flow and pressure to dissipate across the up and down wind inlet holes. This should maintain a fairly steady pressure on the diffuser inlets as the remaining flow is basically across that surface.

The exhaust is more difficult. The ideal would be to have a central chimney through the pot which has been done but practicality..... We probably can't totally eliminate pressures from the exhaust. We could bring the shield edge up around the pot, certainly above the pot base. The gap between the pot and shied area should be the minimum needed to not adversely effect combustion. All holes should be sized with this in mind.

Hmm, does that make any sense at all?

Regards,
Ken

Franco wrote:Hi Tony
I do think that many underestimate the advantages of a well designed windscreen as well as the importance of matching burner/screen and pot for the expected conditions
(water temperature and wind)
There are lots of examples of windscreens that are too open or at times even too sealed or close to the flame to be efficient.
A 10% or so increase in fuel usage just by having a few holes in the wrong place would indicated a much more substantial increase with larger holes or gaps.
Multiply that by a few burns a day and it adds up.
Finding the exact balance is a bit of a science and that is one of the reasons why I like my TiTri Caldera Cone.
(the work is already done for me)
One of the problems I found with the typical loose screen around the pot is that in the wind it ,of course, moves around so it is hard to keep a set gap between it and the pot.
With the Trangia all of that is taken care of.

Thanks for the report
Franco

Hi Franco,

thanks for your comments.

Last January, while trying to cook with my upright Kovea Supalite stove and basic open sided windscreen at a windy 2150 meters in the Australian Alps, I ended up using a lot more gas than I predicted, it was then I decided that when I have some time I will do some testing of existing windscreens to see if I could design a better lightweight windscreen, this project was started a couple of month ago but due to some distractions things have become a bit delayed, I am hoping to get back to testing soon.

I do have some interesting test results on the JetBoil PCS and GSC stove systems that I will post soon.

I have run some tests on a Caldera Cone windshield for my BPL 550 pot (alcohol stove) and it performed very well on my test bench, I have also tried the CC WS with my remote canister modified PCS JetBoil stove and pot and it did not perform as well as though but that was one test and more testing is needed.

Tony

John Sheridan wrote:I am working on a wind shield for my Trangia, something that supply the air directly to the flame, rather than it taking air from everywhere it will take air from specific areas, so it has to draw the air from the outside with more force, pressure to the flame with more.

I am thinking pipes from the outside to the flame, maybe 4 of them will do maybe more.

Also will try to close the pot in so the only air coming in is from below, I am just tinkering to see if anything makes any real difference, I just like to tinker and gives me a reason to us e my dremel

Might have to put a pressure hole on the top of the windshield so it don't blow

I am just a wannabe mad Scientist.


Cheers.

Hi John,

I am very interested in your work, would love to see some photos of what you are doing and I look forward to see some results.

One thing that I have noticed over several years of testing alcohol stoves is that the Trangia is a well designed and very efficient stove as it is but it is heavy.

I think you would love my testing gear, check my stove section of my blog out.

Tony

sailfish wrote:I once made a windshield stand for a spirit stove that worked pretty well. Much faster to heat a meal than any butane stove used in the canoe club at the time. It is here along with images of a standard mini trangia.

http://www.flickr.com/photos/16440739@N ... 110821727/

Anyway my shield was pretty basic but I took some trouble over the intake and exhaust areas and perhaps I can offer some tips.

We have to ensure that the wind does not change the air pressure at the intake and exhaust of the combustion chamber. This despite gusts and direction changes. If a surface is parallel to the airflow then it or a hole in it experiences ambient pressure. Therefore the wind must be across the hole but it gets trickier if the air is diverted around an object and turbulence is always an issue.

I suggest a stand with intake holes all around the base. A horizontal diffuser plate above these holes to separate the intake chamber from the combustion chamber. This plate should have a number of holes, to feed just enough air to the flame. So we have an intake chamber below the plate and the combustion chamber above. We want to keep the flow in the intake chamber as smooth as possible and parallel to the plate. Perhaps we could press the base intake holes to form a hole and baffle that directs the flow to swirl. Now we should have a pretty well controlled pressure and therefore flow into the combustion chamber. In any case, the inlet chamber serves to slow the wind and allow variations in local flow and pressure to dissipate across the up and down wind inlet holes. This should maintain a fairly steady pressure on the diffuser inlets as the remaining flow is basically across that surface.

The exhaust is more difficult. The ideal would be to have a central chimney through the pot which has been done but practicality..... We probably can't totally eliminate pressures from the exhaust. We could bring the shield edge up around the pot, certainly above the pot base. The gap between the pot and shied area should be the minimum needed to not adversely effect combustion. All holes should be sized with this in mind.

Hmm, does that make any sense at all?

Regards,
Ken

Hi Ken,

Many thanks for your post, it appears that you have a good understanding of aerodynamics and I appreciate your suggestions, it is very interesting the what you have suggested with the intake and exhaust, I will have a serious think about them.

One reason I do not use my Trangia is that it is too heavy, for the weight of the Trangia stove system alone (no fuel) I can go for a week or more with my gas stove including fuel.

One of the outcomes of my project is to design the lightest most effective windscreen.

Tony

I am a great fan of the Trangia, and these tests do indeed point to what is good and not so good. On the plus side is the convenience, efficiency and ability to cope with bad weather. The downside is of course the rather heavy weight. The good news is that the UL version has partially dealt with this. The pots and pans are now about is light as the (titanium) competition, and have a superior heat distribution compared to titanium. The question is where the remaining excess weight is, and if there is something that could be done about it, at least in principle. At 110 grams, the actual burner is on the heavy side. The Evernew titanium alternative is much lighter, but uses more fuel, and lacks both simmer ring and lid. So we need the real thing, but in titanium, for a saving of some 50 grams. The gas stove is equally on the heavy side at 180 grams. I am sure it could be put on a diet and loose a third of its weight. At least as important is that it really needs the DUO valve system for both LIndal valve and Camping Gaz cannisters that Primus is now using on more and more of its stoves. And finally, there is the weight of the windscreen. At 262 and 326 grams for the 27 and 25 respectively, these are indeed heavy windscreens even if they work well. Much of the weight is in the steel ring and tabs that hold the pots and pan. A redesign in titanium could certainly save at least 50 grams on the 27 and 75 on the 25. And last of all, the grip could be lightened by making it in titanium as well, saving perhaps another 20 grams. If implemented this would make for a 575 grams alcohol Trangia 27 and a 700 gram alcohol Trangia 25. The gas conversion would add perhaps 75 grams. That is still not light, but not as bad as it is now.
Willem