Saturday, 22 August 2009

Home Built Stoves from Japan

I've just had a comment from a Stove builder in Japan and I've been looking at his Youtube page. There's lots of interesting stuff including home made gas stoves. Well worth a look.

Video Clips


Friday, 21 August 2009

More on Windshields

I've spent most of this week working on windshields after my experiments with 2 x layer foil. I've decided that the cone type suits me best and thats what I'd been working on. Ideally the vents would go all the way around the cone but while that may provide the best performance when indoors the vents reduce the cones effectiveness as a windshield when outdoors. I usually try to bias the vents to one side/half of a windshield but even doing so the performance of the stove is badly affected by stiff breezes.

Cone with Vents biased towards the front

Rear of Cone

As I use a 550ml pot rather than the stainless steel pot I used in the previous tests I wanted to optimise performance with my actual cooking set-up.

In addition to the 550ml pot I carry a 375ml mug so I started testing using 350ml water/15ml meths. Using the cone on it's own indoors I managed a boil in 5.54 mins. In an attempt to come up with a repeatable method of simulating a breeze I used a 3 speed pedestal fan set up 1.5 metres from the stove. I checked the windspeed using a cheap anemometer held about 6 inches from the fan, speed 2 on the fan came up at about 5mph, speed 3 at about 8. I'm not sure how this relates to windspeed outdoors but at least it's repeatable.

Trying the cone set-up with the fan set at speed three the fuel ran out prior to reaching a boil, the maximum temperature was about 92 deg. I noticed that even with the vents towards the front of the cone the flame was being blown around too much. I tried the same set up again but with a 2x layer foil windshield around the cone. With the fan set to speed 2 (5mph approx) it actually boiled slightly quicker at 5.49 mins than the cone on it's own in still conditions (fan off) and at speed 3 (8 mph approx) was less than 1 minute slower at 6.38 mins.

I think that makes a secondary windshield worth carrying. The results are laid out below together with a video clip.

I've also included a pic of my cooking set-up. The main pot is a Tibetan titanium 550ml pot which comes with a lid and a Tibetan titanium 375ml mug. The Cone is made to suit my EK meths burner and 550ml pot, the wire mesh potstand allows me to use the smaller mug with the cone. The Plastic container holds a long spoon, teaspoon, cone, foil secondary shield, lighter and home made permanent match together with a measuring cup and the burner.

Cooking Gear unpacked/packed

Time/Temperature Table

Graph Illustrating the Above

Saturday, 15 August 2009

Windshield Foil, Does Thickness Matter?

Windshield with 40mm Air-Gap

I was curious to test what effect foil type and weight had on the performance of a stove (meths specifically) due to a post by Fenlander He'd noticed that his EK meths burner was performing worse when he used a windshield made from a few layers of kitchen foil rather than a single layer of heavier windshield foil. Not only was it burning the fuel up faster but it was failing to reach boiling point.

I've noticed myself when experimenting with meths stove designs that increasing the temperature of or around the stove leads to increased fuel consumption thanks to the fuel vapourising more rapidly. This might not effect a closed top meths stove or even a side burner but the EK burner (like the other stove Fenlander has noticed was playing up with the Kitchen foil Windshield) is designed to burn off a wick. Due to the double wall design of the EK burner there is some pressuried effect and my initial reaction was that the stove was heating up due to the improved thermal barrier provided by a multi-layer foil windshield and the fuel was been burned off more rapidly. This didn't quite explain why the stove could no longer achieve a boil so I decided to run some tests.

I used a standard MSR foil windshield (Whisperlite Int'l) and made an identical one from 2 x layers of normal kitchen foil (I think Fenlander used 4 x layers). I used a stainless steel pot as it has a hole in the lid to take the probe of the thermometer which allowed me to record the temperature at regular intervals without removing the lid. For the initial tests I set both windshields with a 40mm air-gap to the pot, used 500ml of water at 17.0-17.5 deg C and used 20ml of meths. I ran 3 tests on each set-up alternating between windshields to account for the stove heating up between runs. Taking the results I averaged them out, the results can be seen in the graph below. Clearly the kitchen foil windshield was superior and with a gap of 40mm there was no trade off in fuel consumption.

I ran a further two tests, one with 250ml water/10ml meths/40mm Air-Gap using both windshields and another as above but with the air-gap reduced to 30mm. Both graphs are shown below.

(Image) Windshield with 30mm Air-Gap

(Graph) 250ml/10ml, 40mm Air-Gap

(Graph) 250ml/10ml, 30mm Air-Gap

I think it's clear whats happening, in spite of being behind initially, when used with the Kitchen foil windshield the stove starts to get ahead as early as 4 minutes and almost reaches a boil well ahead of the MSR windshield set-up but simply runs out of fuel. Interestingly it still manages to achieve a higher absolute temperture with a burn time of approx one minute less.

All the tests were conducted in the garage and may not transfer to the outdoors where wind will affect the results but I think it's something to look at again. For what it's worth a windshield made from kitchen foil folds up much smaller making it easier to store, is lighter if you only use 2 x layers and much much cheaper than the type of foil normally sold for making windshields. I'd like to conduct a further test which would help to confirm what I believe is happening. If I was to place the stove in a tin lid filled with water the stove should run cooler and thus burn longer. I'll probably try that in the next few days, 1 run with a kitchen foil shield set at 30mm Air-Gap and the stove as is and another with the stove cooled.

I also tested both windshields with my gas stove but the difference was only a few seconds which tends to support my theory that the problems Robin (Fenlander) has experienced is due to fuel evaporation/vapourisation. The shots below illustrate how small a kitchen foil windshield folds up.

Cyclone c/w 2 x Layer Kitchen Foil Windshield

Cyclone c/w 2 x Layer Kitchen Foil Windshield Folded

Thursday, 13 August 2009

Cyclone S-11 Remote Stove Modified

I started to make a few modification to the Cyclone to make it fit my pot better with a 100g Cartridge. It just about held the Coleman 100g cartridge but I normally use the slightly taller Primus 100g cartridges.

I wanted to trim the pot supports back a bit so that the stove sat a bit lower when stored in the pot and to make the burner head smaller in diameter. Ideally the diameter of the stove when folded would be the same diameter as a 225g gas cartridge so that it would fit pots sized to fit the bigger cartridges e.g 1.0L Eta Express Pot. Unfortunately the legs would need sorted as folded they're still too wide.

I cut the supports off in line with the leg pivot point and filed them down which was easy enough but still didn't allow me to get the Primus 100g cart in. What I then did was cut the pot supports away on the inside so the the cartridge would sit right down on the burner shroud. I can now get the stove with the cartridge nested on the burner into the Snow Peak pot.

I tried to file the legs down a bit adjacent to the pivot screw(there's a wee hump that sits out past the pot support when the legs are folded) but it wasn't enough to make a difference so I'll have to make 3 new legs if I want to further reduce the diameter.

I decided to remove the Piezo igniter as I always have a lighter and carry a Steel as back-up, I also removed the rubber foot pads and in a final desperate attempt to get the weight down I cut the regulator knob down to half the original length and countersunk drilled the end. Sad ;-)

Size wise the stove is fine but I'd still like to get it to fit an Eta Express sized pot and see if I can reduce the weight a bit more. I think if I had 3 Alpkit type Titanium V pegs I could sort something out but it would add to the cost significantly for very little actual benefit. I have a few spare Alloy V's though and they might fit the bill.

As it stands the stove is compact enough for the pot I had intended using and the weight is now down to 216g

Edit I had to try the alloy V pegs to see it I could make a set of legs, managed ok and it now fits the EtaExpress 1.0l pot but only just. The weight is now 198g without the Piezo Igniter.

Wednesday, 12 August 2009

New Stove, Cyclone S-11 Remote Cartridge.

I was looking for a stove for winter use and wanted to get a remote cartridge type so that I could use a wrap around windshield, possibly even a cone type, I also wanted a stove that had a pre-heat tube. The pot I intend to use it with is the larger of the 2 pots that make up the Snow Peak Compact Cookset. I had a look at what was available and looked at the Gelert Inferno, the MSR Windpro and the Optimus Stella. The Gelert has a pre-heater but is heavy at around 340g but reasonably priced at £20 (Winwood Outdoor), the Optimus is light at 250g and compact due to the folding burner head but doesn't have a pre-heater and is pretty expensive at £65 (Webtogs) and the MSR weighs 193g which is very light, has a pre-heater and costs £54 from Outdoorkit co uk.

I initially considered the Optimus but ruled it out when I saw the MSR but then I found the 'Cyclone' on ebay. With a claimed weight of 242g, a pre-heater and Piezo igniter and costing £12.95 including shipping I had to try it. It's an unusual burner design, I haven't seen anything like it on any other stove but it meant that it wasn't very compact. With a diameter of 125mm folded (due to the fixed pot supports) it was going to be a tight fit in the Snow Peak pot and wasn't going to leave room for even a 100g cartridge but I figured I could trim the supports back a bit.

The stove arrived today, shipping from Hong Kong took 10 days from purchase. The Stove comes with a heavy cordura type zipped case which weighs 38g, the stove itself I'm pleased to say was 239g just under the advertised weight. The burner is brass, the body a casting of some type and the legs probably stainless steel with push in rubber foot pads. There's a piezo igniter which works fine. The finish is fine with just a little flashing on the the body where the legs attach.

The downsides so far are that it isn't very compact due to the shape of the burner. It won't fit a Primus EtaExpress pot as the diameter is too great, it will fit the pot that I intended to use it with but there isn't room for the gas cartridge.

I can trim back the pot supports though and that should allow me to at least get a Coleman 100g cart into the pot together with the stove (Coleman 100g cartridges are flatter than Primus 100g cartridges) and maybe even a Primus 100g cart. Trimming back the pot support still won't allow it to fit the Primus EtaExpress 1.0L pot due to the shape of the legs when folded.

It's very stable when set up and capable of taking any pot likely to be placed on it, I had 33kg of training weights on it and it didn't budge!!

The proof of the pudding's in the eating so I gave it a quick test in the garage using the Snow Peak pot but with no windshield.

500ml tap water @ 16.6 deg c to 99.0 deg C = 2.39 mins x 10g gas.

I gave it a 2nd run turned right down, same pot etc = 99.0 deg C = 4.27 mins x 7g gas.

So seems like a good enough stove for the money (£12.95 inc shipping), ripe for modification too, the legs and fixing screws weigh 39g and could probably be replaced with something lighter, the pot supports can easily be trimmed back to make it more compact and the Piezo which weighs 12g can be removed. I have an idea for lighter legs/pot supports that would allow me to remove the integral pot supports completely which would reduce the weight and make the stove more compact.