just wondering if anyone has gotten their fettling mits on one yet. Looks very interesting but expensive for now. Wonder if it will come down in price soon.
I'd not heard of it but having looked up the spec it looks pretty dreary and 'multi' fuel is stretching a point when it's for white gasoline or iso-butane fuels only, so dual fuel in my book. Kovea's website says the stove is "... designed to prime the fuel before it reaches the head, reducing noise". Like sipping wine rather than slurping it? John
Click on the additional info on there website and you get Additional Information Attribute Information Weight 31 kg Dimensions 29.7 x 26.6 x 9.7 cm At 31kg you might be right about the pony
I heard the Hydras have an adjustable choke for the multifuel function, I'm more than sure you can burn alcohol in them since they have a fixed jet size but the opening for the air intake is the variable factor. Worse case you just end up drilling the jet so its able to burn alcohol and have much higher output on the other fuels afterwards. ...But there's no way the Hydra weighs 32kg. I think they screwed that up and probably dropped the decimal in front of the 3.
I've gotten a Hydra to play with. Interesting stove, although I hardly think revolutionary. It is rather quiet compared to a roarer burner. It reminds me a bit of the Soto Muka, although not quite as sophisticated (in my opinion). One thing I noticed in field testing with petrol (Coleman fuel) is that the flames go yellow when ever there's a bit of a cross breeze. I got a little bit of sooting on my pot. Not horrible, but definitely some. Intrigued, I tried some night tests at home. I shot the following video: I apologize in advance for the shakiness of the video. I dropped my camera a few months ago when doing some rock scrambling. It fell several meters before impacting the rocks below. Oddly enough, the camera still turned on after the drop, but now the whole world is in shades of pink. Now, it won't even turn on. So I shot the video with my hand held phone. Hopefully though, it illustrates what I've been seeing. So, what do you suppose might be causing this? I've seen dozens and dozens of stoves over the years. All stoves are impacted by wind to one degree or another. This stove though has the flames go yellow. It's not quite the same as a priming flame, but similar. My working theory is that the fuel air mix gets impacted. There are ports on the bottom of the burner "bell". The vaporized fuel is injected from the side, which is an interesting configuration. If one looks at the right hand side off the photo above, one can see the fuel line attaching to the bottom of the generator. The fuel then flows up across and over the flame and then enters the burner bell from the left. One can see a sort of round attach point where the fuel enters the bell. The nipple/nozzle/jet is mounted at this point. The vaporized fuel has to mix with the air drawn in through the ports and then be distributed around the periphery of the burner evenly. This would seem to be no small trick to me. I *think* what's happening is that when there are various cross breezes, they cause whorls and discontinuities in the air flow. This in turns causes inconsistent air pressure and therefore inconsistent mixing as the air is drawn through the ports. Perhaps you might watch the video and render an opinion? I suppose it's not the end of the world to have a flame go yellow, but I have to admit that I'm a little disappointed. I have not seen this happening with other stoves. HJ
@hikin_jim It looks like your windscreen completely surrounds the burner. You were speculating about whorls and discontinuities. Is it possible that the wind across the top of the screen is preventing sufficient air reaching the base of the burner? Have you tried with a small gap at the bottom of the shielding, perhaps on the leeward side? regards John
@hikin_jim You've been absent too long Jim and I've missed your presence and posts here on CCS greatly. The Kovea? I'm puzzled as was John (@Jeopardy) as to how the breeze from the fan reached the stove with the windscreen set-up. I'm guessing through the gap the fuel hose pokes through. Is it right that there's an adjustable air intake? If so, I wonder what effect adjusting that might have on the phenomenon? Some early butane stoves (you'll remember, Jim, that I've made a point of collecting most examples!) have a Bunsen-burner type sleeve on the air inlet hole and they have a 'sweet spot' where the flame's on the cusp of being too rich - yellow - and at which it's very susceptible to drafts. John
Thank you, Wim. It's a good group, and it looks as though Ross has done it yet again, making a good site even better. HJ
Indeed @hikin_jim, but you invited feedback on your video evidence and Jeopardy and I have responded, which I'd assumed would lead to further discussion to get to the bottom of what you'd described.
John (Jeopardy that is), I had not considered that the problem might be too little air, although it might indeed be just that. I suppose that air across the top of the cylindrical windscreen could actually suck air away from the flame? Not sure. A test is most likely in order. It's raining today, so not a good night for a test, but perhaps some time later this week. HJ
Absolutely, John. I have been at work most of today, which doesn't really look favorably upon my stove and backpacking (hillwalking) habits. My boss is a stickler about such things. So, I responded quickly to Wim, but the others required, at least for someone with my limited brain capacity, a bit more thought. I am most grateful for suggestions as to what is happening. Now, as for your suggestion that perhaps the mix is very precise, I think that makes sense. Perhaps overpressure, caused by the fan acting more or less like a bellows, causes the fuel air mix to change and causes yellowing. Not sure there. My first guess would be that more air would cause better burning not worse. I suppose I could test it by running a tube to the intake ports and blowing into the tube. If the flame yellows, then perhaps we have our culprit. Thinking out loud here, I wonder if wind currents cause the vaporized fuel distribution/air mixing to be inconsistent, thus causing the yellowing I'm seeing? Maybe I'll shoot another video. HJ
Oh, and you asked about a variable choke. I don't see anything of that nature. I know the Brunton All Fuel had that sort of arrangement, but the Hydra doesn't appear to have any such. There's no mention of it in the instructions, and I can't see anything that moves on the burner bell -- unless I'm even more obtuse than usual. Presumably, they optimize the jet size for petrol and live with a somewhat reduced output on canister gas although there may be something more sophisticated going on with the ports on the bottom and the side jet for the fuel. HJ
@hikin_jim My profuse apologies Jim, it was such a treat to hear from you I reacted a touch impatiently to the opportunity engage in conversation after what seems far too long! Thanks for the additional information Jim. More to ponder, that's for sure, but you're the right guy to explore the conundrum. John
No worries, John. It's stopped raining here, so perhaps some more testing tonight after work. I'm going to try three things if I have time: 1. Leave some space on the leeward side under the windscreen. 2. Orient the hose opening in the windscreen away from the wind. 3. Blow directly into the ports by means of a tube. I'll report more later. HJ
All right, so, I promised some more tests. It's late, so I don't have time to write a lot, but I'll post the videos. Please comment as your stove intuition gives you insight. Best regards, HJ
@Jeopardy in the second video, above, I tried your suggestion. I raised the windscreen by about 1 cm. It didn't seem to make a difference. Still scratching my head a bit. In video three, I set the windscreen off too one side; one cannot even see the windscreen in frame in the video. Still yellow. @presscall I'm now suspecting that it is neither the richness nor the leanness of the mix that is the critical factor, although richness/leanness no doubt comes in to play. I'm really thinking that the combination of the pot and the windscreen -- note in video #3 that both pot and windscreen must be in place for the severe yellowing to occur (except when I manually forced air up the ports). What I suspect is that the Hydra is just really susceptible to air currents. It's more vulnerable than most due to the nature of its design. Now, how to rectify this yellowing? (which I find wholly unacceptable) Well, I suspect that it may actually be fairly simple. The Hydra is a fairly tall stove. Kovea's provided windscreen is of the same dimensions as the standard MSR windscreen, but the Hydra is a much taller stove. I suspect that all it may take is a taller windscreen. When one has a stove that is sensitive to wind, then one needs to take more steps than usual to shield it, at least that's my thinking. Recall that my 8" fan (about 20 cm diameter) sits up on it's base about 5cm. The windscreen is maybe 9 cm tall. With a fan of this configuration, a lot of wind is going to be striking above the upper edge of the windscreen. The pot extends well beyond the upper edge of the wind screen. When wind hits the side wall of the pot, some of it (apparently) is forced down between the pot and the screen, causing irregular wind currents within the windscreen, playing hob with the fuel air mix, and thus causing yellowing. I think. If I get time in the next couple of evenings, I'll try a test with one of those stiff folding panel windscreens. I have a couple that are about 30 cm tall. If that's not enough shielding, then, good night, the stove is simply a dud, lab wonderful, but field impractical. I hope that the test is successful. Wish me luck. Best regards, HJ
@hikin_jim Meticulous analysis Jim. I hope the taller windscreen works and that the stove's not a dud, though it's on the way to being so if it's so draught-sensitive. John
Thanks Jim, Have you got the wherewithal to try the stove on (ISO)butane? Just wondering if the single sized jet is actually (too much of) a compromise and it might run better on canister gas. When you blew air into the ports at the bottom it might have disturbed the vortex mixing that has been identified in the past as the reason that the jet to spreader plate difference is so critical for efficient burning in the like of the 96 and 123. Does it do the same at all flame levels? Regards John
