[Stoves] DIY camping TLUD with walnut shell fuel

[Mangolazi]

I've always wondered what causes that towering inferno to occur. I've had this happen a few times with a tiny tin can stove and with a big paint can biochar burner. I try to avoid it so my pots don't get damaged. 

Is it too much primary air? Lots of wood gas from certain fuels? Fast gas flow from a tall chimney? 

Looking at a bunch of papers on TLUDs, it seems there's a trade off between temperature and burn time. You can throttle primary air to get a long burn time but temperatures may not get high enough to burn cleanly, whereas a more complete and hotter burn means the fuel is turned to char much faster. 

On June 15, 2016 6:23:02 AM GMT+08:00, neiltm at uwclub.net wrote:
>On 14 Jun 2016 at 16:17, Mangolazi wrote:
>
>> Hi Neil, thanks for the recommendations. I think I'll get one of
>> those cheap Chinese stoves to see what they can do. Most of them
>> look the same so I assume they're all from the same factory. 
>
>They do seem to be all the same.  The main difference between them is
>in 
>which type of pot support/concentrator top you choose.  There are the 
>fold out sort, with a gap between top of concentrator and pot of 2cm,
>and
>the fixed higher rise top (4.5cm) with open side that permits easier
>fuel
>feeding without removing the pot.  I have both, and now prefer the
>latter
>as the increased height between secondary air holes and pot makes for a
>
>slightly cleaner burn, and interferes less with the draught.  It has 
>closer support points though, although I have yet to suffer instability
>
>from that.  All the parts between the two stoves, bought years apart,
>are
>interchangeable.
>
>> They're
>> also rather squat - more power, less run time? 
>> 
>
>They are squat, but run time really depends on the fuel.  It is about
>10 
>mins of towering inferno run as a TLUD with dry wood, but double that
>and
>up to half an hour with moister/denser/larger fuel, and I've read an
>hour
>with pellets, but haven't tried that.
>
>Depth of fuel chamber to centre of secondary holes is 85mm.  Internal 
>diameter is 110mm (122mm external).  Its a decent practical fuel
>chamber 
>size, making fuel preparation in the wild easier.  With the high rise I
>
>imagine it is very similar to the Bush Buddy, but that is smaller over 
>all.
>
>They are not sold as TLUD stoves but as wood gas camping stoves, but
>the 
>architecture is the same as a TLUD and runs very well in that mode. The
>
>secondary air gap behind the holes is only 8mm, but the secondary air 
>flow is certainly not lacking. 
>
>They are very easy to use by say holding a match under an upside down
>fir
>cone in the bottom of the stove, and then placing more fuel on top - 
>cones or twigs.  You can simply build a smaller fire from the bottom 
>that, or in any other way, if you want less heat.  It is possible to
>lose
>the flame as Kirk describes when very low, but that usually only
>happens 
>in these stoves from increasingly ash congested primary air which a 
>stirring stick can very quickly remedy bringing the stove back to 
>vigorous life, or just tickling along as you choose.  His suggestion of
>
>lower pilot holes for enhanced turn down is one I would definitely 
>experiment with if making new tin can stoves though.  At the moment I
>am 
>enjoying my fuelling learning curve to see how good my heat control can
>
>become, and so far the experience has been so encouraging as to cause
>me 
>to stop taking my two Reed fan stoves on camping trips, relying now 
>entirely on the two chinese stoves (and a kelly kettle) because I know 
>they will be easier with more difficult fuel.  Incidentally 3 days ago,
>
>the kelly kettle boiled 2 litres of water in two batches from wood that
>
>was dripping wet, once I had made a good start from my cache of dry. 
>It 
>surprised me.  I lost the wet bark off some thicker branches/twigs I 
>split with the aid of a pair of secateurs to reach the dryer heart
>wood, 
>and burnt these in conjunction with thin pine brash just as it was.  It
>
>was a strong and fairly smokeless burn too.  No starter additives of
>any 
>sort, not even paper which I never use. Techniques for kelly kettles
>are 
>a whole other fascinating and rewarding subject, and I even use the
>kelly
>kettle on the chinese stove base for the coffee and washing up water 
>after cooking a meal.  That is just too easy!  
>
>> The main reason I want to throttle primary air on tiny tincanium
>> stoves is to allow some turndown for simmering. Right now, I have to
>> boil something first on wood gas flames and then simmer on the
>> leftover char. It would be nice to get a long flame burn time from a
>> small can. 
>> 
>
>All I can do is repeat that you can achieve this with trial and error
>by 
>controlling the fuelling with these stoves, and from the sound of it 
>yours, from the similar characteristics you describe.  You have already
>
>reported the difference in burn time and heat output from different
>fuels
>- you could try exploiting these differences further to see if it gives
>
>you the heat you want when you want it, the way I seem to be
>increasingly
>managing, and especially in the wild where immediately found wood might
>
>be damp or even dripping wet, whereas I also maintain a bag full of dry
>
>starter, and this you can mix to suit . Its a learning curve, just as 
>cooking on an open fire is, and would be no less with a turn down lever
>
>controlling primary air, just a different set of factors to understand 
>and master. The first time I used the chinese stove as a TLUD in the 
>Pyrenees where the fuel was very dry, the flame was about the two feet 
>high and the pan I was frying in caught fire, but I soon worked out
>ways 
>to obtain a more useable heat, but even that meal wasn't spoiled.  You 
>can go from a robust TLUD boiling heat to a gentler simmer still on 
>feeding in wood, but things you have to watch out for are approaching
>the
>end of a potential fools paradise of thinking that you have really easy
>
>control, (which you do for a while, and maybe long enough), when in
>fact 
>this is masked by the consumption of all the char from TLUD mode which
>is
>about to leave you with no fire base to add fuel to if you're not 
>careful.  This is where just enough riddling can keep good control over
>a
>simmer heat potentially indefinitely, as can poorer or damper wood. 
>The 
>char stage is really also quite vigorous with all that primary air, 
>giving off a lovely blue flame to begin with, but it will soon be all 
>gone without refuelling, but still lasts long enough to make a slice of
>
>toast or maybe two.
>
>> I'm still amazed how so much heat can come from a tiny amount of
>> fuel, especially compared to a campfire. Learned that the hard way,
>> grabbing a not-quite-cooled can after a test run... 
>> 
>
>I agree it does seem amazing, and that as you say such a 'squat' stove,
>
>the pot standing a mere 6 inches off the ground can have such a fierce
>ND
>heat under it, and just how much heat there is in so little fuel.  When
>I
>was a boy scout at camp, each patrol used to make several forays with a
>
>treck cart and felling axes to bring 'enough' wood back to cook for
>about
>8.  Issued with these stoves, one cart load would probably have served 
>all 6 patrols for the duration!  
>
>Best wishes,   Neil Taylor
>
>
>
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