Nick Ax

Thanks Fox, watched with great interest

I would say I have triple your fuel consumption and half of the heat output … perhaps not comparing apples with apples as much of my heat will be going into my mass

Half the (immediate) heat output is actually fine for me .. there is enough immediate heat for the room (which is well insulated)

Today I have noticed (although it might be my imagination) that the (concrete) floor is warming up …
Actually … no ..  I just measured it and it’s not my imagination .. under the carpet, within 1” of the stove it’s 20c … fully 5c warmer than under the same Carpet on the far side of the room

So I may have unwittingly created an underfloor heating system

I like your cook plate p, Are you saying that the hole is a necessary feature for the dishing deformation ?

One theory for the lacklustre performance of my stove is that the relatively non-conductive barrel is not ‘dumping’ enough heat to ‘drive’ the downdraft, perhaps cutting the top out of my  beautiful barrel and replacing it with a (much more thermally conductive) mild steel cook plate would help.

Thank you chaps .. time zones delay my reply

Converting from pipes to a bell isn’t on the cards - not for this year any way, The stove is indoors, and I don’t really trust my masonry skills to produce an airtight chamber, the pipes have a good airtight seal silicon gaskets at all joints, plus foil tape, plus cobbed in - I am comfortable they are gas tight.

I am trying to find a steel 55 gallon drum with a clip top (or two) , not too battered and within striking distance - but actually, for the ‘experiment’ anything would do

I will keep you all posted

Hi Scott

I’m a rational man, an engineer (albeit, majoring in software) .. so no I don’t expect magic … just a clean burn and a cool exhaust temperature, I totally get that you can’t do much better than that - the whole journey started for me (as I imagine it does for many) contemplating just how much heat was going up my chimney.

I would like to heat more space, for longer, with less fuel than my previous “efficient” Morso stove … I think that is probably  happening now, but my feeling is not by a factor of 3 (which I’d settle for), let alone a factor of 7

Mr Wheaton seems like a nice guy, and I don’t think he practices to deceive .. which leaves me thinking I am not quite there with my RMH..

Today we flipped the riser over, so the (minor) constriction is now at it’s top, not it’s bottom - intuitively (and possibly wrongly) I feel that might help.. create a little more pressure inside the riser

I also sealed some fairly obvious gaps between bricks .. 1mm or so at riser end of the burn tunnel

I fitted (as best I could) my remaining foot square of 1” ceramic fire blanket on the back side of the end wall of the burn tunnel, and made a pretty shoddy attempt at insulating the sides of the burn tunnel/riser base with perlite refractory mix - didn’t go well did NOT want to stick even to itself, let alone anything else.

So anyway .. it’s back together now and I’m burning it gently now to cook off some of the wetness before I crank it harder later.

Today is flat calm and it’s noticeably less rockety, I even had a puff or two of smoke into the room

More radical experiments, with bigger barrels and/or viewing windows and mild steel top plates await, I will keep you posted.

There is no insulation under the mass … that seemed pointless .. the floor IS extra mass n’est-ce pas?

(The stove is very deliberately at the heart of the house, away from the external walls)

The core was built on a 30mm foamed cement ‘fireplace construction’ board ..

https://shop.vitcas.com/vitcas-fireplace-construction-board.html?gad_source=1&gclid=Cj0KCQjwqdqvBhCPARIsANrmZhNGXTFFMlg3bkX1cs12FY0HYY7yr8DZFwueKiPYas_-wPHuK5OWddQaAl04EALw_wcB

I am lucky enough to have solid (poured concrete) floors in a 60’s bungalow, it perhaps doesn’t have the U-value of a 2” perlite bed, but it seemed like a good option

It would be quite difficult to swap it out now

Hi Scott, thanks for the reply, which I have read a few times

Removing the outer jacket saves 1.4mm .. like you say, not a lot, and it risks trashing my riser completely …
Flipping the riser, and removing the square ‘teeth’ formed when cutting the inner circle might be worth doing, theoretically that is the tightest point in the whole system

I plan to mix up some more perlite/waterglass/cement insulation and cake the burn tunnel and riser bottom where airflow will permit tomorrow

Bounce *might* be a thing .. there is a third clearout too … but I think it’s going to make sense to try a large barrel first -  I can make some plugs up from drywall I have handy to prove the point… possibly something more robust if it helps.

The thickness of the wall of my riser is 75mm (3 inches)

The barrel-riser gap is notionally (440-350) /2  = 45mm  .. it’s  actually not perfectly centered .. so might be 40 one side and 50 the other but the CSA is over 160% of the ‘system’ CSA (314.159 cm2)  (spot pi)

Maybe I’m just burning it wrong - if one is supposed to pack the firebox to 80% full with kiln dried hardwood, split to matchsticks, light the blue touch paper and retire to a safe distance, well - I’m not doing that

I’m burning a bright fire .. at times with white flames, with fuel filling 40-60% of the feed tube … that’s where I feel it ‘wants’ to be, but temps are low - around 170c in that scenario

3-4 burns a day sounds like a whole lot more than .6 cords of wood a season - perhaps my expectations are unreasonable

Honestly, I don’t care about absolute barrel temperatures.. lower would (in many ways) be better - but it’s my yardstick for ‘success’ in terms of clean burn

Also.. my mass is incomplete, uncovered and possibly still damp - so I am unconcerned about it falling to room temperature overnight … I’m sure the cat is enjoying  his new nighttime sauna - that is all solvable

If I can get another big barrel soon, with a removable lid I can drop it on and also potentially cut out a big window and borrow my old stoves glass so we can peer straight down the riser with it  fully burning, might even be able to get a cross section of the flow out of the top of the riser using the laser level beam through the glass - not sure it will tell us anything useful, but it would be fun.

Thanks fox - good morning

What is your analysis of this …



Is that a “roar” ?

I can control the ferocity as you say, by using smaller wood and/or choking with firebricks on the intake

I burned a moderate fire, 2 or 3 wrist sized logs at a time for about 3 hours last night, barrel temperatures were between 100 and 150c , there were always bright flames, and the now insulated feed tube got very hot

There is a minor choke point at the very bottom of the riser, where I cut the ‘polo’ which supported the inner former .. it’s a delicate operation but I might try and flip the riser over this morning .. possibly even removing its jacket

Insulating the sides of the firebox and end of the burn tunnel makes sense too, although the rate at which heat is lost through 4” of silica brick I would have thought was pretty low

Meanwhile I’m on the scrounge for a big barrel

Filled around the feed tube/tunnel with perlite

No miracles to report

Nichrome tumbleweed …  ‘glow plug’ igniter/sustainer/catalyst  idea …

Nope, no detectable difference .. still ‘hits a wall’ at 175c (actually the laser IR says more like 200c, but I tend to believe the bimetallic contact thermometer more .. or at least that’s the benchmark I’ve been working with)

Just going to burn it for a good few hours now, a couple of logs at a time and see what happens (and see if I can get some heat into this mass)

The interface between the round (8”) pipe and the ‘square’ 10” (I’m guessing) chimney is a simple register plate, cut from a washing machine side panel, the 8” pipe pokes 6” through the plate and points it the general direction of the square ‘funnel’ … there is a 45 degree ‘dog leg’ inside the chimney.. which I understand is normal.

Again, the seal is imperfect, pending a working stove, but there is no leakage there, which perhaps tells us something… I.e.  the chimney is sucking harder than the barrel is blowing

Is that wrong ?

The (existing, masonry) chimney is not insulated, no, never has been it’s always drawn well.