Matt Walker tiny cookstove build in Portugal

Jay Angler wrote:I had a possibly crazy thought - if you aren't using the oven right now, could you put slabs of marble with gaps for air flow in the oven section to add a little extra thermal mass until you are ready to build the bench? I'm not sure what the cubage is in the oven, so how much difference it would make?

I had a different but similar thought. If I remember correctly, and it's been a while so I might be mixing them up with something else, the Walker stoves are built such that different areas of the cooktop are different temperatures. If so, perhaps you could put a huge pot of water (large canning or stock pot maybe?) with a lid on one of the cooler burners as additional mass. Basically, the idea would be to heat it up, but not to a rolling boil. Similar thing could probably be done with the oven. My thought it that when you don't need it you can use the water and store the pots. Heck, if there's a spot that's the right temperature you might even be able to make something that takes long simmering, like bone broth, some days.

Thyri Gullinvargr wrote:...the Walker stoves are built such that different areas of the cooktop are different temperatures. If so, perhaps you could put a huge pot of water (large canning or stock pot maybe?) with a lid on one of the cooler burners as additional mass. ... Heck, if there's a spot that's the right temperature you might even be able to make something that takes long simmering, like bone broth, some days.

That is exactly how the walker cooktop works, and when the downstairs area is ready to use as a kitchen we will indeed be doing that kind of thing. Hopefully next winter the bench will be in place and enough work done down there that we can experiment and report. I'm looking forward to it!  

But for now I'd like to introduce you all to the puxmi-pulyu!

That's pronounced push-me-pull-you in case you hadn't worked it out. Also puxe is portuguese for pull, which as you can imagine causes endless amusement watching the Ingleses failing to open doors by pushing on ones which are clearly labelled puxe.

This is the tool Austin made for pushing the hot coals to the back of the firebox prior to reloading, and also for pulling the cold ashes out the next day to put on the garden.



This is the business end...



Once the fire is reduced to hot coals, if we want another burn we shove them to the back of the firebox (near the secondary air feed) and lay more sticks on top. They will then burn nice and hot from the back to the front. If all the wood burns at once there is a bit of danger of overburn which is kinda wasteful as even this wondrous device can't handle all that heat at once without letting too much escape up the chimney. The bricks need time to absorb the heat, and the more it absorbs, the longer it can keep giving it out again.



The next morning we can pull all those ashes out of the way. There were a couple of days' worth in there cos I didn't do it yesterday. Ooops...

I might chuck those little unburned bits back in too. Waste not want not and all that!

That thing sticking up at the back is the tube that forms the secondary air feed.



The ashes pull out quite nicely with this little contraption. As far as the start of the air tube anyway...



There's still ash left beyond the start of the secondary air feed tube, but not to worry - turn the puxmi-pulyu on its side and it can fit in the gaps.



There. Ash from either side of the feed tube has been pulled forward a bit and can be pulled right out.



Photo to show how the puxmi-pulyu fits, just in case it wasn't clear enough last time.

Burra Maluca wrote:

Thyri Gullinvargr wrote:...the Walker stoves are built such that different areas of the cooktop are different temperatures. If so, perhaps you could put a huge pot of water (large canning or stock pot maybe?) with a lid on one of the cooler burners as additional mass. ... Heck, if there's a spot that's the right temperature you might even be able to make something that takes long simmering, like bone broth, some days.

That is exactly how the walker cooktop works, and when the downstairs area is ready to use as a kitchen we will indeed be doing that kind of thing. Hopefully next winter the bench will be in place and enough work done down there that we can experiment and report. I'm looking forward to it!  

Burra, I was thinking more in terms of doing this before you're doing more generic cooking as a way to increase mass quickly now, but in a way that is easy to "put away" later once you have the bench. 😉

Thyri Gullinvargr wrote:
Burra, I was thinking more in terms of doing this before you're doing more generic cooking as a way to increase mass quickly now, but in a way that is easy to "put away" later once you have the bench. 😉

I don't have the energy for any more experiments at the moment, especially before the downstairs area is usable. When I am able to be down there for longer periods of time with somewhere comfortable to rest up while I'm down there I should be able to do more. But for now I'm totally up to capacity!

Even my little dragons have noticed I don't have the energy to go outside much and have bought me a little vase which they are putting flowers from the garden in to keep me in touch with what's happening outside of my room...

Burra Maluca wrote:
I don't have the energy for any more experiments at the moment, especially before the downstairs area is usable. When I am able to be down there for longer periods of time with somewhere comfortable to rest up while I'm down there I should be able to do more. But for now I'm totally up to capacity!

Fair enough. 🙂

Burra Maluca wrote:
Even my little dragons have noticed I don't have the energy to go outside much and have bought me a little vase which they are putting flowers from the garden in to keep me in touch with what's happening outside of my room...

Lucky you. It's been below 0° F (-18° C) where I'm at lately. Flowers are but a memory at the moment. 🥶

Well yesterday was the first burn of the season.  I did prime the flue just in case, and I lit it with a regular lighter 'cos I'd mislaid the gas blowlamp.  But she did us proud and fired right up and burned very nicely.  As yet still no bench, that's lined up for building this winter with luck.

Today, didn't bother priming just bypass open and off she went.  Feels like I can shut the bypass sooner but that may just be the wood is nice and dry, so it gets going fast. Anyway, the stove is burning nicely.  It's not all that cold here, mind, but recent rain made the house damp downstairs.  

Great news, Austin!
I love the fall when the stoves get lit.
With your adjustments last season, dry wood, dry mortar, and of course, holding your tongue just right... She leaped into life!
Congratulations!
Perhaps this winter, after building benches, you will meet the requirements to become a full-fledged Rocket Scientist...
I will submit your name to the committee.
Just to let you know, your dragons do have representation there.
You're off to a great start!
Good Job!

Time for a stove update I reckon.  She's been running well this year, much easier lighting than last year.  I did have an issue recently with some of the firebricks in the core either getting loose (see another post about clay-sand mortar) or in a couple of cases breaking.  

Now, the core gets pretty hot.  However, I would expect fire bricks to cope with that. A bit of the clay mortar that was filling a gap fell out and it's semi-fired the clay so it's almost like stone.

Anyway, lifted the cooktop off and removed enough of the core top to get at the broken/displaced brick which was the top rear one in the firebox which defines the far end of the flue path.  That brick turned out to be in about 3 pieces.  As I didn't have a spare one that size to hand, I glued it back together with "massa refrataria" which is 1500°C-proof stuff in a tube, used to join chimneys onto stoves etc. and glued it back into place with the same.  I also found a couple other cracked bricks to fix while I was in there.  Mostly, though, it's all stayed together.

Next job is to build the bench, when I have time, then we can burn it more than 3 firebox-loads at a time and harvest some more heat.  Without the bench, by the end of the 3rd firebox of wood there's what I consider an unacceptable amount of heat going up the chimney.  3 fireboxes of good wood burnt leads to the whole stove body being nicely hot, so tend to do 2 or 3, then leave it for a few hours so the heat gets used up some, and then burn it again later in the day.

Do you think the broken brick is due to the supreme heat in the fire path Austin, or maybe down to a faulty brick?

Ah well that I can't say.  Since the whole core is made from the same bricks, and only 1 or 2 have issues, I'm gonna optimistically assume that it was a bad brick.  The one that broke is in quite a hot place, but so are quite a few others which seem to be ok.

In a recent podcast Paul mentioned his quest to shut down rocket stoves when you're done burning, so as to avoid the possibility of losing heat up the vertical exhaust.  

This got me to thinking about our Matt Walker stove.  I'd kind of assumed that without the fire driving it, the exhaust would fairly rapidly cool (after all most of it is outside, although insulated) enough to stop it drawing.  Recently however, on checking it some time after the fire was out, the stove was all nice and toasty warm and emitting heat into the room as it should, but feeling the base¹ of the exhaust it was still distinctly warm - and worse, there was a perceptible draft entering the air holes in the firebox door.  Clearly there was still some convection going on and heat was going up the chimney!

So, how to solve that?  I could make a cover for the air holes in the door which could be deployed once the fire was out to prevent air from entering.  But that seems a bit like work, and besides I kinda like the door as it is, aesthetically - a draft blocker would need some kind of slots to fit in which would detract from the appearance.

Now, today I had the fire on in the morning as it's a bit cold and damp.  I did 2 batches (initial lighting and one refill) and then let it die down, as without the bench I still haven't built it's prone to start wasting heat up the exhaust if you burn it 3 times in a row.  Once the fire was down to just a couple of small live embers I experimented with a handy offcut of plastic wrapping, and sure enough there was enough draft happening to suck that onto the air holes in the fire door.

At this point I had an Idea!

At the bottom of the stove is a black "oven" space although with the burning regime I've been doing it never gets all that hot.  I'd already noted that opening the door to that even slightly kills off the draft for the fire quite dramatically.  So, with the fire mostly out, I opened that door.  Immediately, the draft into the firebox ceased, and within a minute or so the base of the exhaust was significantly cooler to the touch.  Looks like I may have hit on a solution for stalling the flue so as to stop heat going up it after the fire is out.  Opening that door can only realistically let heat out into the room, which is no issue.  Unless somehow the exhaust were to reverse and suck cool air back down from outside, but I feel that's unlikely.

Later on I'll experiment with opening the door for some minutes and see what the effects are.  It might be that it can simply be left ajar until next time the stove is lit, or it might need to be shut again for some as-yet unknown reason.  


¹ the first bit off the stove isn't insulated, as it has no need to be and also that allows you easily to check if the flue is getting warm enough when lighting

Update on the previous post:

Last night when the fire was pretty much dead, I did some more messin' with the oven door.  

Opening the door a couple of inches made the exhaust, which was quite warm, cool down within a few minutes.  If I shut the door again, it started to warm up again.  

Of note is that I want to check the bypass to make sure it's shutting adequately; if it isn't then heat could leak out from under the cooktop into the exhaust.  If I'd been on the ball when I was fixing the broken firebrick issue recently, I could've checked it then

As may be, having the oven door opened a bit caused the flue to stay cool so I left it like that, and before I went to bed I checked it again: the flue was quite cold and there seemed to be a slight cold airflow entering the oven and travelling across the bottom of the stove into the exhaust.  Cold air doing that can't really have much effect on the heat output, I don't think, since the hot part of the stove is all above that level.  

This morning when I went down and checked it, the cooktop was still a bit warm to the touch which I regard as a good sign.  As to how much difference this makes overall, that would hard to test - but any obvious heat going out of the exhaust once the fire is out can't be helpful.

ola


WHAT can we do to make an enterprice for buildig RSMH in north Portugal. I want to buy the first one but I am not skilled enough to build it on my own. I live in Mondim de Basto, north Portugal.

I think this type of heating in more than just  an idea, it is saving money and helping the climate.

Please react to L}eo OOrd 962782006 or email lejooke@hotmail.

Thanks

leo oord wrote:ola
I am not skilled enough to build it on my own. I live in Mondim de Basto, north Portugal.

Maybe you can learn the skills yourself. Have you ever laid bricks? Maybe start with a bit of wall somewhere.

If you start your own thread here on permies you can post your experiences there and we can all join in with advice and talk you through it.

Mondim de Basto is too far away for us to be of any practical help to you, and the skills needed aren't so great that you couldn't learn them yourself if you are physically capable.

Try to follow previous builds here on Permies, try building a rocket stove in your yard, do some reading.  It might be possible.  

Is Braga close by for you? A full service Leroy is there for materials,  as a last resort, but probably better prices near your house.  Good luck on your  efforts.  

Finally, we have cut those bits of granite, giving three pieces the same size to lay next to each other to form the top of the heated bench.

I think we might actually have the bench itself before winter!

Note also duck-patched T-shirt, grey water pipe to take the laundry water to the fig tree, old marble kitchen sink also waiting to be installed...

hoping you get a bum warmer!

He's laying out the basic shape of the bench, at long last...



Another smallish load of used blue insulation sheets showed up a couple of weeks ago so we'll be using some to insulate between the bench wall and the outside wall of the house. The two hollow clay bricks are marking out the width of the bench having cut the scrounged granite to size. It will be wide enough to sleep on and fits the old caravan mattress I also managed to scrounge. The bricks were full price though, because even I can't scrounge everything...

Laying it out also involved removing the two bricks that were blocking the outlet from the stove to the bench. They were put there so that the rocket mass heater ran nicely before the bench was made. Which means that he's now kinda committed to getting it finished else I be moaning if it turns cold and we can't light it up.

Today he's figuring out how to connect the back of the RMH, in particular the outlets, to the mass and back out again to the chimney.

It seems to involve long, thin, weird, hollow brick things that He scavenged from somewhere and has been busy cutting to size so he can create ducts.



My son seems to have run off with the trowel though so sticking the bricks in place is going to have to wait until we either get it back or find another one.

Great news for your Portugal Homestead,  perfect timing before those cold rains come in,   that bench is so warm I can feel it here from 5 time zones away!  

Burra Maluca wrote: It seems to involve long, thin, weird, hollow brick things that He scavenged from somewhere and has been busy cutting to size so he can create ducts.

My son seems to have run off with the trowel though so sticking the bricks in place is going to have to wait until we either get it back or find another one.

Those hollow bricks sound intriguing. Scavenged anything has less embodied energy than having to buy new! I hope it works.

Tools, magical disappearing tools... I know that song! Good luck at retrieving your trowel! If he happens to have my 11/32 socket drive that fits my 1/4" ratchet driver, I'd like it back, however, I'm highly suspicious that he's not the one that relocated it. My driver handle itself was missing for over a year. I looked everywhere. "Someone" had left it in a bucket with other tools and had totally forgotten why it was even there.

Jay Angler wrote:Tools, magical disappearing tools... I know that song! Good luck at retrieving your trowel! If he happens to have my 11/32 socket drive that fits my 1/4" ratchet driver, I'd like it back, however, I'm highly suspicious that he's not the one that relocated it. My driver handle itself was missing for over a year. I looked everywhere. "Someone" had left it in a bucket with other tools and had totally forgotten why it was even there.

I think it's a safe bet that the Socket Squirrel came to snatch your prized 10mm socket but  the 11/32 was the closest he could find...

Jay Angler wrote: If he happens to have my 11/32 socket drive that fits my 1/4" ratchet driver, I'd like it back, however, I'm highly suspicious that he's not the one that relocated it.  

Highly unlikely that he has it, for several reasons. Apart from that pond thing between us, he's a lad of his times and I suspect that all his sockets are in mm, not archaic imperial, to match the materials and fittings he works with here. Austin has a good selection of both sorts though!

I did however find a guy on facebook called Tenmil Sokhet who I was terribly tempted to send a friend request to, with a comment about 'Where have you been all my life - I've been searching for you!" but I managed to control myself. 11/32 would be about 9mm though, so still no use to you. Hope you find what you're looking for!

Burra Maluca wrote: ... Apart from that pond thing between us, he's a lad of his times and I suspect that all his sockets are in mm, not archaic imperial, to match the materials and fittings he works with here. Austin has a good selection of both sorts though! ...

Canada is officially bilingual. Apparently that includes the need for complete sets of both metric and imperial - and the first case I looked in when I couldn't find my 11/32, was, of course, metric. 11/32 is a weird size to begin with, but we've got a lot of stainless steel hardware in that size and being in a soppy wet climate, stainless is worth the cost.  I'll go hunting today while there's better light in the tool area.  

Looking forward to more pictures and updates on your bum warmer!

Jay Angler wrote:Canada is officially bilingual. Apparently that includes the need for complete sets of both metric and imperial

Any tools of mine, except sewing tools, seem to get gradually absorbed into one or other of the boys' tool supplies. So I've taken precautions.

This is Linguista! As you can see, she's completely bilingual...



She's sufficiently unlike any 'real' tools that they know not to pocket her if they pick her up. I also bought a cute little boxed set of pink tools, just to make sure I always had access to very basic stuff, like a hammer. Because pretty much any tool could be anywhere at either property or missing in action in vehicles or at job sites anywhere miles and miles away.



My son is currently away for a week with his van full of tools, having taken basic living stuff like a mattress and the lovable loo with him, to save all the driving backwards and forwards. But he knows that if a tool is pink he isn't to touch it. He does, however, paint pink splodges on all of his own tools to stop his workmates accidentally taking them home with them though. It seems to work.

My late husband, of course, also had a set of whitworth stuff. There may even be a few pieces still around but goodness knows where.

Hi Burra,

My mom got me a very similar pink tool set after a frustrating day of not having or being able to find the tools that I needed. It's really handy and everyone knows never to take away the pink tools!

I seem to recall the 'official' tool set in the Fisher Price house is also one of those pink jobbers (isn't Barbie made by Mattel? I guess Mattel does own Fisher-Price...).

Is this some sort of Permaculture secret rite or something?

Coydon Wallham wrote:Is this some sort of Permaculture secret rite or something?

Not that I'm aware of.  Though I am beginning to suspect we may have stumbled on some form of behavioural convergent evolution. It seems to be the same sort of need being filled - a small, easily distinguishable tool box that has to stay where it's put, not end up spread through the scenery. Like a very basic first aid kit that you might keep in the car.

It it a known thing? Do other permies do it? Or only the ones that hang out on the rocket mass heater threads? Is pink the only colour that works for this purpose?

I think brainstorming and note-comparing may have to happen.,,

Tools I have concerns about, get the "nail polish" treatment. I use that convenient little brush in the jar to paint my initials on some part of the tool where it's not too likely to wear off. One jar lasts a long time. It also does a fair job of keeping a nut in place if you don't have a jam nut or nylock to use.  

I actually have one good pair of scissors which have my name engraved on them using a hand engraver - nothing fancy. At one point Hubby tried to insist they were his (he does have a near identical, but not quite so nice pair), until I suggested he look at the name on them.

However, in general I agree with the concept. Having at least one set of basic tools with the firm rule that all the bits stay together, and the box lives in a specific spot, is a very important method of keeping one's blood pressure at a healthy level!

Of course the tool situation here is actually more complicated than it first appears, because I inherited my husband's tool collection. I took the decision to keep them as mine rather than just give them all to my son so that I could use them any time I wanted and to stop him lending them out to people.

Things did get a bit amusing when I was first with Austin though. I'd gone back to the UK to help him look after his dad while the farm was sold, then we ended in a kind of limbo and house-sitting for someone while we waited out the 90 days for Rock (the Welsh sheepdog, because the Portuguese police had insisted I get a dog and send to England for a new man so just to keep them happy Austin's sister gave me one of her young sheepdogs) 's rabies vaccination to kick in before travelling. He offered to take me on his version of a date, which was to a shopping complex which included a giant tool shop. Then while he was in the tool shop he admitted that he intended to splash out on a really nice chop saw, the sort that has a slidey thing and you can set angles and was fitted on a sturdy table. The shop assistant was looking very hopeful of making a nice commission that day, until I pipe up "I already got one!" Austin didn't really believe me, then said that it was likely to be old and worn out but I assured him that it was only about a year old and had done virtually nothing. He still wasn't convinced so I messaged my son, who was back in Portugal farm sitting for me, and sent him to take photos and the poor salesman watched in disbelief as Austin confirmed that yes, I did indeed already have exactly what he was looking for.

I consider those tools to be 'family tools' though. Austin turned up with a collection of his own tools, though the bigger stuff like the big metal-working lathe got sold off. And since then my son has been busy building up his own collection. Which I think entitles me to have my own little mini collection. In pink. Even if I do get the boys to do any decent-sized job around the place.

But then, all those tools get used to build things like willow feeders and rocket mass heaters for me, so I get the best of both worlds really!

before I put the lid on it, here's a picture of the adaptation at the back of the stove to connect to the as-yet-virtual bench.  Space considerations meant that this space is a bit tight.  On the right is the inlet* for hot air from the stove, and on the left the outlet to the base of the flue.  The outlet part looks constricted but actually it's not, the ports in the stove body are about 8x6" (20x15 cm approx) and that outlet at the narrowest part is about 16x3" so in fact it's the same size.  Since the chimney is 6" / 15cm inside diameter anyway, none of this restricts it excessively.  



Yet to decide if I divide the bench lengthwise until part way along so that the warm/hot gases from the stove are constrained to go along the bench further before they can go off down the exit.  Probably not needed, but also, not a great deal of work to achieve, I just need to extend that central divider some.  The bench will be a strat chamber not a mass, at least to begin with.

* if you're the bench, it's the inlet...

The first layer of bricks is down for the bench!

Well, most of them anyway...



Nobly helped by my favourite bostik bucket.

I'm rather hoping that things will pick up speed a bit now, before either of us feel the need to light it up. And I'm starting to dream of having a nice warm place to air damp clothes off if we have six solid weeks of rain. Or a cozy place to rest and put my feet up without having to haul my butt upstairs.

A few more bricks are down!



And he seems to have figured out the junction to the exit...