Peter van den Berg

Cedric Noussan wrote:
thanks for the detailed answer, i really appreciate it!
so since the chimney is very encrusted i will opt for a 19cm system
also since one part is not insulated and it is not possible to do so, how should i count this in the isa calculations? the absorbent surface divided by 2?

Hard to say, normally a chimney isn't part of the calculation.

Mark Miner wrote:Has an off-center throat been explored?

Since you asked, as a matter of fact, it has been. It turned out that the off-center venturi was only as effective as the centred one when the chimney draw was really strong, wind force at least Bft 7 with gusts. For this reason, I ditched that sideline.

Mark Miner wrote:Is notching the outer bell to embed the chimney a dumb idea?

In my book, it is. Please, try very hard to avoid compromises, otherwise you'll get problems later. Just my two cents.
It would be much more clear to the reader to call every part of the heater by its accepted name. There's a firebox, riser, port, floor channel, bell wall, top gap and whatnot.

Brandon Hands wrote:Very cool. I was thinking of designing a similar thing. I was considering the idea of using 85 gallon "salvage drums" which have an inner diameter of 26 inches (66cm). (Repainted with a high temp wood stove paint)
I hadn't gotten far enough to solve a method for connecting them together once stacked, but there might be a kind of band that could join them.

The salvage drums are open top types, with a separate lid and clamp. The bottom rims are nuch smaller, there's a good chance two of those will fit in a standard clamp. For this goal, you have to cut out the bottoms of the barrels. Be careful not to cut the bottom out completely, leave a ring of around one inch. Doing it this way, the stability of the round shape will be maintanted.

In order to discuss this further, it would be best to start a new topic about your ideas.

Brandon Hands wrote:You may consider one of those blower fans that are commonly used to dry carpet after a flood. The impeller design allows them to work with high static pressure. Letting it force air though should dry it much faster and reduce possible corrosion

Or simply, fire the heater repeatedly. The inside of the steel panels aren't rust protected in this prototype. But for a business building this type it would be a good thing to have it all powder coated, also the inside.

Brandon Hands wrote:So are you going to start selling this flat pack sheet metal kit? Is it already for sale?

It won't be me, going to sell this flat pack kit. And it isn't for sale at the moment by a third party. It is meant as an open source design, anybody who want to, can take the design and make a business out of it. I did this just to satisfy my own curiosity, could this be done in a reasonable way and with cheap mass? Up til now, it seems to be affirmative.

Brandon Hands wrote:Also, have you experimented with storing heat in water?

No, I have not, my interest lies in the combustion side of things, almost exclusively. In order to make it possible to measure the results, I had to look around for a way to cool down the exhaust gases. A bell system turned out to be the simplest and most effective way. For quite some time, I used 55 gallon barrels to this end. The question kept coming in my head: what is the possibility to make a real mass heater out of this? The barrels proved to be too small for this goal, so I did my own design, just for the fun of it.

After a tiring but successful annual meeting of the AFPMA, the association of French mass stove builders, see https://permies.com/t/281596/Mass-bench-fed-modified-sidewinder, I am starting to recover a bit. The octagonal pepper shaker doesn't seem to be getting any drier now, so today the lid was put back on. To prevent condensation on the inside of the lid, a ring of 8 mm (0.315") holes was drilled in it, 14 in total. I am assuming this is sufficient to allow any moisture to escape. The whole thing now really looks like an oversized pepper shaker. 8-)



The lid is loose, although it is a tight fit so it won't be blown off. I'm not going to use pop rivets anymore, it's not worth the effort and it (the lid) will no longer be gas-tight. Today I also stoked it up again with an estimated 5 kg (11 lbs) of softwood, in two batches. Everything gets really hot, of course less so at the bottom. The hottest above the door, up to 115 ºC (239 ºF). Just within the possibilities of regular powder coating, which is cured at 200 ºC (392 ºF). Combustion was very calm and even, only at the last moment could the bypass be closed completely.

A few weeks ago I already tried how warm starting went with the bypass closed. Not bad, I must say. It starts up calmly and as far as I can see there is not a whisp of smoke to be seen. The temperature inside the workshop was raised from 20 ºC (68 ºF) to 24 ºC (75 ºF) in about four hours today. Firing was over in an hour and a half, the outside was already starting to get quite warm at that point in time.
My workshop is of course part of a passive house so heating up is quite easy. According to the last full test run, started from cold, the efficiency is 92% on average, just as high as a large batch rocket mass heater.
In all, I'd think it's safe to call it a succes!

I won't do any more test runs or configuration changes, summer is already upon us now.

After firing a few times in as many days, I still didn't feel like this was the final configuration. It took too long to my taste before the bypass could be closed. Those concrete paving bricks can absorb a lot of heat!
So: on the morning of May 3rd, I lifted the lid again. On the inside of the lid, a lot of condensation moist and rust stains, not good. After walking back and forth between the drawings on my computer monitor and the stove itself, I decided to remove the brick ceiling again, plus the ring of 8 bricks that had been placed there earlier. I did that late Saturday afternoon, it was a bit disappointing, it was all much more just a solid mass than I had thought it would be.

And then to build the whole thing back in on Sunday morning, with the ceiling placed 8 cm (3.15") lower. This made the bell a bit smaller and hopefully it would took a bit less time to warm up.
This was the beginning.



Everything went in quite easily, after all, this was not a renovation but a re-renovation instead.



Unfortunately I didn't have enough 1/2" superwool left to do the closing with, so everything was stuffed all around in clay/sand mortar to make it as airtight as I could. With pieces and fragments of leftover refractory bricks and kiln plates in it wherever there was ample room to fit it in.



As you can see, after this re-renovation there was now a space of +/- 10 cm (4") left, which space I filled in with another layer without mortar this time, using the same clinker bricks.



The accumulating mass increased by another 18 bricks compared to the situation without a brick ceiling at all. The total weight wasn't really clear at the time, the concrete of the bricks still contained quite a lot of water according to my construction moisture meter. I now have 10 bricks on their short side on the workbench and I check the moisture content every now and then. That's slowly decreasing, time will tell to what extent the bricks want to dry out. The first firings were very promising, no smoke leakage at all and the exhaust gas temperature is now increasing a bit quicker again. I didn't replace the lid at the time, I planned to make a ring of 10 mm (0.394") holes in it. Completely in the style of a pepper shaker with sprinkle holes. 8-)
The goal is to provide holes for the water vapor to escape. The lid should remain on in order to keep the correct shape at all times.

Scott Weinberg wrote:Peter-Having all the tools at hand, this intrigues me a great deal,  ( Casting hi-frequency vibrator plate-  Heavy bending break-lazer- large wet saw- CAD background and all the materials  I presume this was considered a success?

Yes, I would call this a resounding success. The laser cutting and brake bending were done by a specialized, though small, company.

Scott Weinberg wrote:Warning- there is more than one question! 1) Can we cast anywhere near the same cost as fire brick itself?   Using larger bulk quantities of the castable material.

Assuming you are able to produce the moulds and build the vibrating table yourself, it's about the same cost, volume-wise. Mark that there is only refractory used for the core and the immediate area above it at the front. All the rest, being 90% of the mass, is ordinary, plain vanilla, building quality concrete.

Scott Weinberg wrote:2) just an example, if I firebrick weights 2 Kg or 4.5 pounds,  Will it take roughly the same weight of castable material to achieve the same volume of area? This I guess would answer question #1

Most castable refractories are somewhat lighter as compared to dense firebricks. In case you are talking about the majority of the mass: I also made plans for specialized bricks, with a trapezium-shaped footprint. Any specialized prefab concrete plant could make those, opening up the possibility to stack most of the mass completely dry. Because of mould costs, only meaningful when bought in bulk.

Scott Weinberg wrote:3) In this upright "mass"  was there a ISA formula that was followed for this sized shorty core?

Yes there was, assuming a good chimney and so on. The cross section area of the chimney in square meters, multiplied by 255 will result in an ISA that's awfully close to ideal. Normally, this number would be 300. This particular core will take it's time to consume the fuel, not racing through it. Resulting in a slightly lower maximum power in any given time. With other words, it's tuned down a bit.

Scott Weinberg wrote:4) The use of the steel exterior cladding I can see have many benefits on the building ease,  does it serve as a quicker heat dissipater?

As soon as the heat is coming through the bricks, it will be dissipated in the room. The steel itself isn't the limiting factor, it's the mass itself.

Scott Weinberg wrote:The stove looks great!

I totally agree, I think she's really cute, thank you.

Alex Ronan wrote:Do you have any temperature readings inside the bell?
I am curious if the temperatures are high enough to allow for a modification to add a white oven.

No temperature readings inside, sorry. A white oven can't be added just because there's very little space left. Having said that, the firebox itself is a very potent oven by itself. Once there's only glowing charcoal left, a stainless steel grid could be place above the coals and there's your oven!

The last full week in April I have been busy removing the bricks from the lid, prying the lid off the sealant, removing the top ring of bricks. The goal was to create a brick ceiling inside the metal shell.



Then placing a ring of 8 bricks on flat, 8 cm (3.15") high.



Using a set of steel T-profiles 40x40x5 mm and strips of ceramic felt, make a support, the brickss on their side, 105 mm (4.13") high this time.



And knitting the whole thing closed with small pieces of brick and clay mortar in the corners.



The picture shows the lid loosely on top, on a knitted glass strip. That lid is quite tight, no signs that it was leaking there.



In the meantime she has been run a few times, the top was still getting quite warm but about the same temperature as the walls. The heater fan still comes on, but only after an hour instead of 5 minutes after lighting as before.



The flue gas temperature to the chimney is very stable, after closing the bypass the thermometer remained at a level of 100 to 105 ºC (212 to 221 ºF).



There were still a few very small adjustments I could make, but there was no rush and I could just leave it like that.
At the time everything was cleaned up and she was showing off like this, I am quite proud of her.