Peter van den Berg

Leonardo Bevilacqua wrote:As I was "building" the stove in Sketchup I noticed something. My firebrick size is 220x110x60 mm, and it  looks to me that it doesn't fit very well for the 180mm system measurements. I fear it would mean many cuts during the build. Am I right?

Most firebricks aren't a good fit for a 180 mm system. Sorry for that, it can't be helped.

Leonardo Bevilacqua wrote:In the back of my mind I remember reading something about tweaking the measurements to fit better with the brick size one has at hand.  I guess it would involve tweaking the base number B in Peter's formulas. Could you help me doing that?  Or, is it better if I just stick to the standard measurements for a 180mm system?

Tweaking the base number can be done, that's true. But I don't think it would help much, a lot of cutting is what one is stuck with.

Leonardo Bevilacqua wrote:Another question. I understand the strong recommendation to stick faithfully to Peter's proportions in order to have a good result. At the same time, though, I'm sure there's a tolerance within which no big difference can be noticed it the end result (performance wise) but may make the build easier. What tolerance would you say I have with the measurements? I guess it would be in the range of a couple millimeters.

There's some tolerance on the measurements, that's correct, specifically regarding the firebox. This could be a bit higher or lower, wider or narrower and deeper or not. About 10 mm tolerance won't hurt the workings, provided the first and second gate are correct dimensioned.
I delved into older drawings, and found the core of one heater done in Februari 2024. The ink of the design was still wet at the time, and it shows.

But at the time I stumbled over the same problems as you did and here's the solution. On top of the firebox' floor there are two bricks on edge and on top of each other, all around, nothing special. Then in order to get the first port right, all around the structure there's a strip of brick that's 53 mm high. And on top of that layer, there's another full brick on edge also over the port. Now, the height of the firebox is a bit too shallow, about 7 mm but in practise that might be less due to the thickness of the seams. The way I did the riser liner I wouldn't regard that as correct anymore. Better to follow the method of building the walls and doing the liner as a separate item.

Here's a picture:

This already is looking much better, the placement of the exhaust pipe in particular.

Extending on the left side of the core and bell: it would be best to have a layer of 1/2" superwool between the brick and firebrick. This will take the gap between those down to roughly 12 mm.

I don't know if you calculated the core also. If so, best to insulate the core all around, so it is out of the calculation in its entirety.

On the idea of doubling one or more walls: the front wall above the firebox do need a shield consisting of firebricks. This paricular spot will be the hottest area of the entire bell/bench combination.

A bit of shifting here and there, and the situation is completely different. This highly creative process is called "designing as you go".

Alan, maybe my description wasn't quite clear. That's what you get when I am getting ideas while typing.
What I meant was this:
When all walls of the bell are staying in place and the core is shifted to the left, *against* or nearly to the bell wall, that part of the bell wall won't be counted in the ISA calculation. At the same time, all things being equal, the space at the right side of the core will be larger, creating more space for the gases to come down.

It might be that the core should be shifted somewhat forward, enlarging the bell a bit to the front. The chimney pipe would fit beautifully in the corner at the right, where the bell and wall meet each other.

Just ideas, it's up to you what and how to implement.

As I see it, the gases that ought to stream to the exhaust of the bell aren't able to reach it. Remember, the stream is drifting into the bench, goes down at the end and streams along the floor to the exhaust. Much more space at the back corners of the core and channels under core would help.

Keep in mind that the floor of the entire bell, bench included, should be one level and smooth overall. So no bumps, obstructions and holes. I see what you are trying to do with rising the whole of the heater, but the bench will also get quite high like this. The internal size of 30x30 cm for the bench isn't exceptional, the exhaust should be at least in the lower half.

Moving the chimney pipe to the other side of the bell would be a good idea, lots of space there. By minimizing the space left of the core and maximizing the other side would be another possibility. In the bell around the core, there should be at least a horizontal space of 5 times the cross section area of the chimney, all connected by spaciously passageways. Having that space all at the side where the bench is, means gases are able to enter the bench more freely. Having a low and wide opening leading to the exhaust that's twice the size of the chimney pipe would help a lot as well.

When done correctly, the whole of the bell and bench will get warm, right to the end. I did the Mallorca build in 2017 this way and it worked exactly what it was meant to do.

Hi Alan,

I am assuming you are geared to building a 150 mm system. You are going to run into trouble with extending one dimension and trying to keep all the others (or most of it) within the specs of a proper 150 mm system.

There's a simple solution to this, namely enlarging the base value slightly. In fact, in a proper 150 mm system, the base number is the width of a brick. This isn't a happy accident, it came out this way during development of the first generation batch box rocket. In order to keep all the measurements within specifications, with slightly larger bricks a lot of cutting need to be done.

By enlarging the base value a bit, the brick pattern will be a much better fit and the slightly larger core will run on a 150 mm dia chimney just as well. So, the base value for a standard 150 mm system is 108.51 mm. By upping this to half a brick, it will be 114 or 115 mm, fitting for a chimney that is 159 mm dia, according to specs. But the enlargement is well within reasonable tolerances, so the core built according to this specification will run without any problem on the 150 mm chimney.

The bell could be done the same way, take the cross section area of the theoretical larger chimney in meters, and multiply that by 255. The result will be the internal surface area of the bell, excluding the floor. Since the bell do need a bypass anyway the whole thing will run beautifully.

Now you'll need to break down the beginnings of the core, make a complete floor with the walls on top of it. This way, you'll need three bricks on edge for the height of the firebox. The height of the port of 2.1B will be very close to two firebricks on edge, also.

I also would like to suggest that you elevate the core a bit more, by using a layer of firebricks extra on top of the AEC blocks. They tend to crumble over time when repeatedly being close to their maximum temperature. Keep in mind, the temperature inside the firebox could be up to 900 ºC, the underside of the firebricks could be dangerously close to the maximum specs for the AEC blocks.

Just vent your questions here, I will keep an eye on your progress.

Lots of succes!

P.S.
The depth of your firebox looks a bit on the short side. As it looks like, it's just 1.5 bricks deep, this should be at least two bricks as the standard depth. Eventually, this could be even 25% more without repercussions.

Regarding calculation of the bell, think of it as a completely closed box, without the core at all. When the calculation is applied to this, you'll get the best efficiency out of it.

The batchrocket.eu site is running as complete as it can be, thanks to Sebastian. The DNS server is pointing to the copy now, the certificate is in place and recognized. Even the temporarily address is pointing to the site copy.

What need to be done next is choosing a Static Site Generator and rebuilding the site. The whole process could take quite some time, but it need to be done in order to be able to adjust and modify the site from home in an easy way. Which is meant as an ongoing process, due to the aim to add other designs and applications when relevant.

As it is, a copy of the site is running on a server in France. The address batchrocket.eu is pointing to that server now, but the safety certificate isn't in place yet. The site is accessible, although without https.

The article about the DSR3 and the Shorty core in the Dutch version are reinstated. Google Translate is able to provide a passable translation.

Sebastian found the source of the broken links and implemented a fix. As far as I can see, all pages are properly linked now.
What a luxury.

Dear readers, one of you lot, Sebastian Köln, offered to retrieve the batchrocket site from archive.org and having it running on his server awaiting a more permanent solution.

At the moment it isn't complete, some of the links aren't working properly but most of the information is there. The latest information about DSR3 and Shorty core isn't, but that was only available in the Dutch version anyway.

You do need to have a look? Go to https://batchrocket.artisan-ma.net/en/

Any relevant changes of the situation will be announced here. In short: I'll keep you posted.