Walker Riserless Core - Sketchup Model

[Bram]

Because I had difficulty imagining Matthew's pictures and need to send out an order for materials to Greece I decided to make a Sketchup model of the Walker Riserless Core as described here:



walkerstoves.com/walker-riser-less-combustion-core.html



It took me a couple of hours but I believe I was able to copy them perfectly. I have a couple of questions but ask them below.



The brick sizes are:



Insulated Fire Brick: 230 x 114 x 64 mm

Red brick: 210 x 100 x 50


I used different colours to reflect the different stages of the build. I will post only two pictures here to reduce the size of this post, the rest can be seen in the album over here:



goo.gl/photos/ULB5HNrv15Pt1rbh7



I encourage you to copy them and use them in your own projects / folders / models / etc!! Can't guarantee google isn't gonna change their mind again and move something around.



The sketchup file:



drive.google.com/open?id=0B-BOr0AviV19OXNXTi1MWnFTVFk



Matthew, if you would be so kind to give feedback?



Is it close enough to what you did? For instance the size of the channel is smaller where the back window is in your stove... 37mm vs 57 in the rest of the channel. I included two pictures to show what I meant. I can widen this easily to make for a 57mm channel but didn't know if it was intended. [edit: this question was answered by Matt. The pictures that showed these measurements have been updated]



Cheers everyone! Thanks for all the great work!!!

Regards,
Bram

[matthewwalker]

Hi Bram,
Awesome work! Thank you so much for taking the time and sharing your work. I'm not near one of the IFBs at the moment, but I'll grab one of mine today and check. Your measurements sound right.

That gap where my secondary monitoring window goes is crucial. It must not be pinched there, so I set those two bricks back. I've been suggesting to other builders to go no less than 2.5" at the narrowest points. In the first corner that should be corner to corner, like I show measured in the slideshow. I'm not sure what that is in mm, and I don't know what the true minimum is, but it starts to get finicky as that gap narrows.

edit: Also, the secondary air port should end equidistant from the back and inside walls of the firebox. The top routing is optional depending on your design goals. My serpentine is designed around my cook top preference, but any cook top or RMH layout is fine from there.

[matthewwalker]

Wait. Do you have red brick in the core? It has to be IFB throughout.

[Bram]

Cheers for the response. I modeled it without the window as its easier to take things out than put them in afterwards. The red brick is not in the core at all, just used as a shell.

Also the last layer is copied straight from your images. I am aware it will vary per build. I get kinda perfectionistic with sketchup

I am trying to adjust the model to the specs you gave now, whilst keeping it on the foundation of IFB. Might end up slightly different from your pictures. Perhaps its a difference in the brick sizes?

[Bram]

Alrighty then. Adjustments are done. The firebox itself comes down to a nice 200mm width. The channel at the window side is 70mm (2,75") and the one leading 'down' from there 65mm (2.5"). I also moved the secondary air back a bit. 34mm (1.3") from either wall. Pictures will be updated in a moment.

[Bram]

Updated pictures can be found here:

goo.gl/photos/ULB5HNrv15Pt1rbh7

edit: also updated the skp file:

drive.google.com/open?id=0B-BOr0AviV19OXNXTi1MWnFTVFk

Ah and I understand why you asked about the regular firebrick being used in the core. Because I coloured the 2nd stage as red, correct? It IFB, no worries. I'll recolour them next update  

[matthewwalker]

Excellent. That looks right, all of it. The window-delete version is a bit awkward due to that set back. A builder could remedy that if desired by slightly enlarging the firebox, or shortening the center wall, or using splits in the set back location, depending on what was behind it. Good work Bram, and yes, I was confused by the coloring in the JPG. I wasn't until I read your first description with the brick dimensions, then I was just wanting to verify. I didn't doubt you!

[Bram]

Cheers Matt! Perhaps you can post the skp on your webpage for other builders out there. This thread will drown at some point.

And yeah I thought about moving the wall back as well so it would be flush with the back channel but figured it looked more similar to what you had with the window setup. I guess its up to everyone to make up their own mind on what to do. I'm thinking to have a small window on the right side of the burn chamber like in your taller Walker stoves. Dunno yet. Gotta find/fab myself a door next.

The top plate is a neat 68x68 cm btw. Pretty much what a countertop is around here

Oh and I'll do a count on the amount of bricks and post back.

[boscovius]

Not to hijack this thread, but I've a question.  I've been working on a design for my own build and due to the constraints of a 7 foot ceiling, and my knees not being what they used to be, I'm looking for something between Matt's riser-less core, and the BatchBlock core.

I want to build the entire core from 2 inch ceramic fiber, with only the floor and maybe sides lined in firebrick splits for durability.

This core is to drive heat to a large stone and cob bench for radiant heating.

The thing is, I want to scale this up to the point where my burn chamber is the size of a standard Peterberg 8" batch box.

Will Matt's design scale up?

I'm willing to forego a cooktop, but I need the burn chamber to be a foot and a half to two feet off the ground for comfort and convenience.

What do you all think?

[DCish]

Jan 29, 2019 6:16:20 GMT -8 boscovius said:

I've been working on a design for my own build and due to the constraints of a 7 foot ceiling, and my knees not being what they used to be, I'm looking for something between Matt's riser-less core, and the BatchBlock core.

...I want to scale this up to the point where my burn chamber is the size of a standard Peterberg 8" batch box.

Will Matt's design scale up?

I'll let Matt weigh in on whether or not he thinks his core can scale as you describe, but your question brings up a point that often arises. There are *so* many unique situations where it would be desirable to tweak standard designs such as Peter's and Matt's to fit existing circumstances, needs, and preferences. However, Peter is quick to point out that the devil is in the details, and you never know what tiny change might throw burn efficiency off considerably, and in ways that the eye, ear, and nose cannot detect. At that point, you're basically in uncharted territory and nobody here can say with any certainty what the outcome will be.

I'm in a similar boat as you, trying to re-jigger the standard core to fit space constraints and aesthetic preferences. I've done enough outdoor testing to be convinced that it will burn with no smell or visible smoke, but I have no idea how efficient it might really be. I recently made a pitch for purchasing a community-shared flue gas analyzer so that when folks such as you or I inevitably make tweaks, we and the community can benefit by seeing if those tweaks completely trash the efficiency, or if additional adjustments can be made so that it will behave well in these new configurations. I think the community as a whole would benefit greatly from this, and since not everyone has a spare $1200 kicking around to spend on a flue gas analyzer of their own, a community-owned one might make good sense.

[Bram]

The difference of the WRC compared to other RMHs is that it used uses highly insulative firebricks to cut down on the riser height. The whole core is to be built out of them so that you get the most optimal burn and shape for both cooking and heating.

But in doing so it does cut down a bit on a few other aspects. Burning fucktons of wood to heat your bench from cold to hot in 3 hours comes to mind

When you write that you want to enlarge the burn chamber I am thinking that you want to burn more wood at once, lessening your burn time. Is that correct?

[Bram]

In short: The combination of both cooking and heating is its /design goal/.

Can you describe the design goal you have in mind?

[graham]

There's probably a point of diminishing returns since the heat transfer rate to the bench might limit the size of the combustion chamber.

[matthewwalker]

I have not built an 8" riserless core, and I don't believe anyone else has either. I have a few people who have expressed interest in scaling it up from my plans, but so far, I have yet to hear of one burning.

That said, my guess is it would scale up well, although it would be a very large footprint for a core.

[DCish]

Jan 29, 2019 10:53:50 GMT -8 Bram said:

The difference of the WRC compared to other RMHs is that it used uses highly insulative firebricks to cut down on the riser height.

I wouldn't say that this is what the insulating bricks do. Matt's "riser" can be short because it is just the final portion of the afterburner. Most of the afterburner in his design consists of multiple turbulence-inducing elements along a horizontal path from the back to the front of the stove. The insulating firebricks are how he achieves insulation throughout the build, allowing the whole thing, both firebox and afterburner, to heat quickly, and maintain high heat at relatively lower burns, contributing to better combustion at a wider variety of burn levels.