Walker Core Variation

[keithturtle]

Dec 7, 2015 2:41:25 GMT -8 Vortex said:

 I read online they are rated at 500*C.

Interesting.  I'll have to recheck my source, and it's good to hear you had some success with them, TYVM

Turtle

[Vortex]

This post contains the sources of my info: donkey32.proboards.com/post/10254/thread

Many years ago I used to make metal wood burning stoves out of all sorts of junk, I used pyrex casserole dish lids for the door windows on many of them. They were fine so long as you kept the flames off the glass and didn't touch the hot glass with anything cool. There's loads of them available in thrift / charity / secondhand shops, so cheap enough to replace.

[ronyon]

Walkers core doesn't use insulation, does it? Are you just trying something out?

[DCish]

ronyon
Correct, Walker doesn't use insulation. And although his numbers are pretty good, they aren't as good as the original PvdB batch. I've always liked the idea in the original rocket stove of isolating combustion and heat harvest, so I thought adding some insulation might be a good idea. However, following the more recent comments of Shilo and Adiel following their collaboration with Peter that achieving proper mixing seems more important than adding more oxygen, I'm not sure if it will make a difference, or if so, how much. Seems it would be worth some testing with/without if I can get my hands on a testo.

[matthewwalker]

Dec 16, 2015 6:56:02 GMT -8 DCish said:

numbers are pretty good, they aren't as good as the original PvdB batch

My experience has been the opposite. YMMV.

[DCish]

Dec 16, 2015 8:47:26 GMT -8 matthewwalker said:

Dec 16, 2015 6:56:02 GMT -8 DCish said:

numbers are pretty good, they aren't as good as the original PvdB batch

My experience has been the opposite. YMMV.

Oh! I was taking my conclusion from Peter's response early in your "riserless core" thread (http://donkey32.proboards.com/post/16866/thread). Maybe I'm interpreting that wrong, or maybe there has been other work that I'm not aware of, I'm happy to be corrected.

[matthewwalker]

I'm only referring to my personal experience.

[DCish]

Got it. Thanks.

[DCish]

Ok, updates from winter break building spree.

Finalizing secondary air. Lacking an angle grinder I opted to drill 52 holes at 3/16" each for a total of roughly 1.5"csa (less, I'm sure, due to the added resistance of flowing through a hole vs a slot). I was curious to see if the holes would "jet" into the gas stream like the overhead secondary air pipes / holes in my box stove. No such luck. The flow was so fast that, while air visibly exited and produced secondary flame, it didn't appear to create additional turbulence


Rough mock-up of the fuel box and afterburner, with a single piece of salvaged 36" insulated flue pipe as the stack.



Fire box with secondary air tube installed (offset to the right due to lack of ability to bevel bricks at this moment)



Half-inch ceramic fiber lines the afterburner. Ceramic glass added on top later to observe flame pattern.





First fire lighting. Note lack of turbulence at low burn, fire drawn directly toward exit.



As the fire intensifies, it picks up a ram's horn on the left, while the right side is swept straight up the flue with no additional mixing.



In this snippet the glass has burned clean and I'm attempting to show secondary air exiting from the injector holes.



Shot of the burn chamber after the fire went out. Primary air was completely blocked, the fire fed from all directions through leakage between the dry-stacked bricks. Walls seem pretty clean, soot only in corners. More ash than I expected, but incredibly light and puffy, and a very few bits of charcoal left. How does this compare to what remains after others burn down a batch box?


Modified the afterburner by adding a wall two bricks high to the right of the port to force gases up and hopefully encourage formation of a double ram's horn / better mixing. Seems to have worked well.




Overall *very* happy with this build. Despite being only dry stacked with lots of visible gaps, it was easy to tune to a smokeless burn. In fact, once up to temp (~32F outside), its dirtiest burn smell was at least as clean as the cleanest burning smell that I get from my box stove, and the clean burn smell was nearly indetectable. Looking forward to refining, figuring out a door, and bringing it inside! Any and all suggestions / comments welcome.

[Vortex]

Hi DC, Looks like you had fun over the holidays. Good write up. I could only watch the videos if I was logged into google, even though it says Publicly Shared. Look forward to seeing the real build.

[DCish]

Thx Vortex. I'll have to see if I can find a better way to get those videos up.

[DCish]

Vortex, by the way, how does the leftover ash bed compare to your firebox? Do you get a few lumps of charcoal left over, or does it pretty much all burn up?

[dkeav]

I would think the leftover ash would decrease as you insulate the burn box and close off the gaps. The glow phase was probably shorter from the box cooling down faster and losing some draft to keep glowing?

[ericvw]

Dang, DC!!!! You've been killin it with your bricked up test! AND, I've been away too long
great work, anxious about the final product....
Eric VW

[Vortex]

Jan 5, 2016 6:55:50 GMT -8 DCish said:

Vortex, by the way, how does the leftover ash bed compare to your firebox? Do you get a few lumps of charcoal left over, or does it pretty much all burn up?

Usually everything is reduced to fine white ash, occasionally I get one or two fingernail size pieces of charcoal left, never anything more. Normal firebrick makes the fire less efficient at the start because it's sucking heat, but it gives it all back at the end of the burn.