1st build...lotsa questions!

[hpmer]

Donkey,

Any advice on the heating process (time, temp, how to, etc.)? I know the best answer is the longer and higher the temperature the better, but are there some minimums that we should keep in mind?

[Donkey]

Yer just trying to see how yer clay stands up to the shock..
GIVE IT THE WORST!
See how it does.

[Donkey]

That's how I tend to run ALL my tests..
With materials, I make the candidate mix and subject it to the worst conditions. Floor patches laid unevenly and left in direct sun to dry, plasters same way, stove materials subjected to extremes in temperature with extremes of shock (change in temperature). And so on..
If it stands up to hell, it'll do fine under normal, more reasonable conditions.

[hpmer]

I've taken to placing my pucks into the heat riser of an older rocket stove I built for an hour or so at full throttle. Seems to give me a good idea of things, but I wondered if there was a better test.

[Donkey]

Build a good hot campfire and toss the pucks in the middle.. Then pull 'em out and toss 'em on top of something really cold.
Or better yet, stick 'em in the freezer for a while THEN toss 'em in the fire.

[chupacabra]

Ok, I made a new batch of puck's yesterday..after a weekend of rain!! Will test tommorrow...in the meantime, my impatience got the best of me....Yesterday I also poured the clay/sand(at 1/2 ratio) foundation it measures 1 1/2" thick,it looked pretty good when I poured it but woke up this morning to some pretty big cracks!! Could this be due to a poor mix(too much clay) or too thick? Can I fill in the cracks and continue or is this a redo? I did use a big piece of wood to tap the floor all around the foundation to help get rid of air pocket's but making a cement floor vibrate isn't that easy! Au secours!!!!

[chupacabra]

Here's the RMH yesterday, it seems to be performing well, despite windy conditions and no insulation around the heat riser....I would like to have an air intake on/in the feed tube, and am trying to figure out how to do that before I cut the barrel...I read that the feed tube/barrel shoud be no more than 12" above the burn tunnel., has this measurement been pinned down to a more precise number? Any info/links would be of great help!
Back to work!
p.s.folder for this post is now on fire, we're cookin!

[Donkey]

Sept 28, 2010 4:56:46 GMT -8 chupacabra said:

Ok, I made a new batch of puck's yesterday..after a weekend of rain!! Will test tommorrow...in the meantime, my impatience got the best of me....Yesterday I also poured the clay/sand(at 1/2 ratio) foundation it measures 1 1/2" thick,it looked pretty good when I poured it but woke up this morning to some pretty big cracks!! Could this be due to a poor mix(too much clay) or too thick? Can I fill in the cracks and continue or is this a redo? I did use a big piece of wood to tap the floor all around the foundation to help get rid of air pocket's but making a cement floor vibrate isn't that easy! Au secours!!!!

Looks like you don't have enough sand. Also, you used the word "pour" which makes me think your mix is too wet. "Pack" is more the word you're looking for.
You can probably just fill over it.

What sand are you using?? It looks rather -- blond.. It suggests to me quartzite sand, which can cause cracking in the heat. You want a non-crystalline sand if you can get it. Like black quarry sand, etc.

[Donkey]

Sept 28, 2010 5:02:19 GMT -8 chupacabra said:

I would like to have an air intake on/in the feed tube, and am trying to figure out how to do that before I cut the barrel...I read that the feed tube/barrel should be no more than 12" above the burn tunnel., has this measurement been pinned down to a more precise number? Any info/links would be of great help!

Those measurements are always relative to each other. As a general rule (and thumbnail guess), I'd say keep it below a third of the height of the heat riser.. (Measured from the center of the burn tunnel)

Be aware that Ianto has been using the small barrel over the feed with SIX INCH rocket stoves.. Even though the model used in the book is an EIGHT INCH design, Ianto's feed barrel thing was put in there without cross checking size relationships.. OOPS! I repeat! The feed barrel as shown in the book is for six inch stoves, NOT eight inch ones.
The air intake ratio should be somewhere between 1/3 and 1/2 of system size. No, this measurement hasn't been exactly pinned down either. Anyhow, as a note of interest, remember that when you halve the size, you quarter the volume.
What you want is for the air intake to be blowing on the fire, making that roaring, rocket sound.

[chupacabra]

Thanks Donkey,

I think your right on with the mix being to wet...I got lazy....It's the first batch I've done in the cement mixer and I got it a little too wet in order for it not to stick to the sides. Also, I forgot to wet the floor before...anyways after posting I went and lightly pushed all the cracks shut and lightly "packed" the rest...It's currently getting a layer of bricks and after another thinner layer of clay sand mortar "packed" on top..Does this sound decent enough for a foundation? Canyon said "at least" 5 inches of mass above clay sand mortar, my bricks are about 2 inches thick which will leave me approx. 3 inches shy...I have enough bricks to make another run/layer but I'm tryin to keep the overall height of the RMH down so that my wife doesn't need a step to get the tea pot. But I'd rather build a step than end up with my floor burnt/stressed.

Donkey,
The sand I've used is river sand 0/4(4mm?) , not sure if that means it's quartzite or not but I have seen the "black quarry type", or at least some sand that resembles that type over here. gonna try'n find me some.
Here's a pic of the different sand's that I currently have on site

Front row: On the left is said "sable de riviere" river sand, and on the right are four different 0/2(2 mm?) for finish work.
Back row: on the left the chopped sunflower stalks, and on the right filtered clay.

[Donkey]

'Yer doing this on top of a concrete slab, right?? Really, all yer doing is trying to keep the concrete from heat shocking. The brick and cob (whatever) under should help even up the heating/cooling, slow it down, smooth out the curves, so to speak. I imagine that your plan should be fine, though I don't fool with concrete much, Canyon is probably a better judge of this one than me..

Sand:
Firstly, the sand needs to be angular and rough. If your sand has been washing around a river for a long time, it could be worn smooth and/or fine. Smooth, fine sand won't work very well.
Quartz sand will have little shiny crystals in it and it will tend towards white.

Your image didn't make it..

[chupacabra]

here it is sry.

[Donkey]

Yeesh!!
Well, the white one on the upper left and the gray one on the far left look chunky..
Other than that I can't tell what the heck I'm looking at.

You do want your sand to be as chunky as possible. That is for the Cob bits and whatnot. Chunky and rough with a large variation in sizes.

[canyon]

I wouldn't worry about the concrete floor shock for the bench flue down to even 2 1/2 " of mass but for the rocket and the high temp area I would want some more buffering/slowing/spreading of the upper temperatures. If you have an 1 1/2" of mortar (not sure why you are laying so much mortar without embedding bricks or urbanite?) and a 2" firebrick and then some more mortar and then your 2" fire brick again for bottom of your burn tunnel then I would be plenty comfortable with that 5 1/2" from burn area in terms of heat shock to your slab. If you aren't doing one more layer of fire brick I think you need some perlite clay (or the like) in there in the lower layers.

[chupacabra]

Donkey,
Sorry, that pic is worthless. I did get my hands on some "quarry sand" , it's not black but more of a grayish/light blue color with fairly good size chunks, and very little silica(err white stuff) , I used this for the layer of bricks/foundation that I put in yesterday...I threw out the other test pucks and made new ones w/ the new sand...although these tests will be for future builds as I don't really have time to observe the results...As long as it holds up this winter I'm fine with that.....

Canyon,
I did 1 1/2 inches of mortar because I saw you wrote to start with a "foundation" of mortar in your earlier post and didn't take the time to ask how thick...I guess you were just talking about a layer for the first round of bricks.....oh well, we'll see how it holds up. I'm gonna do 2nd layer of bricks on top, except for the ash pit hole. Would it be a good idea to put a layer of vermiculite/clay on top of the ash pit bricks?

The RMH will be moving inside this weekend, as I don't think there's much more I can do as far as testing outside.
I must admit building outside is essential, not only to test performance, but also(for 1st timer's) a great way to learn how to get the thing burnin' and keepin' it stoked...It's been fun, and I'm lookin forward to bringing it in.

One more question for today....as for the cleanout/ash pit after the heat riser, will a regular "T" work for or a cleanout? I've noticed that book and other's have made this area/space a bit bigger....I haven't tried with the "T" outside as I'm still waiting for it to be delivered.

Once again, thanks everyone for all of your help, and sorry if I'm asking to many stupid questions....once this thing's up and runnin, I'll try and take some time to answer some of my own questions.