|
|
Post by josephcrawley on Jul 9, 2015 8:22:35 GMT -8
After following the recent thread from mattwalker I decided to give the masonry cookstove a go. I opted for a standard peterburg batch box with a shortened riser. The alternative side riser just made the stove way to big, I included an electric oven I pulled out a range from the scrap yard which is the other reason I did not use the side riser(the oven is huge). I'm sad to report that compared to my existing knox mealmaster stove it's not very good. The riser limits the high heat to the burner directly overhead only. The oven took 2 hours two reach a temp of 300. My next attempt I will attach the firebox to the oven for direct heat maybe with some thin brick splits to keep from burning out the thin metal side. This will make the heat uneven but since it is how my existing stove does it I'm used to spinning things around half way through baking. I will also raise the firebox to near the top of the stove and have the flame exit the top around the secondary air intake. I think if I cut slots in the intake every few inches and make a narrow gap on either side of the intake I should get pretty decent combustion. Thoughts? Comments? You can see photos here.Attachments:
|
|
|
|
Post by satamax on Jul 9, 2015 12:19:16 GMT -8
|
|
|
|
Post by josephcrawley on Jul 10, 2015 15:25:40 GMT -8
Here's a mockup of how I was thinking of redoing the fire box. The top gap around the secondary intake would be the normal p channel dimensions. Cut splits would face the oven wall to prevent burn out. The firebox would be bigger but the burn area would be the same dimensions. www.flickr.com/gp/45224908@N03/Y58Ckd Sorry for the link but tapatalk will not attach my photos |
|
|
|
Post by josephcrawley on Jul 13, 2015 14:54:39 GMT -8
Here's a view from the top of the new fire box. There are 48 1mm slots 24 per side of the secondary air intake. There's no appreciable amount of secondary burning going on. Occasionally a little flame will pop out of one of the slots. I think the slots are too skinny to allow air flow. Any comments? flic.kr/p/v2iFa5 |
|
|
|
Post by josephcrawley on Jul 14, 2015 16:18:11 GMT -8
Well slot size had no effect. It seems clear now that taking a p channel and expecting hot
Air to come out of it within inches of the intake is ridiculous. Oh well. Next I'm going to replace the orginal piece of 3 x 1 with one not filled with holes this will run back to another piece of 3 by 1 sitting on edge perpendicular which will have to two more 3x1 pieces attached .6 inches above one to the right and one to the left with a .6 overlap. Picture a trident with the middle tine lower. This middle tine will carry the air to the outer two which will have slots on the bottom inside corner. My hope is the overlap will mix the (hopefully very hot)air and with the smoke and boom or at least puff flame. Maybe I'm treading worn ground with this but I've followed this forum for years and don't recall seeing this. Anyway under a deadline to replace my indoor cookstove before it gets cold so any help or insights even snide comments are welcome.
|
|
|
|
Post by Daryl on Jul 14, 2015 19:47:10 GMT -8
So is the flame going towards the top of the box or the back? I am a little lost.
|
|
|
|
Post by josephcrawley on Jul 15, 2015 4:42:06 GMT -8
Out the top
|
|
|
|
Post by Daryl on Jul 15, 2015 8:05:55 GMT -8
Have you changed the size of the burn box?
|
|
|
|
Post by josephcrawley on Jul 15, 2015 8:16:32 GMT -8
I shortened the height by 2" to get the fire closer to the air channel
|
|
|
|
Post by josephcrawley on Jul 15, 2015 8:59:57 GMT -8
|
|
|
|
Post by Daryl on Jul 15, 2015 11:39:15 GMT -8
Novice but...The pressure should increase if you have the flame going through one point instead of at three different points. The pressure should increase temperature.
Not sure how much that secondary air will effect the gas temp. |
|
|
|
Post by josephcrawley on Jul 15, 2015 13:43:19 GMT -8
I got it in there this afternoon. I'm getting secondary burning but it is intermittent. It will burn for a few seconds then stop back and forth. I know it's hard to say why but if you have any ideas I'd like to hear them. Maybe I should modify it to have juat the one arm instead of two. Thanks for the feedback.
I should add it is draft related. If I blow air in the intake it just goes. So I guess I need to tighten things up or improve the draw. Or perhaps increase the size of the input?
|
|
|
|
Post by Daryl on Jul 15, 2015 15:11:05 GMT -8
I'm thinking you can have two arms with secondary air but make them so they flank an exit. Try only one exit from the burn chamber. Try not to have multiple exits or to block the exit with an arm. That should help with the draft as well.
|
|
|
|
Post by josephcrawley on Jul 15, 2015 15:57:40 GMT -8
I could move the air intake to the bottom of the firebox instead of it being in the top. I had thought that my design would help with mixing and turbulence
|
|
|
|
Post by peterberg on Jul 15, 2015 23:36:55 GMT -8
Joseph,
Why are you trying to invent the wheel? I've spent 6 months of work in 2012 to optimize the batch box so what a good configuration is should be well known. But you are changing the firebox, riser, primary air, secundary air and probably more as far as I can see. So you are doing development all over again with a design which happens to be very tight to begin with.
For example, the horizontal part of the p-channel inside firebox won't work as well. The reason could be that the air need to be go down in the vertical part of it. So the hotter the air, the more it will resist to go down. Hot air wants to rise after all...
May I suggest you check out the tried and tested setup first and work your way from there?
|
|
