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Post by briank on Sept 20, 2017 16:05:12 GMT -8
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Post by briank on Sept 20, 2017 16:20:40 GMT -8
The secondary air assembly is simply 1 1/4" square steel tubing, the horizontal is 4 1/2" and the vertical (slanting away from the Venturi port) is 5". A 2"X 1" recess is already built into the ceramic fiber board floor and is covered with firebrick and extends to the base of the Venturi port.  |
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Post by pigbuttons on Sept 20, 2017 16:53:30 GMT -8
It's all looking very professional. Keep up the good work.
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Post by briank on Sept 20, 2017 16:58:53 GMT -8
It's all looking very professional. Keep up the good work. Thanks! That means a lot, since I had no experience with metalwork whatsoever prior to building these prototypes. I've built this by hand with bargains from Craigslist (including the used 55 gallon straight sided barrel) and Harbor Freight, and had no trips to the ER this time! (My first rocket heater involved falling on outside cement cellar steps and a torn ligament in the wrist.) |
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Post by peterberg on Sept 21, 2017 1:24:36 GMT -8
Brian,
I spotted a possible disastrous mistake regarding the floor channel. There's one circumstance that'll make any batchrocket smoke like mad: an object in the port. Your floor channel is likely to disrupt the gas streams in the port as it is now.
The vertical part should be in front of the port, rotated 1/8 turn so a corner is pointing to the port's opening. Left and right of that vertical part there should be enough space of half the port width so there won't be any restriction. This is the specification that yields very good results, what you are building now looks very creative but it is in uncharted territory.
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Post by briank on Sept 21, 2017 6:50:48 GMT -8
Brian, I spotted a possible disastrous mistake regarding the floor channel. There's one circumstance that'll make any batchrocket smoke like mad: an object in the port. Your floor channel is likely to disrupt the gas streams in the port as it is now. The vertical part should be in front of the port, rotated 1/8 turn so a corner is pointing to the port's opening. Left and right of that vertical part there should be enough space of half the port width so there won't be any restriction. This is the specification that yields very good results, what you are building now looks very creative but it is in uncharted territory. Thanks Peter! It's really easy to change this out, so I'll go ahead and test it in this configuration, and if there's any hint of trouble I'll swap out to a different design. I just wanted to avoid cutting fire brick. I wonder if drilling two 1/2" holes in the horizontal tube segment, directly in front of the base of the Venturi, to the left and right of the vertical tube base, might alleviate some of the problems? |
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Post by keithturtle on Sept 21, 2017 7:09:56 GMT -8
I just wanted to avoid cutting fire brick.
I found that cutting them on a wet tile saw does wonders for making straight and accurate cuts, and no dust.
Small notching is done dry with the 4 1/2" diamond wheel on small grinder
Turtle
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Post by peterberg on Sept 21, 2017 7:24:52 GMT -8
It's really easy to change this out, so I'll go ahead and test it in this configuration, and if there's any hint of trouble I'll swap out to a different design. I just wanted to avoid cutting fire brick. I wonder if drilling two 1/2" holes in the horizontal tube segment, directly in front of the base of the Venturi, to the left and right of the vertical tube base, might alleviate some of the problems? It's highly unlikely that drilling holes would alleviate problems caused by an object in the port, I'd say. I tried several times in the past five years to find a way to avoid this effect but to no avail. If you want to change the design because you like to avoid cutting bricks you most certainly need a Testo to see whether or not the good results are maintained. But by all means go ahead, you are entitled to make your own decisions. There's a lot to be learned from cutting corners with blunt objects that's for sure. |
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Post by briank on Sept 21, 2017 7:39:19 GMT -8
Actually I haven't welded this assembly yet, so I'll take the sage advice born of your experience and modify this. I have some heavy gauge metal c channel the size and shape of a firebrick split and open on the bottom (from an old USSC wood stove secondary air supply) that I can easily modify and include the change in vertical tube orientation you recommend. Thanks again!
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Post by briank on Sept 21, 2017 8:34:44 GMT -8
I just wanted to avoid cutting fire brick.
I found that cutting them on a wet tile saw does wonders for making straight and accurate cuts, and no dust. Small notching is done dry with the 4 1/2" diamond wheel on small grinder Turtle I picked up a 14" abrasive wheel metal chop saw from Harbor Freight to cut tubing. I wonder if that can be used to cut fire brick? |
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Post by briank on Sept 21, 2017 14:52:01 GMT -8
But by all means go ahead, you are entitled to make your own decisions. There's a lot to be learned from cutting corners with blunt objects that's for sure. I revised the design based on your advice. Again, many thanks.   |
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Post by Dan (Upstate NY, USA) on Sept 21, 2017 17:13:42 GMT -8
You should test both ways...
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Post by briank on Sept 21, 2017 17:27:04 GMT -8
You should test both ways... Hmmm. I can do that...but I suspect what the results will be based on Peter's experience. If I used my original design but rotated the vertical segment so one point of the square tube points towards the port, it might be interesting though as an experiment. But even if it doesn't visibly smoke either way, I'd need a Testo to see which version works best. If they both appear to work, I'll bring both to Montana for the rocket stove jamboree and maybe some kind soul will let me use their Testo to test them. |
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Post by keithturtle on Sept 21, 2017 19:04:29 GMT -8
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Post by briank on Sept 23, 2017 17:51:45 GMT -8
Ready for first fire tomorrow   |
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