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Post by grizbach on Jan 23, 2010 1:39:09 GMT -8
Here is another progress report.
I only have so much room to work with here so I've built a small bench to go along with my rocket. It has more style-points than the stove does. I estamate it weighs in about 900-1000lbs. I still need to finish the top of it though.
It's been burning almost every night for about 5weeks now.
My steel feed tube started to disinegrate with the heat so I remade it out of stainless. I went from 5 inches to about 5 3/4. For only 32% larger my bench warms up twice as fast! It actually gets to hot to sit on!
When I'm really stoking her up, the top of my barrel barely glows in the dark (850deg F). Usually it runs between 500 and 700. I have a meat thermometer in the middle of my bench. the hottest I've gotten it is 160. The first tile closest to the stove gets to 180 after only 2 1/2 hrs.
When it was a 5 incher, my exhaust would run from 150-200 deg. Now it runs from 200-250. You can see I'm running galvanized pipe right off my radiating barrel and there are no fumes.
Once I have a bed of coals, I put a drain oil drip on to a burning log . I first had it preheat by looping through the fire,but it would coke up. It actually gets heated fine with it about 2 inches from the burn tube.
I'm not sure what I'm going to do from here. I wish I didn't have to babysit it though. Maybe a 30 inch closed feed tube with side air intake?
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hpmer
Full Member
Posts: 240
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Post by hpmer on Jan 23, 2010 9:15:06 GMT -8
Very clever!
Questions:
Are the small wood spacers under the firebox sufficient to keep the wood floor protected?
What did you stuff the bench with?
The heat riser seems pretty slim, what did you use for the guts?
What is the mix you used for the burn chamber surround?
Do you plan to break it down and store it during the off-season?
Does the bottom opening near the feed tube serve as a cleanout?
What is the metal surround made of and how did you form it?
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Post by Donkey on Jan 23, 2010 9:34:02 GMT -8
Oh wow...
That's just TOO COOL!
Nice job.
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Post by canyon on Jan 23, 2010 12:25:26 GMT -8
Yeah Man! Very nice fabrication work. Are you an HVAC 'er or just bent that way? Where are you located (region or climate)? Have you had any condensation showing up anywhere? I imagine we're all holding back loads of questions! Yes, I'm keeping warm this winter, the difference being I haven't burned a drop of oil now that I have a 1.5 ton bench to even things out. With the mass you don't have to tend the fire for too long every day once you are up to coasting temp. I got my bench to 160 after firing all day once and didn't have to have a fire for three days (It wasn't that cold out though, just the lower twenties). It is interesting how different it is playing with wool blankets on sections of the bench and even cotton cushion pads. I've had to look out for the fire hazzard when overfiring the bench though. Keep up the good work and thanks for sharing!  |
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Post by grizbach on Jan 23, 2010 12:38:57 GMT -8
hpmer,
I have a thread over in the experiments forum on how I built the rocket.
The spacers are 1 1/4 and the floor is holding up great! I can put my hand under it with no problems. (unless I touch the metal).
The bench is filled with sand I got from ditching my driveway.
The heat riser is 5inch id and 12 1/4inch od (no pic of that though) The radiating barrel is 14 inches.
Yes, the stove is seasonal. (The wife does not aprove of the monstrosity in our den). The bench on the other hand is a lot to move around.
The side opening has a drawer that fits into it. Is for air intake and ash cleanout.
The base is just sheet metal. I cut out the footprint, then just tacked the wall to it and bent it as I follow the perimeter.
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Post by grizbach on Jan 23, 2010 13:30:24 GMT -8
Canyon,
No HVAC here, just a mechanical mind. I'm in Michigan and it's been strangely warm for Jan. I'ts been getting above freezing for the last few days.
I was expecting condensation, but even when it was running 150 deg, it's been running dry! I do wonder where the moisture is going though.
I wish I could have a larger bench. My house to bench size ratio is way out of wack. It takes about 36 hrs to drop down to room temp, but I dont feel the heat off it after it drops to about 100 (maybe 12 hrs?). The surface seems cooler than the center when the stove is off.
Just a guess, but I feel I get 3/4 heat off of the barrel and 1/4 off the bench. I be curious to what the actual btu of both over 24 hrs would be.
I follow your concern about fire hazard on the hot tile. I do have wood trim just 1/2 inch from the pipe entering the bench and there isn't any charring. I do believe there is no moisture left in it though.
Please don't hold back on questions. We are all here to learn!
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Teach
Junior Member
Posts: 89
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Post by Teach on Jan 24, 2010 12:06:23 GMT -8
Very creative. I can just imagine how nice a job could have been done if the rocket and bench had been built in place when the house was going up rather than afterwards but well done.
What I am curious about is the base where the firebox is. What did you use for what looks like a castable refractory? Thanks
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Post by grizbach on Jan 24, 2010 18:33:26 GMT -8
Teach, may I direct you to a thread called "bottom intake" at the experiments forum.
It's made of perlite and masonry cement.(with a spash of clay)
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Post by Donkey on Jan 25, 2010 11:27:19 GMT -8
Have you got a chimney thermometer?
It'd be good to know what yer chimney temps are.. Even better get the temp at the center of the flow (like a meat thermometer, stuck into the pipe)..
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Teach
Junior Member
Posts: 89
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Post by Teach on Jan 25, 2010 12:06:45 GMT -8
Griz, "bottom intake" got it. Good read thanks.
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Post by grizbach on Jan 25, 2010 15:53:32 GMT -8
Yes Donkey, the temps are taken just outside the bench in the exhaust pipe. I pulled the type k thermocouple from my gassifier to take the readings. Overkill I know but my meat thermometers are in the bench.
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Post by Donkey on Jan 26, 2010 19:02:46 GMT -8
Ergh... Sorry, brain damage... You actually said what the stack temp was.. I read it and then asked a stupid question.  Like I said, drain bramage. |
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Post by matthewwalker on Nov 27, 2012 10:56:58 GMT -8
Hey Griz, old bump here, but I'm wondering about the duct loop for the heated seat back. I've been thinking along these lines and wondering how well it would work, and come to find out you've done it. Care to share your thoughts on that little detail?
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Post by grizbach on Nov 27, 2012 12:11:10 GMT -8
Matt, You can see I have 2 runs exiting the bench. I have a restrictor plate in the bottom to make sure gas hits the upper run. I'm glad I have a heated back, but it could be better.
I feel the most important feature of heat exchange is surface area. Round duct work is easy to work with, but is wrong for heat transfer. If the exhaust could touch all of the concrete slab, I'm sure it would be ten times better.
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Post by matthewwalker on Nov 27, 2012 13:17:37 GMT -8
Just to be clear, you are saying that the upper loop is comprised of two runs of ducting, correct? With the lower run restricted? I hear you on the surface area. It's one of the things I like about the half barrels for mass. Used as a bell they offer quite a bit of surface area for transfer.
I suspect in a narrow enclosure like the seat back transfer is going to be mostly limited to a strip along the highest part of the exhaust path regardless of construction or configuration. Slowing things down with a bell configuration seems to help decrease the stratified heat transfer some, but still, the hot spot is always on top in my experience.
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