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RMH autopsy and redesign modifications

 
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Guys,

It was merely a suggestion... John seems to be a very intelligent and competent man. I don't think it would be too hard for him to make something like that work.

Allen, I understand that there are some bad videos on youtube. But at the same time there are some good ones aswell. Are Paul's not on youtube? There are many ways to extract heat from a RMH or traditional wood stove. Hell even some running hose through compost to heat water. Or some that I've seen that use a brand new radiator as a heat exchanger to heat the water. I only mentioned these as an idea. A way to help a fellow member. The last thing I'd want to do is get anyone hurt. That's not why I'm here.

I think this is a great project and was only trying to help.

Jennifer
 
Posts: 126
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The daily results show...
I started up the heater late today as the sun got it up to 60 in the dome for a while (even though it was only around 40 and windy). After trying to get a heat lamp going for the chickens (low of 14 tonight) I blew the breaker going to the coop and dome. I thought I had just blown the lamp bulb So when I tried to start the heater using the booster fan I didn't actually check to see it was going. It wasn't. So after a dome full of smoke and running to the house to reset the breaker, 15 minutes of a fan going, got the heater up and running fine. Switched to the 10ft stack, all was well for about 5min then a wind gust and direction change caused a back draft. Dome full of smoke again. Back to the fans, all is well. An hour later winds calmed down so back to the stack, all is well again.
Tonight my wife went out to tend the fire for a while and 30 minutes later she comes running in and screams "get out there, the hose broke and water is everywhere!!!" Oh the joy of it all Ran out to find the output hose on my radiator heater setup had blown off and because the pump was running water was spraying all over the floor next to the barrel. Why my wife didn't just shut off the pump or valve is a mystery. I guess she just panicked. Anyway I did away with the radiator since it requires a high degree of attention to maintain safe operation, something my wife is averse to. Water heating is definitely still in my future, just by a different method.
So we've come full circle back to Allen's comments. He might be saying "see I told you so"

Other observations of the day. My wife went crazy stoking the fire and got things really cooking tonight. Barrel temps on top got to 780deg (likely the cause of the radiator hose failure). A bit later temps were: Barrel top 655, side of barrel near top 370 and 515 on rear (the feed tube side, and the least clearance between the riser and the barrel) bottom of barrel (just above the transition area) 280, ground duct@1ft 180, @6ft 125,@12ft 110, pipe coming out of ground outside 75deg. Seems like I've extracted sufficient heat energy before the exit point.
As a side note I thought I have read that the barrel temps should be higher on the side with the greater gap between the riser and barrel side contrary to my observations.

My only question for this post is about the high temp of the duct cob near the barrel and rapid decrease with distance.
When I have more cob over the entire length of the duct will it allow more heat to get farther down stream? It seems like it is losing a lot of the heat in the first few feet as opposed to a more gradually decreasing heat throughout the 12ft cob covered run. I'm also still looking for opinions on the using the concrete cap blocks over the cobbed duct as it relates to the retained and radiant heat factors.
2013-11-24-12.38.31.jpg
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experimental Radiator for coffe cup warmer and aquaponics water heating
 
pollinator
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John Adamz : In the Wood Stove contest, one of the units I was keeping my eye on had a Coaxial Fan and double wall chimney I thought would do well. but there was no provision
for changing the speed of the Fan, and their wood box was overstuffed and the Particulates climbed high enough to lower their final place in the standings.

In a perfect world you could find a 2-3 speed inline fan to play with, I think your Barrel top temps, and the reversed hot spots on the side might be a sign you could use a slightly
smaller fan ! but then again with your exit exhaust gas temps I won't want to make a big change !

Of Course your Barrel/Manifold design is breaking new ground ! or to continue the farming analogy, walking on new ground

Does anyone want to weigh in on 'dimmer switches' and electrical motors ?

Rob T. who puts all of his Videos on his own channel at You Tube search for> web4deb channel had an air bubble form in his radiator and the radiator got so hot it melted a safety
seal ( one of those foreign metric-ated Cars !!! ) and his experience was similar to yours !

Something similar to the kind of shipping quilts you rent at a U-haul place making a semi insulated covering will shift the heat farther down your Horizontal exhaust pipe, and now is
the time to figure that out because you want to know now where the Horizontal chimneys sweet spot for the seedling grow bed will be ! Big AL !
 
allen lumley
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John Adamz : Pack McKibben started a thread> Barrel offset distance (rocket stoves forum at permies) I don't think anyone would think it highjacking for you to post a couple of
pictures of your heat riser and manifold and your experiences with backwards temps ! Big AL !
 
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RE: radiators
Although we think you may be on the right track,you have to understand that this piece of technology is being used in completely the wrong way from the inventors intentions.
Hot water/coolant from the engine was supposed to be COOLED by the air rushing over the fins of the radiator. We are doing the reverse of this. In this circumstance you may have to resort to a large truck/towing radiator or one from an 18 wheeler to have enough CSA for the fluid to flow through to suck heat off the fire. You've got it hooked up to garden hose when the design of the radiator outlets is for something more like 1 1/2" hose. I see this as more of the issue than distance at this point but clearly clearances all play a part of the equation. More pumping volume and bigger pipe would do wonders! Might as well be trying to put out a forest fire with a 'Water Pik' toothbrush. It would be very helpful to stick a thermometer inline with the water hose to monitor temps and know when your getting with specs of the water radiator, otherwise you'll be seeing a melttdown or worse. Stay safe out there.
 
Jim LaFrom
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re: Cap blocks
I think the cap blocks would be effective in keeping the weight distributed over the area of the ductwork so it doesn't get crushed or even restricted. It will pickup some of the heat just be the Radiation factor of heat but it would be better to have Conduction by mechanically connecting them to the cob (with more cob.) It always seems to come down to more cob doesn't it? LOL
 
Jennifer Charlton-Dennis
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John,

Hey I'm just wondering if it's possible if you can make a couple short videos about not only the RMH but your greenhouse as well. I know you've been super busy with all the modifications, redesign and rebuilding. So maybe once you're feeling more comfortable with your operation.

My motives are not entirely selfish (I would love to see a video tour) I'm thinking that guys like Big Al, Jim, (people with much more knowledge than me haha) could possibly be able to give more thorough advice if they can see it in operation. Again, just a thought!! No danger this time!!!

Jennifer
 
pollinator
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> ten foot vertical pipe... flow...

Quick thought (w/out reading whole thread): Double wall flue pipe (type B vent pipe) keeps the inner wall warmer to aid exhaust flow. Helps both indoors and on any pipe exterior to the building. Trade off is you lose more heat to the outside if your exhaust stays warmer... And of course B-vent costs more.

> [keep heat in]

Radiant barriers on walls/ceilings helps reduce radiation toward the outside; but you might not like the look of it. I used a couple rolls of heavy duty tin foil and papered the inside of my attic rafters to keep heat _out_ during summer and it helped noticeably. Note, radiant barriers need an air space on the side you want to keep the heat and it helps of there is air on both sides. Tin foild makes a perfect radiant barrier material but it's totally flimsey; if there's any contact at all it just tears.

Rufus
 
John Adamz
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Jim- Thanks for adding to the discussion

Jim LaFrom wrote:RE: radiators
Although we think you may be on the right track,you have to understand that this piece of technology is being used in completely the wrong way from the inventors intentions.Hot water/coolant from the engine was supposed to be COOLED by the air rushing over the fins of the radiator. We are doing the reverse of this.


It's function is a heat exchanger. Hot water inside to cooler air outside. It is equally plausible (but less efficient) that it work in the reverse, hot air outside to colder water inside. That said, air is a poor conductor of heat.

In this circumstance you may have to resort to a large truck/towing radiator or one from an 18 wheeler to have enough CSA for the fluid to flow through to suck heat off the fire. You've got it hooked up to garden hose when the design of the radiator outlets is for something more like 1 1/2" hose.


A larger radiator would help as it has more surface area (as well as a larger volume of water) to be heated. It would still not likely need a greater flow of water than what could be pumped thru a garden hose to keep from overheating (below 260-70). Yes I know garden hose is not rated to handle those temps. Temps of the radiator I used were peaking around 250deg just before the pump would cycle.(15min on, 15min off) The reason for the small hose is twofold. 1-The heat absorbed by the radiator I used is insufficient to heat even a small flow of water. It would cool down to tank water temp of 55deg after only a minute, and never warm up till pump shutoff. So a larger hose would be of no help. 2-It's what I had on hand long enough to go from tank to radiator and back.

I see this as more of the issue than distance at this point but clearly clearances all play a part of the equation. More pumping volume and bigger pipe would do wonders! Might as well be trying to put out a forest fire with a 'Water Pik' toothbrush. It would be very helpful to stick a thermometer inline with the water hose to monitor temps and know when your getting with specs of the water radiator, otherwise you'll be seeing a meltdown or worse. Stay safe out there.


If I had a more direct heat transfer from the barrel to the radiator (no or very little air gap, or in an enclosure over the barrel) a larger pump volume and constant flow would be required. 3/4in heater hose and pvc or pex pipe would work to handle the flow rate.
Here's an example. If your car radiator fan quits working you can use the heater blower on high (heater core supplied by 3/4 and/or 5/8 hose) and it will keep the engine from overheating and doing damage. Especially if you're driving and not idling with the AC on and staring at that pretty red light .

Thermometer in hand, safety first indeed.

All that said, I'm still evaluating the option of heating the water by running pex pipe or maybe even copper tube in the cob over the duct and using a low flow of water out of and in to the aquaponics sump tank or floating bed tank on top of the fish tank, or the fish tank itself.
 
Jim LaFrom
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Re: Radiators pt2
First off Happy Thanksgiving to you all! (and Pocahontas too)
John,
I guess I interpreted your initial question wrong. I thought you were trying to keep the radiator from over heating. My mistake. If your goal was to direct all the heat to the water baths then of course your underground ducts will be starved of heat. If you want heat to flow further down the ducts then you have to forget the radiator because now it is acting as a refrigerator because the water bath is cooler than the barrel. Physics principle (All energy is conserved)

An example in reverse temps. Your task is to get cool water to the far end of a straw. Imagine a long straw (20 feet +) you attach a couple ice cubes to the first couple inches. Your pour lukewarm water into the entry point. As it passes the ice it will cool but after that, the atmospheric temps will tend to bring that water back into balance with that atmospheric temp. So at the far end of the straw, the water is back at room temp. The ice wasn't enough in this case to maintain the change in temperature.
Taking that all back to the stove example, just because you have a high heat source at one point doesn't mean that the distance that the air travels, allows it to stay hot for the rest of the trip. Sticking a radiator on top WILL cool the heat enough to not be able to get the ducts sufficiently hot and stay hot. (but that part also concerns insulation and mass.) The ONLY other way this could happen would be in a vacuum. (Hence Thermos bottles.)
I guess I DID stay awake in my Physics classes!

So your choices are to dedicate one system to the ducts and another to the water baths, or eliminate one system. Even though you think you have infinite heating capacity because it's a RMH , it is ONLY at that one point and the whole rest of the trip it is trying to cool down.

I'm thinking that Paul wants to try and make this all happen with natural drafts and wind currents so that kind of limits the discussion. If you are willing to incorporate forge technologies such as high heat coal or other fuels, bellows and or fans, pressurized combustion air, electronically controlled dampers, ganged RMH's we could probably set up our own foundry! It could get pretty fancy ($$$) pretty quick.
 
allen lumley
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John Adamz : A floating bed tank is a new one, I found a blog site with about 10 people with 15 different opinions on how it worked - Talk about Blind people describing
an elephant ! Ther is a lot of ignorance out there! Can you send me to a good site ?!

Jim LaFrom : Or, we could just use Erica Wisners cook stove, that reaches Forging Hot Temps on the RMHs own natural forced draft, and do simple forge work with Hardwood
charcoal ! For the good of the craft ! Big Al
 
Jim LaFrom
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re: heat to ducts or water media.

I think because I have thoughts of building a green house in the future and live in a similar zone, this thread intrigues me and helps me to mentally work out all the problems I will face before I actually get to them.

John, for this winter I think I would abandon the idea of the ducts because you are fighting a very inefficient system. For my time and effort I would concentrate on the water media and work towards getting your optimal temps. Just like Paul's webcast where he says to "heat the people and not the room", I would build a cloche (or cold frame) for the tanks out of PVC and plastic sheeting instead of trying to heat the entire volume. Maybe even wrap the bottoms of the tanks in 2" EPS foam, if it's in the budget. Right now the tanks are suspended in mid air and allowing heat to escape from every possible surface. (Not good.) Whatever escaping heat from them will help somewhat to heat the surrounding area but at the moment you are trying to push warm air to the plants by heating everything. It doesn't look like you have huge bushes or trees to worry about inside, so this should be doable. So in effect you would have a greenhouse within a greenhouse. I would adopt Rob's sheet metal structure covering the barrel to concentrate heat to the radiator and then enlarge the diameter of the entire piping system to the beds. I would HIGHLY Encourage you to watch Rob's (web4Deb) greenhouse series. That place is a marvel!

Don't try to cool off a cup of very hot soup by standing across the room and blowing towards it with your mouth.
Happy Thanksgiving.
 
Jennifer Charlton-Dennis
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John,

Just wondered if you'd thought of anything like this video to help keep your water warm. http://www.youtube.com/watch?v=WP8H5IOTwYU If we had more room we'd like to build something like this. Hope everything is going well.

Jennifer
 
John Adamz
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Thanks Jennifer,
I think I'll try that out come spring. I don't think it'll work for the winter if it's really cold, but it could with some attention. Would work as a supplemental heater.
On the short list of projects.

Now for the update on operation with some questions.
I have a few days of temps in the 60's before the big chill by weeks end, in to the 10lo-30deg hi range. After 30-40 hours of operation I took off the barrel to inspect, and it looks pretty good. Only about 2/3 a cup of fly ash total in the drum base/transition area ash pit. Riser was clean as could be up to the top, with soot just in the corners a couple inches down. The outside of the riser insulating tube was a little sooty (not easily brushed off) as was the inside of the barrel. Is that normal?

I'm wondering if I should make a bigger riser insulating tube (14"dia now) to lessen the air gap between it and the inside of the barrel. I suppose it might help with draw/flow of exhaust, and I think it will reduce radiant heat off barrel and send more into the duct in the ground. More heat in the ground would be a desireable result as it should get the duct cob hotter, AND the cap blocks I set on top with fresh cob and finished up today. I have another thread on that. blocks on cob

Working on a fish tank heater too. RMH heat for water mass

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fly_ash_btm.jpg
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cap_blocks_on-_cob_duct.jpg
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John Adamz
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Things were running pretty good at last burn but the test run tonight to dry up the new cob didn't go so well. I was having a hard time getting even a moderate draw, and with some questionable wood I was burning after I had it going for a bit had a smoke back disaster. Aside from the added cob (which shouldn't have any affect on draw/gas flow) the only change is I cut off the small straight part of the transition area hole in the the lid I'm using for the bottom of the barrel. This added maybe 8sq in to the area of that hole which I keep thinking was too large anyway. I did it to make the opening smoother into the area below.

I'm recalculating things and think that hole should perhaps be somewhat smaller. It's around 90+sq in now, and I think it should be closer to 70sq in for my 6" J-tube. I think I read about sizing this exit area on the donkey forum, but I forgot. The large distance between the riser insulating duct pipe (14") and the 55gal barrel (22") of 4" all around might also be too large. Although I think the size of that gap will just let more or less heat radiate off the barrel as long as it isn't to small (less than 2")

Going by the book if an 8" system has a CSA of 50sq in, and the 2" barrel gap gives an area of 125sq in (a factor of 2.5) this seem like the right size to start with when creating a tapered transition area (venturi) to the exhaust duct. Give those assumptions then a 6" system might be 70sq in or also a gap of maybe 2" in a 30 gal barrel (I don't have one to know it's size) also a starting point size for the transition area.

Here's how my flow goes, 6" J-tube CSA of 28sq in, coming out of riser with 2" gap to barrel, 125sq in area between riser and inside of barrel, ~90sq in exit hole into venturi transition area and out a 6" exhaust duct. 30ft of duct and a 10ft vertical stack.

If I'm using a 55gal barrel (since I don't have a 30gal one) with a 6" system should I decrease the gap between the barrel and riser insulating cover to less than the current 4"? In doing so if I lose radiant heat off the barrel and it goes into the exhaust duct that's fine, more heat for the mass. Given the formulas that might mean a gap of only just over an inch to get the ~70sq in area. This would be rather hard to transition in to a manifold out of the bottom of the barrel.
Or can I just reduce the size of the transition area manifold hole from ~90sq in to 70sq in?

I need to do something quick, I have about 48 hours til it goes from a high of 60 to a low of single digits and snow!
barrel_manifold_final1.jpg
[Thumbnail for barrel_manifold_final1.jpg]
I cut the straight part at the front side of the hole
 
Jim LaFrom
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Oh man.... my thoughtful post disappeared I guess.....
John et al,
My post wasn't so much about your draw problems but this.

Anyway, I found a series of videos regarding RMH in greenhouses. Many have asked about the mathematics and BTU's and the how to's of doing this in a greenhouse environment. His third video really gets into the 'meat' of the matter, explaining why water makes a better mass than cob. It's about the science of it and not just opinion or how 'organic' you want to be. If you need overnight heat in a greenhouse you need to watch this series. Unfortunate poor production quality but the content is there. https://www.youtube.com/watch?v=FrWtlf_4ny4 Good Luck

Zero degrees in Truckee overnight,got my footy PJ's on. LOL
 
John Adamz
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Jim
OMG that video series is the mother load of info for a techno geek like me. Water is THE way to go for a thermal mass in a green house if not the main house.
THANKS!
 
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John, did you see the reply i made to your post at Donkey's?
 
John Adamz
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Satamax Antone wrote:John, did you see the reply i made to your post at Donkey's?


Not getting any post notifications, hmm? Yes I did now. If you haven't you should really check out the vid links Jim posted up thread a bit. FANTASTIC!
 
Jennifer Charlton-Dennis
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Hey John,

Just wondering how your modifications worked out during the big freeze. Did you guys get as much snow as you were expecting down there? Hope all is well!

Jennifer
 
John Adamz
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Well another day, another experiment. It's been unusually cold for here. lows 5-15, high not above 30 mostly low 20's for a week. Needless to say I'm about tired of spending all my time burning wood between the house the garage, and the greenhouse. I gave up on the house and garage since I'm running really low on wood and my supplier is backed up with deliveries.

I tried a WMO setup for a while with mixed results. It's filtered oil mixed with 15%gas (the fuel I use in my diesel truck) Since I have to deal with the size of the feed tube my Wife found a little 5" cast iron skillet used for a pan cookie kit at WalMart. It burned OK except I had a lot of sludge build up in the pan after only an hour or so that would not burn. It also wold not heat the barrel over 300deg. I spent a lot of time on waste oil heater plans (never got to build one yet) even before I got into the RMH groove and am not sure exactly what the problem was. Maybe just too small a surface to burn oil on and maintain a high enough temp to keep it burning cleanly. I even tried using a little blower on it which usually increases the intensity of the burn but it seem to cool it off instead.
Since I was desperate for heat I am using my 65K BTU kerosene (diesel) torpedo heater at night, and during the day to supplement the RMH deficiency. Used 6 gal in 3 days.

My best guess on RMH output with wood is ~30K BTU, calculated by the formula Area(of wall and roof)/R (R factor of insulation averaged for structure) x delta T (difference in outside temp and desired inside temp) =BTU/h I can keep it just over 50deg, but want 60+. That would mean maybe ~35K BTU/h all day at least during this cold spell. I'd need more than that output to store any for when the heater is not burning. I'm still thinking water mass is the way to go for that.

While going thru all this I observed a puzzling phenomenon. No draw problems, or blow back and easy starting up. My barrel top temps are not at all consistent. Even with what looks like and sounds like a very rockety well stoked fire the temps will vary anywhere for 450- 640max, and usually not much over low 500's. There have been a few times for a while it got over 700 but rarely. I have 2 types of hard wood (oak and walnut). Small chunks or stick type pieces doesn't matter much. (It's all seasoned dry wood with no bark). I still use no booster fan, but play around with my funky feed tube intake on the bottom front of the feed tube (which helps some with burning up the coals when air flow directly over them) and partially covering the top of the feed tube. I tried using a grate over the ash pit in the feed tube, no help with build up of coals. I also added a feed tube P-channel yesterday which helps a bit with flame wicking up the wood and lowers temp of the top of the burn tube. But no real effect on top of barrel temps.
Lucky I'm patient or I'd throw my hands up and walk away right now.
 
allen lumley
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John Adamz : I know this can be frustrating, Imagine driving across a shallow seeming large well frozen puddle, breaking thru the ice in -10 below weather knowing
that any attempt to Touch the brakes would lock everything up I spent most of the night wearing a scott air pack in the locomotive house alternately Toasting the
brakes with a propane torch and cleaning the nozzle of the torpedo heater,by hand with pliers and a head lamp, and finally getting every thing toasty enough to be
able to put it in tractor low and lightly apply the Brakes, They tried to deny me the 2hrs of overtime and I got a bad boy letter in my file for driving across the ice
which after all was in the middle of the road ! OH, and the guys in the Engine house were not happy that i couldn't re-bank up the overhead door bottoms with snow
so all the thawed water refroze to the floor ! Ah, the good old days !

Any way this is about you, and your project, When it all goes wrong, and your journey seems all up-hill, come here and check out the bottom of this page to see just
how many people care, and follow your adventures Good Luck ! For the Good of the Craft ! Big AL !

Late Note! I doubt you will see a puff back before spring with a warm chimney and cold outside temps !
 
Satamax Antone
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John, is it Batch rocket time?
 
Rufus Laggren
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John

Just throwing out ideas. Sounds like mother nature is pressing necessity onto you and you're looking for the best bang for you time and buck.

Heat needs. Salamanders produce lots of heat - you got that covered though it likely costs more than wood. Thinking of heat loss - if you got wind there maybe it'd help to throw up windbreaks of something or other if you can? Pile stuff or park around the green house? Pound in a few stakes and lean plywood on them to form a wind-wall? String large tarps across close from lines between buildings or poles? Put in a low ceiling (6-7') in the green house so you don't heat the whole thing?

FWIW I think you're right, if I understood about the oil - too much space around the burn doesn't keep it hot enough like it does closely packed wood. And Not enough fuel (oil) for that size chamber. Maybe you could try coal?

Best luck.

Rufus
 
Jim LaFrom
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As to your varying temps. The wood is the only varying factor. Hate to suggest 'just one more thing to buy' but if you have made this big a commitment to burn wood, it would be money well spent to get a wood moisture content meter. You would be surprised in the differences between the sleazy wood dealers and the honorable ones. It's that or prepare to buy enough for 2 years supply so that you can properly season that wood one extra year to make sure. It has to be the differing moisture content that is making the difference. Keep a stiff upper lip. we're rooting for you.
 
John Adamz
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Things went pretty good with tonight's burn, got barrel top to mid 600's for quite a while. Nothing changed from last erratic temp burn.

Satamax Antone wrote:John, is it Batch rocket time?


Well I keep thinking about how that might be accomplished with a minor modification. It seems that from what I've seen of batch rockets the horizontal feed chamber is rather large and open on the feed end, and has a normal 6-8" burn tube at the other end. Does the feed end typically get partially covered in some way? Don't you have to keep pushing the wood in as it burns?
What about if I just enlarge the feed tube opening on the top to allow for more wood would that change things negatively as far as draw//flow? Or maybe try a horizontal batch tube by extending the whole feed area back horizontally. Using full fire bricks make the feed tube ~11.25H x ~7W and ~13" (or more?) deep, feed opening to burn tube opening.
I've also thought about making the burn tube longer, from it's current ~9" (measured on the ceiling of the burn tube) by adding another 1 or 2 full bricks on their side for the top.

RUFUS- Thankfully not much wind to deal with but I have thought about putting an old solar pool cover on the north side of the dome. The type of dome I built only has a 9' peak for a 22' dome. Other 22 footers can have a 11-13ft height.
I would be thrilled if I could find coal but not likely around here. Maybe steal some from the power plant a couple miles west of me

JIM- I have been almost exclusively using the cut off untreated railroad tie ends for the past 6-7 years and get them from a guy who works at the tie yard. $50 a truck load which is all I can afford most of the time. They are a bit green most of the time, but burn pretty good in the fireplace insert after a few weeks. I'm using the last bit of wood from last February's load.

Thanks for all the help and encouragement guys. I just can't wait til it gets up to normal temps here (low 40's) instead of below 30! Might not be such a chore to heat things. The sun sure would help too.
 
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John,

Batch rockets do have a specialized shape at the exhaust end. I know that Satamax has a different opinion than me, but we actually put a Testo 330 on it. We found the batch rocket to be much more finicky. It was a lot harder to get good efficiency numbers on the batch rocket than it is to get them from a Dragon Heater cast refractory core. Also, we have found that you can't tell the efficiency just by checking whether or not there is smoke. The Testo 330 measures the CO PPM and an estimate of efficiency based on the moisture in the wood.

Cindy
 
Satamax Antone
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Cindy, i haven't said that batch rockets are not finicky.

All i can say, without a testo is, they're good enough for me

And they are less finicky on the loading side of the game. So, i'll trade a bit of efficiency for the ability to burn more, and with less chores

John, dimension wise, look there http://donkey32.proboards.com/thread/734/peterberg-batch-box-dimensions

Ps Cindy, did you get my email? Just checking.
 
Jennifer Charlton-Dennis
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Hey John,

Just wondering if any of winter storm electa passed by you and how things have been going. It was 12 degrees here yesterday but 30 today so much better!!
Hope thing are going well!!

Jennifer
 
John Adamz
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Jennifer- The past 2 days are the first above freezing in about 10 days. Yes we got another bit of freezing rain and a few more inches of snow Friday. Mostly calm winds all but a day or 2 in the past couple weeks.
The next week is going to be in the 30-50 range. Yeah!

During that time I hope to once again reevaluate my RMH operation and adjust accordingly. You all can look forward to additional posts to this thread in the coming week.
Recent observations and other puzzling things.
I tried again to use WMO with a bit better results. I added a handful of nails to the drip pan which reduced the sludge build up and caused a cleaner/hotter burn. However I still could not get barrel temps over 450 with any regularity even with what looked like a blow torch of a fire rivaling the sound of my torpedo fan forced kerosene heater. I was only using less than a quart an hour, but higher flow rates didn't seem to increase temps.

So back to wood (same as I've used all along) last night when it once again dipped in to the low teens overnight. During last night and this evening's burns I noticed that my dragon has become a mute! What's more bizarre is that with almost no rocket sound I'm getting barrel temps of 600+ ? It does seem to have a rather weak draw having a tendency to burn up a bit and therefore produce a large pile of coals, but no smoke back. So I let it die down to burn down the coals (still have barrel temps in the high 300's) stoke it up again and back to 550-600 in 5min. About a 25-30 min cycle.

With the warm temps came some melting of the ~8" of snow. I cleared the pileup of slideoff snow from around the dome base a couple times recently to keep it from melting and seeping into the floor inside. Of note is that the duct in the ground (surrounded by grave at that point) turns vertical to the 10' exhaust stack about 1 foot outside the dome's edge. I have kept that area clear of snow at all times.
It's possible that area might be a cold plug in the exhaust but I saw no easy way to have it exit vertically from inside thru the marine shrink wrap covered dome. I might need to isolate and insulate that outside area from the surrounding frozen gravel. With that thought in mind I wonder why I had a really rockety draw even at startup when it was in the teens and single digits and now in the 30's no rocket? The only thing that does make sense in that regard is that to reach max temps before I had to burn for 4-5+ hours. Today I got to 600deg on the barrel top faster than at any time before???

I couple mods I am contemplating are rather ambitious like maybe changing my J-tube to an 8". I don't think that would fly to well given my 6" exhaust. Or maybe changing my riser insulating media (in the 14" duct around the riser) from fiberglass to perlite/cob mix. On that, do I mix the 2 (at what ratio?) or fill the space with perlite and cap with cob? Or lastly maybe enlarge the diameter of the riser insulating duct to maybe 18".
Still on the agenda is the heating water for mass and fish tanks.

It's a good thing I have a full head of hair and an 18" ponytail or I'd be bald from pulling my hair out trying to solve these dilemmas;)
 
Satamax Antone
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John, insulate that last elbow in the ground outside at the vertical chimney. Better yet, put a T in place of the elbow, with a plug, so when your exhaust temps are real low, you can open it and let flow directly on the ground untill it warms up. Your stalling in the range of 30F°, and not stalling in the range of 10F° seems normal. Your temperature differential between exhaust temps and outside temps not being enough top have a strong stack effect when you are in the thirties. Hence the previous comment. My opinion is, you have too long a pipe into the ground. This cools off your gases too much.
 
John Adamz
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Satamax Antone wrote:John, insulate that last elbow in the ground outside at the vertical chimney. Better yet, put a T in place of the elbow, with a plug, so when your exhaust temps are real low, you can open it and let flow directly on the ground until it warms up.


I've tried it with no vertical stack. I get a reduction in draw, and smoke back. I don't have any problem getting a draw on cold start up.


Your stalling in the range of 30F°, and not stalling in the range of 10F° seems normal. Your temperature differential between exhaust temps and outside temps not being enough to have a strong stack effect when you are in the thirties. Hence the previous comment. My opinion is, you have too long a pipe into the ground. This cools off your gases too much.


Would not a colder stack cool off the exhaust reducing draw? I even tried using a section of double wall pipe on the bottom of the stack and saw no improvement.
To reiterate I have an 11' straight run out of transition area to a 90deg turn, 5' to a 45deg, 5' to the 90deg elbow going vertical, and a 10' stack. Does that really seem too long for my 6" system?
With extended operation I get temps on the initial straight run of duct with cap blocks on top of ~135deg@1', 115@5', 90@10'.
I have heard it suggested that an exhaust temp of 140 where it exits the structure is an indication of sufficient extraction of heat from the exhaust stream. If my barrel top temps are only ~600+ (bottom edge right above transition area is ~225) would I get such high temps in an otherwise perfect exhaust system? I don't remember for sure, but I think I had temps of around only 90-100 at ground level of stack.

Another modification that wouldn't be as hard as some other possibilities would be to increase the length of the feed and burn tubes as well as the riser height. Just an increase of the riser height should help with draw. It would be almost as easy to make it an 8" J-tube.
 
Satamax Antone
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John, cold temps are better for draft, The temperature differential is greater, hence the presure differential, so it draws more.

To me, your pipe is at about 27-29 equivalent in straight feet. IIRC, the max sensible lengh is 30 for a 6 incher. And you're in a sub optimal situation, with your pipe in the ground, which acts as a huge heatsink. if your temps are in the 90/100F° at the last elbow before the stack. That would sugest you buried pipe is too long. Have you checked if your cob has dried at the last 5' before the stack? I remember well, you put cob on the sides and top of your pipe?

If not bone dry, you're taking too much heat i think.

Another idea which poped into my head, insulate the first few feet of your buried tube. Between 5 and 10', stuff some perlite or vermiculite around your tube instead of cob. Or anything else you have on hand for testing purposes which is somewhat fireproof. May be you could dry the end of your pipe run. Tho, if it's all dry, your run in definitely too long.
 
John Adamz
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Max,
The entire current run of 6" exhaust duct is in a 12" wide x 8"deep trench. It has 1 1/2" gravel underneath the pipe. The first 10-11ft of duct has cob and gravel on the sides, cob on top and then the 2" paver cap clocks. The rest is just covered and surrounded with gravel, underneath, on either side and 3-4" on top.
All of the cob is bone dry. As is all the ground inside the dome. The outside is currently rather damp from melting snow, and I imagine a little ways inside the perimeter. I will as previously mentioned isolate and insulate the last few feet of the duct at the end. Doing the first few feet will be a next possible step. I guess that would push the heat further down stream before it's radiated out.
Wouldn't higher final temps (>100deg) only occur if the barrel was hotter than my average 600deg?
What about my other ideas regarding the mods on the rocket heater itself to increase output?
 
Satamax Antone
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John, your farenheit reading of 600 seems ok. IIRC, Peter van den Berg has the same with a batchbox.

Well, insulate your last few feet and elbow would help. I'm under the impression that you're trying to get too much from your six incher.

I'm affraid to say, go on make it a 8 incher. I think it could be possible, even with 6 pipe. Tho, may be another try you could do, if simple enough, to dismantle, you could try a 6 batchbox. That would increase the output. Don't know about your temps draft or else. But if it burns, well, you'd be sorted.
 
Satamax Antone
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John, another thing, what is your cob mix around the burn tunel and begining of the heat riser? Any straw? Sawdust? Ashes in it? Perlite?
 
John Adamz
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Satamax Antone wrote: I'm under the impression that you're trying to get too much from your six incher.
I'm afraid to say, go on make it a 8 incher. I think it could be possible, even with 6 pipe. Tho, may be another try you could do, if simple enough, to dismantle, you could try a 6 batchbox. That would increase the output. Don't know about your temps draft or else. But if it burns, well, you'd be sorted.


I never really knew what the limits of a 6 incher were before I built my system. I figured that I could at least heat up the mass by burning a bit longer. Another failure in planning was the placement of the feed tube on the wall side of the barrel. I just wanted to have the least intrusion of the heater into the floor space while having it far enough away from the wall to keep from melting the skin.
I really don't have enough room to see inside or easily access a batch box if I did add one.

what is your cob mix around the burn tunel and begining of the heat riser? Any straw? Sawdust? Ashes in it? Perlite?


I used fire clay from a pottery supply store. It has just clay and sand, I forget for sure but I don't think I used much if any straw in the base layer, but the 2 additional layers I added to it have none. The top of the burn tube probably is a bit thin as far as cob. Temps around the barrel base cob are only a little over 100deg.
 
John Adamz
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Took til last night to get into the heater again. I took off the barrel and found some problems. The riser looked intact, but due to the non interlocking or overlapping stacking of the the fire bricks I have 2 of the 4 vertical seams cracked most of the way top to bottom. The mortar just didn't hold:( On the good side the inside of the riser was squeaky clean. NO soot, even near the cracks in the mortar. The next bad thing is that the fiberglass insulation I used around the riser in the 14" surrounding pipe had melted to about half it's thickness about a third of the way up. Lastly there is a LOT of black sooty fly ash Likely from the inefficient oil burning.

So I'm sort of back to square one AGAIN.
1st thought on next redesign is while keeping the same feed/burn/riser length ratios increase the size of the J-tube to a 6" square (currently 4.5x6), trying to reuse as many of the current fire bricks as I can and stacking the riser differently. I will likely also have to slightly increase the riser to barrel top gap. I am in hopes that the 6" exhaust duct will be able to handle the increased flow and not be a problem as I am NOT going to redo that.

2nd The riser insulation. Although I have no money to get any perlite now what ratio of mix would I use of perlite/cob or other cheap materials to insulate the riser? Is the 14" diameter surrounding big enough? For now I think I will have to use more fiberglass in that space.
3rd I have never had much cob around the feed tube, and none on the back end so I can get to the ash pit easily for cleaning. Is this lack of insulative cob a problem? What problems might it cause?

Once again I'm at the brink of another arctic blast and need to get things going pronto.
 
allen lumley
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John Adamz : Wow, in this case it is impossible to tell from the information you shared which of your two problems occurred 1st, though probably the mortar
failure, you need to soak the bricks probably for a long 5 count to prevent your bricks from sucking out all the moisture out of the motor before it can set up !
Do I understand that you built your heat Riser without using a running bond pattern to allow staggering of your bricks ?

I personally do not like the fiberglass insulation, its binder fails at such low temps that it is injurious to your olfactory tissues, and can fall apart, if it then settles
it can be a little more likely to melt! I do Like Rock Wool, I put the blame almost solely on the sellers of Pink insulation who have convinced the American public
if it comes on a roll, or in a Batt or blanket, it must be fiber glass !

Recently I posted new thread in the Rocket stove forum, and Erica Wisners response is very detailed and has left me with much to consider before I volunteer
observations on difficult subjects like yours with out a lot of information and thought !

I can recommend that you check out her observations, while containing few Absolutes it should help point you in the right direction ! For the Craft Big AL !
 
John Adamz
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Allen Lumley-
Thanks for the response. I didn't think my questions needed much thought for a seasoned RMH permie like yourself. But I understand your focusing on something else right now.
More concise restated ?
1 will a 6" square J-tube work OK with a 6" round exhaust duct?
2 do I use perlite by itself for riser insulation or a blend then top with cob. Cheap alternatives?
3 Is it necessary to cob all around the feed tube, or can I leave the back bare?
 
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