Cast burn tunnel/riser and refractory metals

I am looking into building a stove or rocket stove that is efficient and safe to use in my huge 2500sq ft home, not a mass heater but a furnace type unit.... was thinking of building the burn chamber and riser with a 6" refractory cast core, using the 55 gal drum style unit for the heat exchanger, build a sheet metal box around the heat exchanger and hook up a blower to this box to circulate the hot air through my ductwork, just like a regular furnace style setup, I want this to be a pellet gravity fed unit, was thinking of making the pellet basket or grate out of refractory metals and any area that gets extremely hot also, this unit would be set up in my basement and be hooked up to my masonry chimney which is approximately 20-30 feet tall , I want to build this unit to be very durable and safe (meaning I don't have to take it apart and rebuild it every year like some of the units I have seen on youtube or is going to fall apart in a short time). instead of buying a normal furnace that is on the market for 2-3 thousand dollars why not just build a efficient safe rocket stove with that money....instead of building junk or ones that wont hold up and nickel and diming yourself to death..... I am new to this concept so any solid input would be greatly appreciated...
any suggestions ideas or concerns...feel free to let them be known...
thanks

putting any wood stove in the basement may be a bad idea for many reasons... draft house chimney effect will cause smoke back, and very inconvenient to feed and other bad ideas as well.

if you need a nice intermediate UL tested stove that can pass housing code, insurable and looks and sounds very much like a rocket stove and has pellet options and can plug into your current chimney look here: https://permies.com/t/54288/rocket-stoves/UL-tested-Rocket-Heater-burns

John is in the process putting together a cast core out of simple materials around the house and you may get some ideas here: https://permies.com/t/53224/rocket-stoves/Portable-Compact-RMH-Hybrid-internal

and if you are interested in a new Rocket Mag Stove design on wheels I have instructions on how to build it here: https://permies.com/t/54074/rocket-stoves/Rocket-Mag-heater-Rocket-Mag

i would browse the rocket stove section since there are many ideas to pull from.

thanks, I have looked around this website for ideas and have come up with the idea by reading and looking at many ideas here, right now I currently have a regular wood stove furnace in my basement and have been running it for 20 years with no problems of backdraft or creosote problems, I run it as hot as I possibley can 24/7 no problems...except the wood it eats.....very inefficient.... I am getting tired of all the wood cutting etc.... so I thought I would like to build a efficient pellet stove out of the rocket stove concept....that can handle the heat.......cast core/refractory metals self fed etc....
thanks

not everyone has a problem in the basement with stoves and i am sure there are people that have put them there but its not common for a reason and there are disadvantages to such for sure. I would assume your stove burns hot and that heat is an important thing to have in its position and it will eat wood because of that. Rocket stoves are a different animal and you may have a good chimney that is insulated would be a plus and without cutting corners a rocket stove can be done right. it would be advantageous if the rocket stove builder was researched, experienced, and or mechanically inclined could help to reach your goals and desires.

thanks, that's what I am doing...researching, asking questions to and try to come up with the best ideas and materials to do this project, I am a thinker, tinkerer, diyselfer, carpenter by trade, weatherize homes for a living, test furnaces etc... this all started out by me trying to find a different heat sorce for my home because I am getting tired of cutting all this wood and I am running out of places to cut wood so I need to find another way to heat my 2500 sq ft home but have the same comfort as a woodstove...looked at pellet stoves on the market there expensive and inefficient... I estimated that I probably would use anywhere from 5-8 bags of pellets a day to heat my home with the current stoves out there..thats to expensive for me, while doing research for heating I stumbled on the rocket stove concept and it has some possabilities I may try and test, I was thinking of building it in my garage and I could test it out there before adding it to my home, but I want to do it right and not have it fall apart or fail in a short time, my home is a standard rambler style with walk out basement...for some reason my chimney has excellent draft? probably because most of the chimney is inside the home, it is a standard up to code clay flue liner in chimney block unit, even with the stove not running I have a negative draft force in it??? I burn my woodstove hot because my house is huge a lot of area to heat plus I don't want any creosote build up, if I could somehow build a pellet fed rocket stove I was hoping to be able to use less than 3 bags of pellets a day and I would be happy.... I enjoy reading your input on these pages and your mag rocket heater info...for now I am just trying to learn and research, so if I ask stupid questions youll have to forgive me but I want to learn and do whats right and best for my situation, I live in north central Minnestota so we heat our homes 7-8 months a year.....
thanks

if you build your rocket stove in the basement and go straight into the chimney you will not use the rocket stove to its fullest potential and potentially burn just as much wood as your standard wood stove if not more depending on configuration.

my theory was to build the 55 gallon barrel heat exchanger type and enclose it with a sheet metal box (plenum) with a fan to push the heat through my ductwork like a furnace would , my problem is I don't really have any space to make or run a mass storage to heat the whole house that I can think of right now

even if you built the best and most insulated duct air circulation system it would only distribute heat as long as the rocket stove is in action and with no way to store your wasted heat you will have to run your rocket stove 24/7 and having it in your basement will be a pain in the butt babysitting the short feed times and in the end rocket stoves burn fuel fast you will end up using more wood than your wood stove. No mass battery to store heat that normally gets wasted out the chimney will Not be saving wood fuel and end up using more.

bigelow farms made one with a plenum shroud surround and uses it to heat water and almost like a forced induction furnce. he is onyoutube and he burns pellets- but he burns alot of them...

how well insulated is your home? it would have to be damn well insulated to even attempt. are you familliar with "displacement"?

when air is rocketing OUT of the home via chimney- new air has to come IN the home- its displacement - otherwise its an impossible vaccum fighting your draw OUT. its really a catch 22 because you NEED displacement for good draw- and the air coming IN the home is ofter cold. a few people have made fresh air intakes built into the stove - like a certified pellet stove has

I have seen calculations (don't remember exactly where at the moment) that a standard J-tube, 8" probably, needs something like 60-80 cfm of air, and an ordinary house with occupants and appliances should have that much fresh air for health anyway. So the RMH would not necessarily be increasing the air infiltration but directing the exfiltration.

http://www.woodheat.org/the-outdoor-air-myth-exposed.html

all homes no matter what you use to heat your home need to be aware of displacement etc... except sealed systems, because all systems that are not sealed need air/oxygen to burn from inside the home,(sealed systems have a system that have there own intake from outdoors)... and if it cannot get it you will have problems with it etc... are not we looking at rocket stoves for there efficiency ? because if your putting all the heat from the unit out the chimney its not efficient...that does not have anything to do with air coming into your home from cracks etc or your insulation of your house, these are 2 separate things we are talking about here, granted a leaky house is not efficient in itself but this discussion is about rocket stove efficiency isn't it? sorry but I think this is getting a little off subject..any home that is not well insulated and properly air sealed will not get heat to stay in it no matter what kind of heating system they use......and will go through a ton of fuel.

john mcdoodle did you get your cast unit up and running, if it works good what are the dimensions of the unit, I am looking to build a cast unit to burn pellets thanks

Any house, especially one heated by warm air, needs to be insulated and sealed as much as practical before planning the right heating system.

If you plan a pellet feed, you would need to keep the fire burning 24/7 unless you acquire something like a commercial pellet system. I don't know how they work, but presumably they have an igniter to start the fire when needed, or else a pilot. My niece in Connecticut has a pellet stove and it comes on at intervals.

A rocket stove continuously burning would require duct circulating fans going all the time too, if there is only a metal barrel heat exchanger. If you built a brick bell and enclosed it in ductwork, it could constantly accumulate heat and distribute it when the house called for it. I do see any such system having significant losses in effectiveness from the mismatch between firing pattern and distribution/use. I don't think it is impossible, but it needs thought to work well enough to be worth while. Any details you can give on your pellet burning plans would be helpful.

thanks
my plans are.. currently I have a wood burning stove/furnace its hooked into my ductwork from plenum that has blowers that push heat from stove to throughout the house, I was thinking of making a rocket stove on the same order..like build a plenum around the 55 gallon barrel heat exchanger with fans to push this heat from barrel to areas throughout the house like a normal furnace would..but use pellets for fuel instead of wood, make it into a self feeding unit like the many I have seen on this site and on youtube..except build it out of cast able refractory (burn tunnel and riser) and refractory metals for the pellet basket/grate feed tube etc... just a idea

Sorry if I get easily sidetracked but excellent draft relates to displacement and external intakes.

Anthony Donner wrote:

john mcdoodle did you get your cast unit up and running, if it works good what are the dimensions of the unit, I am looking to build a cast unit to burn pellets thanks

My first unit has a cast internal mass and it is up and running, my current build is a larger massive cast core unit and I have not even poured the cast yet, as I do all my work and first trial runs in the workshop which is unheated and uninsulated and I live in Canada so I need a few warm days to cast my current project, which is 32"long, 20"deep ,and 16" wide in the massive cast core area alone, since you asked about the dimensions.

They both contain massive cores to store thermal energy. They are designed to burn for 5 hrs and then let the mass energy radiate for the next 5 hours, essentially giving 10 hrs worth of heat from 5 hours worth of fuel. But the mass is internal to heat up FASTER than a typical RHM and for SPACE SAVING - I have designed these for spaces under 800 square feet , homes with passive solar and or geo thermal foundations below frost level. - small earthships like mine- designed for my needs

Canada knows cold. Lol

thanks, I agree there is many factors that can effect draft and such, anyways I watched your videos on the one you used to feed pellets, I am looking to build one like yours to feed it pellets but want to build the burn tunnel and riser out of cast refractory and the pellet tray out of refractory metal, is there any dimensions that are critical in your design ? besides the burn tunnel and riser being about the same? I was thinking of building a 6" unit, is it critical how long the horizontal burn tunnel is? I was thinking of maybe using the concept of the sky huddlesons feed tube unit for air coming through the feed tube around the feed tube that supplies the pellets? not sure yet?
thanks, by the way I live in Minnesota so I know your situation a little.

That unit has a square 5"x 12" long burn chamber , not including the riser. It has a square 5x12" feed tube on top of that burn chamber giving a 12+5" feed depth, so there is only 6.5-7" burn length in-between the feed and the riser on that unit, I think the riser is 31" tall, and 1.75" gap from the riser top to the lid.

I'm not sure what is "critical" but that's the dimensions of my YouTube rocket.

My current build will have all refractory cast internals and square 6.5" x 6" burn chamber and feed tube , and 6" round cast riser

John has definitely gone bigger. not sure if he has gone deeper though?

thanks,
I think I will do something on that order to, I am having a hard time finding refractory metals for my pellet basket/grate though...maybe I will use stainless expanded metal and just replace as needed...not sure yet something on that order.... yours and styles get there air from the horizontal front of burn chamber do you guys like that better than the air from the vertical j style air inlet with feed tube?
thanks

If you have a Rocket Mag Stove then it is not only preferred, it is essential to have the bottom front air port. the port is also provides easy light and cleaning access. Over sized feed tubes can also take advantage of the front port as long as you have a tight lid it will work awesome.

Anthony Donner wrote:thanks,
I think I will do something on that order to, I am having a hard time finding refractory metals for my pellet basket/grate though...maybe I will use stainless expanded metal and just replace as needed...not sure yet something on that order.... yours and styles get there air from the horizontal front of burn chamber do you guys like that better than the air from the vertical j style air inlet with feed tube?
thanks

i would try titanium or some kind of nickle but idk about metal . pros say avoid it.

i use the front port for intake when burning pellets. i use the top feed for fuel and air both when burning wood - and i use a magnet and steel plate to close the front port when burning wood JTube style. its versatile but its only a prototype i made to educate myself hands-on rather than possible theory and questionable advice.

Anthony Donner wrote: I am looking into building a stove or rocket stove that is efficient and safe to use in my huge 2500sq ft home, not a mass heater but a furnace type unit.... was thinking of building the burn chamber and riser with a 6" refractory cast core, using the 55 gal drum style unit for the heat exchanger, build a sheet metal box around the heat exchanger and hook up a blower to this box to circulate the hot air through my ductwork, just like a regular furnace style setup, I want this to be a pellet gravity fed unit, was thinking of making the pellet basket or grate out of refractory metals and any area that gets extremely hot also, this unit would be set up in my basement and be hooked up to my masonry chimney which is approximately 20-30 feet tall , I want to build this unit to be very durable and safe (meaning I don't have to take it apart and rebuild it every year like some of the units I have seen on youtube or is going to fall apart in a short time). instead of buying a normal furnace that is on the market for 2-3 thousand dollars why not just build a efficient safe rocket stove with that money....instead of building junk or ones that wont hold up and nickel and diming yourself to death..... I am new to this concept so any solid input would be greatly appreciated...
any suggestions ideas or concerns...feel free to let them be known...
thanks

I will try to make this short and painful for your design proposal….. metal risers will spall. Here are the pictures

Hi,
this build is on Vancouver Island. This was my first build over a decade ago. Since then, I have built 4 more and I have documented all of them here on one thread ending with Frankenstove 5, with an announcement of a Frankenstove 6 to heat an heat an aquaponics greenhouse.
Currently Frankenstove 5 heats our home and hot tub, Frankenstove 3 heats my shed and 4 will be dismantled and repurposed  with a post mortem and be part of the Frankeknstove 6 project.
I have only one main thread on this site so everyone could make sense of the progression of the evolution of the Franklenstove franchise builds.
All posted under "Peter Chauffeur" under the rocket stoves forum

Stay tuned, learn from my mistakes and I'm always up for suggestions from this site and its kind people.

my first mistake with rocket stoves was thinking high temperature metal risers would work!

Experience is a horrible teacher.......First she tests - then she teaches!