How To Make A Concrete And Perlite Rocket Stove

- great shorts and it's time to remake my concrete rocket stove using viewer comments I made this a couple of years ago now and it has stood the test of time this was crack resistant concrete and as you can see here it hasn't cracked or exploded it's done a great job but this was a prototype the first time I'd made something like this and I've actually gotten a lot of great comments and suggestions on how to change and improve this design so I want to remake this rocket stove and make those improvements at the same time one quick caveat this is not a true rocket stove it has some of the main components of a rocket stove like a draft that pulls in air using convection and increases the temperature and efficiency of the burn but it also lacks a few key elements - like a secondary combustion chamber a lot of rocket stoves will have a dome over the top and the fire that goes in comes up and then the smoke goes down and out the back and that area here is superheated you get extra combustion and most of the smoke and carbon particles are consumed that makes it burn even cleaner that said I'm perfectly happy with this design for the purposes that I use it for which is outdoor cooking but we're gonna make a few significant improvements namely insulation this massive concrete acts more like a heat sink about several comments to that effect that to be the most efficient possible the mass of the rocket stove needs to be insulated in other words it doesn't absorb heat or absorbs as little heat as possible that's going to make the air stream in here hotter and allow for a higher level of combustion cleaner combustion in this combustion zone not a combustion chamber but the section between the firebox and the opening here will act as a combustion zone high temperature high airflow and a lot more burning happening in this section so we're gonna insulate the concrete using perlite perlite is a mineral that's used in gardens for soil amendment as you can see it's very lightweight this is going to provide a an air gap essentially insulating this concrete is gonna be a huge step in making this stove operate a lot more efficiently and we'll be making a few other simple modifications to the design as we go but let's get started I'm actually going to be using the same form that I used last time to make this rocket stove PVC pipe and a half gallon milk jug filled with water The Chronicles of Chadwick was actually concerned I was wasting a half gallon of rain water on this project but sinua trad wick this is the same 1/2 gallon of rain water from last time it's actually kept just fine and when I'm done using it for this particular build I'm gonna use it to water my plants so it won't go to waste but thanks for your concern David Anstey noted that the bucket is reusable duly noted and appreciated and Stephan Kaiser actually made the point that about half the video would be reusable in fact we're gonna be using a good bit of the forms set up from the first rocket stove build but the first step we're gonna do is we're gonna mark the bottom for drilling holes for our three pot standoffs so we'll start by marking a four inch circle here in the middle of the bottom of the bucket it's gonna be a general idea of where our hole is going to be inside and then we're gonna mark about an inch away from that a third of the way around three holes and then we're gonna drill them out alright let's just test to make sure our bolts fit through they do of course these are going to be coming through from the other side so just to check to make sure that they fit for the last build I used some bolts as pot standoffs on the top of the stove this go-around I'm actually going to use some scraps of rebar a head on hand that'll require re drilling the holes in the bottom of the bucket and I'll take the old ones so that concrete won't drain out through them you can see I still have my outline here where the four inch PVC is going to go on the inside just so I could make sure to space my holes far enough back I'm gonna use my twisted sharpie here to mark some new holes to drill with a larger bit I'm gonna make sure they're about the same distance back from that black line twisted sharpie is actually made by my buddy Greg Porter over at Greg's garage and actually I'll put a link you're interested in picking one up I have number 21 got a spade bit here to match my rebar let's drill the holes [Applause] all right now we're gonna put in our spot for the fire box now what I do with this design is the fire box actually comes out the bottom so that instead of having a tube located about here where the fire box goes in and then up there's no bottom to the fire box and that allows us to stack it on bricks or concrete or something to enlarge the fire box however we want to that's gonna allow us to potentially put more fuel in the rocket stove to make it burn hotter if we needed to we're gonna be using a half gallon milk jug to make our fire box and I like that because it gives us a square profile it's gonna be a little bit easier to get our fuel into the fire box it's going to give us a little more room and the straight sides are also gonna do well as we use bricks or blocks to make our fire box bigger start by tracing the outline of our milk jug on our bucket and we want to line up with the this side one side with the top rim of the bucket here now we'll use our hand saw to cut out our marking then we'll cut across the curve of the bucket to cut the bottom out cutting it this way is a whole lot easier than cutting a circle out of the bottom of the bucket here now let's just check and see that our milk jug fits excellent should go in like this and you can see how our firebox can be formed don't worry about these sections right here just because we're gonna line this thing with cardboard before we pour the concrete and tape up any seams so that allow us to keep concrete from flowing out so while our milk jug is still in the bucket I want to mark the length we'll need for our PVC pipe that's gonna form the chimney portion of the rocket stove just make that mark there and then cut this - link all right so let's do a quick test fit tube goods in the bottom and our firebox sits right on top now that the holes are drilled I'm gonna create a level spot here where I'm going to cast the stove this will be a spot where you want to put it and not move it main reason being because we're gonna drive the rebar through the bottom of the bucket into the ground just a little on the old stove the pot standoffs which we use the bolts for came a full inch and a half out of the bottom of the bucket which gave us an inch and a half rise I'm actually going to cut that in half I had a comment a year or so ago about needing only 3/4 of an inch here I can't find that comment to give them credit but I'm actually going to use that dimension I did notice that when I was cooking on this that there was a lot of air gap between the pot and the stove and I want to reduce that to the minimal amount so that the heat hits the bottom of the pot with greater intensity with my twisted sharpie I'm going to mark each piece of rebar with a black line that's about three quarters of an inch from one in the cleaner end and that's gonna allow me to sink each piece of rebar the same distance through the bottom of the bucket to give me that uniform standoff if it's a little bit different my pot bent and sit straight I can always true it up with the grinder after the concrete has cured twisted I'm going to pull each piece of rebar through to that line and then secure it with some tape as best as I can that ain't pretty but I'm only concerned about cleanliness on the inside right now the goal here really is just to keep these from moving around too much we'll be able to adjust it a little bit once we start pouring the concrete try and crew these up a little bit once we get it back in the ground the game once we put our first layer of concrete in the bottom they should sit in place much better the way we're gonna make this easy to come out of the form is that we're going to line our bucket and wrap our firebox and chimney forms with cardboard the cardboard is gonna provide you know an eighth of an inch of space that's going to allow us to very easily slide the whole rocket stove out and to then remove the firebox and PVC once this thing is dried let's prep our pizza boxes by cutting off the sides and separating top from bottom [Music] this amount of soil is probably okay that amount of residue is probably a little too much once the pizza boxes are cut working with the grain you want to roll them up [Music] [Applause] [Music] [Music] we're gonna tape it into the bucket putting a little outward pressure on the cardboard to keep it against the side to pieces doesn't make it all the way around so I'm going to overlap the pieces of cardboard evenly keep in mind that because this bucket has a taper the cardboard is not going to sit straight on the sides now the tape doesn't have to be perfect but keep in mind that you'll be able to see the edges on the outside of your rocket stove so the meter that can be the better now one thing that's kind of nice about using this cardboard on the inside is that the little vertical lines that we're seeing in the cardboard are gonna become a texture on the outside of the rocket stove which i think looks kind of nice alright now that our bucket is lined we're gonna trim the cardboard to the top of the bucket and cut out for the firebox opening instead of cutting down through the cardboard like this I'm actually gonna work from the inside so I don't undo all my nice taping if you slice down from the top - you hit the rim of the bucket then you can work your box knife through and then just slide it around the lid give a little more caution where you're working through two pieces of cardboard [Applause] [Music] when I get to the fire box opening here I'm gonna stop and work on that [Applause] use caution here this is where slicing your finger becomes a danger now we'll wrap our chimney portion and firebox with cardboard as well but before we do that we need to fill our milk jug with water our PVC is perfectly strong enough to hold back the concrete but our milk jug would just collapse under the pressure so let's fill it with some rainwater and then it's going to be a lot more substantial one half of the pizza box does a great job wrapping four inches of PVC we're gonna make sure that the bottom lines up nicely and then tape this in place don't forget that our pipe stops right about there all right once we got this wrapped we're gonna press down to find out where the pipe actually stops and then we're gonna cut there and cut around half of the cardboard the firebox is going to sit right in here like that and these will form the sides of the firebox all right so I've got my bucket set up like last time with the PVC down the middle the milk jug full of water and cardboard kind of supporting wrapping the inside and the outside of the form I got to say the pizza boxes made it really easy so if you have that option use it now it's time to mix up the concrete our concrete is going to be equal parts Portland cement sand and perlite this is just creeks and I'm gonna mix the ingredients dry before adding water maybe a little light on the perlite here and one more I'm actually gonna try and leave the armature out of this set up I'm not sure the chicken wire actually was strong enough to do anything in fact had a comment to that effect laughing at my chicken wire armature I'm gonna give this a shot just doing this concrete mix without any armature I find that when I'm adding water to concrete that's already mostly wet it's very easy to over wet so I'm gonna put a little more sand concrete just to get this a little more stiff [Music] [Applause] and there's our mixture let's put it in the form had several comments about agitating the concrete to get the air bubbles out using a orbital sander without paper on it or a rubber mallet and got my mallets I'm just gonna I also want to make sure that my rebar is standing straight up as I tap it though I want to make sure I'm not moving any of these elements around especially the that center tube also want to make sure the center tube is stayin fixed to the bottom of the bucket as well I like putting this concrete in in batches just so I can kind of see what's going on and it's just a lot a lot easier to work with but I don't want to wait too long between batches that I get a layer a seam between the two batches of concrete so this makes up another batch not only is this perlite going to add insulation to our concrete mixture but it's also going to lighten it significantly when we get done with this stove I'm going to weigh it against the previous version [Applause] [Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] [Applause] in addition to a drill you could also use a reciprocating saw [Music] [Applause] he more batches how to do it [Music] [Applause] [Music] all right were topped off a little more tapping here level this out just a little bit smoothing hair all right now we're gonna let it cure for about 48 hours all right so it's a few days later and it's time to take our concrete rocket stove out of the form and you're gonna find this funny but I had a comment from Toni on this video that suggested using floor wax paste or fiberglass mold release instead of all this cardboard to help the concrete slide right out of this bucket of course I had just finished filming the first half of this video where I had done all of this work with the cardboard so Tony thanks for your comment it was just a day late anyway I may have to try this project again Tony to try your suggestion to see if I can get this to come right out just using mold release or or even wax alright let's take it out of the form pull my milk jug out perfectly good rainwater that I will use in my garden or save for another build take the tape off the edges here [Applause] you can just stand this up and slide it out and go ahead and peel the tape off of this it's like those did pretty well they're not even when I get the pot on them I can always touch it up with my grinder all right this concrete is still green so it still got a lot of moisture in it and it probably needs to cure until it's a light gray before I can fire it just to be safe let's go ahead and unwrap the cardboard here so a little bit of a concrete getting underneath the edge [Applause] it's like a little bit of edge here where the concrete got underneath the edge of the cardboard at the very bottom where it didn't made up with a corner that's pretty sharp but while it's still green actually I can use something rough like this piece of granite gravel and just knock that edge right off if the concrete we're fully cured it'd be a lot harder to do that more of an overlap here see if I can now I don't want to do that too much because I do want to preserve and protect the the perlite that's inside here you can see when I'm grinding this away that I am revealing some of the perlite one of the byproducts of working with the cardboard is that you get these really cool vertical lines actually like the texture that that gives this rocket stove kind of feels like a an old Corinthian or ionic column from Greek architecture alright so now I'm going to turn this on its side and take out the PVC tube maybe I can just pull right at the top [Applause] cardboard comes out nice and easily I'm just gonna round this edge just slightly here [Music] turn this on its side and I'm gonna address the front edge as well I do want to be careful when I'm doing this especially with this edge right here that's kind of sticking out this is the thinnest part of the rocket stove and I don't want to break that off but I do need to grind it down because I'm gonna take this stove to the next level and in a subsequent video here I'm going to be adding a J tube so an rocket stove normally has a J tube that connects where the wood goes in to the base of the firebox it allows the the wood to self feed and actually had a comment a suggestion to add a J tube to this stove so I'm gonna do that in another video and the reason I'm doing it in this second video is because I really think this operates just fine like this but if you want that extra efficiency extra convenience of having a self feeding stove then I want to create a video that adds that component to this design [Applause] all right so even though this stove isn't quite ready to fire yet I am gonna go ahead and set it up like I will for firing had another comment that referenced the fact I really needed to elevate the fire over an air channel instead of that in the woods sit right on the ground so to provide that elevation for the air channel I'm gonna use a salvaged grill grate but I'm just gonna cut off one section of the great with my grinder safety glasses [Music] [Applause] I'm gonna prepare a permanent area back behind my wall to put the rocket stove first I'm gonna clear then I'm gonna level and then lay down some bricks for the air channel [Music] [Music] next I'll add mine great I'm actually gonna use some Georgia clay to seal around the bottom of the rocket stuff believe it or not this is the native soil here in Georgia good old Georgia clay [Music] trains here [Music] another thing that's great is gonna allow me to do is reach in with a hook and remove ash add another comment on the video that noted that a lot of the rocket stove designs that you see on YouTube do not allow for ash removal so this air channel is going to help with air flow but only if it's open so we'll be able to reach in I'll make a little fire hook for that purpose a piece of flat bar steel reach in and hook that right out alright let's add the stove let's take the excess clay off [Applause] we'll pack that seemed really well I also use the Georgia clay as an ingredient in cob which I use to make this DIY bread oven you can click the link above to see the build video on this cob bread of it these little repairs to a little bit of cracking going on and a deeper at the end of the rebar pieces just a little bit let's see how the pot sits [Applause] a little rusty I'm ready to get this bad boy going well in some eggs my favorite thing to do with this is make boiled eggs for egg salad sandwiches YUM while this cures I'm gonna cover it with a trash can lid held down by a piece of concrete just so it doesn't get any rainwater on it all right now that we've got the rocket stove protected from the rain we're gonna let it cure for another five days or so until it's a nice light gray and then we'll come back and fire it up I'm also curious to see how this stove performs compared to the other one I know my cousin Rob Shamel as well as many others asked the question how much this thing weighs so I will do a comparison between the weight of the original stove with just concrete and this stove which we've lightened significantly by adding perlite I'm also curious if the temperature is any different coming out of the top of this one compared to the other one as well what makes this rocket stove green is that we're able to use small sticks and twigs like this to fuel it rather than firewood or charcoal or something that had to be prepared or cut down to make our fuel as always our mission here at Green Schwarz is to help you see green so you can be green and save a little green by doing it yourself in this case we're gonna be cooking here in our backyard using found fuel at our big oak tree drops on the ground for us so thanks so much for watching for all the great comments that came in on this video I'd love to know if you have any ideas on how to improve this version of my rocket stove and of course in next week's video we'll be adding a J tube to this stove to allow it to selphie fuel and even channel that air in even better so thanks very much for watching please like and share and subscribe for a new green shorts DIY video almost every Friday [Music]

Channel: GreenShortz DIY

Views: 1,070,084

Rating: 4.7398424 out of 5

Keywords: rocket stove, concrete, perlite, DIY, How to, tutorial, green, life hack, GreenShortz DIY

Id: TYr-Uj4HqDs

Length: 36min 19sec (2179 seconds)

Published: Fri Mar 23 2018