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Portable Compact 6" RMH Hybrid w/ internal mass and all cast internals  RSS feed

 
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Well my last design for a COMPACT 6" unit with built-in internal mass works well, although it received a lot of critcism for using metal in the internals. The metal is in good condition, and is protected by stainless hi-temp anti-corrosion duo-therm liners, but I want to impress everyone, even the metal critics.

I've had this "all cast" portable-core idea bouncing around my brain, and I have this amazing antique old-school tub thingy. So here's my design. Last time I showed my design and work after I had already began. This one has not yet begun, but have a look and give me your input regardless.
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cross section diagram from above
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cross section design diagram from the right side. 1 square = 1" for the scale
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I don't know what YOU see here, biut I see a rocket stove waiting to happen. antiquity is awesome
 
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Looks like an excellent container and layout. Use insulating material (perlite-clay or similar) for most of the fill except the inner inch or so facing the heat, and it should work very well and last a long time.

I built a 6" J-tube in an old steel box for a demo project last year, and it worked very well. I don't remember at the moment if we used just perlite-clay, or perlite+refractory, but it got hot fast, and burned and drafted reliably in a complete half-barrel bell setup at an Earth Day demo where the weather was around 90 F. The exhaust was almost cool enough to put your hand in.
 
John McDoodle
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Thanks, sounds encouraging if you had good results with yours.

This bell/barrel would be another 14" LP tank or grease drum, like my first rocket design. So I could possibly use the same lids and/or dutch oven lids. My skech heights are only approximate, I think the tub and the riser and the bell will all be taller in reality, (I forgot to measure the tub depth/height so sketch is only approximate/possibilities)

Step One
The core:
Its way too cold to pour or cast a core in my unheated shop, but maybe I can improvise somehow because of the portability and compact size. It could be poured in someones basement and moved relatively easily if need be.

Yes I would definately have at least 50-60% perlite for the insulative properties. I planned on filling the entire "tub" with refractory concrete mixed with perlite. My burn chamber and the bottom 12" of my riser on my first compact RMH hybrid is surrounded in this custom mix, about 50/50 perlite, and it works well, has not broke, and it sees huge temperature fluxuations all the time. So it works well in the base/core, with the right amount of perlite, so I've learned.

Here is an approximate crude sketch layout of the first step, the ALL-CAST CORE. The tub is about 24x18 inches long and wide at the top, if I remember correctly. I can make better measurements perhaps tomorrow...
IMG-20160123-01998.jpg
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this would be the approximate core layout, step 1
 
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cool looking drawing bro. are you going to put it on wheels/casters?

can i suggest one thing? create a 1'' to 2'' inch layer of loose perlite as insulation for awesome insulation. loose perlite without mixing it with clay or cement definitely increased my insulation value greatly for sure in my heat riser by many fold. if i would have to do it again i would create a larger loose perlite layer for sure.
 
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Been there, done that, well, very similar layout and dimensions, and it ended up not very portable. Well, i have a crane and all the equipement needed. But for lightness, use insulating firebrick for the feed and burn tunnel. and a rigidized superwool heat riser. and fill the rest with perlite or vermiculite.

Look at the standalone unit from dragon heaters. That might inspire you.
 
Glenn Herbert
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One thing abut your tub dimensions: if you fill it with as much as 50% cement of whatever sort, it will be very heavy (mine was about 12" x 24" x 10" high, probably around 75% perlite, and was barely portable by one person). It will also not be the most effective use of mass. You want the heat exhaust to go through the mass with as much contact area as possible, and with as much exterior surface exposed to the room as possible. Your tub with riser and barrel in place will only have half of its side surfaces useful as radiators, so not so effective. You will get better bang for your buck by making the J-tube container as light as possible, and adding another mass unit that the exhaust can travel through with a large exposed surface area.
 
John McDoodle
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I know it is unconventional or unorthodox to have an internal mass, but that's what makes it a compact hybrid. There is a handle on both ends of the tub, so it might be a 2-man portability lol. I plan on casting the riser separately, likely with removable barrel system
 
F Styles
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Satamax Antone wrote: not very portable.



i am sure my system weighs more than this concept and i wheeled mine across a gravel driveway around my house across the yard and into my house then kitchen. i put commercial grade wheels on them and it took two people to drag it across the rocks but it can easily roll across a hard wood floor by my wife.

yes its a heavy summich but mobile. so if i can move mine, with the right wheels you can move yours. if i had a suggestion to pass on to you with experience i would have gotten at least a size bigger. i got the 3" wheels so go bigger if you plan on rollin her across gravel. forget steps unless you got a good ramp and back.

even though i use a full 55 gal barrel its foot print is very small since it only got a foot print the size of 1.5 55gal barrel and is separable from the mass bench so i consider mine compared to a 6 cyl 4x4 with 4 doors, mobile with decent power but not a V8.

with all the concrete my system has in it, she radiates heat for hours after the fire is long gone and you design should do the same.
 
F Styles
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maybe you could use a small metal bucket or something with a lid so you could connect it to the feed J to increase your feed chamber and burn times. i also would not trade my front access port for anything, you would appreciate a front access port for your sanity for ease of lighting, cleaning, and air flow with the feed chamber lid on is a must. my front access port was a last minute decision and i am so glad i chose to do it.
 
John McDoodle
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Hell yeah put some off road tyres on it lol. I think it will be okay, since I can move my original stove around, which weighs about a quarter of a metric ton. Having removable parts and the tub with handles will help a lot in portability

Hey FStyles,
I bought a raw/unbaked apple pie, as per your request, to test my simple dutch oven BBQ lid theory. This lid I got even has the built in temp gauge and some kinda aero-aluminum insulaion liner.

You are totally right, I need a front access port! I will likely make a few design mods before I build this one, including the front access door/window like my original rocket has

Pie gets baked likely tomorrow. I want to thaw it out first since its frozen.

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well R2D2 here looks rough, I think he
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PIE? raw/frozen/unbaked. Reccommended dutch-oven test subject, thanks to FStyles for the idea. pizza next time?
 
Glenn Herbert
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I would estimate that 80-90% of the heat generated will go to instant radiation or up the chimney, as you have practically no mass in contact with the final exhaust of the core. If you are okay with only a tiny bit of storage relative to heat produced, go ahead.

You would get much better storage if you had mass of whatever sort around the barrel instead of surrounding the burn tunnel. What you really need around the burn tunnel is insulation, to keep the fire hot and efficient.
 
John McDoodle
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Glenn,
I have the same internal mass setup in my original compact RMH hybrid, and the exhaust pipe temperatures are 200F or less, I've measured them, and the burn temperature is close to 1000F,

that means I'm capturing 80% of all the heat generated! That's amazing if you ask me!

And to top it all off, if my exhaust was any cooler, if I tried to rob more heat out of it, it wouldn't operate as well as it does now.

It works well and I've tested the internal mass theory for a total of over 50 hours with great success. The exhaust AND the burn chamber are BOTH in contact with my mass. And that's one reason why it works so good.

Whoever told you that most of my heat is going out my exhaust, is wrong. And if you watch my proven measurements on youtube, you will see that I'm capturing at LEAST 80% of all the BTUs generated by my selectable fuel sources.


This is good info that you all should know, since the internal mass is alien and unknown, new territiory.

I want you to know that it works well, and my videos can testify to that, with laser accurate temperature measurements also
 
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i would put legs on the tub before casting in it. the bottom will flex when you pick it up and could crack your core/mass. besides you can also use the heat coming off the bottom of it. if no legs it will heat sink into the floor. and that bottom will get very hot. i had 4" of clay mix, under my burn tunnel, and it got hot enough to melt the plastic tub it was cast in. lol and that one was only a 4" j tube!

neat lil priject man.








 
John McDoodle
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Thanks ronald, and yeah having it up off the ground is a good idea. Which can correspond or collaborate with FStyles "wheels/base" idea.

Don't worry glen, I will use lots of perlite in my refractory mix, it ends up like a huge firebrick
 
F Styles
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awesome pick with the pie and thanks for taking my suggestion. i love pie. pizza pie is also good but you got a good pie. too bad you dont have smellavision.... just give me your word you will video you pulling the pie out all hot and toasty mmmm.

hey John if you are up for suggestions the reason i get good high temps is because of the loose perlite. the wheels keep the bottom from catching my floor on fire because when its running full dragon the summich gets hot.. so your wheels will give you safety and portability.

think about the loose perlite by pouring down a 1 inch layer then using plywood cut to the length of the tub and 2" away form the core and fill around the core tube your custom refractory mix and then create a 1 to 2 inch gap and fill it up with loose perlite. you will create a super indestructible insulated portable rocket stove with mass in it.

have you thought about enlarging the 6" feed tube to the bucket with lid feed chamber?

cant wait to see the pie come out all piping hot. just as long as you dont eat it on video without sharing.
 
John McDoodle
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I'm tight on available working space/material room in the tub, and I want my cast to be strong/thick all around, so the feed tube and the burn chamber will likely end up as a 5"x5" square tubular shape. The riser will likely in-turn be 6" round. I measured the 14" diameter grease drums, and they are all about 26" tall. So my first sketch is wayy too short, the riser and bell will both be much taller, to make use of all of the the 26" tall bell/barrel, which maximizes the radiant surface area of the bell/drum. I measured the tub and its 12" tall.

I'm toying with slight design mods: front access port, and much taller riser and bell, new revised design sketch to come soon I guess.

As far as the pie, I can already smell it I will have to stabilize and measure my oven temp, then adjust the cooking time slightly according to the oven temperature. Hopefully it will cook, and not burn lol. That's why I test this stuff hands-on, first before writing anything in stone
 
F Styles
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do you have a grate or something to lift it off the metal surface or it will burn. it has to have air circulate all around it including the bottom or it will burn.
 
F Styles
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are you baking it right now?
 
Glenn Herbert
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"the exhaust pipe temperatures are 200F or less, I've measured them, and the burn temperature is close to 1000F, that means I'm capturing 80% of all the heat generated!"

Aside from the fact that dividing 1000F by 200F doesn't actually show any particular total heat capture, what I said was that 80-90% of the heat would be radiated OR go up the chimney, and only 10-20% stored. You haven't said otherwise. You do have a good total use to chimney ratio. Where exactly is the 1000F temperature? Is it inside the burn tunnel or riser? If so, that is barely reaching efficient burn temperatures. If that is an exterior surface measurement, then you could be getting efficient combustion.
 
F Styles
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John you better not have baked the damn pie and ate it without the daggone video of it coming out. wheres the pie dude?
 
John McDoodle
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Pie was frozen bro, has to thaw, I'm baking it tomorrow. At least that's the plan, to test the dutch oven. I do have a nice round grille so the pie won't sit on the lid.

I know there is over 1000F in the burn chamber of my original stove, but not on the surfaces, although my laser gun only reads up to 610F, I have maxed it out trying to read my cumbustion zone temperatures, hell I've even maxed it out reading my lid/cook top, we've seen blue in my flames, so there's 1000F in there somewhere. And only 200F comes out the exhaust, that's an average reading at the hot end of the exhaust nearest to the (original hybrid) stove. Its cooler than that by the time it goes out the wall, so I wouldn't try to capture any more of the heat due to risk of losing the excelent draw.
FlameTemperature.jpg
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there's 1000+ inside of pretty much every flame
 
John McDoodle
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I found this bulgarian design somehow by accident today. It reminds me a lot of my original stove, but I think the bulgarian Gamera rocket is a 5" system, and I think the burn chamber is composed of "expanded vermiculite, perlite, alumina-silicate wadding, high temp silicon"

https://rocketheatergamera.wordpress.com/

I found a 25 lb bucket of "rutland castable refractory cement" for 58.oo online with free shipping, and I will likely buy that and dry mix some of that with about 1:1 equal parts perlite (by volume) for my ingredients on this cast project.

Thanks
 
John McDoodle
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Well I ordered the refractory cement from amazon.ca today. It's been out of stock/waiting for stock for at least a week, so god knows how long it will take to even ship out. Then another 4 days or more for the actual shipping.

I admit, I'm excited to get this next all cast portable unit started in development. I will need to get some more perlite and refresh/revise and update my design with a few slight mods.

More updates to come soon on this all cast internal stove
 
F Styles
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hey did you see that recent thread about the insulated vacuum casted ceramic cores buddy is trying to get a group order? the i see it, it looks like $36 a core if they buy them in a group.
 
John McDoodle
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Yeah that's a good idea, but I'm in canada so it would be expensive for me. It's a great idea though for locals or people who don't mind shipping costs. But that's a subject for another thread lol

Here's a revised sketch with 5" burn chamber and access port and more accurate 26" tall bell heat exchanger
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An updated sketch I drew last week
 
F Styles
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goodness everything in canada is getting expensive. i saw food go up at least 40% in the news. its like your whole economy is collapsing. at least youll be warm with your rocket stove. hope you got a big garden?
 
F Styles
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thats a nice sketch brother... real nice. if your sketch is proportionate it looks like you could afford another inch of insulation on each side of your heat riser? right?

here is a suggestion. dont cement your bell in or if you do, make sure you have a removable top lid or you will wish you had one. believe me.
 
John McDoodle
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F Styles wrote:thats a nice sketch brother... real nice. if your sketch is proportionate it looks like you could afford another inch of insulation on each side of your heat riser? right?

here is a suggestion. dont cement your bell in or if you do, make sure you have a removable top lid or you will wish you had one. believe me.



Yes it's defiantly a fancypants mcdoodle for sure lol.
The riser cast could be anywhere between 1" & 2" thick I suppose,
I would have the barrel removeable for sure, or at least the lid, possibly both
 
F Styles
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hey john have you seen this really neat design? it looks close your yours. it has an ash tray area air pass through.

think you could fit that design in your rocket frame?
 
John McDoodle
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Yes that is very similar! I kinda like the ash drawer too. What's it called? What is the base made of?
 
F Styles
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that is a neat system and it is how i would build my system if i had this idea before i started mine. i my mind it is a superior design than mine. I can imagine this in an oval wash tub on wheels with the front access port/ash pit and larger feed chamber and it would be perfect. I may rebuild my entire system just because of this design idea. instead of using steel slats like that guy with the auto pellet feeder rocket stove i would use ceramic tile cut into 2" slats for the grill to allow air through and the ash to fall past. it ingenious. ceramic tile slats would never melt and would be thin enough not to have heat shock... perfect. im serious i may just rebuild my entire system. i had already thought about rebuilding to include a crude oil/gas refiner/cracker/wood gas generator add on.
 
John McDoodle
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Yeah it's a good design for sure. I like the ceramic idea also
 
F Styles
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i just had an idea. do you know how they weld on the carbide tips on saws to increase the strength and cutting sharpness of the saw blade? well my idea is to build metal slats with a groove just so you can put 2" ceramic slats in them to protect the metal since the hot coals and burning wood would not come in contact with the metal and the ceramic would not transfer melting temperatures to the metal it would not degrade and that way you can have the strength of metal with the refractory of ceramic. right?
 
John McDoodle
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I think if you put your mind to it, you can do it. If it's near the intake, it probly won't get red hot anyway...? Steel rack is easily replaced , I had good luck cutting light firebricks with a wet hacksaw. I like simplicity within designs and replaceable or removable parts
 
F Styles
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Remember the guy that had the neat auto feed pellet burning rocket stove and he went through many grates because when the burning action touches the metal regardless if it is stainless steel or not it will eventually break down from the heat touching the grates. stainless lasts longer than carbon steel but a thin cut ceramic or firebrick slats laid over steel grates will last much longer if not indefinitely.

your idea of thin cut fire brick is a great idea and may work better!
 
Glenn Herbert
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Ceramic tile would experience significant heat stress in that application, and would crack quickly. It might or might not continue to fail after initial cracking. Thin firebrick strips set in metal carriers would be likely to survive longer, and in any case could easily be replaced individually as they break down. If you have a good blade for cutting them, it seems like a workable setup. I have a cheap homeowner grade tile saw that cost $50-$60 or so and has done a lot of tile cutting for me. It cuts a half inch deep in firebricks easily. (Ordinary hard firebrick; soft insulating firebrick could not take the abrasion of that application.) Or you could get a masonry blade for a table saw or circular saw.
 
John McDoodle
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The only time I would want a grate or slats would be if I were burning pellets. I want to be able to burn wood from the land so I wouldn't likely need any grates at all. My original stove works great and it doesn't use any grates unless burning pellets, which is not the ultimate goal, but a bonus if need be
 
John McDoodle
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well i finally got an email today from amazon.ca stating that the 25 Lb buckets of castable refractory cement are now in stock and mine was to be shipped out today. i should have it here in about a week- meantime im going to pick up a bunch of perlite and im trying to figure out how upload 1080p videos from my Iphone 4S to youtube- it wont let me upload my 20 min long inspection video or any longer than 3.5 mins...?
 
John McDoodle
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Courrier Mail brought me a present today
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How many lbs??
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Yay good packaging and good delivery condition
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Casting recommendations and directions and all that good stuff
 
It's just a flesh wound! Or a tiny ad:
Two part roundwood timber framing workshop sep 24-29 and oct 1-5
https://permies.com/t/91267/permaculture-projects/part-roundwood-timber-framing-workshop
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