Small portable rmh for mobile home

Hi I'm making a portable rmh with a cast core inside of 30 gallon drums. I'm trying to make a modular design for easy breakdowns for summertime. It's a 6" system. I plan on using 55 gallon drums for a bench. Filled with cob or maybe just clay. I plan on drilling very small relief holes in the barrels for expansion of whatever I use for the mass. I'm just waiting on my refractory cement for the cast core.

Hello Robert, that looks like a very nice RMH build. Keep up the good work!

Are you planning on keeping the RMH 30 gallon barrel holding the core thermally isolated from anything flammable? I've seen a posts where the individual built the core on bricks thinking it was enough insulation but ended up setting their floor on fire. Something to consider.

I'm a not certain about the expansion holes that you are going to drill. It seems like you have thought about some, but I must not be seeing the same thing you are.

I am also curious how much mass you will have and will your RV be able to sustain the additional weight load. Have you looked into this?

I was planning on cutting a couple 55 gal barrels in half long ways and filling with perlite to set the rmh on and everything will be set on concrete blocks. Everything will be centered on the house support frames. I'll have corrugated steel covering the walls behind it to reflect the heat into the room. Those will be mounted on 2x4's screwed into the studs and rock wool between the wall and steel. I'll add one barrel of mass at a time to see how much mass I actually need as my house isn't that big.

Robert Johnson wrote:I was planning on cutting a couple 55 gal barrels in half long ways and filling with perlite to set the rmh on and everything will be set on concrete blocks. Everything will be centered on the house support frames. I'll have corrugated steel covering the walls behind it to reflect the heat into the room. Those will be mounted on 2x4's screwed into the studs and rock wool between the wall and steel. I'll add one barrel of mass at a time to see how much mass I actually need as my house isn't that big.

A few thoughts...

I'd be tempted to weld on a few feet or brackets to keep the half-cut barrel stable, so that it does not want to roll to one side or the other.

Everything I have seen says to leave at least an inch of free air space behind the heat shield. This allows the air to flow behind the metal shield and carry away the heat. If there is no air flow, the temp may keep building higher and higher. There should also be an air gap above and below the face of the air shield, so allow free air movement. Somewhere I came across heat shield recommendations for wood stoves. You might try an Internet search for the details of typical installations.

The ones I saw specified that the stand-offs were non-combustible and also did not convey the heat to the supporting wall. Sounds expensive to me. I've been wondering if a bent C or D shaped piece of metal might act as a suitable stand-off? I'm thinking along the lines of the handles for wood burning stoves and other items that are very close to extreme heat. It seems that they all have in common the ability to quickly shed heat, so that the free air movement carries away heat before it builds up in the handle, or whatever the item is.

Thus, I was thinking that a C or D shaped piece of metal would allow one to bolt it to the sheet metal, on on side of the C- or D-bracket, and then screw that to the wall on the other side. Heat would not carry through to the wall because it would be carried off into the air before it made it to the wall. Sound reasonable??

I have been waiting for others, and/or I have missed something, so apologies if this has been said. RMH made of metal like this, even with insulative additions...in most (90%) of the cases...are not going to last a season...

Most only last one or two burns...

METAL IS DOOMED...has been written so many times here, I am not sure why the examples keep getting asked about? That alone has me concerned for the safety of the structure.

Again apologies to all if I have missed something or sound to negative...but I am concerned that too many of these RMH in metal could lead to unwanted conflagration.

Jay, he said he's gonna cast with refractory cement.

Tho Robert, that thing gonna weight a ton by itself. If you can cast the first inch or two around the inner pipe out of pure refractory, then switch to a perlite/refractory mix, it would weight less. Even better, cast a thin core as i was saying, and fill around with loose perlite, that would save weight.

Masswise, if you can get your bricks to a very high temp, you don't need much. I heat 300sqft aproximately, with an electric accumulator. This thing must weight about 150 or 200kg.


Your best bet would be a multi channel bell, for ease of fitting, and heat storage.

The plan is to make the entire bottom barrel a perlite/clay/refractory cement cast core. Like the video on YouTube but instead of being in a wooden box and hardy backer burn tunnel I just use the barrel to hold the cast and use 6" tubing to form the burn tunnel. (Knowing it will burn out quickly, leaving a refractory/perlite/clay burn tunnel). I have access to a ton of barrels of all sizes so I figured I'd put them to work.
And yes I totall plan to put feet on it. I'm still working on it. I just wanted to show it off LOL. I'm totally having a ball with my welder. Just started welding 2 months ago! As you can probably tell from the ugly welds LOL.

i dig the barrel housing idea! very durable on a move im betting. i like the bed of perilite idea too.

like others, im not a fan of the 2x4 touching the tin either.

i would also burn the core and riser for some experiments before continuing on with a barrel over it. read up on burn tunnel configurations. i think there are better shapes, channels, grates, notches.........., than just the plain duct work. without the barrel on top you can see what happens with changes, and better tweak/understand your burn.

looks like a winner of a start! very nice Robert

Yes I totally plan to burn without the bell and heat riser first. And then more burns with heat riser. And then I'll test with the bell on with no mass and then test with one barrel mass before I take it inside.
I think you have a good point about the 2x4's. I'm thinking of a couple of nested half barrels filled with perlite and vermiculite between the two and set between the wall and bell? Not sure yet until I see for myself the heat coming off of it. If nothing else I can make a metal frame to hold the reflector metal away from the wall. With no conductive metal touching the wall at all. That would make it even more convenient to break down and move.

Well I cast my core last night! It turned out better than I expected! No leaks at all! I first caked the outside of the burn tubes with about 1/2" of 3000° refractory cement and then packed the barrel with clay/perlite/refractory cement mixture. Weighs about 150 lbs altogether. Gonna pack the riser and do tests tonight after work!

This core is really solid. Been burning for 9 hours and the barrel is still cool. I don't think there will be a need of excessive perlite bed. I think the concrete blocks will suffice for now.