Rocket Mass Heater in a Caravan

[milo]

Hi,

I've been reading through bits of the forum to try and get an idea on how I could build a rocket mass heater in a 5mx2m caravan. I want to design it so that there can be a air intake vent that feeds the burn chamber that can be opened up once the fire has been lit that will then allow me to close the burn chamber from the top (so that air intake is from external and doesn't consume oxygen in the caravan).

The bench area will be 2 metres, around a corner (1 metre each side) where it then meets the vertical that goes up and out as the chimney.

My concern is that if I were to cob the entire bench area (and the chimney part) it would be far too much weight for the caravan floor to bear. Perhaps not? Either way it would be a lot of weight and a lot clay (that I don't have so much of right now) and if I ever need to transport it again in future (unlikely, but not out of the impossible) then it might not be so practical. So one idea is to reinforce the floor underneath the intake, feeder and barrel so that I can build it up with fire brick and cob. But what I want to ask is about the 2 metres of bench that I will have after the barrel. Is it possible to just leave this encased within a wooden bench with adequate spacing between the floor and bench (effectively creating an air chamber under the bench)? Or perhaps it would be better to insulate the exhaust tube with fire wool of some sort?

Is it necessary for this horizontal exhaust part under the bench to be well covered in thermal mass in order for the exhaust to be drawn out effectively?

Does perlite have thermal mass and could it be used to fill the bench and act as the (lightweight) mass. I guess that 'lightweight' thermal mass is a bit of an oxy moron. Can anyone make any suggestions? Has anyone ever seen a RMH in a caravan before? Something lightweight? Would love to see some examples if anybody's done it.

Oh, btw the caravan has been stripped right down to it's guts and the insulation along where the heater will go will be . The areas that will be sitting close to the heater will be replaced with a more heat resistant insulation like rock wool or something like that, not styrofoam as was previously.

Thanks in Advance.

[woodburner]

Pearlite is an insulator, consists mostly of air, and has little thermal mass (or any mass). Rocket mass stoves, or any other massive stove, and caravans do not really go together. You would need to have supports from the floor to the ground to take the weight. This effectively stops it being a caravan. you could fit a girder construction perhaps, but that stops it being a caravan too.

[Donkey]

You would just have to go with FAR less mass. It would be a lighter weight rocket stove with mostly radiated heat off of a metal barrel or something with a light masonry bell of some sort.

[frankdaly]

Here ya go www.sciencedaily.com/releases/2007/07/070708185757.htm now you just need to convince them to sell you enough of the stuff. 

[woodburner]

Er..., yes....., but what would you use it for?

[frankdaly]

Lightweight "Mass". It says it is extraordinarily conductive for it's weight.

[Donkey]

Well.. Metal is plenty conductive for it's weight.
I don't think it says much about how heat resistant that stuff is. (I confess I didn't read the ENTIRE article)

It seems to me that you can get away with a small brick bell and a 6 inch j-tube rocket with barrel (or barrel and a half).

[doggy1969bc]

the carbon will bond whit oxigene at higher tempraturs (it will burn )

[frankdaly]

It was meant to be tongue in cheek not a serious solution to the "lightweight mass" problem.