riser material in a RMH


Hi, All, I burn about six cords of hard wood per year heating my home and would like to greatly
reduce this amount. Reducing the amount to two or three cords would be great. Hence, I would
like build a Batch Rocket Heater and would like the aide from experienced contributors to this
site to develop a BRH design. Your aide would save a lot of trials and errors.

I have read that a big problem is the durability of the riser or secondary burn chamber. Peter and
others say that metal is not a good fabrication choice and prefer masonry of some sort, e.g., fire
brick. I have considered using “ready made” masonry chimney liners for a riser but the experts
say that they will crack and fail. I wonder if cracking could be prevented by cutting a masonry
liner in the axis direction to get four pieces or four curved sections. Then wiring the sections
back together with stainless steel wire to form a durable a riser. I have seen a video of Matt
Walker forming a riser by using metal foil to hold ceramic panels together.

I would be pleased to read comments about this riser design idea, especially about durability
and/or other considerations. Best regards to every one, Dr. Larry.

Larry,

I wanted to extend a hearty welcome to Permies!  I am afraid that I am not an authority on RMH, but not to worry, this is the place for RMH information and I am sure that you will get plenty of information soon.

And just for the record, I think that a RMH is a great way to drastically improve your wood heat efficiency.  I tinkered with a sort of micro TLUD kiln made from a 1 gallon paint can and 3 soup cans.  I just wanted to see how/if the process works.  I tried my first batch and it was HOT!  As in I-was-afraid-the-car-was-parked-too-close-and-might-damage-the-paint kind of close!  And you have a really good point about longevity.  My TLUD only lasted a few burns after which it was plainly damaged by intense heat.

Welcome to Permies and good luck on your query.

Eric

Welcome!
The 5 minute riser has a lot of fans:

https://m.facebook.com/photo.php?fbid=10154992096951974&l=3e4ec1844f

That's the best picture I could find.

Hi Larry;   Welcome to Permies!
Your at the right place to ask about RMH.  Other good sites are. Our good friend Kirk Mobert (aka Donkey) has an excellent site, specific to RMH here is a link, http://donkey32.proboards.com/
Another site, specific to batch box's is master builder Peter Bergs site here is a link to it http://batchrocket.eu/en/

In regards to Risers,   5 minute risers are the newest thing in risers. here is a link to one of my posts about them, https://permies.com/t/95849/Working-Morgan-Superwool-ceramic-blanket
Insulated firebricks built in a circular pattern are a long time favorite.  Heavy firebricks can be used although they have a warmup time.  A Matt Walker style fireclay and perlite riser has been used by many including myself.  I currently have a 5 minute riser in my shop rmh and a Walker style fireclay/perlite in our greenhouse rmh.
Standard clay chimney liners will ultimately fail ,  pre split ones  would last longer but thermal shock would deteriorate them.

Read some posts here at Permies , then check out Donkeys and Peters site.
If you don't have one. A copy of the RMH builders guide by Ernie & Erica Wisner is highly recommended.