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

You mention the package says "natural bentonite clay"... bentonite has a very high swelling/shrinkage rate when it gets wet and dries. It is the worst kind of clay for making cob.

i was told bentonite was best and is used for refractories.  
so much confusing info, one guy says this, one guy says that.
 thats why i do it and learn for myself.  so much confusion.  one guy says plaster is awesome in forges, one guy says it wont work,
one guy says bentonite is best, and used in fireproof applications, one guy says it is the worst.  so much confusion.
good grief charlie brown...

well i will share my findings regardless.   now that i think about it, i spent 100 $ in perlite alone.  i could have bought 20 firebricks with that much $.

live and learn, the only way, apparently

looking back, i would use this design i drew back last year, this photo is in my '6" Compact RMH HYbrid' thread from last season on page 3.  it seems doing my feed/burn chamber/riser like this would be better/easier.  i have shared this design for more than a year, but i have yet to do this.  it just seems like it would have been cheaper and easier to build, rather than casting expensive ingredients like perlite and refractory cement

"Bentonite can be used as a binder in a refractory recipe, but it is not a substitute for fireclay. I have a recipe in my book that uses 5% bentonite as a binder--and with bentonite, 5% is enough to make a workable refractory. A fireclay shrinks much less, but it's also much less plastic (the two factors are related!), so you would need 25-30% fireclay for the same result."

There is more useful information in that post.
For cob, the expansive properties are very bad. For refractories, the minor quantities used in recipes apparently serve a useful function.

i like the sound of that.  its good to know others are using the same ingredients in similar quantities.

if it truly is a "good refractory binder" , hopefully it will bind the plaster and perlite together well.  ive noticed the entire cast is still kind of sticky and and not hardening like plaster of paris normally would.  i burned just a few pieces of paper in it to warm the riser and to hopefully aid in the drying process.  i feel like it should be "fired" like a clay pot or something.

finally...
some new updates/ videos on this particular cast-cored unit

episode 46, cast core riser update


episode 47 brick riser possibilities


episode 48, rectangular brick riser testing




I've also just opened my new bale of fire bricks, and they are not as dense as my other ones, more insulative, slightly lighter, but they are the exact same dimensions which is good.  I will use them as much as possible in the riser areas of my latest hybrid stoves.   I will use them as little as possible in the areas that get a lot of use and wear, like the feed ports, and the match box.   I've been told that the light ones don't stand much abuse, so I will use the slightly more dense bricks I have in those areas.

Doooooood hows it going! long time no hear bro. glad to see you progressing with some good stuff. i see you said your heat riser gap was 3'' ? is that correct? did you measure the temps on the cook plate of your bell to see if its getting hot enough to cook on? I think i have about 3'' on mine and i can cook on it but its not as hot as previous smaller gap. i increased my gap so i would make my bell lid last longer.

F Styles wrote:Doooooood hows it going! long time no hear bro. glad to see you progressing with some good stuff. i see you said your heat riser gap was 3'' ? is that correct? did you measure the temps on the cook plate of your bell to see if its getting hot enough to cook on? I think i have about 3'' on mine and i can cook on it but its not as hot as previous smaller gap. i increased my gap so i would make my bell lid last longer.

hey bro!
yes that is correct, gap turned out to be 3".   i agree on the temps, i think im getting around 500 F on the cook top.   ive been experimenting lately playing lego with firebricks!  theyre awesome.  good to hear from you

I have found that you can experiment with clay and just add a bit to the top of the heat riser to find your best height. since it wont be touched the clay will be safe.

your new higher temp design looks fabulous buddy. once you get her inside your home and start only using your rocket for heat, you will probably desire a bigger hole. Having a tighter hole for most things is good but here, having her large and wide keeps you from having to poke her every couple of minutes to keep her happy. I love being able to shove a long full size log in mine with out having to spend all day chopping splinters.

hey... did you end up making a front access hole on this model?

Hahah

yes it does have a front port.   as far as the bigger feed hole, i have been experimenting with small firebrick batch-box variations.  they hold more wood, but im not entirely sure which is my favorite yet.

have you tried this and if you have what were your experiences and results?

have you tried to put wood in and cap the top off and then open the front access port... make sure you have a screen over it though. then let me know what your results are. I find it burns much better from my experience.

i have not tried that on this model.   i have used that method to burn pellets in my other compact hybrid.   that is a good idea to experiment with...   but since my cast core isnt very deep, i would only be able to fit 13" long pieces with a lid/cap, unless i made an elevated collar with a lid.   i have only used the front port for ash clean-out so far, but it works great for removing the ash.  i had planned on building a door for the front port but ive been busy tinkering with several other winter-prep projects lately.