Cast Batch Box Rocket Mass Heater using LTGS

Satamax Antone wrote:Fill with concrete. Sand insulates.

Another alternative would be to fill them with Cob.  I have plenty of sand and clay on hand.  

Steve Shelton wrote:

Satamax Antone wrote:Fill with concrete. Sand insulates.

Another alternative would be to fill them with Cob.  I have plenty of sand and clay on hand.  

Yes. Tho it's not as fluid as concrete.  Ans, since i've been there and donne that.  Vibrating witha vibrating sander work not too bad.  

Here's a pic of the same cement block that is covered in thin-set is now further covered in Geopolymer (GP).    The big test is which trowel notch size provides the best adhesion.  I will go with the smallest notch size with good adhesion.   This will provide the most efficient use of materials.  

The "redneck solution" Bell is now built.  It will be used temporarily to test the flow of air through the system.  Some time within the next week or so I'll fire it up.  

I hope to achieve a solid "Rocket" sound and temps exceeding 900 degrees F at the bell.  

Temperature just above the riser inside the bell.

Temporary Bell is leaking badly

Extending the chimney to 6' above bell top increased the temperatures.

I ran one last test to document the temperature progression through the initial stages of a burn.    This demonstrates the insulative properties of the Geopolymer Settings.

This was a small burn with half of the Batch Box filled with wood.  

Here's a pic of the 1st layer of the permanent Bell.  It is nearly complete.  I need to fill the remaining blocks with Cob to finish it.   The frame of the DSR is shown to show where it will fit.  However, it will be located on top of the 4th layer.  

The Bell is complete.  Next steps include installing the Bell Roof, Fire Wall behind, and hooking up the Chimney.  

Here's a quick update so far:

- DSR is performing above my expectations
- Our Electric furnace and heat pump have not run for the last 10 days.  Yeah, it's only November, but it could be the coldest November on record in Kansas City.  Also, yesterday a blizzard hit with 50mph winds and 6 inches of snow.  Some areas got dumped on.  It just missed us.  
- So far, we have been using 1 - 2 cubic feet of wood a day.  This is largely dependant upon if it's sunny.  If the sun shines, the solar gain from our south-facing windows allows us to only have 1 fire a day.  Each fire uses about 1 cu ft of wood.
- this would extrapolate to about 1 cord of wood for the year.  This is more than what I was expecting but is not bad considering I can collect wood for free.  
- It took several days to figure out the best way to set up the set-back thermostat to work together with the DSR.  We ended up setting the thermostat to 55o F.  This in effect only uses the furnace as a backup device.  
- Downstairs, where the DSR is located, is very comfortable at all times.  The lowest temperature recorded was 63o F. The average temperature overall was 67.5o F. The upstairs is a tad on the cool side.  During the daytime, the average is around the upper-60s.  The lowest temperature recorded was 58.5o F.   The average temperature overall was 65.1o F.
- 2450 sq ft home.  2/3rds of that is the upper level.
- I was worried that the DSR room temperature would be uncomfortably hot when it is burning.  This turned out to NOT be the case.  After the learning curve, the high temperatures were just a tad over 70o F.   Not bad IMHO.
- The electric savings should more than make up for the construction costs in less than 2 years.  WOOHOO!

Very nice.  How are you distributing the heat to the rest of the house?

Graham Chiu wrote:Very nice.  How are you distributing the heat to the rest of the house?

A thermostat controlled fan pushes air from the ceiling into the ductwork.

Final Build prior to a stone facade.

Exhaust chimney

Looking GREAT  Steve !

Can't wait to see pictures of your stone work when done!

Keep them pictures coming !

Could this chimney cowl be adversely affecting my chimney draw?

Hi Steve;  Hard to say from the photo. Does it have wire mesh in it ?    I have always used the simple cap (coolie cap) and never had a problem.
EDIT)   Steve with warmer temps and a brick bell sometimes its colder in the bell than outdoors. Draw can be harder to get going. Try heating the exhaust stack with a hand held torch … see if that helps.

Upgrade to DSR2

Hi Steve!
It's been a while since you've posted on this topic and I was wondering if your refractory mix held up since then?

Thanks!

Yes it has held up well.  I have a fire going as I type this reply.

I'm glad to here that!

I've been thinking about using this geopolymer recipe for the three cores I need but the refractories available locally are either inadequate (temp rating of only 2000°F for firebricks at 6$ CAD each!) or extremelly expensive to get shipped, at several hundred dollars in shipping...

Is there someplace I can see your design?

I plan on making an 8 or 10 inch sidewinder with a five minute riser with see through doors* and a big masonry bell and I'd like one or two 6 inch DSR cookstoves.

*Similar to this build:

A few suggestions:
- make the roof of your firebox several inches thick.  Geopolymer needs to be cured by fire to reach full tensile strength.
- metal rods can be imbedded into the geopolymer to help with spanning the roof section until the geopolymer is fully cured.
- geopolymer can be easily cut after the initial drying phase.  The riser can be made from dry flat sheets that are angle-cut to make the octagon riser.
- the 2 angled floor pieces can be made in the same manner.
- when possible, smaller pieces are easier to work with.  Sometimes this is not an option.
- you can make flat molds, once dried, can be cut into the smaller pieces for assembly.   The dried pieces can be cut into precise sizes.  
- there is considerable shrinkage in the initial drying phase.

Keep me posted on your progress.  

Steve Shelton wrote:A few suggestions:
- make the roof of your firebox several inches thick.  Geopolymer needs to be cured by fire to reach full tensile strength.
- metal rods can be imbedded into the geopolymer to help with spanning the roof section until the geopolymer is fully cured.
- geopolymer can be easily cut after the initial drying phase.  The riser can be made from dry flat sheets that are angle-cut to make the octagon riser.
- the 2 angled floor pieces can be made in the same manner.
- when possible, smaller pieces are easier to work with.  Sometimes this is not an option.
- you can make flat molds, once dried, can be cut into the smaller pieces for assembly.   The dried pieces can be cut into precise sizes.  
- there is considerable shrinkage in the initial drying phase.

Keep me posted on your progress.  

Thanks for this precious information!
When you talk about metal rods, could refractory stainless steel needles work? Or did you mean rods spanning all the way through the slab? (I guess that the smaller the diameter, the better?)
I also have access to Kyanite grog (and mullite also) from 35 mesh up to 100 mesh that I could add to the Kaolin or fireclay without affecting the plasticity while being able to improve the alumina content and the shrinkage issues, I think.

The metal rod I used was salvaged from a section of cattle panel fence.   They were about 1/4" thick or possibly less.   The final thickness of the roof pieces should be 2" or more.   Imbed the rods in the middle of that 2" thickness.

I suggest you test whatever mixture you come up with prior to your final pour.    I went through many component variations before settling on the formula that I used.   What you are thinking about trying might be better or it might be worse.    The testing process was very time consuming.    

Steve Shelton wrote:The metal rod I used was salvaged from a section of cattle panel fence.   They were about 1/4" thick or possibly less.   The final thickness of the roof pieces should be 2" or more.   Imbed the rods in the middle of that 2" thickness.

I suggest you test whatever mixture you come up with prior to your final pour.    I went through many component variations before settling on the formula that I used.   What you are thinking about trying might be better or it might be worse.    The testing process was very time consuming.    

Thanks alot for the valuable information. I will probably try out ''ciment fondu'' also, as I may have a really good price on 95 lbs bags