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Cast Batch Box Rocket Mass Heater using LTGS  RSS feed

 
Posts: 55
Location: Kansas City, Missouri, United States
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I am currently planning to build a Cast Batch Box rocket mass heater (RMH) using Low-Temperature Geopolymer Setting (LTGS). 

I've built a working J-Tube RMH out of LTGS in order to test the techniques and materials.  So far so good.  I will attach pics of all the items mentioned in this post as replies to the post. 

My primary sources of information in this endeavor are:
- this website
- Erica and Ernie Wisner's book "The rocket mass heater Builder's Guide"
- Peter van den Berg's web site:  http://batchrocket.eu/en/
- the LTGS website I was using is no longer available.

The primary design components are as follows:
- 6" Chimney and overall system
- The batch box will be 7 cast parts: (Floor, Right side, Left side, Back wall which includes the front bottom portion of the heat riser, Back bottom heat riser, Front top heat riser and Back top heat riser)
- I will use 5 forms to cast the batch box and heat riser (2 are reusable)
- Bell will be 3 layers with a 1/4" steel "lid" on top.  The layers consist of 1 1/4" LTGS on the inside, 4" concrete bricks outside of that and a decorative stone veneer
- the Batch box will be raised off the floor 9"
- the Bell will be 13.5" x 13.5" x 67.4"
- the Bell ISA computes to 25.6 cu ft
- the Heat exchange will be a total of 8' long with 3 turns
- the Heat exchange ISA computes to 31.4 cu ft
- for a Total ISA of 57.0 cu ft .1 under the target ISA of 57.1 cu ft
- there is 2 3/4" clearance on each side of the heat riser inside the bell giving a 185 sq in CSA.  This gives a 6.6/1 ratio exceeding the 5.0/1 requirement.
- a 1 1/2 story class "A" chimney will be installed inside the house through the ceiling and the roof.
- approximately 5 cu ft of LTGS will be needed at a cost of about $200 total (not including the J-tube prototype)

My questions:
1 - Will the LTGS use within the bell inhibit the system "draw"?
2 - Am I missing anything else?





 
Steve Shelton
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My J-tube Cast LTGS RMH uses the 1 - 2 - 4 structural ratio target

It was poured using a single mold.  The burn tunnel was formed with wood and wood-glue and was designed to "burn out" upon first use.

It fired and drew appropriately.

The external temperature of the 1 1/2 inch thick LTGS was around 100 degrees F

The internal temperature exceeded the 500-degree max temperature of my infrared thermometer.  So it was "Really HOT!"

Note: I did not add enough water to the LTGS mixture.  This prevented it from settling properly.  I have adjusted my LTGS recipe to correct the issue.

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Steve Shelton
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Here are some snaps from my Batch RMH Sketchup
Final-Mass-RMH.jpg
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Batch-RMH-Front-View.jpg
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Batch-RMH-Top-view.jpg
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Steve Shelton
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Here's a pic of the form used to build the J-Tube

J-Tube-Form.jpg
[Thumbnail for J-Tube-Form.jpg]
 
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Thanks for sharing Steve. I really like the direction you're headed. Please keep us updated as you install and learn to run it.
 
Steve Shelton
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Cast Batch Box Rocket Heater
 
Steve Shelton
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15g of rock wool after it was run through a kitchen blender
Rock-Wool-15g.jpg
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Steve Shelton
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Here is the latest and hopefully last pic of my target Batch Box rocket mass heater.  My intent is to:
- build an aesthetically pleasing heater
- add value to my home
- add an alternative heat source (wood)
- utilize a renewable energy source (wood, many don't consider this in their definition of renewable but I do)
- efficiently convert the wood to heat
- efficiently distribute the heat to the entire house
RMH-Walls.jpg
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Steve Shelton
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Geopolymer cuts easily with a hand saw
2018-02-13-08.40.27.jpg
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Steve Shelton
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I am exploring another Batch Box design.  It is known as the Double Shoebox Rocket (DSR).  I will be experimenting with this idea for the next few months.  It utilizes many of the same modular components as the BBR.  Therefore, if I need to revert back to the original design, I can do so with little waste.
DSR-Top-View.jpg
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DSR-Front-View.jpg
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Steve Shelton
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Latest sample of LTGS
IMG_20180220_121923.jpg
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Steve Shelton
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Bell
DSR-Bell.jpg
[Thumbnail for DSR-Bell.jpg]
 
Steve Shelton
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End result look
RMH-Walls.jpg
[Thumbnail for RMH-Walls.jpg]
 
Steve Shelton
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Plumbers Torch Test after 10 mins
IMG_20180222_145341.jpg
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IMG_20180222_150451.jpg
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Steve Shelton
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Here are the results of the temperature testing using a geopolymer piece 7/8" thick.

Geopolymer-Temp-Test.jpg
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Steve Shelton
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The first form is poured for the DSR.  It's inside the curing box.  Temps currently 102F on a hazy 80F spring day.

DSR-Backs-1st-form-pour.jpg
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Steve Shelton
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This is a view of the "Internal" components.  This comprises the actual DSR and Bell. 

DSR-Internal-View.jpg
[Thumbnail for DSR-Internal-View.jpg]
 
Steve Shelton
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The next 3 forms are ready to go.  I've adjusted the allowance for shrinkage to 11% after reviewing the first poured form's results.

Left to right they are:  Batch Box side, Batch Box floor (cut in 2), Batch Box and Shoe Box roofs (cut in 2)

2018-04-20-14.49.01.jpg
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Steve Shelton
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6 forms have been poured so far.  At this time there haven't been any visible cracks.  :)

IMG_20180430_160823.jpg
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pollinator
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Looks promising. What is the LTGS recipe, and how sensitive is it to local material composition?
 
Steve Shelton
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Phil Stevens wrote:Looks promising. What is the LTGS recipe, and how sensitive is it to local material composition?



You can read all about it here.

http://donkey32.proboards.com/thread/3283/geopolymer-code-named-kansas-city?page=1&scrollTo=29144
 
Steve Shelton
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Here's the batch box.  Next steps are to add the P-channel, cut the port in the batch box roof, cut the shoe box sides and roof to size and set it all up.
DSR-Build-1.jpg
[Thumbnail for DSR-Build-1.jpg]
 
Steve Shelton
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cover pic
RMH-Walls.jpg
[Thumbnail for RMH-Walls.jpg]
 
Steve Shelton
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"Dry Stacked" Double Shoebox Rocket - next steps - mix up some cob to temporarily assemble the heater for testing, weld the metal exoskeleton.  The p-tube will be trimmed to its final length once the doors have been built. 
IMG_20180610_123248.jpg
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Very babylonian or egyptian looking !
 
Phil Stevens
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Thanks for the updates, Steve. The dry stack looks great. In the DSR design, is the upper chamber also loaded with fuel? What are the reputed advantages of this over the standard batch box?
 
Steve Shelton
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Phil Stevens wrote:Thanks for the updates, Steve. The dry stack looks great. In the DSR design, is the upper chamber also loaded with fuel? What are the reputed advantages of this over the standard batch box?



You can read about the concept and see some videos here:

http://donkey32.proboards.com/thread/2341/different-batch-core-riser-all
 
Steve Shelton
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Phil Stevens wrote:Thanks for the updates, Steve. The dry stack looks great. In the DSR design, is the upper chamber also loaded with fuel? What are the reputed advantages of this over the standard batch box?



From my perspective, the DSR is simpler to build with cast components over the Batch Box Rocket style.  Another huge advantage is the ability to see the "Rams Horns" or "Vortex" in the Shoe Box via a window.  It's also slightly shorter. 

 
Steve Shelton
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DSR exoskeleton is started.  This will provide some structure to the overall heater and also provide a foundation for attaching doors.
DSR-Exoskeleton.jpg
[Thumbnail for DSR-Exoskeleton.jpg]
 
Steve Shelton
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The exoskeleton is complete.  I've added a small (5") riser on top of the top shoebox.  I understand it's not necessary.  I already had built all of the components so I went ahead. 
DSR-Exoskeleton.jpg
[Thumbnail for DSR-Exoskeleton.jpg]
 
Steve Shelton
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The Threshold has been added and the p-channel cut to size.  I've also cut a "redneck solution" door.  :)  Getting closer to the first test . . . I think.

00000IMG_00000_BURST20180707104249_COVER.jpg
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Steve Shelton
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Here's the "redneck solution" door

IMG_20180707_104330.jpg
[Thumbnail for IMG_20180707_104330.jpg]
 
Steve Shelton
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I fired up the DSR today with good results.  It appeared to need more air than the recommended air inlet provided. 


IMG_20180708_095152.jpg
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Steve Shelton
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Steve Shelton
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The "Temporary" Bell is now nearly complete.  It will be used for testing the air flow through the system.  Once I'm satisfied that everything is working properly, I will move the DSR into my house and construct the permanent Bell.

2018-07-21-14.56.08.jpg
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Satamax Antone
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That's quite clever!
 
Steve Shelton
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My plan for the "Permanent Bell" is as follows:
-  External Layer is made from 4" x 8" x 16" Cement Blocks
-  Trowel onto that a layer of thinset with "ridges"  - see pic of test block below
-  Trowel over the top of that layer a layer of Geo-polymer (GP)

The test block pictured below shows 3 different "ridge" depths.  Once the sample dries, I will mix up some GP to trowel over the thinset.  My thinking is that the thinset will provide structure and help the GP to adhere to the concrete blocks.  The GP will also provide a heat shield to the concrete blocks.

From left to right is a sample of 1/2", 1/4" and 1/8" ridges. 


IMG_20180723_123945.jpg
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Satamax Antone
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Your cement block, hollow or filled?
 
Steve Shelton
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Satamax Antone wrote:Your cement block, hollow or filled?



The blocks are hollow but I could fill them with rock or sand.
 
Satamax Antone
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Fill with concrete. Sand insulates.
 
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