Riser options

[gbfisher]

Hello,  Gary here.  I'm getting my materials around to make an 8 inch batch box.  I have bought enough firebricks to make the firebox and riser.  I would however rather cast a round riser.  I have searched quite a few threads,  but am still not sure the best way to go about it.  
I have seen the thread on heatcast40,  and I have seen some talk about perlite/fireclay mixtures.

I could use some professional opinions on my best way to proceed.
Thank you in advance for your help.

Gary

ps. I have roamed around on Permies site as well under gfisherdvm.  Wasn't sure which site to post on, as I see most of the mods are the same.  

[pinhead]

IMHO, casting the riser is much harder than it needs to be.

My preferred method of making a heat riser is using ceramic fiber. Either blanket or board, depending on your available funds.

Blanket is cheap but requires a "form" and board is more expensive but will support itself.

Here's Matt's CF Board post: donkey32.proboards.com/thread/2315/ceramic-fiber-build-discussion

Here's my CF Blanket post: donkey32.proboards.com/post/24992/thread

[peterberg]

Hi Gary, welcome to the boards.
In order to cast a round riser successfully it would require quite some craftmanship and a lot of experience. Big air holes on the inside surface will disrupt the gas streams quite a bit, smooth is the magic word here.

You'd better to follow the advise of Pinhead in my opinion, or build the riser from bricks in one of the patterns that are available on batchrocket.eu/en/designs#brick2.

[Jura]

Sept 27, 2017 11:56:25 GMT -8 gbfisher said:

  I would however rather cast a round riser.  I have searched quite a few threads,  but am still not sure the best way to go about it.  

As to the materials choice i'll not help you as I used a ready mixture of high alumina cement with andalusite aggregate to cast my 8" 138 cm high heat riser.

unfortunately only after casting it I had a pleasure to talk to a professionals in an institute of refractory ceramics and they enlightened me on the issue.
In order to avoid cracking it is advisable not to cast such elements in one piece. (tensions in unequally heated cement)
I was told the best would be to cast half cylinders (and the optimum would be quarters ) of height max 45 -50 cm (with 4 cm thickness)
I forgot to ask whether this conditions were given for my cement specifically or it can be taken as a rule of the thumb.
Anyway with my second stove I  went for this  system as it required cutting the brick in half  at 45 angle

[gbfisher]

I appreciate all the advice, and the welcome.

[gbfisher]

Sept 27, 2017 12:11:24 GMT -8 pinhead said:

IMHO, casting the riser is much harder than it needs to be.

My preferred method of making a heat riser is using ceramic fiber. Either blanket or board, depending on your available funds.

Blanket is cheap but requires a "form" and board is more expensive but will support itself.

Here's Matt's CF Board post: donkey32.proboards.com/thread/2315/ceramic-fiber-build-discussion

Here's my CF Blanket post: donkey32.proboards.com/post/24992/thread

Thanks Pinhead for showing your design.  So its really as simple as lining a stove pipe with the fiber blanket?
I'm understanding that you can either salvage this from a glass topped stove,  or purchase it new?
Do you have a source preferably in the USA?  

Ps.   Would this be what you are talking about?   

www.grainger.com/product/34DA12?cm_mmc=PPC:+Google+PLA&cm_mmc=PPC:+Google+PLA?campaignid=175663197&s_kwcid=AL!2966!3!56542798197!!!!!&ef_id=WcxCYgAABAJ0Ot2E:20170928002922:s&kwid=productads-adid%5E56542798197-device%5Et-plaid%5E102361527717-sku%5E34DA12-adType%5EPLA

If you were making an 8 inch system,   Would you start with a 12 in pipe,  thus ending up with an 8 inch ID after you added 2 inches of fiber blanket all the way around?  

[gbfisher]

Thank you Jura for your photo. Very nicely done.

[matthewwalker]

Where are you located? You can find ceramic fiber risers in most metro areas. Here's one example:

www.firebrickengineers.com/

The risers themselves are not too expensive, the shipping is the killer. Search for refractory suppliers near you and you can most likely find a source.

[gbfisher]

Sept 27, 2017 16:39:53 GMT -8 matthewwalker said:

Where are you located? You can find ceramic fiber risers in most metro areas. Here's one example:
www.firebrickengineers.com/

The risers themselves are not too expensive, the shipping is the killer. Search for refractory suppliers near you and you can most likely find a source.

Thank you very much Matt.  I live in South Dakota.  I will look at your link 
Gary

ps. I see they have an office in Minneapolis, MN.

[sparks]

Greetings All,
Sparks here. Gary and I have been collaborating on this project. We got enough firebrick to make two batch box stoves and are now working on the preliminary issues before we commit to a location. The heat riser is clearly the issue for us right now. I noted the beautiful set up posted by Jura and am motivated to ask what he is using to cut the bricks so beautifully?
I have a small "table saw" with a diamond cutting wheel and a 12" chop saw but no diamond wheel for that. Is a diamond wheel necessary or will a masonry blade work as well. It looked like most of the cuts are "cross-cuts" vs. rip cuts.
I managed to accumulate 20 bags of refractory clay and we have been working with the idea of casting the heat riser. It appears that this might be a good process but it also looks as though some of you recommend casting vertical sections vs. vertical whole parts. Since we don't have any opportunities to get some of the materials suggested here, does anyone have any strong feelings about casting the heat riser between a 12" cardboard tube and an 8" cardboard tube?

We're out in the remote area of northern South Dakota and the closest masonry dealer is 230 miles away.
Hope you can lend some advice to this project. My first rocket heater works pretty well but if I had to modify it, I'd make the magazine at a 45*angle vs. 90* because the wood burns too close to the magazine rather than the burn chamber.

Cheers,
Sparks sends

[Jura]

Sept 27, 2017 17:32:44 GMT -8 sparks said:

I noted the beautiful set up posted by Jura and am motivated to ask what he is using to cut the bricks so beautifully?

Ugh! I used the large hand angle grinder 2000W and cutting is not that beautiful as it looks.
In fact the blade quality is of more importance than the grinder make. (Mine costed some 35€)
In case of cross section the blade was still to short to make a cut so one needs to start cutting a brick from two sides so the cut surface is not always as flat as with a table wet saw.
The cut surface needs to be polished afterwards.
(I did it with a side of the grinder blade)
btw. do not forget to plunge & store the brick in a water overnight before cutting them(unless you have a wet saw) as dry cutting is a blade killer)

[grga]

Sept 27, 2017 23:36:16 GMT -8 Jura said:

this is the key, less dust, better cut and longer life of the diamond disk. Enough is also 5 minutes in water - until you see no bubbles. I have a cheap (less than 10 eur) 115mm blade and 700W grinder. Cutting the bricks is relatively fast, cut on one side and on another then "boom" on the table edge to get two peaces and make some final corrections if needed. 

[pinhead]

Sept 27, 2017 15:54:06 GMT -8 gbfisher said:

Sept 27, 2017 12:11:24 GMT -8 pinhead said:

IMHO, casting the riser is much harder than it needs to be.

My preferred method of making a heat riser is using ceramic fiber. Either blanket or board, depending on your available funds.

Blanket is cheap but requires a "form" and board is more expensive but will support itself.

Here's Matt's CF Board post: donkey32.proboards.com/thread/2315/ceramic-fiber-build-discussion

Here's my CF Blanket post: donkey32.proboards.com/post/24992/thread

Thanks Pinhead for showing your design.  So its really as simple as lining a stove pipe with the fiber blanket?
I'm understanding that you can either salvage this from a glass topped stove,  or purchase it new?
Do you have a source preferably in the USA?  

Ps.   Would this be what you are talking about?   

www.grainger.com/product/34DA12?cm_mmc=PPC:+Google+PLA&cm_mmc=PPC:+Google+PLA?campaignid=175663197&s_kwcid=AL!2966!3!56542798197!!!!!&ef_id=WcxCYgAABAJ0Ot2E:20170928002922:s&kwid=productads-adid%5E56542798197-device%5Et-plaid%5E102361527717-sku%5E34DA12-adType%5EPLA

If you were making an 8 inch system,   Would you start with a 12 in pipe,  thus ending up with an 8 inch ID after you added 2 inches of fiber blanket all the way around?  

Yep, that's the stuff though I believe there should be a higher-temp-rated version.

Believe it or not, Walmart also sells the stuff now: Walmart

I opted for the cheaper 1-inch blanket for the inside of the stovepipe and then further insulated the outside of the pipe with cheaper mineral wool insulation. It would definitely be simpler to use two-inch blanket and be done with it though!

[Deleted]

As you have a lot of refractory clay:

Tubes or half tubes can be easily formed with clay slabs.
Even a fire box could be formed with slabs.

Search youtube for:
Clay slab round vase
Clay slab hump mold
Clay slab slump mold

If the clay slabs are prepared with a LTGS binder sintering will start at low temperatures.
Could also be used to make beveled bricks without cutting.
The result is comparable to fired bricks.

[gbfisher]

Thanks Pinhead