Need to get a pic of the probe.
Graphs from first night. Had a problem around 5:30AM. Reset the controller. Still need some work on the code but its up.
Wednesday, December 26, 2018
Refractory Curing Box is now Heated
Need to get a pic of the probe.
Graphs from first night. Had a problem around 5:30AM. Reset the controller. Still need some work on the code but its up.
Tuesday, December 18, 2018
Casting furnace wall
Mixed up the dry ingredients for the furnace cylinder wall.
Currently I am using silica flour in place of sand. This is expensive in that the sand is mostly free and the silica flour has to be shipped. Need to experiment to see what replacing some of the silica flour with sand will do. Later. For now lets do this furnace.
Scaled up the formula, made about twice what I needed. Just to be safe.
Sifted everything but the silica flour using a flour sifter. So the perlite is fine.
The powder is tumbling to dry mix it. Debating if I should mix it all with the power mixer or mix smaller batches by hand in a mixing bowl. Trouble with the power mixer is the corners never get fully wet. But I guess thats OK because I can add water as I go because it was well mixed dry. I think I am going to use the power mixer because I have never had a batch crumble using it and the operation will go faster.
The core has been prepped by removing the PVC spring clips and wrapping with suran wrap.
The clamps ensure the can stays in place and holds the PVC core centered.
The wall thickness is .8 inches. Will have to see how that works out. Next time I may split the can so it can be easily removed and reused. Then embed the thing in aircrete.
I need to learn to let the mixture rest for 5 minutes or so after power mixing it. Need to beat this into my head. If I don't it ends up too stiff and maybe without enough moisture to hydrate what needs hydrating to set. Sigh. Maybe it will come out anyway if I keep it wet, think I tried that without much luck. In two weeks I will dry it out, at that point I will know if I need to recast it. Sort of got used to casting little trial bricks. Not quite the same here.
Currently I am using silica flour in place of sand. This is expensive in that the sand is mostly free and the silica flour has to be shipped. Need to experiment to see what replacing some of the silica flour with sand will do. Later. For now lets do this furnace.
Scaled up the formula, made about twice what I needed. Just to be safe.
Sifted everything but the silica flour using a flour sifter. So the perlite is fine.
The powder is tumbling to dry mix it. Debating if I should mix it all with the power mixer or mix smaller batches by hand in a mixing bowl. Trouble with the power mixer is the corners never get fully wet. But I guess thats OK because I can add water as I go because it was well mixed dry. I think I am going to use the power mixer because I have never had a batch crumble using it and the operation will go faster.
The core has been prepped by removing the PVC spring clips and wrapping with suran wrap.The clamps ensure the can stays in place and holds the PVC core centered.
The wall thickness is .8 inches. Will have to see how that works out. Next time I may split the can so it can be easily removed and reused. Then embed the thing in aircrete.
I need to learn to let the mixture rest for 5 minutes or so after power mixing it. Need to beat this into my head. If I don't it ends up too stiff and maybe without enough moisture to hydrate what needs hydrating to set. Sigh. Maybe it will come out anyway if I keep it wet, think I tried that without much luck. In two weeks I will dry it out, at that point I will know if I need to recast it. Sort of got used to casting little trial bricks. Not quite the same here.
Monday, December 17, 2018
Progress on furnace forms
The mold for the cylinder is finished. Was finished yesterday but I hemmed and hawed about the burner inlet.After much work by my sub conscious I have decided to make it part of the base.
The central core is on the long side. I was thinking I might want to use it for a taller furnace down the road.
Prior to casting the PVC clips will be removed from the core and it will be covered with plastic wrap. The core is in 4 parts with 3 lightly glued to several 1/8" plywood disks. Each disk has a string to flip it and pull it out.
The wall thickness was determined, nay dictated by the materials at hand. It is just slightly less than the test tiles I have been making. About the same as thin fire bricks used in the Kerr 666.
On this first go around the 1 gallon can will be the outer shell. Down the road I may be encasing the shell in foamcrete and will need a removable shell. Maybe try bonding the lid to the cylinder with a shell of foamcrete and have it lift off the base.
Started work on the burner. Don't think the burnzOmatic will work. I am thinking the regulator I got to use with it does not have enough pressure. Plan B is to go with welding regulator and cast a bell end so I can use a mig tip. The pipe is 1"
The base will be a bit larger than the cylinder. Maybe a groove for the cylinder to rest in. If all goes to plan the base will have a flat center to accept a plinth with an rising one turn spiral starting at the pipe inlet to help the gases flow.
The cover will be nothing special. Just need to figure out if I need to add any support to it. Would at least be nice to have a metal ring with loops to pick it up. Maybe make it a polygon or even square. Then I can cast it into an angle iron frame. Now how big to make the vent. Better too big as I can stop it down. LOL with a 4.5 inch diameter maybe 3 inches?
I may cast the shell tomorrow afternoon when it warms up. Use the morning to work on the base and lid forms. The plan is to use Styrofoam in the base to build up the complex shape. It will be a lot easier to pack the refractory around the burner inlet than it would be in the bottom of the cylinder.
The near brick has no perlite the back has 8 parts. It is the original formula.
Monday, December 10, 2018
Start of the furnace build" Molds aka Forms
Gathering the Material
==================
Been scouting.
The burner will be a burnzOmatic torch with a steel pipe to feed into the furnace. Maybe introduce a bit more air between the existing torch and the furnace.
I have a 2" OD metal water pipe to use for small crucibles. If I use a 4" schedule 40 PVC pipe for the core this gives an inch on each side which should be more then plenty for the 2" crucible. Maybe a 3" or 3 1/2" might work. Slice it into 4 staves then tape it back together around a set of wood discs.
It would be nice if I could fins a 6" ID sono tube but that will not happen. I do have an 8" ID schedule 40 PVC pipe that I can cut into staves and reassemble inside wood rings. The OD of the 4" is 4.5" and the ID of the 8" is 8" a difference of 3 1/2". So the walls will be 1.75". A bit on the thick side but I can live with it or create a larger Styrofoam core to replace the 4" PCV.
Building the Mold/Form
===================
The refractory core. AKA the form for the inside of the refractory cylinder. The pipe is being sectioned so the two narrow sides can be easily removed.
Created a 12" section with square ends with the chop saw.
Replaced the table saw cross cut blade with a plywood or rip blade with a narrower kerf. The less removed the rounder it will be when reassembled.
First cut was easy as it only needed to be straight.
Second cut. I wanted the cuts on each side to be in the same plane. The blade of this adjustable angle tool (Square) fit nicely in the previous cut. That allowed me to align the flat bottom of the tool to the table saw bed knowing the blade was 90 degrees.
Third cut. Aligned the existing cuts with the speed square. This ensures the next cut will be parallel to the 2 previous cuts.
The four staves. Tape or string will hold them together around two or three wood disks. The edges on the smaller staves have no draft so they can be pulled away from the inside of the refractory. This will release the larger staves.
The outside form for the refractory cylinder is cut from 8" schedule 40 PVC.
Neither end of the pipe was cut straight.
This was to big to easily fit into the miter saw. I made a cut, rotated the pipe using the saw blade in the existing kerf as a guide, and made another cut. Several cuts later it was finished. Not perfect but close enough that I can sand the ends flat.
figuring
==================
Been scouting.
The burner will be a burnzOmatic torch with a steel pipe to feed into the furnace. Maybe introduce a bit more air between the existing torch and the furnace.
I have a 2" OD metal water pipe to use for small crucibles. If I use a 4" schedule 40 PVC pipe for the core this gives an inch on each side which should be more then plenty for the 2" crucible. Maybe a 3" or 3 1/2" might work. Slice it into 4 staves then tape it back together around a set of wood discs.
It would be nice if I could fins a 6" ID sono tube but that will not happen. I do have an 8" ID schedule 40 PVC pipe that I can cut into staves and reassemble inside wood rings. The OD of the 4" is 4.5" and the ID of the 8" is 8" a difference of 3 1/2". So the walls will be 1.75". A bit on the thick side but I can live with it or create a larger Styrofoam core to replace the 4" PCV.
Building the Mold/Form
===================
The refractory core. AKA the form for the inside of the refractory cylinder. The pipe is being sectioned so the two narrow sides can be easily removed.
Created a 12" section with square ends with the chop saw.
Replaced the table saw cross cut blade with a plywood or rip blade with a narrower kerf. The less removed the rounder it will be when reassembled.
First cut was easy as it only needed to be straight.
Second cut. I wanted the cuts on each side to be in the same plane. The blade of this adjustable angle tool (Square) fit nicely in the previous cut. That allowed me to align the flat bottom of the tool to the table saw bed knowing the blade was 90 degrees.
Forth cut. There was no good way to align the last cut. I used the first narrow sections as an alignment guide to estimate where it should go.
The four staves. Tape or string will hold them together around two or three wood disks. The edges on the smaller staves have no draft so they can be pulled away from the inside of the refractory. This will release the larger staves.
The outside form for the refractory cylinder is cut from 8" schedule 40 PVC.
Neither end of the pipe was cut straight.This was to big to easily fit into the miter saw. I made a cut, rotated the pipe using the saw blade in the existing kerf as a guide, and made another cut. Several cuts later it was finished. Not perfect but close enough that I can sand the ends flat.
figuring
Sunday, December 9, 2018
Considering: Refractory aircrete bond experiment.
I would like to know if aircrete will bond to my refractory if air create is cast over it. Maybe try at 24, 48, and 72 hours. I expect the refractory to be too weak to demold at 24 hours but if the other two fail it may be the best option.
Plan
Cast 6 refractory slabs in the new slab mold.
Let the refractory set wet for 1 day.
Starting then coat two of the slabs with aircrete every 24 hours.
I could do 1 every 12 hours but don't want to double the aircrete mess.
The aircrete foam will be made with an electric hand mixer. Need to come up with a foam generator.
UPDATE
Shortly after writing this I was thinking it was a waste of time. As long as I make a refractory shell that can support itself it will work. But what I can do with this is try different thicknesses of aircrete to see how much is really needed. But I am still unsure if this is worth my time. Need to think about it.
Plan
Cast 6 refractory slabs in the new slab mold.
Let the refractory set wet for 1 day.
Starting then coat two of the slabs with aircrete every 24 hours.
I could do 1 every 12 hours but don't want to double the aircrete mess.
The aircrete foam will be made with an electric hand mixer. Need to come up with a foam generator.
UPDATE
Shortly after writing this I was thinking it was a waste of time. As long as I make a refractory shell that can support itself it will work. But what I can do with this is try different thicknesses of aircrete to see how much is really needed. But I am still unsure if this is worth my time. Need to think about it.
OPTION B: Small Propane Furnace prototype with aircrete (rev 2)
Overview
=======
This maybe easier to build providing one can make aircrete. I have made a test block.
When finished this furnace will be similar to OPTION A but with aircete where there was perlite. For the first furnace I am going to try about a 1" refractory shell with 4" of aircrete cast around it..
"The insulating R-Value of Air Crete blocks that are 8” thick is 18."
No idea what the R value of the refractory is. I only want to melt copper based metals. When I go to cast iron I may use more.
Build Sequence
============
=======
This maybe easier to build providing one can make aircrete. I have made a test block.
When finished this furnace will be similar to OPTION A but with aircete where there was perlite. For the first furnace I am going to try about a 1" refractory shell with 4" of aircrete cast around it..
"The insulating R-Value of Air Crete blocks that are 8” thick is 18."
No idea what the R value of the refractory is. I only want to melt copper based metals. When I go to cast iron I may use more.
Build Sequence
============
- Cast the aircrete sub base
- Cast a refractory base for under the cylinder
- Cast the refractory cylinder
- Cast an aircrete cylinder around the refractory cylinder
- Cast a refractory layer to cover the aircrete cylinder
- Cast the lid maybe a layer of refractory over an aircrete base
The options for the refractory core are the same as in the OPTION A furnace. A removeable outer form will have to be made for the refractory.
The refractory shell will be the core for the aircrete insulation layer. The furnace outer skin will serve as the outer form but it will need to be supported.
Forms Required
=============
Sub base, A circle shaped depression with a Styrofoam drain hole plug.
Refractory base. Same as above but smaller.
Refractory cylinder. The core is the same as furnace OPTION A. The outer from will be sheet metal supported by wood rings. This will be removed.
Aircrete cylinder. Only need the sheet metal outer skin but it will require wood support rings.
Failure Mode
==========
I am counting on the sheet metal shell to hold the furnace together should it fail. The lid is something I need to think about. Maybe a angle iron frame. Rebar inside aircrete is not such a good idea.
OPTION A: Small Propane Furnace prototype
This post will be updated as progress is made.
Theory
=====
Create a mold for a small gas furnace that can be reused.
Cylinder
----------
PVC pipe as the outside cylinder form.
Inside cylinder form. On the first go I will use option 2 which is not easy to repeat because it may be a lot of work and foam to create the core. But it should be the easiest to remove so lets hope I am wrong.
OPTION 1: Make the core from a split PVC pipe that can be removed without damage to it or the refractory. Split the pipe in 4 parts with the saw cuts orientated so the saw blade is always in parallel planes and the pipe not rotated. This will make two sides that can be pulled to the center, no draft on the cuts. Support the inside of the pipe with discs with two opposing flats. When a disc is rotated about the axis of the flats they fall out. Problem is finding a properly sized pipe. Maybe have to make one from wood.
OPTION 2: Make up a Styrofoam core for the inside that can be melted out with solvant. Hot melt glue it to the base and use spacers for centering that can be removed as the refractory is filled. Styrofoam insert for the burner hole. The core will be layers of Styrofoam cut to shape and laminated. If needed they can be turned on the lathe.
Create a lip around the top of the refractory cylinder. Ensure it is flat so the lid fits well. Cylinder is cast upside down so the lip is on the bottom.
Base
------
Base is a disc. A groove for the cylinder to rest in. Top surface has a center flat for the plint surrounded by a sculpted/slanted ring and a drain hole to deal with spills. All Styrofoam inserts. Maybe make the base and top lip the same size as the outside skin which will be riveted sheet metal from a water heater. A little unsure about this not wanting to crack either the lip or base.
I am thinking of casting a robust sub base from aircrete which is aireated Portland cement. Maybe it can be cast in the same form as the base with a ring added for additional height.
Top
-----
Top is another disc but with the exhaust vent hole. This will be a Styrofoam insert in the mold.
The space between the cylinder wall and outside skill will be filled with perlite that has been sifted to remove the fines. This will allow reuse of the perlite should the furnace liner fail. The question is how much space do we want between the outside of the refractory cylinder and the outside skin.
Prep Work
========
Build a foam generator for making aircrete.
Make a bow for cutting Styrofoam to a specific height using blocks/sticks as guides.
Mold Implementation
================
About the same as above but with less musing. Maybe the best way to do this is from the bottom up. So lets start with the base and sub base.
Sub Base
-----------
A board with rings to form the cavity for the disc. Make a removable top ring to reduce the height for use in casting the base. Styrofoam plug for the drain hole.
Base
------
Remove the top ring from the sub base mold. Cut a Styrofoam hoop the same dimension as the base of the cylinder. Maybe a wee bit larger because the cylinder can be mortared in. Attach that to the base form which is a depression for a disc
----
The form for the lid is a disc with a Styrofoam plug for the exhaust vent.
Theory
=====
Create a mold for a small gas furnace that can be reused.
Cylinder
----------
PVC pipe as the outside cylinder form.
Inside cylinder form. On the first go I will use option 2 which is not easy to repeat because it may be a lot of work and foam to create the core. But it should be the easiest to remove so lets hope I am wrong.
OPTION 1: Make the core from a split PVC pipe that can be removed without damage to it or the refractory. Split the pipe in 4 parts with the saw cuts orientated so the saw blade is always in parallel planes and the pipe not rotated. This will make two sides that can be pulled to the center, no draft on the cuts. Support the inside of the pipe with discs with two opposing flats. When a disc is rotated about the axis of the flats they fall out. Problem is finding a properly sized pipe. Maybe have to make one from wood.
OPTION 2: Make up a Styrofoam core for the inside that can be melted out with solvant. Hot melt glue it to the base and use spacers for centering that can be removed as the refractory is filled. Styrofoam insert for the burner hole. The core will be layers of Styrofoam cut to shape and laminated. If needed they can be turned on the lathe.
Create a lip around the top of the refractory cylinder. Ensure it is flat so the lid fits well. Cylinder is cast upside down so the lip is on the bottom.
Base
------
Base is a disc. A groove for the cylinder to rest in. Top surface has a center flat for the plint surrounded by a sculpted/slanted ring and a drain hole to deal with spills. All Styrofoam inserts. Maybe make the base and top lip the same size as the outside skin which will be riveted sheet metal from a water heater. A little unsure about this not wanting to crack either the lip or base.
I am thinking of casting a robust sub base from aircrete which is aireated Portland cement. Maybe it can be cast in the same form as the base with a ring added for additional height.
Top
-----
Top is another disc but with the exhaust vent hole. This will be a Styrofoam insert in the mold.
The space between the cylinder wall and outside skill will be filled with perlite that has been sifted to remove the fines. This will allow reuse of the perlite should the furnace liner fail. The question is how much space do we want between the outside of the refractory cylinder and the outside skin.
Prep Work
========
Build a foam generator for making aircrete.
Make a bow for cutting Styrofoam to a specific height using blocks/sticks as guides.
Mold Implementation
================
About the same as above but with less musing. Maybe the best way to do this is from the bottom up. So lets start with the base and sub base.
Sub Base
-----------
A board with rings to form the cavity for the disc. Make a removable top ring to reduce the height for use in casting the base. Styrofoam plug for the drain hole.
Base
------
Remove the top ring from the sub base mold. Cut a Styrofoam hoop the same dimension as the base of the cylinder. Maybe a wee bit larger because the cylinder can be mortared in. Attach that to the base form which is a depression for a disc
Cylinder
----------
The cylinder will be cast upside down. Start by making the form for the top lip with a central support for the outside PVC wall
Cut the large PVC pipe such that two opposing sections can be pulled out. Its not important now but I may reused this pipe latter as the inner cylinder form for a larger furnace.
I plan on using the blade from a battery powered skill saw. These blades are narrower. The PVC will fit back together better.
Lid----------
The cylinder will be cast upside down. Start by making the form for the top lip with a central support for the outside PVC wall
Cut the large PVC pipe such that two opposing sections can be pulled out. Its not important now but I may reused this pipe latter as the inner cylinder form for a larger furnace.
I plan on using the blade from a battery powered skill saw. These blades are narrower. The PVC will fit back together better.
----
The form for the lid is a disc with a Styrofoam plug for the exhaust vent.
Saturday, December 8, 2018
Additives for Castable Refractory
From Refractory Bricks and Refracotry Material
Yellow dextrin is widely used for grinding tool and abrasives, foundry casting, refractory materials, rubber products and other industries, particularly abrasive and refractory materials, refractory charge, light brick, shaped bricks and others, having an superb effect on the early setting of its products. It matches in appropriate proportion and mix well, which plays an excellent role in collapse preventing and edges and corners protecting.
Yellow dextrin is widely used for grinding tool and abrasives, foundry casting, refractory materials, rubber products and other industries, particularly abrasive and refractory materials, refractory charge, light brick, shaped bricks and others, having an superb effect on the early setting of its products. It matches in appropriate proportion and mix well, which plays an excellent role in collapse preventing and edges and corners protecting.
Did I miss something ?
Going to have to give this a try but at what proportion ?
From Binders for Ceramic Bodies
Dextrin also improves the plasticity of clay slips.
and
From Binders for Ceramic Bodies
Dextrin also improves the plasticity of clay slips.
and
Darvan
Polymer deflocculant, de-flocculant
Alternate Names: Darvan 811, Darvan No. 7, Darvan 821A, Darvan C
Darvan is a deflocculant and used to disperse ceramic suspensions to minimize their water content. It is a liquid alternative to the long popular sodium silicate. About twice as much is required typically (0.4-0.5%) however Darvan does offer a number of advantages. Typically soda ash is not needed as a complement and Darvan does not attack plaster molds. In addition slurries are much less sensitive to over deflocculation and are more stable. It is thus easier to reprocess scrap. However a number of engineers still prefer using a sodium silicate:soda ash mix to control thixotropic properties better, especially if little scrap is being added.
From
| How to... Make and adjust casting slip This article is interesting because a ceramic slip (casting pottery) and castiable refractories have some things if not much in common.
Super Washing Soda is soda ash. Have that on hand. |
thinking about 'add mixtures'
They make products called 'add mixtures' to modify concrete. One sort makes the concrete more fluid with less water, maybe a lubricant of sorts. I wonder how that would work with a refractory mix. They make 'add mixtures' specifically for refractories but its not something one can buy a tiny bit of.
The concrete version can be had on amazon and fairly reasonable. Its called a superplasticizer and is about $12.
Fritz Pac Superplasticizer 5
I don't want to mess with this just now as I already have too many variables. But then I don't want to forget about it either.
Asked about it on amazon
What I take away from that is that it will breakdown and ruin the refractory. Still a good idea for counter tops and such. But the lime I am adding is a flocculant which should help reduce water use some.
The concrete version can be had on amazon and fairly reasonable. Its called a superplasticizer and is about $12.
Fritz Pac Superplasticizer 5
I don't want to mess with this just now as I already have too many variables. But then I don't want to forget about it either.
Asked about it on amazon
Answer:
It will sort of burn/melt. But if you do a thin 1/2 layer of refsctory cement over it like i did on mine it works great. The interior 1/2 layer will break up over time but it super easy clean clean out and rework because the base layer stays strong.
By Eldon L Eslick on December 4, 2018
By Eldon L Eslick on December 4, 2018
Sunday, December 2, 2018
Try original formula again.
Every sample in the previous test was a flop. They either crumbled when dried or after firing.
So time to work from the last know good. Today I made up what I think is the formula used on the good brick. Originally I was going to do without the perlite but went to far with the water. (I should know enough to hold back some of the dry ingredient mix) and added 8 oz of perlite. This was perlite sifted through a crank type flour sifter.
This is also an attempt to see if I can do this in cold weather. The first day will have to be in the house. If the forms were not wood I could let them cure in the heated wet freezer chest. Tomorrow afternoon I will remove them and transfer the samples.
My intended formula was
10 : Silica Flour
6 : Native Clay
2 : Portland cement
3 : Lime
5 : Perlite
And I ended up with 8 Perlite. Tomorrow I will make sample with 0, 2 perlite and I expect they maybe short bricks.(did not happen)
To make the bricks easier to release I glued vinyl to the bottom and used a light film of crisco on the bottom and packing tape covered sides.
Thinking about doing the zero perlite yet tonight. hmmm OK going for it. Mixed up a 1.5X batch to ensure I get a full brick and have dry to hold back. Going to start weighting the water if I remember when I get out there. The mix is currently doing 15 or 20 minutes in the mixer.
OK that is done and worked well. Think I used 12 OZ in 2 lbs of dry mix.(WRONG) Need to check the check marks I made.
EDIT: Used a 2 oz cup and made 7 check marks which is 14 dry oz of water for this 1.5X batch. For a 1X batch use 2/3(14) or 9.3 oz. A fluid oz is too close to one avoirdupois aka weight oz to matter. So they should be interchangeable. The dry weight of the mix without water came out to some even number of lbs, I think 5 but that sounds too high. No lost info since we have the exact formula for the ingediants.
Now to make sure they do not dry out while they are in the forms aka molds.
So time to work from the last know good. Today I made up what I think is the formula used on the good brick. Originally I was going to do without the perlite but went to far with the water. (I should know enough to hold back some of the dry ingredient mix) and added 8 oz of perlite. This was perlite sifted through a crank type flour sifter. This is also an attempt to see if I can do this in cold weather. The first day will have to be in the house. If the forms were not wood I could let them cure in the heated wet freezer chest. Tomorrow afternoon I will remove them and transfer the samples.
My intended formula was
10 : Silica Flour
6 : Native Clay
2 : Portland cement
3 : Lime
5 : Perlite
And I ended up with 8 Perlite. Tomorrow I will make sample with 0, 2 perlite and I expect they maybe short bricks.(did not happen)
To make the bricks easier to release I glued vinyl to the bottom and used a light film of crisco on the bottom and packing tape covered sides.
OK that is done and worked well. Think I used 12 OZ in 2 lbs of dry mix.(WRONG) Need to check the check marks I made.
EDIT: Used a 2 oz cup and made 7 check marks which is 14 dry oz of water for this 1.5X batch. For a 1X batch use 2/3(14) or 9.3 oz. A fluid oz is too close to one avoirdupois aka weight oz to matter. So they should be interchangeable. The dry weight of the mix without water came out to some even number of lbs, I think 5 but that sounds too high. No lost info since we have the exact formula for the ingediants.
Now to make sure they do not dry out while they are in the forms aka molds.
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