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.
Friday, November 16, 2018
Air Entrained Refractory: Will it Float ?
Which late night comedian did the "Will it Float" segment.
Anyway. I used the original mix, #1 in the test, that subs silica flour for sand and mixed it up like the air crete people do. I am not sure if it will be as light as it could be. I made the foam with an electric mixer like one used to make a cake.
It looks like the top of the refractory is right at the water line. Given that there is the added weight of the container and water that will evaporate maybe it will.
At any rate it is close. Need to play with the foam and such to see if I can make it lighter.
Prior to doing the air entrained refractory I mixed up a bit of aircrete. 1:32 dawn:water, 1:2 water to Portland cement, and equal amounts of the wet cement and foam.
Maybe the cement could have been thicker. Some bubbles escaped. And it seems quit hungry for water. Much more so than the refractory mix. It rather fragile so adding water without messing up the surface takes some care.
It is starting to harden but I suspect it is drying rather than setting or curing. I am thinking of doing a test with additional Portland cement in several steps.
The puck has been fired to 800C.
OK I had to see if it would float. I did not think it would be all that interesting and did not record it. The air-crete floated with the water just below the top of the slab. The air entrained refractory was much more interesting. It initally floated much like the air-crete. But it started absorbing water and soon when to the bottom. I may dry it out and record it.
I plan to try this again but with no perlite and maybe samples with a bit more Portland cement.
The puck did not seem like it was fired. So I have loaded it and both parts of the original non air entrained brick into the oven and am firing to 850C for one hour after reaching temp. At 830C I noticed something rising from the stuff in the furnace so I open the vent. Not sure that the smoke/steam whatever is actually from the stuff I am firing. Just the same I am going to fire it for another hour.
Yeah should have written down times. Begs the question why I have not setup a controller so I can use firing schedules yet.
Anyway. I used the original mix, #1 in the test, that subs silica flour for sand and mixed it up like the air crete people do. I am not sure if it will be as light as it could be. I made the foam with an electric mixer like one used to make a cake.
It looks like the top of the refractory is right at the water line. Given that there is the added weight of the container and water that will evaporate maybe it will.
At any rate it is close. Need to play with the foam and such to see if I can make it lighter.
Maybe the cement could have been thicker. Some bubbles escaped. And it seems quit hungry for water. Much more so than the refractory mix. It rather fragile so adding water without messing up the surface takes some care.
Later in the day I became impatient and removed the air entrained refractory sample from its cup/mold.
It is starting to harden but I suspect it is drying rather than setting or curing. I am thinking of doing a test with additional Portland cement in several steps.
The puck has been fired to 800C.
OK I had to see if it would float. I did not think it would be all that interesting and did not record it. The air-crete floated with the water just below the top of the slab. The air entrained refractory was much more interesting. It initally floated much like the air-crete. But it started absorbing water and soon when to the bottom. I may dry it out and record it.
I plan to try this again but with no perlite and maybe samples with a bit more Portland cement.
The puck did not seem like it was fired. So I have loaded it and both parts of the original non air entrained brick into the oven and am firing to 850C for one hour after reaching temp. At 830C I noticed something rising from the stuff in the furnace so I open the vent. Not sure that the smoke/steam whatever is actually from the stuff I am firing. Just the same I am going to fire it for another hour.
Yeah should have written down times. Begs the question why I have not setup a controller so I can use firing schedules yet.
Wednesday, November 14, 2018
Another version of the sand snake, sand fluffer, rotary muller ?
"Components are a 1/4hp 1725 rpm motor mounted inside a large coffee can (the can
keeps the sand out of the motor, and old canner, an old salad bowl and angle iron to make
up the frame. The wheel shown is a steel disk 8" in diameter with a2 1/2" expanded metal
ring welded to it. The mesh could be replaced with studs spaced an inch or so apart."
Found more info at http://schoepp.hylands.net/fluffer.html
Tuesday, November 13, 2018
First Electric Furnace Design
I would like the furnace be used both for casting as well as tempering parts to large to fit the Kerr 666 burnout oven. This suggests a rectangular shape. Thinking about a shape that is tall, narrow and deep. Big enough to fit a cruciable into and deep enough to temper stock to long to fit in the Kerr 666. Just thinking. Don't want it to be too big and slow heating. If I feel confident about it set it up so it can be rotated 90 degrees to make a wide low instead of a narrow tall.
Lets consider the design from the inside out.
For some time I have been thinking about casting the floor and ceiling with grooves to accept the sides and back. The back would have a groove on each vertical edge to accept the ends of the sides. This design would provide a free standing interlocking shell without casting it in one piece. The channels for the heating coil will be created by gluing Styrofoam strips to the forms. After the refractory dries these can be removed with flame or solvent. The shell will be fairly thick to accommodate the cavities for the coils which I plan to run around the sides and back.
The shell will be surrounded by perlite. I am not sure if it will be loose or bonded with sodium silicate. Maybe a bonded section for the floor to rest on and the rest packed loose around the shell.
I am currently working on a refractory variant of air crete.
Lets consider the design from the inside out.
For some time I have been thinking about casting the floor and ceiling with grooves to accept the sides and back. The back would have a groove on each vertical edge to accept the ends of the sides. This design would provide a free standing interlocking shell without casting it in one piece. The channels for the heating coil will be created by gluing Styrofoam strips to the forms. After the refractory dries these can be removed with flame or solvent. The shell will be fairly thick to accommodate the cavities for the coils which I plan to run around the sides and back.
The shell will be surrounded by perlite. I am not sure if it will be loose or bonded with sodium silicate. Maybe a bonded section for the floor to rest on and the rest packed loose around the shell.
I am currently working on a refractory variant of air crete.
Monday, November 12, 2018
Research Notes aka Book learning
My notes are in purple.
B. Thermal Shock (1)
This is measure of the refractory property when the refractory is exposed to alternate heating and cooling. It is an important property for a refractory material.Most high-temperature processes experience heating and cooling. Both refractory grains and the bonding system expand while being heated and contract during cooling. Having similar grains in the structure, the thermal shock resistance depends on the matrix bonding the grains. Thus, refractories having structures with built-in micro cracks of defects show better thermal shock resistance than with rigid systems. In some refractories, the bonding system, by nature, possesses micro structural defects or cracks that provide better thermal shock resistance.
--------------------------
BENEFITS OF CEMENT-LIME MORTAR (2)
Pozzolan (3)
Pozzolans are a broad class of siliceous or siliceous and aluminous materials which, in themselves, possess little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties.[1] The quantification of the capacity of a pozzolan to react with calcium hydroxide and water is given by measuring its pozzolanic activity.[2] Pozzolana are naturally occurring pozzolans of volcanic origin.
Reaction. The pozzolanic reaction is the chemical reaction that occurs in portland cement upon the addition of pozzolans. ... The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties. --------------------------
(5) Calcium Silicate Insulation
Over 1100 °C calcium silicates begin to sinter, therefore the
calcium silicates are limited to 1100 °C.
I need to take the oxy propane torch to a sample and see if I can break it down. Need to know if the additional components will take it past 1100C. 200C more would make bronze casting easier. OK looked up the melting point of Calcium Silicate. 2,130 °C (3,870 °F; 2,400 K) NICE
we do advise heat curing, before the first use as a front
layer, as this will be beneficial and will ensure an even
longer working life for your insulation.
-------------------------- Silica flour aka silica fume is a pozzlan. Are all the pozzolan bond based on water like the Portland cement bond ? ANSWER NO see above
(4) Pozzolan a material that, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both.
Clays → contain high amounts of silica & alumina but have a crystallic structure! (Do not possess pozzolanic activity) – However, by heat treatment, such as calcining ~700-900°C crystallic structure is destroyed & a quasi-amorphous structure is obtained.
Burned clay → possess pozzolanic property
Limestone breaks down at 825C but the temperature which calcified lime breaks down is over 4000C. (check this) Things are looking good.
--------------------------
Thermal shock (1)
I was planning on making rings to test the refractories for resistance to thermal shock but this table has me wondering if this test only makes sense for dense refractories. The 2nd entry "High thermal conductivity" is especially troubling.
On aggregates (1)
Given that my native sand has irregular edges that interlock well it may be a good choice.
BENEFITS OF CEMENT-LIME MORTAR
This is regarding mortar and not refractory but parts may still apply.
B. Thermal Shock (1)
This is measure of the refractory property when the refractory is exposed to alternate heating and cooling. It is an important property for a refractory material.Most high-temperature processes experience heating and cooling. Both refractory grains and the bonding system expand while being heated and contract during cooling. Having similar grains in the structure, the thermal shock resistance depends on the matrix bonding the grains. Thus, refractories having structures with built-in micro cracks of defects show better thermal shock resistance than with rigid systems. In some refractories, the bonding system, by nature, possesses micro structural defects or cracks that provide better thermal shock resistance.
--------------------------
BENEFITS OF CEMENT-LIME MORTAR (2)
- Autogenous Healing - When hairline cracks develop in the mortar, hydrated lime reacts with carbon dioxide in the atmosp
- here. This reaction produces limestone which helps to seal the crack and fill voids in the mortar. This explains the increased moisture resistance
- noted after six months of curing in two studies.
- Extent of Bond - The extent of bond is the percent of brick to which the mortar adheres. The low air content and the fineness and stickiness of hydrated lime particles increase the extent of bond of mortar to brick. These factors allow cement-lime mortars to penetrate deeply into the brick and seal the brick/mortar interface.
Hydrated lime improves the strength of the mortar by several mechanisms:
- Carbonation - Hydrated lime reacts with carbon dioxide in the atmosphere to form limestone.
- Cementitious Reactions - Pozzolonic reactions can occur between hydrated lime and silica compounds in the mortar mix.
- pH - Hydrated lime helps to maintain high pH levels in the mortar . This makes siliceous materials more soluble and reactive.
Pozzolan (3)
Pozzolans are a broad class of siliceous or siliceous and aluminous materials which, in themselves, possess little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties.[1] The quantification of the capacity of a pozzolan to react with calcium hydroxide and water is given by measuring its pozzolanic activity.[2] Pozzolana are naturally occurring pozzolans of volcanic origin.
Reaction. The pozzolanic reaction is the chemical reaction that occurs in portland cement upon the addition of pozzolans. ... The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties. --------------------------
(5) Calcium Silicate Insulation
Over 1100 °C calcium silicates begin to sinter, therefore the
calcium silicates are limited to 1100 °C.
I need to take the oxy propane torch to a sample and see if I can break it down. Need to know if the additional components will take it past 1100C. 200C more would make bronze casting easier. OK looked up the melting point of Calcium Silicate. 2,130 °C (3,870 °F; 2,400 K) NICE
we do advise heat curing, before the first use as a front
layer, as this will be beneficial and will ensure an even
longer working life for your insulation.
-------------------------- Silica flour aka silica fume is a pozzlan. Are all the pozzolan bond based on water like the Portland cement bond ? ANSWER NO see above
(4) Pozzolan a material that, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both.
Clays → contain high amounts of silica & alumina but have a crystallic structure! (Do not possess pozzolanic activity) – However, by heat treatment, such as calcining ~700-900°C crystallic structure is destroyed & a quasi-amorphous structure is obtained.
Burned clay → possess pozzolanic property
Limestone breaks down at 825C but the temperature which calcified lime breaks down is over 4000C. (check this) Things are looking good.
--------------------------
Thermal shock (1)
I was planning on making rings to test the refractories for resistance to thermal shock but this table has me wondering if this test only makes sense for dense refractories. The 2nd entry "High thermal conductivity" is especially troubling.
On aggregates (1)
Given that my native sand has irregular edges that interlock well it may be a good choice. BENEFITS OF CEMENT-LIME MORTAR
This is regarding mortar and not refractory but parts may still apply.
Sources
- Charles Schacht Refractories Handbook 2004
- BENEFITS OF CEMENT-LIME MORTAR
- Wikipedia
- aybu.edu (best ref)
- Calcium Silicate Insulation
Remember: Glucose in Sodium Silicate Cores 1/2%
From Martin. Allows cores to be easily removed.
7 1/2 % Sodium Silicate
1/2 % Glucose
Power Mix
Riddle
Hand Mix
7 1/2 % Sodium Silicate
1/2 % Glucose
Power Mix
Riddle
Hand Mix
Sunday, November 11, 2018
Refractory Experiment In progress
Further experiments.
This is the formula by volume. 10 parts perlite is a guess, it can be increased in a later experiment after these are evaluated.
10 : Silica Flour or Sand
6 : Native Clay
2 : Portland cement
3 : Lime
5 : Perlite
The variations from the mix are listed for each sample. Play sand is a quartz sand.
Mixes tested.
Whats wrong with this picture ? 6 and 7 are identical but 7 lacks portland cement so it is lighter. So yeah, I knew which one it was. LOL
Test ingredient variations.
This is the formula by volume. 10 parts perlite is a guess, it can be increased in a later experiment after these are evaluated.
10 : Silica Flour or Sand
6 : Native Clay
2 : Portland cement
3 : Lime
5 : Perlite
The variations from the mix are listed for each sample. Play sand is a quartz sand.
Mixes tested.
- ✅ the formula aka control
- ✅ local sand instead of silica flour
- ✅ play sand instead of silica flour
- ✅ silica flour without Portland cement
- ✅ play sand without Portland cement
- ✅ local sand and silica flour 5 each
- ✅ local sand and silica flour no Portland cement
𝥷 Not started ⑇ Dry mixed ✅ Drying 🔥 Firing
Whats wrong with this picture ? 6 and 7 are identical but 7 lacks portland cement so it is lighter. So yeah, I knew which one it was. LOL
If all goes well tomorrow I can hydrate them and move the flags to ✅
Currently thinking a day of natural drying in the house then bake them below the boiling point of water till dry. Then fire. This is a bit of a rushed schedule and I reserve the right to change my mind. LOL
Aside: I knew a geneticist who said "It's all book keeping".
All were hydrated in one afternoon. Containers were covered with snap on lids assumed to be mostly air tight. Solo brand containers.
In addition to the normal sample and additional one was made with 1 spoon of sodium silicate. Total of 14 sample. I should have enough to make 1 or 2 more samples from each bottle.
It took considerable time to create these samples. I am now thinking a week to dry.
The perlite is not of a uniform size. I think it would be better to sieve it so a more uniform sample could be made.
It would also work better to add the perlite to each sample as it was hydrated. That would ensure a more even distribution.
---------------
Its the next morning about 12 hours after the tests were cast.
Moved the labels to the lids as they were not going to make the trip on the sides.
Took the lids of the samples which we heading in the direction of dry. So I gave each 2 teaspoons of water. Shortly after casting I had given each sample a dribble of water. It will be interesting to see if the absorb this water and how long it will take.
If you are thinking the water is only needed to hydrate the Portland cement you might be mistaken. The samples with no Portland cement were just as non-wet, don't want to say dry. It may be that water enables processes that unlike the Portland cement bonds are not destroyed by heat. If this is or is not the case adding water will at worst waste my time. And if you look at it this way I should have gone out and purchased chimerical refractory. But at this juncture I have more time than money.
The original tile/brick was mixed to a consistency of peanut butter. I would call that ramable refractory. These were slightly more fluid maybe more along the line of a castable.
It seems that ramming the refractory produces better mechanical interlock between the particles. This provides additional strength in the green and fired stages. However if you are using a commercial refractory follow the makers instructions. This is about DIY.
Again with not so good image of my sand.
It looks like the sand particles would interlock when forced together. A good thing. But note that the original test tile/brick was made with silica flour instead of sand.
---------------
48 Hours after cast
IB needed water
2B and 5B were soon to need, and were watered
B is identical to A but has a small spoon of sodium silicate added. Adding sodium silicate to this mix may flux it so maybe a bad idea.
Why am I bothering to keep these moist when the Portland cement bonds will break down anyway? The lime and possibly the sand may form pozzolan type bonds which need water to form and may not break down with heat.
---------------------------------
Saturday November 17th.
Interesting difference between sample 4 and 5.
Currently thinking a day of natural drying in the house then bake them below the boiling point of water till dry. Then fire. This is a bit of a rushed schedule and I reserve the right to change my mind. LOL
Aside: I knew a geneticist who said "It's all book keeping".All were hydrated in one afternoon. Containers were covered with snap on lids assumed to be mostly air tight. Solo brand containers.
In addition to the normal sample and additional one was made with 1 spoon of sodium silicate. Total of 14 sample. I should have enough to make 1 or 2 more samples from each bottle.
It took considerable time to create these samples. I am now thinking a week to dry.
The perlite is not of a uniform size. I think it would be better to sieve it so a more uniform sample could be made.
It would also work better to add the perlite to each sample as it was hydrated. That would ensure a more even distribution.
---------------
Its the next morning about 12 hours after the tests were cast.
Moved the labels to the lids as they were not going to make the trip on the sides.
Took the lids of the samples which we heading in the direction of dry. So I gave each 2 teaspoons of water. Shortly after casting I had given each sample a dribble of water. It will be interesting to see if the absorb this water and how long it will take.
If you are thinking the water is only needed to hydrate the Portland cement you might be mistaken. The samples with no Portland cement were just as non-wet, don't want to say dry. It may be that water enables processes that unlike the Portland cement bonds are not destroyed by heat. If this is or is not the case adding water will at worst waste my time. And if you look at it this way I should have gone out and purchased chimerical refractory. But at this juncture I have more time than money.
The original tile/brick was mixed to a consistency of peanut butter. I would call that ramable refractory. These were slightly more fluid maybe more along the line of a castable.
It seems that ramming the refractory produces better mechanical interlock between the particles. This provides additional strength in the green and fired stages. However if you are using a commercial refractory follow the makers instructions. This is about DIY.
Again with not so good image of my sand.
It looks like the sand particles would interlock when forced together. A good thing. But note that the original test tile/brick was made with silica flour instead of sand.
---------------
48 Hours after cast
IB needed water
2B and 5B were soon to need, and were watered
B is identical to A but has a small spoon of sodium silicate added. Adding sodium silicate to this mix may flux it so maybe a bad idea.
- A B
- A B
- A B
- A B
- A B
- A B
Why am I bothering to keep these moist when the Portland cement bonds will break down anyway? The lime and possibly the sand may form pozzolan type bonds which need water to form and may not break down with heat.
---------------------------------
Saturday November 17th.
Interesting difference between sample 4 and 5.
- ✅ Mix from previous video
- ✅ local sand instead of silica flour
- ✅ play sand, quarts, instead of silica flour
- ✅ silica sand without Portland cement
- ✅ play sand without Portland cement
- ✅ local sand and silica flour 5 each
- ✅ local sand and silica flour no Portland cement
Both lack Portland cement. But sample 4 with silica sand is much firmer than sample 5 with play/quartz sand.
Sample 5 show no signs of firming up, it is about the same as it was mixed. I had been thinking it was the lime which was doing the bonding but apparently the silica sand is. Strange because the lime only sample from a video or two back dried/set into a nice puck not unlike the refractory. Interesting.
Thinking I should try crumbling the lime only sample. See if there is any bonding past drying going on there. The silica sand only sample dried to a puck but easily crumbled to dust.
Thinking I should try crumbling the lime only sample. See if there is any bonding past drying going on there. The silica sand only sample dried to a puck but easily crumbled to dust.
I see I should have made a sample with local sand and no Portland cement.
Wednesday, November 7, 2018
lime mortar with perlite part 2
The sample has been kept wet for a week.Yesterday I broke it in two and put one part in the. now heated, defunct wet freezer. The other half was allowed to dry for a day then baked in the electric furnace. Currently it is on its way from 550C to 750C. I am not following an exact firing schedule. Cooked of the water with temperatures below 100C. One hour at 50, 75, 90, Then one hour at 150, 250, 350, 450, 550, and 750.
For kicks and giggles I measured the oven temperature rate of change. Came out to about 1C in per 10 seconds. So about 2 hours from freezing to 700C. But this is sort of useless in that the test tile have very little mass. This is the time for an empty oven. It also assumes that the temperature climes at a fixed rate which is not true. As the oven gets hotter it looses more heat. But since this was done at the upper end of what I normally heat to it might be shorter.
And I turned the controller up to 800C. Going to turn it off in two hours. Let the oven cool with the door shut overnight. Examine the tile in the morning.
My friend at Chirpy's Tinkering suggests adding 1 part talc to this mix.
"in very small amounts, it'll lower the vitrify temp, but in larger amounts, it takes the melting temp way up some clays react to it in different ways, but usually talc is used in pottery to change unknown clays with low melting temps to something more managable"
"I thought sodium silicate crackling was pretty cool but I believe the one guy made some refractory out of sodium silicate, sand, talc, and bentonite, and made a hot face to go over it with sodium silicate and talc, and he was doing brass castings for quite a long time with a propane burner, and the lining seemed to hold up pretty well"
Oven turned off 800C @ 10:50PM
90C @ 3:15AM
Its morning.
Oven turned off 800C @ 10:50PM
90C @ 3:15AM
Its morning.
And a video summing this up.
Saturday, November 3, 2018
Tub Muller build II
While looking for a jack shaft I figured I'd check the slowest moving table. The sit up table. Instead of a jack shaft it had a 150:1 double worm gear reducer from Hub City. If the input is driven at 3X the 1725 motor speed the output shaft will run at 35 RPM. Or with a 3450 motor and 1:1 the speed is 23 RPM.
The gearbox may leak a bit of oil. Need to check the level.
Maybe after the muller is built I will change seals.
It might be a bad idea to couple the gearbox output shaft too tightly to the sand muller drive axle. Given the low RPM it need not be complex. Just something that interlocks and stays centered.
Still thinking about using the left over new bearing from the HF concrete mixer repair. They are 62mm outside and 30mm inside. Quite good sized. It maybe better to use tapered bearings like a car's front wheel but if they are good enough for the mixer they should work on the muller. After all its what is running on the HF mixter to muller conversions. Need to determine what is a suitable outer pipe and what to use for a drive axle.
I am musing about making the the base unit for several different machines. Build the tub and related parts as a unit that can be removed from the base drive unit.
Friday, November 2, 2018
Tub Muller Build Starts
While tearing down one of the spa tables I found it contained 2 small right angle gear boxes. From this image I dentified them as Hub City model ADS 05404-007 with a 2:1 gear reduction. 
They look like this.
Unfortunately the output shaft is about 80 RPM. I could put the 2 gearboxes in series and get 40 but I think I am going to go with a jack shaft and belts.
The drum will be stationary with the wheels and plow rotating within it. A pipe will be fited to the center of the drum floor and a drive shaft will come up through it to power the rotating assembly.
I have a tube of bearings ordered to replace the ones in the HF cement mixer drum. They are 30mm ID, 62mm OD, I may have to create a bushing to match the bearing ID's and the shaft OD. But some sort of thrust arrangement would be needed so as not to load up the bearings in the right angle drive. Perhaps a lawn tractor axle would serve as this shaft ?
I have an 18" diameter water heater tank to use for the tub wall. Still need to find a tub floor and a pipe for the center.
Now to find shafting for the jackshaft and the vertical driv.
Wednesday, October 31, 2018
lime mortar with perlite part 1
Yesteday I used the leftover mortar from rebricking the Kerr oven to make a small test brick with perlite.
The mortar formula
10 : 6 : 2 : 3 – Silica Flour, Native Clay, Portland cement, and Lime.
I did not measure the perlite. Mostly I want to see how this sets in the presence of water. In retrospect I should have weighed the ingredients and the perlite then worked out the ratio.
"Baby its cold outside" Well maybe too cold for a little sample to set properly. So I could not use my defunct chest freezer and water logged bath towels as per usual.
Shortly after it started to firm up I added 3 layers of paper towels. This was not enough and it looked to be a bit short on water so I increased the layers to 6. It is covered with plastic.
Current thinking is to use a refractory similar to this for my first electric oven. That is if this sample works out and I determine a good perlite ratio.
I am not about to try this on the first oven but it would be interesting to makeup 2 batches of refractory. Have the second batch higher in lime and use it as the top layer which would end up on the inside of the oven making for a better hot face.
I am thinking about putting a heater in the defunct chest freezer I use to water cure this stuff. Was thinking about going fancy and maybe some day I will but in the short run I am going to try a submersible aquarium heater.
It is hard to keep the samples wet in the house using the paper towels. Twice now I have come close to crossed the line where the concrete hydration will stop. Need to dump the aquarium heater into the freezer tomorrow and see how it does overnight.
Subscribe to:
Posts (Atom)