High temperature displacer

[Engineire]

This presents another interesting possibility for making porous ceramic high temperature displacers.


https://youtu.be/jfgO4aBF2A8


I can hardly wait to finish setting up my shop and getting the kiln going. Still more structural work to be done on the building though.

If you're going down that route I'd suggest looking into aircrete. It's a type of concrete made by mixing detergent foam with ordinary portland cement. It's very light and fireproof, also easy to mould, cut and machine.

Also possibly look into firebrick/refractory cement if you need something ridiculously temperature resistant.

[Tom Booth]

Thanks engineire,

I'll be building and experimenting with a wide variety of different type and size engines. Probably an aircrete or firebrick displacer would be suitable for some wood or coal fired engines.

The order for various thickness composite mica sheets finally arrived. Identical to the thinner stuff, but thicker. This appliance mica is the most flame/heat resistant and durable material I've found so far for "pancake" type engines with thin, wide displacers.

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Generally speaking though I've found un-fired cement/refractory based material too fragile, crumbly, to have much hope of enduring use in a Stirling engine, which is why I've been experimenting with ceramics.

The bit of porcelain displacer I fired in the coal stove (mixed with glass microspheres) seemed close to ideal. Quite light and seemingly indestructible. I could not break it by simply snapping it with my fingers, which I can't say about any cement/refractory type material I've tried so far. It felt as hard as carbide steel, I thought.

Of course, I'm also experimenting with doing away with any conventional reciprocating displacer altogether and experimenting with rubber/silicone membranes.

[Tom Booth]

As far as the supposedly large 6" and greater natural mica I ordered and received, the vendor has not been very helpful when I pointed out that all but one of the pieces were less than 6" wide. Most were long skinny pieces I could not get a useable 5 1/2" circle out of anywhere. I said I don't care about a refund, but there were simply no pieces as large as advertised available. I was told that the measurements advertised were just "estimates".

I didn't see any mention of any "estimate" in the ad, and 3 or 4 inches is nowhere close to the "between" 6 to 8 inches advertised.

Anyway, I found another Etsy vendor who specializes in hard to find Steampunk type items who has a wide variety of mica who was very helpful to find exactly what I needed and is also communicating with the suppliers about the availability of more (larger sheets of natural mica).

A beautiful piece for the Brent Van Arsdell Limited Edition restoration is on its way special order, and only cost $6 a larger piece selected out from this or a similar lot:

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https://www.etsy.com/shop/EKSupplies?re ... =838732846

[Tom Booth]

I'm going to re-try the above experiment with the plaster using these water beads intended for plants.

I'm not sure what the difference is, but these, though similar, appear to have more structure. That is, I don't think they will completely dissolve just by mixing them with plaster. After all, they can be put in flower pots and mixed with soil. Basically small clear Orbeez.

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[Tom Booth]

These lava rock chew blocks for rabbits and such might be the ticket.

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Very light, but seems to be coated with something.

Seems completely fire proof:

https://youtu.be/RET638sfKNk


Maybe it could be found in a larger size for really big rabbits?

I don't know what the white coating is. There is nothing on the package. Probably titanium dioxide I would guess.

I sent for a plate made of "lava" a while back , from Mexico, that I thought could make a good high temperature displacer. Very expensive, but it was not at all light weight as I had hoped.

Apparently there are different kinds of lava rock. Some very lightweight can even float in water, but some very heavy.

Either one can appear to be quite porous, so it is hard to tell just from a photo.

[Tom Booth]

Well, I called the sales representative where the pumice stone is mined. (https://hesspumice.com/) He said, unfortunately, that the largest stone they can supply is about 1 inch.

He said there was another company to the south that could supply larger blocks but they went out of business.

Apparently, similar "glass foam" or foamglas® is/was being made artificially as insulation board of various sorts, and I believe it might be possible for me to make it in my ceramic kiln.

The process seems rather simple. Crushed glass heated up mixed with a foaming agent.

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This video is quite old and in Russian. I have not, as yet, had any luck finding any kind of retail source for the stuff. Still looking

https://youtu.be/NuOlApx3zFo

Not sure why I'm having trouble finding somewhere to get a relatively small sample of the stuff

https://youtu.be/lVwJIzC_ATg

There doesn't appear to be any shortage,

https://youtu.be/GhsZaA1uKYI


Though made in gigantic sheets, most is broken up into aggregate/gravel before it leaves the plant.

[Tom Booth]

The process is apparently quite simple.

Carbon, when burned, combines with oxygen to form CO2 gas. So, mix some crushed/powdered glass with powdered carbon, activated charcoal for example, or anthracite coal or just about any high carbon material to act as "leavening" and it's just like baking bread.

DIY pumice/volcanic glass.

The density/porosity can be controlled by the amount of carbon powder material added to the mix, and I suppose, how finely the material is ground up.

I'm curious if this stuff could be cooked up in a small microwave kiln. They are largely intended for fusing/melting glass to make jewelry.

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About $25 - $50 depending on the size.

[Tom Booth]

As it turns out, the inexpensive microwave kilns are all, even the "extra large", a little too small for my purposes; (a 5 1/2" pluss size displacer).

There is one supplier in Canada that makes a microwave kiln big enough, but at over $300 I think I may try just making my own. The main ingredient is the heating element, which apparently can be made from a common grindstone.

https://youtu.be/xHPp50cwXKY

[Tom Booth]

It seems there is a nearly endless abundance of scientific studies about various types of, and methods for, making foamed glass, as well as craft/art methods and materials; powders, paints etc. for making decorative "bubble glass".

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Copper carbonate as a foaming agent for example, will produce blue bubble glass:

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There are "artisan" pre-mixed bubble paints for a variety of colors. A pattern is painted on a sheet of glass, then a cover sheet of glass is used to sandwich the bubbling agent in and the glass sheets are fused together in the kiln.

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Lots of room for creativity in this glass foaming business.

[Tom Booth]

BTW, just because I was curious and like mostly clear glass, apparently to make clear bubbles with no black or other color in clear glass, just a little baking soda does the trick.

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https://chatterglass.wordpress.com/2013 ... or-bicarb/

Hopefully, a little baking soda mixed with powdered glass and maybe some water glass and glycerine would create a lightweight clear glass foam. It might take some experimenting.

I like natural mica and I think that would work fine for some pancake type engine that can use flat displacers, but I'm finding good mica rather hard to come by and often quite expensive.

Foamed/bubbled glass may have more potential for wider application. Natural volcanic type pumice I'm also finding difficult to obtain.

Foamed/bubbles glass can be made from easily obtainable recycled/scrap glass and simple, easily obtainable foaming agents and practical methods and can be formed into different shapes and sizes, so is not limited to just flat sheets.

[Tom Booth]

I had a few minutes to kill this morning so I decided to try mixing up some water beads with Portland cement.

I just soaked the beads in water and then gently sprinkled the Portland cement over them and swirled it around a little.

The water beads seam to have a tendency to float.

Just used one layer deep water beads in the bottom of an empty 36 ounce plastic yogurt tub, just covered with water.

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In general, cement cures best if kept wet for several days, but wet is one thing. These water beads tend to hold water for a very very long time.

I'm curious to see what happens anyway.

I'm not really sure if the water beads are finished expanding, if they will draw water out of the cement or vice versa. Will the cement cure normally?

[Tom Booth]

After about 1/2 hour or so, the water beads have continued to expand and absorb water from the mixture, getting a little crowded now, some are beginning to push up around the sides.

So, at this point I'll be leaving for the rest of the day and letting this sit to dry, expand more, or whatever it's going to do.

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I came across something from years ago, where someone was trying to do something similar.

One suggestion is intriguing. To carry out a similar process but using an alcohol based gel similar to Sterno fuel.

https://crafts.stackexchange.com/questi ... s-of-holes

If this works with Portland cement, it should also work with porcelain slip (thin liquid clay) for a more resilient material.

I was thinking that perhaps using a dilute water glass solution instead of water might produce a better refractory type cement, if plain Portland cement turns out to be not strong enough.

Anyway, I think the results are looking pretty good so far. Better than the powdered Sodium Polyacrylate. The water beads are retaining their spherical shape and should result in a more sponge like structure with large hollow voids like I had been trying to achieve with the powdered Sodium Polyacrylate.

Or maybe the difference is just due to the "shaken not stirred" extra gentle mixing. Or perhaps because I resisted the temptation to keep adding more dry powder to absorb the apparently watery mixture that would not firm up no matter how much dry powder was added but would just get watery again until all the moisture got drawn out of the "Orbeez" like water bead things.

The same thing seemed to be happening with the Portland cement, it seemed watery and I added several tablespoons of dry powder but it did no good and finally I had sense enough to stop.

Eventually maybe I'll work out some kind of formula for the proportions of dry water beads / water / dry cement.


It seems to work pretty well with epoxy resin.


https://youtu.be/i74qaednm6E

[Tom Booth]

Some useful videos about DIY microwave kilns.

https://youtu.be/wEF1T-AZScw

https://youtu.be/n_JUJHGbCZ0

https://youtu.be/rAIyLWEKt8U

https://youtu.be/hnLhI0U4bfY

I think I will try just painting some silicon carbide and water glass onto the inside of a Teri Cotta flower pot.

I'm not sure what 'ink" he's using in the last video.

[Tom Booth]

Another candidate for a high temperature displacer:

I just received some Ceramic Fiber Board in the mail that I sent for recently.

I could only find this material in large 12"x12"x1/2" boards or larger, but it was easy enough to cut a thin piece from the corner with a razor blade.

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It is somewhat fragile though but not too bad. In general it is good and rigid and strong, but far from indestructible.

It is probably a good idea to wear a respirator when working with this stuff in any way as the fibers are quite powdery and easily airborne and probably not good to breath at all.

It would probably benefit greatly from a spritz or two of water glass to add additional rigidity and strength, and lock in the fibers.

I think it has potential. Much much better than the very thin ceramic fiber paper which just completely turns to powder after being heated

https://youtu.be/GY4-pgSI2VA

It doesn't conduct much heat, but does conduct some, as can be seen in the video, I take it out of the flame several times when it started getting too hot to hold.

It cools off very quickly once out of the direct heat of the torch flame.

[Tom Booth]

The cement is not completely cured, but the water beads are starting to pop lose.

If I didn't know any better I would think I was looking at a wasp nest, or some kind of honey comb.

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One problem so far is that the "Orbeez" want to float to the surface, so...

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The "honeycomb" is only superficial on the surface rather than evenly dispersed through to the bottom, but that was at least partly intentional, as I only made one layer, but how to keep them down if more were used?

Maybe experiment with the consistency of the cement, weight the Orbeez down with something?

Maybe clay slip might result in a more uniform dispersion if the density of the "soup" is different.

Another problem is the water beads continued to swell and squeeze out the cement from in-between themselves, so the resulting cell walls are so thin as to be non-existent. Certainly too fragile anyway.

Probably these various problems could be solved, so probably this method is worth experimenting with further.