The use of concrete for models

Discussion on Stirling or "hot air" engines (all types)
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terrence thompson
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Joined: Sun Aug 20, 2006 6:27 pm
Location: australia

The use of concrete for models

Post by terrence thompson » Mon Aug 21, 2006 4:59 am

Hi List,
Thanks Daryl for setting this forum up especialy for tincan engine enthusiasts.
I'd like to pass on my experience of the use of concrete in my engines.
I started out using silicone to seal and to make my displacers and displacer cylinders because of the lack of equipment in my shed.
I have always needed to re-invent the wheel so I didnt follow anyones plans for my first engine. It took three rebuilds before I managed to get it to work. I only managed to demonstrate it about three times before I cooked it. It was from my frustration at having to virtualy start from scratch after every breakdown that I decided to make an engine that I could take apart and modify easily.
I now make my displacer cyinders in two parts ( hot end , cold end ) I have made up a reusable mold to cast a flange on the open end of two cans with dowels to ensure correct location and bolt holes to enable quick assembly. Silicone is still used as a gasket material but by oiling one of the surfaces before assembly the ends come apart easily when required.
If this is usefull to other builders I will post photos etc on request.
The system also gives better performance to the engine by providing a signifcant barrier to the exchange of heat between the ends.
regards
Terry

Crazyguy
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Re: The use of concrete for models

Post by Crazyguy » Sat Mar 05, 2016 7:03 am

I like the idea of a two part displacer to minimize conduction of heat between the two sections. I keep wishing for a durable material to use that approximates the cylinders on LTD gamma and the Pringles can metronome.
Needed is a material that won't burn or melt and has poor heat conduction.

mastrovetraio
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Re: The use of concrete for models

Post by mastrovetraio » Sat Mar 05, 2016 8:54 am


Tom Booth
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Re: The use of concrete for models

Post by Tom Booth » Wed Jun 08, 2016 8:19 pm

I've been considering making various engine parts out of a mixture of perlite and waterglass (sodium silicate) often used as a DIY furnace cement. This should, I think, be both lightweight and heatproof. There are several YouTube videos on how to make this cement. I've had several styrofoam displacers warp or melt.

Tom Booth
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Re: The use of concrete for models

Post by Tom Booth » Wed Jun 08, 2016 8:22 pm

For example:

mastrovetraio
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Re: The use of concrete for models

Post by mastrovetraio » Thu Jun 09, 2016 1:06 am

You can make the displacer directly with panels of ceramic fiber. It's stiff and light weight, and easy to work.

Wellington
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Re: The use of concrete for models

Post by Wellington » Thu Jun 09, 2016 2:07 am

terrence thompson wrote:Hi List,
Thanks Daryl for setting ............
Terry

I had thought of this myself and have considered putting a layer of fire cement on the hot end of the displacer with a thin alum disc embedded in it to reflect some of the radiant heat.
Wellington

Tom Booth
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Re: The use of concrete for models

Post by Tom Booth » Fri Jun 10, 2016 6:56 am

mastrovetraio wrote:You can make the displacer directly with panels of ceramic fiber. It's stiff and light weight, and easy to work.
I see some online sources for ceramic fiber of various types/brands/compositions

Ebay, Etsy... some appears to be flexible (comes in rolls).

Also, is it permeable ? Could air get through it ?

I was also interested in making the engine body (displacer chamber) out of some kind of ceramic or cement. Of course that would need to be air tight.

mastrovetraio
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Re: The use of concrete for models

Post by mastrovetraio » Fri Jun 10, 2016 11:42 pm

Hi Tom. Ceramic fiber come also in rigid panels. Airtight, but can not afford pressure. Ceramic fiber panels come in a variety of density in front of a variety of temperature to withstand. I've maded kiln to work up to 900° C with C.F. 5 cm thick and you can put hour hand over, was barely warm with the hell i side. Absolutely insulator, I think the best material for a displacer.

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