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Firebox lining

For hot air engine

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steamdave29/08/2021 16:47:12
510 forum posts
44 photos

I need to line the cast aluminium firebox of a hot air engine. I have some welder's ceramic blanket. What is the best way to secure this inside the 'box? The 20th cent. building notes suggest using furnace cement, but I was wondering whether there was a different suggestion for the 21st cent. Would beads of JB Weld around the top/bottom and joints be up to the task?

07. firebox 2200-4.jpg

For the next project. Another hot air engine. Again, firebox lining, this time it is a steel tube. I was going to use Kaowool, but giving my 2mm sheet a quick blast with my propane torch, the Kaowool curled up and died. The engine will be gas fuelled, so is there any other material I could use? And how to secure it?

The Emerald Isle

pgk pgk29/08/2021 16:59:12
2549 forum posts
293 photos

You can get thin sheets of material to line/insulate the access port in wood burner flues which should be flexible enough to use a few layers. It would take experimentation with wood burner rope glue to see if it'd stick it?


noel shelley29/08/2021 17:06:48
1278 forum posts
21 photos

American K 23 is a furnace and kiln lining ! It is in brick form but very soft so can be cut by knife of saw. making an inner liner of this material and fixing in place with air setting cement would work for where the flame hits and then the rest could be lined in ceramic fibre, possibly beefed up with rigidizer to keep its shape. 1/4" is not thick enough to keep much heat in, but for this application I assume the flame will be small. Good luck Noel.

John P29/08/2021 19:46:38
400 forum posts
255 photos

Just follow the instructions on the drawing that you have shown , the lining
will hold fast ,the engine that i made for a friend the lining is still holding in
after nearly ten years ,looks very similar to the Rider Ericsson engine
that i made as you can see here.Some other photo's in album.
Johnrider-ericson  firebox.jpg

steamdave29/08/2021 21:05:28
510 forum posts
44 photos

I believe the main reason for the lining is not so much to retain any heat, but to prevent the paint coating getting damaged by the heat. With the (hopefully) small flame, there should not be as much heat as from my gas torch and maybe the Kaowool in greater thickness will be adequate for the second engine (steel firebox, about 3" diameter).

John P. What did you use for the lining in your firebox? Engine is the Improved Rider, 2" bore from Myers.

The Emerald Isle

JasonB30/08/2021 06:55:06
22560 forum posts
2634 photos
1 articles

In that case Dave why not just use a stove paint, that is what I have used on my Robinson and Heinrici and CHUK without problems as well as quite a few IC engine exhausts. Thermacure is the one I like

John P30/08/2021 10:02:21
400 forum posts
255 photos

Hi Dave

The engine that was made was also a Myers it was 3inch i think,
the firebox was lined with 4mm thick sheet similar to that below from RS
they still sell it its around £75 a sheet, they do sell the 2mm thick sheet
here for about £45 + vat Flame Retardant Calcium-Magnesium
Silicate Thermal Insulating Sheet, 2.8m x 610mm x 2mm , RS
Stock No 724-8906. Would probably be easier to fit in using 2 layers
with the fire cement that is how i fixed mine by laminating some layers
with the fire cement.
I could post a link here but it will be taken down almost instantly and
replaced with "online" which is of no use to anybody so i will send you
a PM with the link to the same material for a fraction of the price.
When i made mine i made some alteration the the firebox casting
by adding a support to form the lining at the roof of the firebox,
the two photo here show this ,it makes i easy to mold the shape
at the top ,the baffle is fitted low enough to allow the ring of bolts
that attach the hot cap end to fit and clear the space above is filled
with loose ceramic fiber blanket when assembled.

The engine was in model engineer from June 2013 4459 to
January 2014 4472.and is also seen here.

The photo gives no idea of scale it is about 24 inches to the top of the chimney.

rider-ericson  firebox 3.jpg

rider-ericson firebox 2.jpg

rider ericson  engine.jpg

steamdave30/08/2021 12:06:14
510 forum posts
44 photos

Very nice looking engine there, John.

The Emerald Isle

steamdave30/08/2021 14:11:48
510 forum posts
44 photos
Posted by JasonB on 30/08/2021 06:55:06:

In that case Dave why not just use a stove paint, that is what I have used on my Robinson and Heinrici and CHUK without problems as well as quite a few IC engine exhausts. Thermacure is the one I like

I might just do that.

The Emerald Isle

John P30/08/2021 17:44:40
400 forum posts
255 photos

Hi Dave

The lining is there to insulate the firebox from the rest of the engine,
without the insulation layer in place the heat will transfer more quickly
to the upper parts of the engine,i expect that it is the same on your
engine in that the hot cap cylinder is isolated from the upper cylinder
with a heat resistant ceramic paper gasket similar to material
in the link that you have and sealed with some heat resistant
compound, i painted the hot cap cylinder end with black
heat resistant paint from Halfords (exhaust paint) .
I think that it would be a mistake not to have the insulation
layer in place ,substituting heat resistant paint in this application would be
completely useless.


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