Brazing Hearth

Any tips and ideas for creating a hearth suitable for making a medium size 5" gauge loco boiler?

Thanks

John B

Buy loose 9x4.5x1 bricks off Ebay and screw them together. Three for each end and as many L shaped ones you need for the middle section. I got 12 bricks for £26 from solidfueladvisoryservice.

Other more complicated and expensive ways are available

See photos of my brazing hearth made for me by the Iron Dwarf who advertises cooking ranges and related items for medieval re-eneactors on eBay. His charge for the steel parts was very reasonable and firebricks are readily available.

Rod

There are commonly available buff coloured 'firebricks' weighing in at about 4kg. They are not intended for insulating but extreme heat resistance. They are only good for building large pottery kilns so I don't understand why they are so common except for ripping off piza oven builders. They absorb a lot of heat by design to stabilise such a kiln. You don't want them.

There are lightwieight white insulating bricks weighing in at 1.5kg which absorb little heat and do insulate. Ideal but more expensive than any other brick.

There are compressed vermiculite insulating boards for lining wood stoves. Also pretty good but more fragile. Probably a good option.

There are lightweight grey building blocks like Thermalite (size of but not breeze blocks). These are a pretty good bet as cheapest by volume and could be further lined with the vermiculite boards. Easy to carve to shape.

All materials must be kept scrupulously dry or will spall when heated.

+1 for Bazyle's input on firebricks.

The insulating ones seem expensive per brick, but you don't need that many. They are fragile, and can be cut to size with an old woodworker's handsaw. It's quite a good idea to use a pizza oven shelf, which is strong and hard and heat resisting but not that insulating, to use as a working surface on top of the firebricks that form the base of the hearth, to take the wear.

Rod

You can get ceramic fibre insulation blankets, good for wrapping round the shell when working on the firebox end. It dissolves in flux, so not for use where you are actually silver soldering

High temp rockwool for want of a better description.

American K23 kiln bricks, light as a feather, absorb little heat and throw it back. Ceramic fibre also keeps the heat in as Duncan says. DO NOT use nightstor heater bricks, they absorb heat. Noel.

Hi John,

I used compressed vermiculite bricks to build my brazing hearth. You can cut them to size easily and mine are still working well after several years of use.

Thor

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Thank you all for your comments - much appreciated. I have some Thermalite blocks or similar that I might use. Plan to mount them in an angle iron frame - I just wonder what the best size would be? I can visualise a 5 1/2" boiler barrel red hot - I don't want it going anywhere else!

John B

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Or a hole in the metal or whatever base and suitably shaped firebricks to allow the tubeplate or backhead of your boiler to poke through from below.

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We supply vermiculite blocks which are lightweight and reflect the heat back into the brazing area. Anything that helps speed up the time taken to get the joint up to brazing temperature is good practice.

They can be bought individually or as a set with a kaolin wool mat. As an optional extra we supply a laser cut frame for them to fit in.

The kaolin blanket in itself is a good insulation material. If wetted it can be shaped and when dry will retain that shape. In the olden days we used to put a bit of the mat on our hand and heat a piece of copper up to cherry red. Not allowed now of course!!

If you are going to the Midlands (fingers crossed) they are 25% cheaper than on the internet.

Shaun.

I used vermiculite blocks bought off eBay a reasonable price plus a kaolin blanket from CupAlloy to make my small mini hearth, have a look in my albums for 'mini hearth'

George.

Usual disclaimer applies.

Edited By mechman48 on 09/06/2021 12:55:03