[Regia-NA] Ironworker

[Chris Boulton]

A couple of suggestions if you'd like....

If you're in the enviable position of being able to build a permanent forge, then how's about this:

(For clarity I'm using the word nozzle to describe the pipe coming out of the bellows, and turere to describe the hole through the firewall that conducts the air into the forge from the bellows)

You will need to make your bellows before you start building your forge, because the measurements depend on the size of the bellows. Big bellows are good. Huge bellows are much better. The air inlet valve hole should be not too small, so the bellows can be rapidly reinflated. This hole must be in the fixed bellows plate, not the hinged plate. The bellows are installed fixed plate down, so the air intake is underneath where dust and dirt won't get into it. Single action bellows must have non-return valves behind the nozzles, otherwise you can  - will - suck white heat into your bellows and destroy them.

Build a frame in 3x3 oak about 30 inches high, 36 inches wide, and long enough to accomodate the length of your bellows plus nozzles plus firewall (with integral turere cast into it - the advantages of fireclay!) plus forge bed plus space all round the fire so it's not too near the edge - at least 8 inches. You want an upright under where the nozzles of the bellows will be as well.

Plank the inside of the part of the frame where the fire will be but not where the bellows will be. The top plank of the wall that divides the frame will need to be an inch higher than the surrounding frame. Make cut outs in the top edge of this top plank for the bellows nozzles to slot into so they're level with the top edge of the frame and infil where the fire will be with earth and sand to 2 inches below the top. This makes a very solid and stable base. Next, put a batten on the bellows side of the top middle plank below the nozzle cut outs and plank the area under where the bellows will be, leaving gaps under where the bellows air intakes will be (they go underneath, on the fixed, not the hinged, bellows plates).

Cast your firewall with integral turere (carve a 'Y' feed from candles if you like and incorporate into the mould - the wax will melt out on first heating to leave a nice cast in shape). It needs to be at least 2 inches thick - 2 1/2 would be better. 

Now here's a neat trick: If you make the hole through the firewall (the turere) conical, about three sixteenths of an inch larger on the bellows side than the end of the nozzle, and only a sixteenth larger on the fire side, then by positioning your bellows so that the nozzle points squarely at the hole from about three quarters of an inch away, you can take advantage of the suction caused on the bellows side of the firewall by the air blowing through the hole. This drags extra air with it, so you get more blast for your air, so to speak, and also keeps your bellows nozzle away from the heat so it doesn't burn away. 

Once you've got your firewall, position it with the bellows in the frame with the nozzles pointing at it from 3/4 of an inch away, and infil the firebed in front of it with fireclay to about 3/4 of an inch below the turere. Bank the fireclay up to the edges to keep stray hot bits off the wood. Arrange a clamp to hold the lower handles of the bellows so they can be vigerously pumped without moving about. A plank across the back with a hole to slot the bellows handle into works very well. A latch down clamp for the bellows nozzles may also be needed. Light the fire immediately (without the bellows installed) to bake the fireclay hard, and after a couple of hours slot the bellows in and use a light blast to gradually increase to heat to about 1200 degrees centigrade (mild steel burns about there, so that'll do).

Second option:

Make a portable lighter frame with a metal forge tray (with clay bricks to build the fire on) and folding legs which angle outwards front to back for stability. This will be of necessity smaller and more limited in what you can do on it. The fire has to be smaller so that the heat gets dissipated before it reaches the wood frame, but it can be done - I've got one.

If I've been teaching my grandmother to suck eggs - appologies!

Chris.
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