Primitive Technology: One-Way Blower Iron Smelt & Forging Experiment
Fire pit for making charcoal Lighting the fire in the bottom of the pit Adding layers to the fire in a similar way to the kon tiki charcoal method As each layer carbonizes, a new layer is added When all the wood has been converted to charcoal it is doused with water The residual heat dries the charcoal This charcoal will form the fuel for the iron smelt The creek has iron bacteria in it, identifiable by the yellow orange color The iron bacteria forms easily recognizable slimy orange flocs seen here The orange slime is collected in pots The iron bacteria settles to the bottom and the clearer water is decanted off the top More settling and decanting occurs The bacteria is then added to another pot to congeal into a paste Over time the iron bacteria dries to a soil like texture This will be the ore used in the iron smelt Stacking wood to roast the ore Roasting ore in a fire drives off moisture and other volatiles, removing a heat consuming step from the smelt, making it more efficent The ore is spread onto the wood pile A space is made to light the fire Fire by friction The fire is lit at the top and burns back down the heap ore is roasting nicely Red hot ore falls through the pile Coals are stoked to burn to ash Ore and ash mixture is collected The roasted ore and ash Note, ash may act as a good flux, lowering the melting point of the slag Setting up the one way blower, a bed of mud is put down to hold the housing The lid and rotor are put in place The rotor is put into notches between the 2 posts The rotor then spins fairly easily The rope stick is looped around the rotor The one way spinning technique is employed (down and back, up and forward) to produce continuous one way rotation. A furnace made of bricks will be built The position of the tuyere is determined and the other bricks are set in place A gap is left for the tuyere using a half brick and the tuyere is plastered in with mud The next layers are added as normal The gaps are plastered with mud The preheat for the smelt begins Charcoal is taken to the furnace for the smelt And placed in a pile next to the furnace The ore The charcoal The furnace The blower The furnace is pre heated for 1 hour with wood and then allowed to burn down to tuyere level The furnace is then filled to the top with charcoal 2 single handfuls of ore are then added The furnace is then blown till the charcoal burns down enough for the next charge 3 double handfuls of charcoal 2 single handfuls of ore Flames start coming out the top The charcoal portion of the smelt took 1 hour 21 minutes, using approximately 5.8 kg charcoal, 1.6 kg ore total slag/iron mass Iron prills fall off the mass as it cools Iron prills can be seen on the surface of the slag, these are small droplets of cast iron (a high carbon alloy of iron) Larger pieces of iron are inside the slag so it is crushed to get it out. The brittle slag crushes easily whereas the harder iron prills remain intact The prills are larger and more numerous than those made with the old blower design The crushed slag is set aside for further processing later The iron picked out by hand Smaller pieces of iron can be recovered from the slag using a panning technique The lighter slag is washed out of the pan while the heavier iron prills remain in the pan The total yield of iron is 51 g of cast iron prills (weighed with a modern scale for the sake of scientific accuracy) This is a record iron smelt with the previous record being 41g, set 3 years ago. The new blower is a significant improvement
Testing viewers suggestions that I should use 2 sticks at once on the fan rotor With practice it's feasible, maybe one either side of the blower Testing viewers suggestions of some how making a foot powered fan. I came up with this method of tying the rope to the knee and foot. It also produces one way rotation but is clumsy Testing my own idea of a continuous loop pulled with 2 hands It works ok. A pulley would be the next step but it's harder to make than this simple set up Making a flat nozzle tuyere The end is flattened to spread the air flow 10 cm wide, 2.5 cm high (1 knuckle = 2.5 cm) Digging the forge, placing the tuyere Walls of the forge Sand into bottom of forge Using old blower as it's easier to set up on a ground level forge Iron from previous smelts (not the most recent one) Adding water (rusty, high carbon iron gets hotter when melting) Making a clay mold for a bar Indent is 10 cm long, 2.5 cm wide, 1.5 cm deep Filling mold with iron prills Putting mold into forge Tuyere points down 15 degrees directly at mold which is just in front and below A fire is lit on top of mold Charcoal is heaped on 3 double handfuls at a time 30 minutes, 18 double handfuls charcoal (3 kg approximately) The mold out of the furnace A very crude bar of iron Attempting to anneal the bar in a wood fire so it becomes forgeable In theory, getting the cast iron to a red heat with lots of oxygen should cause the carbon to migrate to the surface where it burns off After slowly cooling in the ash over night Testing it in the forge A piece came off The main piece It crumbles Seeing if it can be decarburized in the forge and consolidated It didn't consolidate well and only partially became malleable Iron from previous experiments The iron can be recycled by adding it to future smelts
2024-03-01 18:53
