Primitive Technology: Flywheel blower smelt/Monsoon begins
At the A-frame hut The standard one way spinning blower A clay fly wheel from a fire starting device Attaching fly wheel to the rotor of the blower The fly wheel is harder to get spinning but once it does it helps maintain a more constant high speed Standing dead wood in the forest The wood is broken up by snapping in between trees wood is taken to charcoal making site First, a small pile is made from sticks larger pieces are then laid against it to enlarge the pile Logs are then placed against it with as few gaps as possible Finished pile is about 1m wide x 75 cm tall Mud is slaked in a pit The mud is dusted on one side and then placed on the wood so it won't stick The mud is added in layers from the bottom up, each layer takes less mud Dusting the mud Dusted side touches the wood so it won't stick A small hole is left in the top of the mound 8 holes are made around the base of the mound Hole left in top of mound Fire by friction The fire is kindled in the top hole of the mound The coals are pushed in through the hole and the fire burns back downwards towards the air entries The fire front burns back down converting the wood to charcoal by boiling off the volatiles, without burning the solid matter, leaving a pure carbon fuel Cracks are patched to stop air getting in that would otherwise burn the charcoal to ash When the fire is visible through the air entries, they are plugged up The air exit is plugged after all the entries are closed and any cracks are sealed too Water is thrown on the mound to help cool it. The next day, the mound is opened The dry mud is thrown to the side for reuse next time Unburnt wood is thrown to the side to be used next time. The resultant charcoal heap This was a good batch as most of the wood is converted to charcoal, only some wood remains near the outside Most of it has completely carbonised right through The charcoal is nice and glossy with no brown, unburnt portions. There are also no white, ashy over burnt bits either At the two walled, tiled hut A record 13 pots of charcoal were made Building a furnace of bricks stacked on their sides A half brick leaves an opening at the base for air entry Mud is placed in the opening and the tuyere is installed The tuyere penetrates 2.5 cm in from the wall so air won't go straight up the wall but through the charcoal bed A base of mud is put in place to hold the blower housing The housing is placed so it connects the tuyere base exactly Then the stakes are place so the fan will sit central to the housing Setting the furnace and blower up in this order ensures everything fits properly in the given space The lid is placed on and the fly wheel added The lid is sealed with clay as air can be felt leaking out here Testing the new flywheel blower As can be heard, the fire continues to be blown after the stroke ends due to the continuous spinning of the fly wheel The fly wheel evens out variation in speed as well as maintaining the top rotational speed once it gets going Each stroke requires more force but fewer strokes are needed Adding bricks to make a taller furnace The furnace is 1.25 m tall and all the charcoal and ore will be added before the smelt begins An unusually tame eel Iron bacteria sludge The iron bacteria is collected in a pot and water is decanted off the top It is allowed to settle in another larger pot and the scooped out to dry into a iron rich soil (this batch was prepared earlier) Fire wood to preheat furnace Bark fibre is prepared by striping the bark from fallen branches of a certain tree The inner bark is stripped and used for string The fibre is wetted before use so it dries tight To make string, the two strands are twisted clockwise independently, and then twisted together anti clockwise The string won't unravel this way More strands are added as previous ones run out, forming a continuous cord Note, the new one way spinning blower produces about 1/5 the wear on the string compared to the previous intermittent spinning blower design, saving material The furnace is filled with wood prior to the smelt Fire by friction, close up The fire is lit from the top to reduce smoke Wood, charcoal , ore and blower all ready to go More wood added as it is burnt and the blower is used With the furnace preheated, all of the charcoal and ore are added before the smelt begins.
9 double handfuls of charcoal and 2 single handfuls of ore are added Then another 12 charges (3 double handfuls charcoal and 2 single handfuls of ore) are added until the furnace is full. Normally I make the furnace shorter and just add charcoal and ore as space appears. The reason I added it all before starting this time is so I don't have to stop the blower to add charges every 5-7 minutes With the furnace full, the blower is started The furnace was blown for 3 hours, a couple of times the rotor came out of the bearings causing the fan to stop which didn't help the smelt The next day the blower was dismantled The furnace door was dug out to get the result The resultant slag/iron mass Note the protruding slag trail that ran along the floor of the furnace The slag at the bottom is the least magnetic and contains no iron prills The whole mass is crushed to get the iron droplets out Some iron drops are picked out by hand during crushing These do not crush like slag and are strongly magnetic when tested with modern tools The crushed slag is then panned to get the iron out The lighter slag is washed away in the water while the heavier iron stays in the pan The result of the smelt is disappointingly small for the amount of ore used but it's not the worst I've done. It's an average result and would have gone better if the rotor hadn't come out of the bearings Here's what happened during the smelt, the rotor would sometimes come out of the pits carved into the stakes A close up shows the rotor end coming out of the thrust bearing. It's a low friction bearing but unstable. The answer is a journal bearing, where the hole goes right through the stake Wood is cut from both sides to reduce the amount of wood to drill through The rotor is narrowed at the ends so it won't slide too far through the holes, keeping the fan in position.
Testing the rotor The new set up is more stable thanks to the journal bearings. I'm going back to using a short furnace as the product can be accessed from the top rather than breaking the door each time. New tuyeres drying Setting up as before Narrowing ends of new rotor to stop it from sliding too far into the holes, keeping the fan in place horizontally. The new setup will be more stable and increase the reliability of the blower in future with no breakdowns during use Just as I was about to test the new set up, the monsoon season began and I couldn't make fire The open plan hut let rain blow in both sides making the wood too wet and moldy It would rain like this on and off for a over a week with no sun the whole time The creek became a river for 7 days The A frame workshop, built to make the tiles for the most recent hut, rotted and leaked like a sieve An unhealthy mould grew on the thatch Massive old trees became uprooted and fell over I decided to build a 3rd wall. Most of the water that got inside splashed in after hitting the ground outside. Clay was used as mortar Fired bricks were used to build the wall As long as the walls don't get too wet, the clay mortar will stay dry and hold the bricks together. Half bricks were used at the start of every second layer so the brick joints were staggered for stability.
You can't drystack bricks this way without some type of mortar or the bricks will break under the weight By placing the bricks in a bed of mortar the weight of the wall is spread across the whole face of each brick instead of just the ends (not having perfectly flat faces) The 50cm wall somewhat stops water splashing in this side of the hut. I'll add more to it later. Then some tiles came off the roof. The culprit was likely rotting bark slipping off this purlin.
Fortunately, some replacement tiles were sourced from the ruins of the old brick and tile hut that was destroyed by a falling tree from last episode. Some tile sherds were put under the new tiles and over the purlins to prop them up slightly, preventing future slide offs. Good as new. The rain kept falling for days, creating a wet, miserable and destructive environment.
"When life gives you water, build a water wheel" -Albert Einstein. I invented this toy when I was about 11 years old. When the water wheel is place on tracks over the water, it rolls uphill against the flow. Bigger wheels would speed things up but you get the idea. And so the "Primitive Technology Railway Company" was founded Note, the narrowed rotor ends keep the vehicle on track. If one end rolls too fast and starts to go off track, it narrows in diameter slowing it down so the other end catches up. The new blower in the hut during a rare gap in the rain. More wet season projects to come.
2025-02-07 20:07
