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I built a natural draft furnace to test ideas about how hot a furnace could get without the use of bellows. Natural draft is the flow of air through a furnace due to rising hot air. The hot gasses in the fuel bed are more buoyant than the cold air outside the furnace causing them to rise. Fresh combustion air then enters the base of the furnace to replace the rising combustion gasses, keeping the fuel bed burning. This effect increases with: 1. the average temperature of the fuel bed relative to the outside air and 2. The height of the furnace. Two other important factors are the size of the tuyere (air entry pipe) and lump size of the fuel bed as these effect the resistance to airflow through the furnace. The furnace was tested with wood fuel and some ore was melted but produced no iron. High temperature were indeed produced (probably about 1200 c). These types of furnaces were once used for smelting copper and iron ores in around the world in ancient times, usually using charcoal as a fuel and in some cases wood too. I designed the furnace using a formula from the book “The mastery and uses of fire in antiquity” by J.E. Rehder. It was designed to have a space velocity (air speed within the furnace) of 6 m per minute which is recommended for iron smelting. The furnace was 175 cm in total height but with a height of only 150 cm above the tuyere. The height between the air entry and the top of the furnace is what determines the strength of the draft, the space beneath the air entry is not included in the formula. The internal furnace diameter was 25 cm. The walls were about 12.5 cm thick at the base but got thinner with height. The tuyere (air entry pipe) was 7.5 cm internal diameter and about 20 cm long. The tuyere was placed into an opening in the base of the furnace and sealed with mud. The whole thing took about a week to make due to the slow drying time that was assisted by keeping a fire burning in side it. The furnace was designed to use charcoal (which in this case should be 2.5 cm diameter lumps) but I used wood to test it instead as it was easier to acquire. To test its melting ability, bog ore was found further down the creek and roasted. The roasted ore was then crushed and stored in a pot. The furnace was filled with wood and lit from the top. The fire burnt down the furnace producing charcoal. On reaching the tuyere the fire then started burning the charcoal. Wood was also continually added from the top along with a few small handfuls of the roasted bog ore (not shown in the video). The temperature of hot objects can be visually estimated from their incandescence. After about an hour, the light coming out of the tuyere was high yellow to white hot indicating a temperature of at about 1200 c. Colour temperature charts vary but white hot is usually given to be at least 1200 c, examples of these charts can be found on the internet for reference. It was uncomfortable to stare into the tuyere and doing so left an after image when looking away, indicating the strength of its brightness. After about an hour and a half the furnace was left to burn out. When opened the next day the tuyere was covered in slag with bits of slag found on the furnace floor also. This experiment shows that high temperatures can be achieved without the use of bellows or charcoal, which might significantly reduce labour in the production of iron. The furnace was technically easy to build as it was a simple vertical cylinder. When running, the wood added to the top of the furnace converts to charcoal in the upper part of the stack and is consumed in the lower part. The ore I used was new to me, normally I use iron bacteria as an ore. This new ore produced no metallic iron so I’m inclined to use iron bacteria in future. Natural draft furnaces were once used to smelt copper and iron ores in the past, usually with charcoal fuel and less frequently with wood. The main benefit of these furnaces seems to have been the reduction in labour they provide and simplified infrastructure (fewer workers and no bellows required during operation).
I built this tiled roof hut in the bush using only primitive tools and materials. The tools I used have been made in my previous videos. It should be pointed out that I do not live in the wild and that this is just a hobby. It should be obvious to most that this is not a survival shelter but an experiment in primitive building technology. To cut and carve wood I used the celt stone axe and stone chisel made in this video. To carry water and make fire I used pots and fire sticks made in this video. Finally, to store fire wood and dry, unfired tiles, I used the wood shed built in this video. The wooden frame was built with a 2X2m floor plan and a 2m tall ridge line with 1m tall side walls. 6 posts were put into the ground 0.25 m deep. The 3 horizontal roof beams were attached to these using mortise and tenon joints carved with a stone chisel. The rest of the frame was lashed together with lawyer cane strips. The frame swayed a little when pushed so later triangular bracing was added to stop this. Also when the mud wall was built, it enveloped the posts and stopped them moving altogether. A small kiln was built of mud from the ground and a perforated floor of clay from the creek bank. It was only 25 cm internal diameter and 50 cm tall. Clay was dug, broken tiles (from previous batches) were crushed and added to it as grog and it was mixed thoroughly.This clay was pressed into rectangular moulds made from strips of lawyer cane to form tiles. Wood ash prevented the clay sticking to the stone. 20 tiles were fired at a time. 450 flat tiles and 15 curved ridge tiles were made with only a few breakages. 26 firings were done in all and the average firing took about 4 hours. The fired tiles were then hooked over the horizontal roof battens. An underfloor heating system was built into one side of the hut to act as a sitting/sleeping platform in cold weather. This was inspired by the Korean Ondol or “hot stone”. A trench was dug and covered with flat stones with a firebox at one end and a chimney at the other for draft. The flames travelled beneath the floor heating it. After firing it for a while the stones stay warm all night with heat conducted directly to the sleeping occupant and radiating into the room. The wall was made of clayey mud and stone. A stone footing was laid down and over this a wall of mud was built. To save on mud, stones were included into later wall courses. The mud was dug from a pit in front of the hut and left a large hole with a volume of about 2.5 cubic metres. The finished hut has a swinging door made of sticks. The inside is dark so I made a torch from tree resin. A broken tile with resin on it acts as a small lamp producing a lot of light and little smoke. The end product was a solid little hut, that should be fire and rot resistant. The whole project took 102 days but would have taken 66 days were it not for unseasonal rain. For a more in depth description see my blog (https://primitivetechnology.wordpress.com/). Wordpress: https://primitivetechnology.wordpress.com/ Patreon page: https://www.patreon.com/user?u=2945881&ty=h I have no face book page. Beware of fake pages.
Primitive Technology:Watering system!Primitive life-wilderness! Share and sub my chanel if you like this video!thank you very much! .
Hello Everyone, Today i'm build new mud house , we build this house using mud mix with grass. Generally the whole family joins in the construction of these houses that are more resistant than wooden houses and they have a good thermal insulation. Next video i will make door , bed. Thank you for watching please like and subscribe to get more video.
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I made a brick mold that makes bricks 25 x 12.5 x 7.5 cm from wood. A log was split and mortise and tenon joints were carved using a stone chisel and sharp rocks. The mold was lashed together with cane to prevent it from coming apart when used.
Next, I made a mixture of mud and palm fiber to make the bricks. This was then placed into the mold to be shaped and taken to a drying area. 140 bricks were made.
When dry, the bricks were then assembled into a kiln. 32 roof tiles were then made of mud and fired in the kiln. It only took 3 hours to fire the tiles sufficiently. The mud bricks and tiles were a bit weaker than objects made from my regular clay source because of the silt, sand and gravel content of the soil. Because of this, I will look at refining mud into clay in future projects instead of just using mud.
Interestingly, the kiln got hot enough so that iron oxide containing stones began to melt out of the tiles. This is not metallic iron, but only slag (iron oxide and silica) and the temperature was probably not very high, but only enough to slowly melt or soften the stones when heated for 3 hours.
The kiln performed as well as the monolithic ones I've built in the past and has a good volume. It can also be taken down and transported to other areas. But the bricks are very brittle and next time I'd use better clay devoid of sand/silt, and use grog instead of temper made of plant fiber which burns out in firing. The mold works satisfactorily. I aim to make better quality bricks for use in furnaces and buildings in future.
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I have no face book page, instagram, twitter etc. Beware of fake pages.