This video details the construction and testing of a traditional, human-powered blower for iron smelting, specifically focusing on the challenges and solutions encountered when adapting existing designs. The creator meticulously rebuilds a broken clay blower housing, demonstrating a unique string-based method for scribing the volute (spiral) shape and explaining its aerodynamic purpose. Key components like a round outlet spout and double-sided air inlets are integrated. The video also covers the primitive yet effective method of starting fire by friction and the process of making durable cordage from wild banana tree fibers to serve as the drive belt. Two pulley designs are explored: a fixed wheel and a "floating wheel" (a wicker cylinder spun in mid-air). After overcoming issues with fragile clay pulleys by opting for a fiber-wrapped rotor, the blower is successfully tested with fire and subsequently used in an iron smelting operation. While the smelt produced high-carbon iron prills within a slag mass (attributed to lower blast pressure), the blower performed ergonomically and efficiently, yielding 21 grams of iron from 1200 grams of ore, surpassing the average yield from previous attempts.
Summarizing the Traditional Blower Construction and Iron Smelting Process
0:00 Rebuilding the Blower Housing: The project begins with rebuilding a broken clay blower housing from a previous endeavor, highlighting the need for a robust design.
0:17 Scribing the Volute Shape: The creator demonstrates a precise method for scribing the housing's spiral volute using a string, ensuring an accurate aerodynamic shape for efficient airflow.
1:07 Purpose of the Volute: The volute shape is explained as crucial for gradually increasing air volume around the fan, leading to consistent air output.
1:32 Round Outlet Spout: A design change to a round spout is introduced to facilitate easier connection to a round tuyere (air pipe) for the furnace.
2:28 Air Inlet and Drying: A 5 cm diameter air inlet is cut into the housing, followed by careful drying of the clay, with a warning not to leave the internal log too long to prevent cracking.
3:02 Fire by Friction: A brief demonstration of starting a fire using the friction method, showcasing a traditional technique.
4:44 Making the Lid: A lid is formed by flattening clay, trimmed to fit the housing, and features a second 5 cm air inlet for the fan.
5:18 Assembling the Housing and Fan: The housing is set on stakes, the fan rotor is placed, and its free spin is tested before the lid is added, ensuring proper alignment.
6:04 Furnace Construction: A furnace pit is dug, and walls are constructed using bricks, positioning the tuyere 2.5 cm (one knuckle) from the pit's edge.
6:51 Cordage from Banana Fiber: Wild banana tree fibers are harvested, split, dried, and then twisted into strong, durable cordage using a specific clockwise/anti-clockwise twisting method.
7:36 Splicing the Belt: The banana fiber cordage is spliced together to form a continuous belt, demonstrating a technique for joining ends securely.
8:58 Clay Pulleys and Keyway: Small clay pulleys are made for the fan rotor, along with a keyway for a wooden key to secure the pulley in place.
10:15 Testing Fixed Pulley Design: A "fixed pulley" design is tested where the handle is directly attached to the wheel, simplifying the mechanism but showing some wobble.
11:34 Making the Floating Wheel: The creator shifts to a "floating wheel" method, constructing a wicker cylinder with handles to act as the driving wheel, spun in mid-air.
12:28 Fiber-Wrapped Pulley: Fragile clay pulleys are replaced by wrapping the fan rotor with fiber, which provides better traction for the belt and prevents slipping.
12:53 Blower Ratio: The fiber-wrapped pulley in action shows a 19:1 ratio of fan revolutions to wheel rotations, indicating efficient air movement.
13:27 Performance Test: The blower is tested with fire, proving to be ergonomically comfortable and providing a consistent blast, comparable to other blower methods.
14:09 Smelt Preparation: The smelting process begins with 30 double handfuls of charcoal and roasted iron bacteria (white from ash) as the ore.
14:38 Smelting Process & Challenges: A 26-minute preheat is followed by six charges of charcoal and ore. The smelt experienced halts due to the belt breaking and the fiber pulley needing re-tying.
17:38 Bloom Analysis and Yield: The bloom produced consisted of high-carbon iron prills embedded in slag, theorized to be a result of lower blast pressure. The bloom was crushed and panned to extract 21 grams of iron from 1200 grams of ore, a better-than-average yield for this method.