Windmill Design
Windmill Design
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Our project involves the design and construction of a large-scale, functional windmill built primarily from balsa wood. The system is engineered to operate in two ways: it can capture natural wind energy to spin the blades mechanically, and it integrates an electric motor to drive the gear system automatically. By utilizing a high strength-to-weight material like balsa wood at this scale, the project explores the practical challenges of structural integrity, aerodynamic efficiency, and the integration of mechanical and electrical powertrains.
Part 1: Initial Planning
Used Kidwind to test different blade models
Used Kidwind to test different blade models
Digital Modeling & Aerodynamic Simulation: Utilizing the KidWind online design simulator to model and evaluate various wind turbine blade configurations. This digital prototyping phase allowed for the rapid testing of blade pitch, twist, and surface area profiles to predict aerodynamic efficiency and lift-to-drag ratios prior to physical manufacturing.
Physical prototyping and empirical testing
Physical prototyping and empirical testing
Translating digital CAD designs into a functional K'NEX-framed wind turbine prototype. The physical model features blades attached to a low-friction drivetrain, paired with a pulley-and-weight system to empirically measure mechanical power output, torque, and rotational velocity under controlled wind-tunnel conditions.
Part 2: 3D Modelling
CAD design on TinkerCAD
CAD design on TinkerCAD
Utilized TinkerCAD modeling to conceptualize the turbine's physical geometry, verify component tolerances, and visualize the complete structural assembly in a virtual environment.
Build Process
Main Base
Main Base
Windmill Blades
Windmill Blades
Executed the physical build phase using lightweight balsa wood, focusing on structural stability, precise geometric alignment, and rigid joint construction to handle mechanical stresses:
BASE:
To keep our windmill freestanding and stable under high winds, we built a balsa wood A-frame truss. The design features two angled side supports braced horizontally to prevent the legs from spreading under pressure. A central balsa dowel serves as the drive shaft, connecting the frames to the rotor hub and blades. While we initially used hot glue for assembly, the twisting force of the spinning blades caused the joints to wobble. We solved this by reinforcing the joints with balsa gussets to stiffen the frame and adding flat "feet" at the bottom to prevent the structure from sliding. The final design was exceptionally sturdy and kept the drive shaft perfectly aligned.
BLADES:
Rotation and Inertia: Our initial blade design placed the blades too far from the center axis, making the turbine too heavy to start spinning under weak airflow. To fix this, we applied the physics principle of rotational inertia, which states that an object’s resistance to spinning depends heavily on how far its mass is from the center. By shifting the blades closer to the center axis, we drastically reduced the torque required to jumpstart the system. We also kept the blades as light as possible by tapering the wood rather than adding heavy supports, allowing the windmill to catch weak breezes easily without sacrificing overall strength.
Blade Angle and Aerodynamic Shape: We selected a 45° blade pitch to perfectly balance the aerodynamic forces of lift and drag. At startup, a wind turbine relies mostly on drag to push the blades forward, while lift takes over once it builds up speed. A 45° angle splits the difference, providing high starting torque while maximizing top-speed efficiency. Additionally, we carved the blades into a tapered, elliptical shape, narrow at the base, wide in the middle, and rounded at the tip. This aerodynamic profile distributes lift evenly and reduces efficiency-killing air turbulence at the tips, keeping the blades fast, lightweight, and structurally strong.
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