Overview and Purpose of the Mechanical Wind Generator

This project proposes the design and construction of a medium-sized mechanical wind generator capable of converting mechanical energy into kinetic energy in the form of rapidly moving air. Drawing inspiration from a toy fan, the project utilizes accessible, everyday components such as standard gears, fan blades, shafts, and mounting plates. Once all components are fabricated or sourced, they will be assembled into a fully functional wind generation device.

The primary objectives of this project are twofold. First, it serves as an opportunity for the developer to apply and refine engineering principles and physics concepts through hands-on construction and iterative design. Second, the completed device can be introduced as a pedagogical tool in a high school classroom setting, demonstrating core energy transformation concepts in a tangible, engaging manner. In this way, the project not only reinforces technical learning but also contributes to science outreach and peer education.

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Complete Design and Construction Instructions

The wind generator is constructed using a combination of accessible materials and UBC-provided laboratory resources. All core mechanical components, including the gear system, mounting plate, and handle, are modeled in OnShape, a cloud-based CAD platform. Fabrication of custom parts such as gears, gear stabilizers, and the handle is completed using a water jet cutting machine operated by a supervising professor, as students do not have independent access to the machine.

The fan blades and aluminum shafts are also provided by a professor. The fan blades are prefabricated plastic components, while the shafts are made from long aluminum cylinders with an outer diameter of approximately 6.35 mm, matching the bore diameter of the gears. Shaft cutting and final assembly are performed in a UBC lab space, using tools including saws, clamps, hammers (plastic and steel), files, chisels, and drills.

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Shaft Fabrication Process

The aluminum shafts are fabricated according to the desired lengths using the following steps:

1. Clamping and cutting: The aluminum rod is clamped securely, and a section is cut using a saw.
2. Edge finishing: The cut ends are smoothed and deburred using a file and chisel to eliminate rough edges.
3. Fitting: Each shaft is inserted into the corresponding holes on the mounting plate and fitted with its designated gear(s).

Gear-to-shaft fit tolerance is critical to mechanical performance:

• If the gear fits too loosely, the bore diameter is oversized, and the gear may need to be reprinted.
• If the gear fits too tightly, a decision must be made: should the gear rotate with the shaft, or should the shaft remain stationary?

In this system:

• The first, second, and fourth shafts are designed to rotate together with their respective gears. These require a tight press-fit, often using a hammer and clamp to fully secure the gear.
• The third shaft, supporting the third gear system, is stationary. The gear rotates freely on it and should have a slightly looser fit, achieved by enlarging the gear bore slightly with a drill, while maintaining a close approximation to 6.35 mm.

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Gear System Design

The gear system comprises four gears: three compound and one single, arranged to transmit motion in one direction, using a ratchet-like configuration.

• The handle is mounted to the first gear, which is fixed to the mounting plate.
• The second gear is stacked above the first on a horizontal sliding platform. Pushing the handle causes the first gear to rotate, which in turn rotates the second gear and slides it upward.
• As the second gear moves up, it engages with the third gear, which transfers motion to the fourth gear, directly coupled to the fan shaft.

When the handle is released, a spring mechanism resets it to the original position. The second gear slides downward and disengages from the third gear, interrupting energy transmission and ensuring that rotation only occurs during the downward stroke. This configuration prevents reverse motion, enabling unidirectional fan rotation.

Figures 1.0-1.2 illustrate the gear system at rest and in operation, showing how input from the handle propagates through the system to drive the fan blades.

Fig. 1.0

Fig. 1.0 shows an overview of the looks.

Fig. 1.1

Fig. 1.1 shows how the second gear system rotates and moves from right to left by the rotation of the first system

Fig. 1.2

Fig. 1.2 shows the scenario where the third gear, which is also a compound gear, is mounted onto the mounting plate.

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Final Assembly and Structure

After all components are fabricated:

• The gear system is assembled onto the mounting plate.
• The fan head is mounted to the fourth gear using a shaft.
• The handle and spring mechanism are installed to enable repeated input motion.
• The entire assembly is enclosed between two transparent plastic shells, providing both protection and visibility of the internal mechanics.
• A central external handle is attached to the shell for ergonomic user operation.

The handle design is intentionally flexible, but must meet the following criteria:

• Comfortable grip for repeated use
• Measurable pivot-to-gear distance for work input calculations
• Clear application of input force

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Engineering Considerations

A key design concern is friction, especially:

• Between the second gear and its sliding platform
• Between the second and third gear systems

Excessive friction between the second and third gear systems may prevent the third gear from rotating. To address this, a small stabilizer can be installed beneath the second gear s small gear, preventing the larger gear from coming into contact with the surface of the third gear. While this may result in slight misalignment between the gear axes, the system should still function as the rotational motion is preserved.

Additionally, since most components are 3D-printed with plastic, some friction is inevitable. Builders aiming to replicate or improve the design are encouraged to consider:

• Applying lubricants to reduce surface resistance
• Using smoother materials or alternative printing techniques
• Experimenting with custom tolerances during the design phase

Finally, gear-to-shaft fitting remains a major determinant of mechanical reliability and energy efficiency. Careful attention to bore diameter precision, shaft edge quality, and assembly force is essential to ensure smooth, consistent operation.

As previously noted, shaft lengths are flexible within a reasonable range. Slightly longer shafts are acceptable and do not negatively affect system performance. However, care must be taken to ensure shafts do not protrude excessively, especially on the fan blade side, as excess length could interfere with blade rotation. Final shaft lengths should allow all components to fit securely within the shell enclosure, without obstructing any moving parts.

Additionally, it is recommended to prepare several extra small gear stabilizers to support gear alignment and vertical spacing. These stabilizers are round inserts with a central bore diameter of 6.35 mm, and can be used in multiple ways across the gear systems:

• To adjust the vertical height of a gear on a shaft
• To reduce lateral play or wobble within the gear stack
• To stabilize the opposite end of a shaft, especially if unsupported by other structures

In this particular build, stabilizers were used on the second, third, and fourth gear systems, but they can be flexibly applied wherever additional support is needed during assembly.

Illustration of my demo in action

Worksheets were made but were not used because of time constraints (2 lectures, each of 40 minutes):

Efficiency and Mechanics Worksheet

Section 1: Multiple-Choice Questions

1. What does the efficiency of a machine represent?

A) The speed at which the machine operates
B) The ratio of useful output energy to input energy
C) The total energy used by the machine
D) The power required to operate the machine
Answer: ______

2. Which of the following improves the efficiency of a heat engine?

A) Increasing friction
B) Reducing energy losses as heat
C) Using more fuel
D) Operating at lower temperatures
Answer: ______

3. What is the primary reason why no machine can be 100% efficient?

A) The law of inertia
B) Energy conservation laws
C) Friction and energy losses as heat
D) Machines always require an operator
Answer: ______

Section 2: Conceptual Questions

1. Why is efficiency important in designing machines and systems?
   A) To reduce energy waste
   B) To maximize cost savings
   C) To minimize environmental impact
   D) All of the above
   Answer: ______
2. How can engineers improve the efficiency of a wind turbine?
   A) By increasing the weight of the turbine blades
   B) By optimizing blade design and reducing drag
   C) By using weaker materials
   D) By reducing the wind speed
   Answer: ______
3. A car engine's efficiency is 25%. What does this mean?
   A) 25% of the fuel is used, and 75% is wasted.
   B) 25% of the energy from the fuel is converted into useful work.
   C) 25% of the engine's components are functional.
   D) The engine runs at 25% of its maximum speed.
   Answer: ______
4. In a gear system, what is the trade-off when increasing torque?
   A) Speed decreases
   B) Speed increases
   C) Efficiency decreases
   D) Efficiency increases
   Answer: ______

Section 3: Calculation-Based Questions

1. An electric heater converts 90% of the electrical energy it receives into heat. If it uses 2000 W of power, how much power is lost as heat?
   
   
2. A wrench applies a force of 50 N at a distance of 0.2 m from the pivot. Calculate the torque.
   
   
3. A gear system has an input torque of 10 Nm and an output torque of 50 Nm. What is the gear ratio?
   
   

Section 4: Open-Ended Questions

1. Explain why improving efficiency in machines and systems is crucial for environmental sustainability.

2. Explain how gear systems can be used to modify both torque and speed in mechanical systems.

3. What are some things you like and/or don t like about today s lecture? Leave any comments/suggestions!

Self-Assessment and Reflection:

I have learned a great deal in this course, from the planning of the project to every specific detail to build it, there has been a lot more than I originally anticipated. My project is rather an easier one if I were to comment on it, and in the beginning, I thought the whole thing might only take me a short amount of time, but it quickly turned out that I was wrong. I have roughly planned out what I needed to do, the steps I would need to take to finish the project, but every step had taken me a lot more time than I thought. The planning stage, the OnShape designing stage, the part-collecting stage, the building stage, and many more, have been much more difficult than I thought. Especially the technical part, or the designing part, there were many subtle details I did not know I needed to consider, each gear and each placement of gear, the shapes and sizes of the gears, the mounting plate and the sizes and placements of the holes, I could go on but basically, there were so many details even in a simple mechanical design like mine. For the construction stage, everything was quite clear at that point where the design has been finished and all I needed to do was to perfect all parts so that they can assemble well. However, the tasks, seemed easy, but were quite time-consuming. There was also the risk of drilling the gears too much so that they no longer fit well with the shafts, in which case I would have to ask my professor to remake those gears for me, which was of course, troubling to him and I would try not to do that. Thankfully the professor was very understanding and caring, and that I did not mess up too much, we did not have to remake too many gears. Overall, the whole process of planning and making the project was a great deal to learn from. If I were to do my demo again, I would try to perfect my presentation skills more, but I think I would not change too much in general. The most difficult part of this course was the project building part. I did find using the tools in the lab satisfying and enjoyable (using the file, the hammer, etc.). I would advise a student taking this course in the future that think more carefully about what they actually are trying to build. Things can get really complicated really fast, with that being said, feel free to challenge themselves. One advice I would have for this course is that if we could have the due dates for all assignments (especially the last one) clearer, it would be more helpful to plan things along the way.