Blog 1: Gears

Hi readers!! Welcome back to my first blog. I'm Mabelle, and these blogs will be all about my journey in Chemical Product Design and Development!! I hope you all stay interested and enjoy my first blog about gears. :)

Definitions of gear module, pitch circular diameter, and the relationship between gear module, pitch circular diameter, and number of teeth.

Gear module: Size of the gear teeth (mm). The larger the gear module number, the larger is the size of the teeth. Gears that are meshed together have the same gear module.

Pitch Circular Diameter: Imaginary circle that passes through the point of contact between two interlocking gears, representing the diameters of two interacting friction rollers in contact and moving at the same linear velocity.

The relationship between gear module (m), pitch circular diameter (PCD), and the number of teeth (z) can be expressed by the equation: m = PCD / z.

Relationship between gear ratio (speed ratio) and output speed, between gear ratio and torque for a pair of gears.

Gear ratio (speed ratio) and output speed: The relationship between gear ratio and output speed is inversely proportional. This means that as the gear ratio increases, the output speed decreases, and vice versa. Hence, when the driver gear is larger than the follower gear, the gear ratio is > 1. The output speed is reduced compared to the input speed.

Gear ratio and torque: The relationship between gear ratio and torque is directly proportional. This means that as the gear ratio increases, the torque at the output also increases, and vice versa. Therefore, when the driver gear is smaller than the follower gear, the gear ratio is <1. The output speed is increased, but the torque is amplified. This is needed when higher torque is needed at the output.

How I designed a better hand-squeezed fan!!

A useful property a fan should have is producing more rotations per squeeze. For this to happen, I must produce a gear train with the best speed multiplier. Hence we ended up with a gear ratio of 0.10 and a speed ratio of 10!

Using gears to raise the bottle!

Calculation of the gear ratio (speed ratio):

The photo of the actual gear layout:

Calculation of the number of revolutions required to rotate the crank handle:

My Learning reflection

Learning about gears has been a really fun journey that taught me the intricate mechanics of these seemingly simple components and also its impact on many aspects of machinery and technology. I was super excited about Practical 1 since we got to do many hands-on activities and experimented with the relationship between gear ratios and the resulting effects on speed and torque. I was surprised at how such a minor change in the size or arrangement of gears can lead to significant changes in output speed or torque.

The hands-on experience of assembling and manipulating gears provided an opportunity to test and apply my theoretical knowledge. Feeling the gears interlock and observing how their teeth mesh to create motion was super cool. It made me think about how this simple design is also interconnected to many large scale machinery. During the practical, Jing Yue and I cracked our heads open trying to find the perfect arrangement for the highest gear ratio to achieve and highest torque needed to pull up the water bottle. It wasn’t easy since we only had a limited amount of gear to work with! However, after many sketches and calculations, we came up with two designs giving a gear ratio of 17.78 and 26.67. Of course, we chose to assemble the 26.67 one first! However, midway through we realised it wasn't possible as there were many gears stacked onto one another creating a slight slope that would cause the gears to jam. Having little time on our hands, we had no choice but to settle for the arrangement that gives a 17.78 gear ratio. After that, we had no time to film the final process with the water bottle. 🙁

This experience instilled in me a sense of appreciation for the timeless ingenuity that has gone into refining and optimizing these mechanisms. I also gained respect for the people who invented gears, whether it be the Greek mechanics of Alexandria in the third century B.C. or the Late East Zhou dynasty from the 4th century BC in China.

Furthermore, it enhanced my technical knowledge and made me realize how there can be many different methods to approach a problem. Finding the right arrangement was tough, but it stimulated my brain, encouraging me to view things from many different perspectives and ultimately fostering my creativity

This is it for my first blog, I hope you guys enjoyed reading it and come back for more next time!!