Gears

GEARS⚙

For our second practical, we learnt more about gears such as the gear ratio and how it affects how the gears work. 

1. These are the definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and the number of teeth:

Gear Module (m) refers to the size of the gear teeth. The unit for module is mm. The larger a module number, the larger is the size of the teeth. Gears that are mesh together are having the same module.

Pitch Circular Diameter (PCD) is the imaginary circle that passes through the contact point between two meshing gears. It represents the diameters of two friction rollers in contact and moves at the same linear velocity. The unit for PCD is mm.

Number of Teeth (z) refers to the number of teeth the gear has.

Relationship between module, pitch circular diameter and the number of teeth:

2. Below is the relationship between gear ratio (speed ratio)and output speed for a pair of gears.

Gear ratio is the ratio of number of teeth of the follower gear to the number of teeth of the driver gear. 

When gear ratio is <1, it becomes a speed multiplier and therefore increasing the output speed of the follower gear. For example, the bigger gear is the driver gear and the smaller gear is the follower gear and the size different is two times, this would mean that for one revolution of the driver(bigger) gear, there would be two revolution of the follower(smaller) gear.

When gear ratio is >1, it will decrease the output speed of the follower gear. 

Below is the relationship between gear ratio and torque for a pair of gears.

Gear ratio is the ratio of number of teeth of the follower gear to the number of teeth of the driver gear. 

When gear ratio is >1, it becomes a torque multiplier, therefore torque of the gear increases.

When gear ratio is <1, it will decrease the torque of the gear.

3. Below are the proposed design to make the hand-squeezed fan better:

The proposed design is to make the wheel of the fan turn faster, hence we need a speed multiplier. In order to get a maximum value for the speed multiplier, we need the lowest compound gear ratio. To get compound gear ratio, calculate the gear ratio of each contact point and multiply it together. Therefore, to get the lowest gear ratio, the two contact gear is from a bigger gear (driver) to a smaller gear (follower) and the larger gear to have more teeth and smaller gear to have lesser teeth 

Here is a sketch of the proposed design:

Green line- line of action

Here is a video of the fan in a slow motion🐢:

4. Below are the description on how my practical team arranged the gears provided in the practical to raise the water bottle.

a. Calculation of the gear ratio (speed ratio)

b. The photo of the actual gear layout.

Driver on the right end and follower on the left end.

Arrangement of our gear layout:

1. Gear 30T with handle(driver)

2. Gear compound 12T-40T

3. Gear Idler 40T

4. Gear compound 20T-30T

5. Gear compound 20T-40T

6. Gear Idler 30T

7. Gear compound 20T-40T

8. Gear 40T with winch

c. Calculation of the number of revolutions required to rotate the crank handle.

d. The video of the turning of the gears to lift the water bottle.

5. Below is my Learning Reflection on the gear activities 

This practical was a 10/10 using brain cells but is also a 11/10 fun. This practical bonded my team and help me know each other's strength and it engrossed each and everyone one of us in my team for the whole 3 hours of the practical session. It help us to cultivate the basic knowledge on gears (especially compound gear). Having knowledge on gears is extremely important as even basic things in life uses a gear. For example, our bikes, watches and even something that transports you from the first floor to your level, a lift. 🛗 Besides these basic skill being used in daily life, it is essential for us to know as chemical engineers as well. 

Throughout the two tasks, it engages my thinking skill and problem solving skills as well as my interpersonal skills. It uses my thinking skill to find out HOW do we use the minimum amount of force to lift the bottle? We need the highest speed ratio. HOW do we arrange our gears to get the maximum amount of gear ratio? By arranging it in a way is smaller to bigger gear as it will have a ratio of more than one and will be a torque multiplier.🤔

Activity 1 and 2 uses my problem solving skill when we faced a lot of challenges during our gear set up for activity 1. After arranging the gears in order of big small big small, we realised there was a problem as a pair of our gears could not turn as they are of the same size. Hence we thought ways to solve. First, we tried switching up the gear with another compound gear but no other compound gear could fit. Then we tried to rearrange the gears but we play with the sequence we put in. Finally, we built the structure and realised it couldn't turn as it collides with the winch and hence our final solution was to flip the compound gear over and used it as an idler gear and giving up our ratio from 13.33 to 6.67.

These activities uses my interpersonal skills as it is needed to convey the message I want to bring across and also my idea I had. It engages my teammates to have a good discussion. 🫂