Gears

Gears Documentation Blog Entry

In this practical, we've learned about how gears work and identifying the relationship between the different factors.

1. These are the definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and 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 the size of the teeth. Gears that 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.

By looking at the formula below, the relationship between gear module (m), pitch circular diameter (PCD) and number of teeth (z) is that the gear module is directly proportional to the pitch circular diameter. The module is inversely proportional to the number of teeth.

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

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

When the follower gear smaller than the driver gear, the gear ratio is <1, it is define as a speed multiplier where the follower gears turn faster.

Whereas, when the follower gear is bigger than the driver gear, the gear ratio is >1, the output speed is slower

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

When the gear ratio is >1 it is define as a torque multiplier where the torque of a pair of gears increases.

Whereas, when gear ratio is < 1, the torque between a pair of gears decreases.

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

To make the hand-squeezed fan better, the proposed design is to make the speed of the squeezed fan to turn faster. To do so, we can arrange the gears in a way that the bigger gear is controlling the smaller gear so that the gear ratio is <1. Thus the fan will turn faster and lesser force will be used.

Photo of the proposed design for the hand-squeezed fan

A sketch of the proposed design for the hand-squeezed fan

Slow-Mo video on the hand-squeezed fan

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.

The arrangement of the gear train are as follows:

1. Gear 50T with handle

2. Gear compound 20T-40T

3. Gear Idler 30T

4. Gear compound 20T-40T

5. Gear Idler 40T

6. Gear compound 20T-30T

7. Gear compound 12T-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 gears activities

For this practical, it was indeed one of the most interesting and fun practical that I've ever done although we have to think a lot on how to position the different gears in order to get our desired outcome.

In this practical, we were required to complete 2 activities, the first activity is to design a gear ratio to raise 0.5L of water in the bottle with minimum force and the second activity is to assemble the hand-powered fan that was given to us.

When doing the first activity, the first thing that came to my mind was that we have to make sure that our gear ratio is less than 1 since the requirement of this activity is to design a gear ratio that is able to raise the bottle with 0.5L of water with MINIMUM FORCE. Since torque is define as the product between the force and the radius (Torque = Force x Radius), we want to achieve a lesser force, the torque between 2 gears should decrease. In order to make the torque decrease, the gear ratio should be <1. With that, we tried to arrange our gears in a way so that the gears are in the sequence of big small big small...

However, one problem that we faced in the first activity is that when we were testing out our train of gears,  some part of the gear teeth wasn't touching very close to each other. This cause the rest of the gear train to not move. Therefore, we have to reconstruct the whole gear train again. By doing so we actually wasted quite a lot of time and ended up eating into our next activity. So our group decided to split ourselves so that Ryan and Haiteng can continue to work on activity 1 while Isabella and I move on to activity 2.

For activity 2, there wasn't any major difficulties that we faced. Hence for activity 2, we completed in less than 20mins including taking all the necessary photos and videos.

Since Isabella and I finished activity 2 early, we decided to do all the sketches and questions that we needed to submit on the day of the practical for activity 1 and 2. However, we still didn't manage to finish the questions within the give time frame. So we kind of rushed through the rest of questions without knowing if we actually did it correctly. If only we could have a time keeper to keep track of the time so that we wouldn't overrun the schedule that much😢. 

Overall, it was still an eye-opening practical where I get to learn about how exactly gears work and what are the factors that affects the way on how the gears work. 

Although this practical was very fun, but there are still room for improvement such us our time management. Aside from that, I still think my group did pretty well for this practical in terms of teamwork and coming to practical prepared👍.