Gears

 

Gears Documentation Blog Entry

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

 Definition of Gear module (m) refers to the size of the gear teeth in mm 

 Definition of Pitch Circular Diameter (PCD) refers to the imaginary circle that passes through the contact point between the diameters of two friction rollers in contact and moves at the same linear velocity.

The relationship of Gear module (m), Pitch Circular Diameter (PCD) & number of teeth (z) :

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

Definition of Gear ratio (speed ratio) : 

Ratio of the number of teeth of the follower gear to the number of teeth of the driver gear.

When gear ratio > 1, the output speed will decrease. When gear ratio increases, output speed decreases.

When gear ratio < 1, the output speed will increase. When gear ratio decreases, output speed increases.

Therefore they are inversely proportional.  

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

Definition of Torque:

Torque is the product of circumferential force mulitplied by the radius of the gear.

When gear ratio > 1, torque will decrease. When gear ratio increases, torque increases.

When gear ratio < 1, torque will increase. When gear ratio decreases, torque decreases.

Therefore they are directly proportional.

 

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

Here is our group's fan in slow motion:

Initial plan and design (sketch)

New proposed idea and design (sketch)

In order to come up with a better idea, we first looked at what we wanted to improve on. This would be the speed of the fan so that it would be faster and cooler. In order to increase the speed, we would need a speed multiplier. 

We have previously learnt that in order to increase the output speed, the gear ratio have to decrease. In order to decrease the gear ratio (number of teeth of the follower gear over the number of teeth of the driver gear), we would need to increase the number of teeth of the driver gear in order to have a smaller gear ratio. 

We also learnt that the number of teeth correlates to the PCD therefore we needed to change the driver gear to one of higher PCD and higher number of teeth as seen in the sketch above.

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.

While planning,

Actual gear layout,

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.    Learning Reflection on the gears activities

In this practical, I had a lot of fun constructing the gears for both the water bottle and the hand-squeezed fan but not so much when it came to calculating the least amount of force required to lift the water bottle. I felt that we spent too much time coming up with finding the least amount of force that it took out abit of the fun. Not only were we unable to fully sit down and slowly calculate, we were hard pressed for time too.

Us thinking really hard

During activity 1, where were required to find the least amount of force to lift up the water bottle, we had to brainstorm really hard as every method we did, we managed to find a minor flaw. This meant that we spent a huge chunk of time just thinking of the idea followed by calculating the method. This was really a headache but I got to admit that the amount of time we laughed at each other's ideas for being totally illogical was worthed it.😂

During activity 2, I was actually busy working on completing activity 1 however at the start when coming up with the answer to Dr. Noel's bonus questions, I had already completed it on my own as I was trying to figure out how it would look like in order to answer Dr. Noel's question. After that, I sat there for a solid 5 minutes just blowing myself with the fan but it was very cool so it was worth it.😃

I've learnt that gears are very important tools that allow us to build many things. Just a few gears allowed us to create a fan. A while ago, I came across a video showing how engineers slowly added gear by gear to create what we know as cars today, allowing it to rotate and turn. I'm very certain that we can use the skills learnt about gears to create many different devices and that is why I found this practical really useful and besides, I think I really bonded well with classmates not only from my group but others as well when they came over to help us.💪🙌

Definitely enjoyed this practical without the time constraint and the lil quiz at the end. From the left is Keith, Tristan, Justin and lastly ME! :)