YAHHŌ mina san! How's it going? Weclome back to my page, TODAY I will be sharing with you my cranky yet fun experience that went down during my practical on spinning wheels with teeth😏.
GEARS 
So as you may have guessed gears are what I am refering to as "weird spinny wheels with teeth" This practical has been insanely enlightening and I must say it was truly entertaining to see my friends and I struggle to build a gear contraption that looks so easy. Surprisingly, there are many way we use gear in our life one such example is the bicycle gear and chain. As an avid road biker I do have experience on the usage of gears and purpose of gear shifting. So, let me show you what other things I have learnt in this blog.
1. This is the definition of gear module, pitch diameter and the relationship between gear module, pitch circular diameter and number of teeth.
Gear module: The word “module specify the size of the gear. Gear module is the ratio of the diameter of the gear divided by the the total number of teeth it has, hence gear module shows the size of each teeth on the gear.
Pitch Circular Diameter (PCD): It is the space or distance between the corresponding point of the the adjacent teeth measured on the pitch circle. In simpler term, it is the space between each teeth.
Relationship between gear module, pitch circular diameter and the number of teeth: It can be expressed as an equation where PCD can obtained by multiplying gear module(m) and number of teeth(z).
PCD = m x z
2. Relationship between gear ratio(speed ratio) and output speed for a pair of gears.
Equation to find gear ratio: gear ratio = output/input
Gear ratio also often known as gear ratio has a unique advantage of increasing torque or speed. In this case , to increase the output speed of a pair of gears, the speed ratio should be <1 (less than 1 speed ratio).
To achieve speed ratio <1, output must be smaller than input and this causes the gear to be a speed multiplier. Therefore speed ratio is inversely proportional to the output speed.
Relationship between gear ratio and torque for a pair of gear.
Torque is the rotational force about an axis.
To get a pair of torque multiplier, the driver/input gear should be smaller compared to the follower gear which makes the gear ratio >1. This means the gear ratio is directly proportional to torque.
3. Below is my opinion on how to improve the hand-squeezed fan.
First let me show you what we have put together on that day of practical.
We used this fan made using 3D printed material. 
From the video you can see a small piece of tape we put on the gear to see a complete rotation. As seen in the video, we came to a conclusion that for every one rotation of the first gear, the blade spin 10 times.
To confirm our theory, Diana calculated the number of teeth on each gear. After calculating the compound gear ratio, we got 0.1 gear ratio. So our calculation and theory match!
So after some thinking there are many ways to improve on the efficiency and effectiveness of this hand squeezed fan.
Firstly, to increase the efficiency, a different material of smoother surface and be used to decrease friction between the teeth.
Secondly, a lubricant can be used to also decrease the friction and reduce the wear and tear of the gears.
Thirdly, the fan internal parts were lose which meant that energy is wasted. We could reduce energy wastage by having a better quality design.
Fourthly, we can also increase efficiency by reducing the amount of gears so that less energy is wasted due to friction.
Next, to increase effectiveness we want the gears to be a speed multiplier. This can be achieved by decreasing the gear ratio which is possible by increasing the driver gear size or decreasing the follower gear size.
Lastly, one very troubling thing was that it was a fixed gear fan. This means that it can either go clockwise or anti-clockwise. This makes using the fan very troublesome. Instead of making a fixed gear fan, we can change it to a free gear fan. Below is an example of free gear hand pressured fan.
Proposed design
4. This part shows how my team put together the gears in order to raise a water bottle.
a. Calculation of the gear ratio
Gear ratio = 40/30 * 40/12 * 20/40
= 2.22
b. The photo of my group’s gear layout
c. Calculation if the number of revolutions required to rotate the crank handle.
Gear ratio: 2.22
Number of rotations: 200/2πr
Winch diameter: 22mm
Number of rotation: 2.89
Number of rotation of the crank: 2.89*2.22
=6.422
d. The video of the bottle being lifted.
In the video it shows that we rotated the handle 9 times because we brought the bottle up in 250mm hence the number of rotation.
5. Below is my learning reflection on the gear activities. 🧠
The practical on gears was really enjoyable. It has been quite some times since I worked hands on with a group and I must say it brings back childhood memories. As a cyclist, I believe I am quite good with gears as I have been cleaning and fixing them every time when I go cycling. To see how diversely gears can be used was truly fascinating. Of course other than hands on activity I also learnt about the principles of a gear as mentioned previously in this blog. From the videos in bight space I learnt about types of gears, gear modules and many more.
Activity 1:
We were tasked to lift a 500ml bottle for 200mm. It seem really easy at first so three of my group members wanted to do this activity. They had one simple task which was to make the gears a torque multiplier which means that the gear ratio must be larger than 1. After some trial and error, they were able to get a gear ratio of 2.22 which needed around 7 rotation to lift the bottle. Although it only needed around 7 rotations, it was quite difficult to lift the bottle up. However we had some strong members hence we were still able to easily lift the bottle. I thought about increasing the gear ratio which will in turn increase the amount of rotation to lift the bottle. However it will take much longer to lift the bottle so I decided not to implement it.
From this activity we actually encountered some obstacles and had to learn from it before progressing.
- We should always tighten the gears to the backboard or else it will be wobbly and hard to turn. This is due to them having no proper pivot point.
- When constructing gears we should only do it from one side not both sides. As my team was rushing for time we placed the gears at the start and end and worked our ways to the middle. However, the gears could not fit in the middle as there was no space. Therefore when working with gears we should always go from one point to another.
- We had to rotate the crank more times than the theoretical number of rotations as there was friction present between each teeth. There are ways to reduce this inefficient use of energy as mentioned above. I believe using a lubricant will definitely help with smoothening the gears in rotation.
Activity 2:
This activity was particularly interesting as it was a fan made of completely 3D printed materials. It was like building legos again but this time with gears. Diana and I had some problems when putting the parts together as they were not sanded and filed properly however we managed to slowly construct the fan. The gears were loose and so the fan could not spin properly when lifted up from a solid surface, however when used it on a table top where it was flat, the gears could spin better. One thing that was frustrating was that it could not spin freely. This means when the user let go of the handle when the fan is spinning, the handle will still move.
Even though this activity was slightly challenging, we were able to easily answer the questions and deduce the amount of rotation the fan will have every handle cranked. Most importantly, it helped us confirm that the theory on the gear calculations where correct.
In a nutshell, it was an insightful practical that opened my eyes on the purpose of gears in our lives. I realised how widely used it is even though we do not really see it in our day to day life. This practical has also reminded me on why I should set a plan before doing anything. One reason why my group was rushing for time in the last thirty minutes was due to them not watching the four videos provided by the school. If I did not watch them I would have been as lost and confused as them during the practical. It truly felt great coming into class knowing what will be ongoing for the class instead of blindly following and copying what others are doing.
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