GEARS
HEY EVERYONE! Welcome to my second blog about GEARS :-)
In this blog, I will describe:
1. The definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth.
2. The relationship between gear ratio (speed ratio) and output speed, between gear ratio and torque for a pair of gears.
3. How I can design a better hand-squeezed fan, including the sketches
4. How my practical team arranged the gears provided in the practical to raise the water bottle, consisting of:
a. Calculation of the gear ratio (speed ratio)
b. The photo of the 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. My Learning reflection on the gears activities.
Without further ado, lets get into it!😝
1. These are the definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth:
1. Gear module is the size of the gear teeth
2. Pitch circular diameter is the imaginary circle that passes through the contact point of the 2 meshing gears.
3. The relationship between gear module (m), pitch circular diameter (PCD), and number of teeth (z) is as follows: m = PCD/z
2. Below is the relationship between gear ratio (speed ratio) and output speed for a pair of gears.
Gear ratio = speed of input gear shaft / speed of output gear shaft
The gear ratio is inversely proportional to the output speed. A lower gear ratio would give a higher output speed, whereas a higher gear ratio will give a lower output speed .
We can think about it this way: a lower gear ratio would mean that the driver gear is larger than the follower gear. One revolution of the driver gear will require many revolutions of the follower gear. The speed of the follower gear will be faster and hence, output speed will increase with a lower gear ratio.
Below is the relationship between gear ratio and torque for a pair of gears.
A high gear ratio will give a higher torque.
Gear ratio = output torque/ input torque.
A higher torque would be better as there is more rotating force being produced by the gears, and so, less rotations will be needed to lift the bottle by a height of 200mm.
If the gear ratio is more than 1, it becomes a torque multipler. This causes the torque of the gear to increase.
On the other hand, if the gear ratio is less than 1, it will cause the torque of the gear to decrease.
3. Below are the proposed design to make the hand-squeezed fan better:
In order to make the fan wheel turn faster, we have to increase the output speed of the gear. Remember how the speed affects the gear ratio? A lower gear ratio will increase the output speed of the gear, hence we have to achieve a lower gear ratio for the fan.
Since gear ratio = follower gear/driver gear, we have to place the gears in a way that the driver gear will be bigger than the follower gear.
Additionally, we can add a lubricator like grease to decrease the friction between the gears and allow it to spin faster.
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.
c. Calculation of the number of revolutions required to rotate the crank handle.
Number of total revolutions = 61
Length of rope = 105cm
61 (2 ℼ R) = 105
R= 0.274
Measured winch radius = 5.7 / 2 = 2.85cm
d. The video of the turning of the gears to lift the water bottle.
5. Below is my Learning Reflection on the gears activities
Initially, it was hard for me to grasp the concept of the relationship between gear ratio with output speed and torque. I found it challenging to visualise the gear ratio of follower gear/driver gear, and it was even harder when we had to construct the compound gear train to lift the bottle in activity 1.
For output speed of the gear, it is inversely proportional to the gear ratio. With a lower gear ratio, the output speed of the gears will be higher. This means that the driver gear is much larger than the follower gear. So, for every 1 revolution that the driver gear makes, the follower gear does many more revolutions. This causes the speed of the output gear (follower gear) to increase.
It took me some time to understand what torque was because the orientation of the diagram provided in the youtube videos confused me. After much research, torque is the measure of the force that can cause an object to rotate about its axis. It is how much an object can rotate about its axis to overcome its turning resistance. A higher gear ratio will lead to a higher torque as there is more rotating force.
During the 1st activity, I had mistaken the method used to pull the bottle up. I thought that we needed to use the least amount of force to pull the bottle up. This led to me trying to orient the gears in such a way that we could get the lowest gear ratio because I had confused torque with force. However, this was wrong. We had to find out the minimum force applied, which means that there needs to be more torque to “compensate” for the lack of force used.
Since torque = force x distance, the distance between the handwheel and the lever remains the same. So if force decreases, the torque must increase to maintain the same distance.
From a gear ratio of 0.2, we managed to increase it to 1.34. Nonetheless, this was not enough! Even after we had tried re-arranging the orientation of the gears, we still got the same values since the fractions of the gear ratios would cancel each other out. But then, we suddenly remembered that we could flip over the compound gears to obtain a higher ratio between every 2 gears along the gear train. We were stuck on the cursed💀 gear ratio of 1.34 for a long time because we were only moving the gears around without thinking of flipping them over, as some of the compound gears had smaller gears on top. If we were to place a small gear together followed by a bigger gear (from the compound gear), we would obtain a bigger gear ratio since the follower gear is larger than the driver gear.
In the end, we managed to get our gear ratio to increase from 1.34 to 9! How amazing is that haha😎
One learning point I can definitely take away from this is to not have a “one-track mind”. In the first place, I did not even think of flipping over the gears because I believed that what we had was already the best orientation we could come up with. I thought that the gear ratios we obtained were the finest we could calculate. This taught me to not be so rigid in my thinking and that I should be open to trying out new methods. After all, if I never start doing it, how will I know whether that other method is wrong? I realised that I had adopted a “growth mindset”, rather than a fixed mindset. In the past, whenever I had some setbacks during a practical session, I would always scold myself for not being “smart” or competent enough to realise the mistake sooner. However, adopting a growth mindset during this practical allowed me to see that, hey, I was glad that I made the mistake of calculating the smallest gear ratio instead of the largest. Because this allowed me to reflect on what I did wrong and I was able to learn from it. I find that this is very crucial throughout my academic journey as I see mistakes as an opportunity for me to grow and apply what I have learnt in the previous practicals to the near ones in the future.
To add on, I am thankful that I was able to clarify my doubts with my teammates and that we were able to work cohesively to try and finish the activities as quickly as we could. I was able to develop my inter-personal skills to convey what my suggestions were to to my team mates. The past me would be apprehensive to ask my classmates any questions as I was afraid of the judgement that I would receive. However, I found that I learn better when asking my friends questions as they will explain the concepts to me in a simpler way such that I can understand it easily. Hence, I also learned that I should not be scared to ask questions as I would only be helping and not harming myself.
I really did not expect this, but I actually enjoyed myself while constructing the gears and using "trial and error" to figure out the best possible solution to get the highest gear ratio. It was exhilirating and also frustrating at the same time whenever we were still stuck on the same gear ratio. However, whenever we managed to get a different ratio, I felt like as though there was an adrenaline rush 😂 and this motivated me even further to try and come out with more ways to increase the gear ratio.
Im glad that I got to work with my teammates for the first time and I had a lot of fun doing so😁This practical also taught me how to persevere and I found this trait to be very important as I progress in my poly life huehue😌
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