Gears
Hello! Welcome back to my 2nd blog!
Today, I will be sharing with you my experience and what I have learned in my most recent practical "GEARS". 👍
Let's Go!!!😊
In this page, I will describe:
- The definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth.
- The relationship between gear ratio (speed ratio) and output speed, between gear ratio and torque for a pair of gears.
- How I can design a better hand-squeezed fan, including the sketches
- How my practical team arranged the gears provided in the practical to raise the water bottle, consisting of:
- Calculation of the gear ratio (speed ratio)
- The photo of the actual gear layout
- Calculation of the number of revolutions required to rotate the crank
handle - The video of the turning of the gears to lift the water bottle
5. My Learning reflection on the gears activities.
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 is the unit of size that indicates how big or small a gear is. It is the ratio of the reference diameter of the gear divided by the number of teeth.
Pitch circular diameter is the diameter of the circle which passes through the centre of the gears.
The relationship between gear module, pitch circular diameter and number of teeth can be seen using this formula:
PCD = m x z
Where,
PCD - Pitch circular diameter
m - Gear module
z - 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 the number of teeth of the output gear to the number of teeth of the input gear.While, speed ratio is the ratio of the output speed to the input speed. This shows that gear ratio is NOT the same as speed ratio.
Relationship:
When the gear ratio decreases, the output seed increases. Vice versa when gear ratio increases, the output speed decreases.
From this, we can conclude that gear ratio is inversely proportional to output speed.
Below is the relationship between gear ratio and torque for a pair of gears.
As I have stated earlier, gear ratio is the ratio of the number of teeth of the output gear to the number of teeth of the input gear.Torque is the measure of twisting force, calculated as the product of circumferential force multiplied by the radius of the gear.
Relationship:
When the gear ratio increases, the torque for a pair of gears will increase as well.
When the gear ratio decreases, the torque for a pair of gears will decrease.
From this, we can conclude that gear ratio is directly proportional to the torque for a pair of gears.
Initial design:
3. Below are the proposed design to make the hand-squeezed fan better:
Here's a slow-mo video on the hand-squeezed fan:
Proposed design:
Modifications
- The number of teeth of the input gear (driver gear) is increased from 20 to 40.
- The number of teeth of the output gear (driven gear) is decreased from 9 to 5.
This is done to decrease the gear ratio. Since gear ratio is inversely propertional to the output speed as stated in Question 2, with a lower gear ratio, the output speed will be higher.
Calculations
Speed ratio of initial design = 9.88
Speed ratio of proposed design = 35.6
Therefore, comparing the speed ratio of both designs, the speed ratio of the proposed design is 3.6 times larger than that of the initial design.
4. Below are the description on how my practical team arranged the gears provided in the practical to raise the water bottle.
For this activity, my team and I initially wanted to use a combination of idlers and compound gears. However, we were not able to connect form a gear train using there due to the lack of skills. To prevent wasting any more time, we decided to just use idlers for our gear train.
Number of teeth of input gear = 30 teeth
Number of teeth of output gear = 40 teeth
Gear ratio = 40/30
= 1.33 (3sf)
b) The photo of the actual gear layout.
Distance travelled by the water = Distance travelled by the output gear
= 200 mm
Diamter of the winch = 22 mm
Number of revolutions of the output gear = 200/22π
= 2.89 (3sf)
d) The video of the turning of the gears to lift the water bottle.
5. Below is my Learning Reflection on the gears activities.
Before coming into this practical session, we tasked to watch 4 youtube videos to learn the basic principles of gears. Having watched the videos, I learned how to calculate gear ratio as well as how the size of the gears affect the number of rotations. Personally, I feel that the videos helped me a lot during the practical session in both the calculations and constructing the gear trains.
Things I have learned through this practical:
- Gear ratio
- Speed ratio
- Torque
- Gear module
- Pitch circular diameter (PCD)
- How the number of teeth of gears affect the gear ratio and speed ratio
- Relationship between gear ratio and speed ratio
- Relationship between PCD, gear module and number of teeth
As you can see, I have learned a lot in this practical. Firstly, I think this is possible because the practical was very enjoyable and very hands-on which helped me apply the knowledge obtained from the youtube videos and further understand them. Secondly, I feel that the activities given to us were very simple which made it extra easier for me to understand the mechanism used.
Aside from my learning experience, I would like to say that I am very amazed at my team's performance. I think we did a very good job and everyone knew what to do. Everyone has good teamwork and we as a team have good chemistry. At the start of the practical, we decided to split the work so that we can finish both activities quickly and efficiently. Jian Lun and Brice worked on Activity 1 which is raising the water bottle using a gear train. While, Jianye and I worked on Activity 2 which is on the hand-squeezed fan. Yu Han was our photographer and she helped us with the calculation part. Because our work were divided, we indeed were able to complete them much earlier than the allocated time and our results were also outstanding.
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