Gears

Gears Documentation Blog Entry 

 

In this page, 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: 

1. Calculation of the gear ratio (speed ratio)  

2. The photo of the actual gear layout. 

3. Calculation of the number of revolutions required to rotate the crank handle. 

4. 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: 

Definitions:

Gear module: Refers to the size of one teeth on the gear in (mm)

Pitch Circular Diameter: Refers to an imaginary circle that passes through the contact point between 2 gears that are meshing, and it represents the diameters of the 2 friction rollers in contact and it moves in the same linear velocity

Relationship:

PCD = m*z

PCD: Pitch Circular Diameter

m: Gear module

z: no. of teeth

Therefore, by referring to the formula, by increasing the gear module or the no. of teeth, the PCD would also increase. This is because by increasing either the no. of teeth or the gear module, it would cause the diameter of the circle created by passing through the contact point between the 2 gears to increase.

 

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

As the gear ratio increases, the output speed of the gears would decrease as gear ratio is calculated by dividing the no. of teeth of the follower gear over the no. of teeth of the driver gear. Therefore, the speed at which the follower gear would turn would be lower with the increase in the no. of teeth of the follower gear, resulting in an inverse proportion between gear ratio and output speed.

 

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

As gear ratio increases, torque decreases as an increase in gear ratio would cause the speed of the output to decrease and with this decrease in speed, the force that causes the rotation of the gear would also decrease, resulting in an inverse proportion between torque and gear ratio.

 

 

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

One way would be to increase the gear ratio. By increasing

 the gear ratio. By increasing the gear ratio, the no. of rotations

made per press would increase which would result in higher

efficiency.

Another way would be to increase the length of the connecting

piece between the handle and the gears. This would prevent it

from resting in a horizontal position, causing it to jam after 1

press. By increasing the length, it would prevent the piece from

resting in a horizontal position, mitigating this issue.

 

 

 

 

 

 

 

4. Below are the description on how my practical team arranged the gears provided in the practical to raise the water bottle.  

1. Calculation of the gear ratio (speed ratio). 

Gear ratio = 4/3 * 10/3

= 40/9

 

2. The photo of the actual gear layout. 

 

3. Calculation of the number of revolutions required to rotate the crank handle. 

h = 200mm

1 rotation = 𝝅d

d = 22mm

No. of rotations = 200/𝝅d

= 2.9

Gear ratio = input/output

4.44 = input/2.9

Input = 4.44 * 2.9

= 13

 

4. The video of the turning of the gears to lift the water bottle. 

 

 

5. Below is my Learning Reflection on the gears activities 

So when Mr Chua told the class that the next practical was going to be on gears, I initially thought that it was going to be easy, I mean, how difficult can a practical on gears be. He then mentioned that there was a e-learning package that we had to go through in order for us to benefit more from the practical and also help us for the quiz at the end of the class. After going through the package, I was quite shocked as I didn't know that there was so much to gears and this helped me to prepare for the practical as it wasn't going to be as easy as I thought.

When the day came, I went into the lab and were tasked to complete a worksheet that helps us refresh whatever was mentioned in the learning package. Once done, we were then tasked to work on the first activity, which was to create a gear train that can pull a bottle of 500ml 20cm above the ground. Initially, I thought that we had to go through the calculations before starting to assemble. However, we found doing all the calculations too troublesome and decided to dive straight in and start assembling. We decided that since we needed to have a compound gear, we would stick it at the end with the string to pull the bottle up. With that, we decided to work backwards and assemble the train that way. Since we had to use all of the gears, it ruined our plan of making it linear as there isn't enough space on the given board and thus, we had to make space for the rest of the gears resulting in the shape of our train. During our assembly, since we didn't really have a plan, it was kind of tricky on deciding which gear should come first since they are all in various sizes. After we figured all of that out, we managed to assemble the train that was strong enough to pull the bottle up. However, since we didn't calculate anything, the cranking of the handle wasn't as smooth as we wanted but it managed to get the job done so we were happy that it's done and we moved on to the next part of the practical.

So, moving onto the next part of the practical which was to assemble a handheld fan using the gears. This part was rather easy as we just had to follow a reference picture and assemble the gears properly. The only part that posed of a small problem was that when we pressed the handle, the fan blades wouldn't turn as the piece that was connecting the handle and the gears was quite loose and didn't turn the gears on some occasions and because of this the wind produced wasn't what we expected. We were expecting a decent amount of wind, but the wind produced came nothing close to it. Therefore, we had to make some minor adjustments to the fan to make it more secured and finally we managed to complete this part of the practical. The fan managed to produce the amount of wind I was expecting and with that, we concluded this practical session.

In conclusion, the whole experiment was quite fun as it was a new experience for me since I've never really dealt with gears before, so this experience was quite enlightening for me. Through this practical, I realised that dealing with gears isn't as simple as I thought it was initially and there was definitely more to it than I realised. This practical also made me have a deeper understanding of gears and how they can be really useful in specific scenarios. I really look forward to the next time we have to deal with gears and really put this experience to good use!