Gears

 1. These are the definitions of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth

Gear module, m, refers to the size of a gear's teeth. The larger the gear module, the larger the gear teeth. Gears that mesh together have the same module.

Pitch circular diameter, PCD, refers to the imaginary circle that passes through the contact point between two meshing gears. It represents the diameter of two friction rollers in contact and moves at the same linear velocity.

Number of teeth, z, refers to the number of teeth on a gear.

The relationship between the three variables is, m = PCB/z.

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

The higher the speed ratio, the slower the output speed for a pair of gears. Gear ratio refers to Number of teeth of the follower gear/ Number of teeth of the driving gear. When the gear ratio is >1, the following gear is larger than the driving gear, so the output speed of the pair of gears is lower. When the gear ratio is <1, the following gear is smaller than the driving gear, so the output speed of the pair of gears is higher.

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

The higher the speed ratio, the higher the torque for a pair of gears. Gear ratio refers to Number of teeth of the follower gear/ Number of teeth of the driving gear. When the gear ratio is >1, the following gear is larger than the driving gear, so the torque of the pair of gears is higher. When the gear ratio is <1, the following gear is smaller than the driving gear, so the torque of the pair of gears is lower.

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

The hand squeezed fan makes use of the speed multiplying gear arrangement in a compound gear train to allow the fan to spin. However, an issue faced was that there was little to no wind from the fan, which means that the fan was spinning too slowly.

The design can be improved by making the chassis of the fan larger so that a larger driving compound gear can be attached.  

By changing the chassis size to fit larger driving gears, the follower gears would have a higher output speed, in turn increasing the speed of the fan and producing wind.

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 gear ratio (speed ratio)

We arranged the gears in such a way where the longest screw provided (2cm) is able to secure the gear onto the board full of holes. With countless time spent on planning, execution, screwing and unscrewing, we were able to come up with our final result.

Speed ratio = 40/30 x 40/12

                   = 4.44

     b. Photo of the gear layout

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

Mass of water = 600g = 0.6kg

Weight of water = 0.6kg x 9.81N/kg

                           = 5.886N

Diameter of winch = 6.3cm

Radius of winch = 3.15cm = 0.0315m

Torque = 5.886N x 0.0315m

            = 0.18541 Nm

Distance travelled by bottle = 200mm = 0.2m

Distance travelled with 1 winch revolution = 2(22/7)(0.0315m)

                                                                     = 0.19792m

Number of revolutions required = 0.2/0.19792

                                                   = 1.0105 revolutions

     d. Video of the turning gears to lift the water bottle

5. Below is my learning reflection of the gears activities

In conclusion, the gears activities were very engaging and also extremely important. Chemical engineering borrows a lot of skills from mechanical engineering as a lot of machines are needed for manufacturing in a process plant. For us to succeed in life and put food in our stomachs in the future, we have to master the basics of mechanisms, especially gears, the most basic of the basic one.

The session was engaging as it forces me to use my brain a lot. To solve most of the problems I faced in this session, I have to use metacognition and recall my past knowledge of physics and robotics all the way back from secondary school. This practical session also added even more knowledge to what I already know. I've learned more about gear ratio and that it is not just the teeth ratio. I learned about torque calculations and the gear ratio for compound gear trains.

My group and I have also faced multiple challenges in our activities. 

In activity one, we faced the issue of gear stacking. We have failed to consider that the longest screw available for us was only 2cm long and stacked the gears too high. As a result, the whole group had to get together, painstakingly unscrew every gear on the board and devise a new plan that can be fitted onto the board. The calculations also have to be redone due to this. I also appreciate how much smaller the holes on the board are compared to the screws. It trains our finger strength screwing and unscrewing the gears using the L screw key which we would put to great use in the future.

In activity two, the middle axle of the chassis was broken before construction, Failing to notice that, our group build the fan with the broken parts and as a result, the fan became defective...

This has taught us that, before we execute a plan, we need to check for any errors within the system as even one small variable that goes wrong can cause everything to go haywire.

In conclusion, I believe that this practical session was very excellent and important. It allows the group to work together and understand an important concept in mechanics that we all can apply in the future. Overall, enjoyed, 9/10.