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, is the size of teeth. A larger gear module means that the teeth is larger. A smaller gear module would mean that the teeth is smaller. gear module need to be same for gears in contact to work

Pitch circular diameter is 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.

The relationship between gear module, PCD and number of teeth is m=PCD/z

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

The gear ratio can be obtained by taking the number of teeth of the driven gear over the number of teeth of the driven gear.

The higher the speed ratio, the lower the torque and therefore the lower the speed of the output.

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

The higher the gear ratio, the higher the torque. When the gear ratio is >1, it is a torque multiplier. When the gear ratio is <1, it is a speeeeed multiplier. So when the driven is smaller then the driving, it is a speed multiplier, When the driven is bigger than driving, it is a torque multiplier.

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

What we are trying to achieve in the hand-squeezed fan is for the blade of the fan to spin faster. Therefore we will need to configure the gears in a way where they have the lowest gear ratio. This means that the driven gear must be smaller than the driving gear to allow lowest gear ratio. 

This is the proposed one by the manual but we did not like it as there was little to no wind. Upon closer look, we realize the last set of gears is a torque multiplier. So we decided to flip the last gear so that the larger gear is driving the blade if the fan. This worked out fine and this is how our fan worked

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)

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

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

5. Below is my learning reflection of the gears activities

This was a fun practical overall as there was a lot of thinking involved. During activity 1, we had to use the least force to produce the most force. So our team stacked all the gears together and manage to hit a gear ratio of 27. We then tried to put it on the grids and realized the longest screw is only 2cm and have to scrape our idea and remake it. This could have been easily prevented if we had read but all is good. Learning opportunity. 

Next was activity 2, we are tasked to build a hand powered fan, We managed to build the fan that generate the fastest speed. However, when we tested it, something was jammed in the fan. We then decided to open up the fan and realized there was a broken piece. We then dismantle the fan and constructed the fan with another set, This again could have been prevented if we had checked. But all is good. Learning opportunity...

Overall, i really enjoyed myself during this practical as it was really interesting, We need to apply what we learn in pre-practical and use it during this practical. Just reading the pre practical would not be enough as we need to really understand what we were doing. It was also fun thanks to my team, everyone was very high during the practical and it made it fun. This practical was definitely one of the most fun and most useful ones.