Gears Documentation Blog

 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:

⛭ Gear module:

Gear module is the unit of gear tooth size.

⛭ Pitch circular diameter:

Pitch circular diameter refers to the straight line that passes through the center of the gear to the midpoint of the length of the teeth around the gear.

⛭ Relationship between gear module, pitch circular diameter and number of teeth:

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

Since Speed ratio = Input ÷ Output,

A lower (🠇) speed ratio would mean that there is a higher (🠅) output speed whereas

A higher (🠅) speed ratio would mean that there is a lower (🠇) output speed 

[Assuming input remains the same]

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

Since Gear ratio = Output ÷ Input,

A higher (🠅) gear ratio would mean that there is a higher (🠅) torque output whereas

A lower (🠇) gear ratio would mean that there is a lower (🠇) torque output

[Assuming input remains the same]

3. Below is the proposed design to make the hand-squeezed fan better
   
   Initial hand-squeezed fan design

Proposed Design

1. Screw the fan onto the spur gear shaft to secure it to the device better instead of just attaching it together so that it does not fall off easily.

2. Add some cover to the fan blades so it would be safer for the user.

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 = Output ÷ Input,
                 = No. of teeth on follower gear ÷ No. of teeth on driver gear

Gear ratio (1) = 30/30 = 1
Gear ratio (2) = 30/30 = 1

Gear ratio (3) = 30/20 = 1.5

Gear ratio (4) = 40/30 = 1.33

Gear ratio (5) = 40/20 = 2

Gear ratio (6) = 20/40 = 0.5
Gear ratio (7) = 40/40 = 1

Gear ratio in the end = 1.5 x 1.33 x 2 x 0.5
                                  =1.995

2. The photo of the actual gear layout.

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

Distance travelled = 200mm

Winch diameter = 22mm

RPM2 = 200 ÷ π22 = 2.89

Gear ratio = RPM1 ÷ RPM2

RPM1 = 2.89 x 1.995
           = 5.76 revolutions

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

5. Below is my Learning Reflection on the gears activities

From the practical, I learnt a lot about gears and how to calculate gear ratios and such. I also learnt how to utilise gears and sequence them in such a way that can have higher speed or torque outputs. For me, it was quite interesting to figure out how to assemble the hand-squeezed fan even though it was honestly quite difficult to construct since some of the parts don't fit together nicely. As a result, it took some coordination to put the pieces together since some of the gears were upside down and kept falling out of place, but I think the end product was satisfying as it managed to work properly and actually quite smoothly.

The second activity on arranging the gears to raise the water bottle was genuinely such a painstaking process since not only did we have to figure out the correct configuration for the gears, arranging them onto the board was so time consuming. We also made the mistake of putting them onto the board from each end and when we reached the middle, the last gear did not have enough space, which resulted in us wasting a lot of time and almost being unable to finish. Moreover, the gears did not turn very smoothly and there were a lot of wear and tear after a while, which made the turning even more clunky. Thankfully, we managed to conquer this obstacle and completed the activity in time. Overall, I think this was a positive learning experience and I am honestly curious to see how I would be able to implement the concept of gears into our product for CPDD in the end.