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:

Gear module refers to the size of the gear teeth. The larger a module number, the larger the size of the teeth. Gear that are mesh together requires the same gear module.

The Pitch Circular diameter is the imaginary circle that passes through the contact point between two meshing gears. it represent the diameter of two friction roller in contact and move at the same linear velocity.

Relationship between module (m), Pitch circular diameter (PCD) and number of teeth (z) :

m=PCD/z

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

The greater the gear ratio, the lesser the output speed for a pair of gear.

The lower the gear ratio, the greater the output speed for a pair of gear

If gear ratio is more than 1, output speed is lower than input speed

If gear ratio is less than 1, output speed is greater than input speed

If gear ratio is equal to 1, output speed is the same as input speed

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

The greater the gear ratio, the greater the torque for a pair of gear

The lesser the gear ratio, the lesser the torque for a pair of gear

if gear ratio is more than 1, output torque is greater than input torque

if gear ratio is less than 1, output torque is less than input torque

if gear ratio is equal to 1, output torque is equal to input torque

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

Simply flip the third gear (9/20).

This will increase the gear ratio of the of the hand squeezed fan

 Old Gear ratio= 10/20 × 9/9 × 20/20 =0.5

 New Gear ratio = 10/20 × 9/20 × 9/20 = 0.10125

As you can see, the new gear ratio is smaller than the old gear ratio, hence speed is greater in the proposed design

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 = 40/30 × 40/10 × 40/20 × 1 × 1  = 6.67

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. Below is my Learning Reflection on the gears activities

 This practical help strengthen my knowledge for mechanism, or gears to be more accurate. Overall, it was a pretty fun practical, however I feel that this practical would be better if it is individual or groups of 2 to 3. This is due to gears being so small, making everyone having to crowd around, but the lab table is so long so it is feasibly impossible. This practical in my opinion is the prime example of too many cook spoil the soup. Just like how increasing the gear ratio decreases the speed. Increasing the amount of people per team decreases the efficiency.