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:

a.    Calculation of the gear ratio (speed ratio)

b.    The photo of the actual gear layout.

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

d.    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:

A gear module is a unit of size that indicates how big or small a gear is. It is calculated by using the PCD divided by the no. of teeth(n) of the gear. PCD is also known as the pitch circular diameter, which is simply the diameter of the gear with teeth.

The relationship between gear module, PCD and no. of teeth: 

m = PCD/ n

 

 

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

Gear ratio = input gear speed / output gear speed

In which, Input gear speed is the speed of the driver gear (the gear that you control) and Output gear speed is the speed of the follower gear.

 

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

Gear ratio = output torque/ input torque 

Torque = Force x Radius

 Higher gear ratio - increases force - higher torque

 

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

To increase the gear ratio, we can alter the number of teeth on the gear.

The provided gear:

1. reduce the number of teeth on the compound gear so that the gear ratio increases and lesser rotations are needed to turn the fan 

2. Adding lubrication such as grease or oil would help gears to rotate smoother 

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 the gear ratio (speed ratio).

Gear ratio 1 = 40/30

Gear ratio 2 = 30/12

Gear ratio 3 = 40/20

Gear ratio 4 = 40/20

Gear ratio 5 = 40/20

Total gear ratio = 26.666 =26.7

 

 

b.    The photo of the actual gear layout.

 

 

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

1 revolution of end follower gear = 2 r = 2 (29mm) = 182.21mm

Length needed to be raised = 200mm

Revolution of winch required= 200/182.21 = 1.097

Revolution of crank needed = 1.097 x 26.7 = 29.3 turns

 

d.    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 focuses on a mechanism that we have learned before which is gears. In this experiment, we went in-depth on how gears work and how it is being used in our everyday lives. In the videos provided, I have realised that gears are commonly used everywhere such as bicycles and pulley systems. The teeth of the gears mesh perfectly causing it rotate together in opposite directions. Usually, an idle gear is placed in between 2 gears so that the driver gear and follower gears are rotating in the same direction. This experiment has also allowed me to experience using a compound gear. The compound gear is a number of gear with different number of teeth fixed together, this causes the gears to rotate in the same speed and direction. It is also used to alter the gear ratio which played an important role in activity 1 of this practical.

In activity 1, we were tasked to configure all the gears provided to achieve the largest gear ratio. The gear ratio is the ratio of number of teeth of the follower gear to the number of teeth in the driver gear. In other words, gear ratio =  where y number of rotations in the follower gear = x number of rotation in the driver gear. Initially, my group configured our gear to have a gear ratio of 2.96. We thought this was the final and largest gear ratio but decided to keep trying until we got our final gear ratio of 26.7. This has taught me the significance of gear ratio and how a slight change in position can result to a big change in values. Additionally, we were also tasked to lift a bottle of water by 20 cm off the floor at the fastest speed. This was a challenging process for us as we had contradicting opinions on the gear ratio needed. We eventually concluded that the highest gear ratio is needed as that would mean that lesser revolution on the driver gear would result in larger rotations of the follower gear, causing the bottle of water to rise faster. However, we were able to secure the gear configuration we made previously on the metal board using the Allen key but the hot glue used to secure the string to the winch gave us an obstruction and we were unable to rotate further than 10 revolutions. All in all, bulk of the time given to us were used to configure the gear ratio. It showed me the importance of teamwork, and how seeing things in different perspectives/ giving our personal inputs would benefit the efficiency of the group significantly (like the gear ratio😐 )

Activity 2 was slightly different as we did not need to configure any gears. However, we used the same method of calculating the revolutions needed from activity 1 to find out the revolution needed to rotate the fan. This experiment showed me how hand-powered fans operate. We also realized that the illustration printed on the worksheet is wrong as the last gear has to be flipped.

In conclusion, gears are a very useful mechanism that we should not take for granted. After this experiment, I also realised the important roles gears play in many machineries and equipment like car engines. I personally feel that using compound gears for the water heater chemical product my group made in ICPD would have allowed us to increase the efficiency of the heater rising up but at the same time reduce the space and the need for an idle gear. In addition to that, gears showed us an important lesson we all should learn which is to work hand in hand with the people around you to see a great positive result :D👉👉