GEARS

 Gears

In this page, I will be sharing about a summary of the important definitions relating to gears and more about the activity conducted during the practical which is to lift a filled 600 ml water bottle using gears.

Definitions

Gear module: is a unit of gear tooth size. Gears will only mesh if they have teeth of the same module.

Pitch Circular Diameter (PCD): is the diameter of an imaginary circular line which passes through the contact point between two meshing gears.

Relationship between Gear Module (m), PCD and number of teeth (z): 

m = PCD/z

Gear Ratio (Speed Ratio):

number of teeth of follower gear/ number of teeth of driver gear


Relationship between Gear Ratio, Output Speed and Torque:

  • Gear ratio < 1, higher output speed, lower torque
  • Gear ratio > 1, lower output speed, higher torque


Proposed Design to Make Hand-Squeezed Fan better

  • For fan to be cooler, output speed of gear connected to blades should increase
  • By using driver gear with greater number of teeth, gear ratio can be smaller.

Activity 1: Lifting Water Bottle using Gears

1. Calculation of Gear Ratio
Gear Ratio

= (40/30) x (40/20) x (30/12) x (40/20) x (30/20) x (40/30)

= 26.67

2. Photo of Actual Gear Layout 


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

Total length 
= 200 mm
= 0.2 m

1 revolution of which to move length of rope 
= 2π (0.063/2)
= 0.1979 m

For 1 revolution
= 0.2/0.1979
= 1.011

Number of revolutions of crank handle
= 1.011 x 26.67
= 27

4. Video of turning of gears to lift water bottle



Learning Reflection

During this practical, my group and I got to use the knowledge from the pre-learning videos to think of the most efficient method to lift up the water bottle. During the discussion, we were all clueless as to how to start. The team decided to approach the problem methodically. In the end, the group aimed to achieve a high gear ratio. When gear ratio is high, torque will be high and it will be easier to lift the water bottle. Although the output speed would be lower, it was not the team's main concern. After many trial and error of rearranging the gears we finally managed to obtain the highest gear ratio we could which is 26.67. Initially we wanted to arrange the gears according to size in such a way where the smallest gest gear is beside the driver and the biggest gear is beside the winch. However, this did not give us the gear ratio we wanted and we had to make many attempts on the arrangement of gears and calculations of gear ratio.