Gears

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.

Gear module (m) is the unit of size that indicates how big or small a gear tooth is. A bigger m means that the size of the gear is bigger. Two meshing gears means that the two gears have the same module. 

Pitch circular diameter (PCD) is the diameter of the pitch circle which will contact the pitch circle of another gear when meshed. 

Number of teeth (z) denotes the number of gear teeth

Formula ➤ m=PCD/z

2.  The relationship between gear ratio (speed ratio) and output speed, between gear ratio and torque for a pair of gears.

Gear ratio can be defined as the (number of teeth of the follower gear)/(number of teeth of the driver gear)

it can also be defined as  ➤ Gear ratio=T2/T1=N1/N2 where,

T1 denotes torque of driver gear, T2 denotes torque of follower gear

N1 denotes rotational speed of driver gear, N2 denotes rotational speed of follower gear

when Gear ratio is <1, the output speed of the output gear is greater or increased. However, the torque of the gear is compromised. 

when Gear ratio is >1, the output speed of the output gear is compromised while the torque of the gear is increased.

3.   How I can design a better hand-squeezed fan, including the sketches

To make the fan spin faster, the value of gear ratio must be as small as possible. Hence, my group decided to arrange big gear to small gear. 

      Hence our proposed design is:                

 Our Sketch: 

Speed ratio: 

Speed ratio = (20/20) x (20/10) x (9/20) = 0.9

Video of the spinning fan: 

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)

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

                                     = 26.67

b.  The photo of the actual gear layout:

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

total length moved = 0.2m

Circimferences = 2πr = 2π(0.063/2) = 0.19792m

revolutions = 0.2/0.19792 = 1.010507

Input revolution = Gear ratio x output revolutions

                            = 26.67 x 1.010507

                           = 27

d.   The video of the turning of the gears to lift the water bottle:

  5. My Learning reflection on the gears activities.                                                                              

This practical was fun and engaging. For the first activity, my group has trouble deciding how to arrange the gears. We went ahead with arranging it from small to big to get a higher gear ratio, We also arrange it in a ZigZag manner to have more space. The hard part of this is to screw the gears in their position, especially from the last one, the one with the winch. The last one had to be screwed from the back as the screw is not long enough to screw it from the front. We also loosen the screws a bit as well for smoother rotation of the gears.

In the second activity, we arrange from big to small to get the smallest gear ratio so that fan can spin faster. it was fun to see how fast the fan move with a single crank on the handle. From this practical, i find that although it was fun and engaging, we should do sufficient pre-preparation before coming for the pratical session. This is so that we can better execute our planning like the arrangement of gears so that we have more time to enhance gear performance if we want to!