Gears

On Thursday, 10th November 2022, my group had our gears practical class. This was to help us prepare for our product design project which requires a gear function in the design. This was helpful to give us a hands-on experience with gears so that we can complete our product design with lesser difficulty.

The practical session was a mixed bag as there were some parts that were much easier than others. For example, the practical worksheet was more difficult than we expected and as such, we spent way too much time on completing it and even then, we still had many questions that we couldn't answer. Setting up the gear train to lift the bottle was also difficult as we wrongly assumed that we needed more speed instead of torque to lift the bottle. This caused us a lot of time and made us panic and have to rush for time at the end of the practical.

However, besides those parts, the rest of the practical went quite smoothly. Our group worked very well together, communicating constantly and making sure we all knew what task we were doing at the moment. Setting up the hand-operated fan was also easier than expected which helped us to complete the task before the end of the practical. The test at the end wasn't too difficult since we had just applied much of the knowledge we learned in the videos and it was quite fresh in my mind. 

These were some of my takeaways from the practical session:

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. The pitch circular diameter is also known as PCD, which is the diameter of the gear, assuming that the teeth cancel out the negative space between each other.

The relationship between gear module, PCD and no. of teeth : Gear module = PCD / No. of teeth

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

Gear ratio = input gear speed / output gear speed, where input gear speed is the speed of the driver gear (the gear that the operator controls) and output gear speed is the speed of the follower gear (the gear being moved by the driver gear).

Higher ratios (lower gear ratio numerical value) give better torque and lower ratios (higher gear ratio numerical value) allow for higher top speeds.

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

Reducing the number of teeth of the follower gear can help to reduce the gear ratio which allows for more torque and thus spinning the fan at a higher speed due to more force being applied.

Adding lubrication, like grease, would help the gears to spin faster and thus spin the fan blades faster.

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.

a)   Our gear ratio calculation:

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

Gear ratio = 1 x 4/3 x 3/4 x 4/3 x 2 x 10/3 x 1

Gear ratio = 8.89

b)

c) 

Measured winch radius = 5.7/2

Measured winch radius = 2.85cm

Circumference of wheel = 2𝝅(2.85)

Circumference of wheel = 17.91 cm

No. of revolutions required = [1/(17.91/100)] x 0.2

No. of revolutions required = 1.12 revolutions

d) 

Video of gear train lifting bottle