Gears

 Helooo everyone!

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:

• Calculation of the gear ratio (speed ratio)

• The photo of the actual gear layout.

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

• The video of the turning of the gears to lift the water bottle.

• 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 (m) refers to the size of teeth of the gear. The larger the module number, the larger the size of teeth. Additionally, gears that mesh together have the same module. 

Pitch circular diameter refers to the imaginary circle that passes through the contact point between 2 meshing gears. It also represents the diameters of 2 friction rollers in contact and moves at the same linear velocity. 

Unit: mm

As for the relationship between gear module, pitch circular diameter (PCD) and number of teeth (Z), it can be shown through the 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.

Speed ratio is defined as the ratio between the number of rotations of the follower gear to the number of rotations by the driver gear.  

Torque is a moment that acts about a longitudinal axis and is given by the formula force x distance of the axis of rotation. 

Unit: mm

The higher the gear ratio, the higher the torque, the lower the output speed. 

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

For the second activity, we were tasked with making a hand powered fan by following the manual given to us. However, the fan couldn’t really turn but we still managed to take a video of it 

This is a sketch that my group and I came up with: 

Based on the above, we calculated the speed ratio which is:

For a better hand squeezed fan, to me, it would mean that the fan would be able to turn faster and more easily with lesser friction. 

Assumptions: 

Types of gear used can be changed 

Gears are the can be taken from activity 1 (1 idle 2 gear compound) 

From activity 1 the idle gear and gear compounds are as follows: 

• 2 Gear compound (20T-40T)

• 1 Gear Compound (12T-40T) 

• 1 Gear Compound (20T-30T) 

• 1 Gear idler (30T)

• 1 Gear idler (40T) 

Using the above, arrange the gears in the convention so that the gear ratio is kept as low as possible for a higher output speed. 

4. How my practical team arranged the gears provided in the practical to raise the water bottle, consisting of:

• Calculation of the gear ratio (speed ratio)

• The photo of the actual gear layout.

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

• The video of the turning of the gears to lift the water bottle.

• My Learning reflection on the gears activities. 

For this activity, we had to lift a bottle of 600L off the ground using the gear system that we came up with as a group. 

We started off by arranging the gears into the arrangement that we thought was the best to help lift the bottle. 

Firstly, we sorted out the gears by the number of teeth they had, this was so that we could figure out which had more teeth than the other which would help us arrange the gears to help us obtain a higher gear ratio. 

The first arrangement we came up with did not work as when setting it up on the ‘board’ itself, we realised that some parts of the gear clashed with each other meaning that it would be difficult to rotate it to lift the bottle.

1st arrangement (only part of it):

It took a few tries and this was what we came up with:

Based on the above sketch, we calculated the gear ratio:

And with that, this is our actual gear layout:

Based on the above, we then calculated the number of rotations:

When we tried to lift the bottle off the ground, we realised it was a bit difficult as our last 3 gears were shaky. Hence, the above value is just a theoretical one. 

This is our vid: 

Learning Reflection:

Initially, I thought that gears would be a dry topic as I thought we would only be doing activities that make them turn. Even though that's true, watching the pre- experiment videos made me realise that there is more to gears than just turning. We have to take factors like: gear ratio, torque and gear module into consideration for the gear system itself to actually work. 

During the practical, as you can already tell, my group and I struggled to come up with an arrangement that would work. By this I mean that, we were ‘ok’ in terms of thinking of an arrangement but whether or not it worked that was the main problem. It took us at least 20 minutes to think of 1 arrangement and set it up and wait for the moment of truth 😰. If it doesn’t work, we would have to dismantle it (which of course takes time) and quickly come up with another solution. Time management was the main objective here as we only had one hour to come up with an arrangement that could actually work, calculate the gear ratio and also film the video. This meant that we had to be quick on our feet hence, we decided to split the work. Firzanah and Kelvin helped to calculate the gear ratio while Darel and I were setting up. 

For the second activity, we had to arrange the gears according to the handout which wasn’t exactly a problem. The only issue that my group had was time as we took too long for the first activity meaning that we had lesser time for this one. But we managed to scrape by and we got to film the video (as shown above) 

Additionally, at the end of the practical, we had to solve the questions which included calculating the number of rotations (we did it after class as during the practical, we were too focused on coming up with an arrangement). It was really challenging but thankfully Mr Chua actually gave us some hints. 

In conclusion, I really enjoyed learning about gears and applying the knowledge we learned during the practical session. The practical session was really fun to me as we were given the opportunity to ‘freestyle’ and come up with our own unique arrangement. We also had to multi- task and do several things at once all within a gruelling 1.5 hours. Despite all the rush, it was worth it as we managed to produce some results. I look forward to more sessions like this 😊 

Till the next!! :D