Gears
Hello again, for this entry, I will be going through week 4's practical, Gears! 😊
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 activity.
Firstly, The definition of gear module, pitch circular diamter and the relationship between gear module, pitch circular diamter and number of teeth:
Gear module refers to the size of the gear teeth. Its unit is in millimetres[mm]. The larger a module number, the larger the size of the teeth. Gears that mesh will have the same module.
Pitch Circular Diameter (PCD) is the imaginary circle that passes through the contact point between two meshing gears. It represents the diameters of two friction rollers in contact and moves at the same linear velocity.
The number of teeth is the number of teeth contained in a gear .
Gear module is related to PCD and the number of teeth by an equation (insert picture)
Gear module(m) is directly proportional to the PCD and it is inversely proportional to the number of teeth.
Next, to obtain a speed ratio, the gear ratio has to be less than one. This decreases the torque which then increases the output speed.
The general relationship between gear ratio and torque is the for a gear ratio greater than 1, the torque will increase whereas if the gear ratio is lesser than 1, then the torque will decrease.
There were 2 activities done during the practical itself, activity 1 is the lifting of a water bottle off the ground using a sequence of gears and activity 2 is the assembly of a hand-powered fan using an axel and gears. Specifically for activity 2, you might ask, how are we able to create a better fan? 🧐
For the fan to be improved, what do we want? 🤔
Faster speed.
How do we achieve this?
Changing the gear ratio. Specifically lowering the gear ratio to be less than 1. Why?
Well, as mentioned earlier, as the gear ratio decreases, it will become a speed multiplier(ratio), meaning that the torque will decrease resulting in a higher output speed. To make the hand-squeezed fan better is to make it go faster in order to produce a more powerful wind. Thus, we need to increase the speed of the fan which is why the output speed needs to be higher, which is created through a lower gear ratio.
Based on the design given, in general to obtain the lowest gear ratio, the follower gear has to always be smaller than the driver gear. Using the 3D printing skills that we have learned in CP5065 Introduction to Chemical Product Design, we can first try to replicate the gears in the drawing given to us. Once the gears have been designed on Fusion 360, we can adjust the sizes accordingly such that it will fit the requirements to obtain the lowest gear ratio with respect to the size of the space available in the fan holder. When designing the gear, make sure to include two gears on one piece. This is to ensure that we can obtain a compound gear, which can lower the gear ratio. 😁
For activity 1, we first need to find the sequence of gears and then calculate the overall gear ratio which is:
Gear ratio = 40/30 x 30/12 x 40/20 = 6.6667
Next calculation describes the number of revolutions required to rotate the crank handle.
Distance bottle needs to move above ground = 200mm
Circumference of the crank handle = 2π(31) = 194.78mm
Amount of revolution of output gear = 200mm / 194.78mm = 1.03 revolution
Amount of revolution of input gear = 1.03x6.6667 = 6.87
Now I will be showing you the video of me turning the gears to lift the water bottle 😆
Last but not least, my learning reflection 👀
This practical was quite fun because it was really engaging. Dr Noel had given us a test on whether we are able to spot the mistake in Activity 1’s sketch and we were able to spot the mistake. Not just that, all of us were sufficiently prepared before the practical so we knew what each term meant in the worksheet and just needed to fill in the blanks. However, there were some questions that we did not know for a brief moment and resorted to asking the other groups about it. There was a total of 2 questions that we were unsure about, and when one of my groupmates, Samantha, went to ask the other groups, the rest of us were somehow able to come up with the solution, which is pretty funny because we figured it out on our own yet Samantha had to ask the other groups about it.
Activity 1 took the longest and I feel that we could have made a better layout. If only we had more time to figure out the best sequence of gears as my group were the last ones to complete activity 1. I also feel that we should be able to somehow have two walls to hold the gear, as if the gear is in a close position, or maybe have a longer shaft connect the two gears in one piece because I heard that one of the groups managed to obtain a gear ratio of 26 but were not able to actually create it because of the limitations of the setup we were given. With a longer shaft then we can definitely create a better layout of gears.
As for activity 2, personally I was not able to take part in the activity with the other groupmates because I was really busy setting up and creating the gear layout for activity 1.
All in all, this experiment was quite fun because of how much hands-on work there is. If given the chance to redo this experiment, I definitely will redo it and plan out the layout before actually doing it.
Thanks for tuning in! See you next entry 😄
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