Blog 1: Gear(s)? I barely know her!
- harrenchd
- Nov 17, 2024
- 5 min read
Hey there! Thanks for coming around. I recall mentioning that I would miss blogging stuff like this last semester, and now that it's happened again... eh. ¯\_(ツ)_/¯
This blog will be about gears, so it might be a lil long-winded, but stay with me here.
Also, I don't know why the formatting is this weird but Wix isn't letting me fix it. Sorry about that!
What are gears?
Even before learning about gears, we ought to know what it is, yes? By definition, a gear is a circular mechanical device that transmits rotational motion and power from one shaft to another. What does that mean? I have no idea.
To put it simply, a gear is an object with teeth that when rotated, rotates other gears touching it.
Parts of a gear:
Surprisingly, as simple as they seem, gears have parts to them, namely the teeth and pitch circle. Most of the time, they are differentiated by the measurements of these parts:
Gear module(m):
To put it simply, a gear module is the size of each tooth on the gear. Not exactly sure what "size" in this context means, since height and width have different terminologies in terms of gear teeth.
Pitch circular diameter(PCD):
The pitch circular diameter is the distance between adjacent teeth on a singular gear. If it's hard to visualize, I added a diagram to show exactly that!
Number of teeth(z):
Seems pretty self-explanatory. The number of teeth on a singular gear is the number of teeth.
Here's a labelled diagram because I can't explain stuff well!
Wondering why this is all getting explained? Luckily for you, we're just getting to that part. These measurements are all related to each other when used in a gear system. Depending on the output you want, gears are placed in a sequence based on these three attributes which may give you a higher speed or torque. In a mathematical equation, they have the following relationship:
This means that increasing the number of teeth decreases the module size, while increasing the pitch circular diameter increases the module size!
Definitions and more terminologies:
It’s only gonna sound more technical and boring here, but theory is possibly the most important part when it comes to gears.
Gear ratio/Speed ratio:
The gear ratio is the ratio of the number of teeth between the driver gear and driven gear. The driver gear is the first gear that, well, drives the driven gear.
Relationship between gear ratio and two gears:
Similarly to the definition, the relationship between the gear ratios and the gears can be expressed in an equation like this:
The gear ratio determines the rate at which the driven gear will spin, or RPM (rotations per minute) for short. For example, if the gear ratio is higher than 1, the driven gear has more teeth than the driver gear, and thus the driven gear has a lower RPM. On the flipside, if the gear ratio is lower than 1, the driven gear has less teeth and therefore rotates more!
Funnily enough, this exact gear ratio can be applied to torque, but that's for a later part!
Torque:
By definition on the Oxford Dictionary, torque is "a force that tends to cause rotation". This means that the torque on a single gear allows it to rotate.
Relation of torque and gears:
Remember the part I mentioned that torque had the same equation for the gear ratio? This is because when the gear ratio is more than 1, the RPM of the driven gear not only decreases, but the torque of the gear increases as well. The relation of RPM and torque in the context of gear ratio can be expressed as this:
When the gear ratio decreases, RPM increases while torque decreases.
Likewise, when the gear ratio increases, the RPM decreases and torque increases, which can be shown in this equation!
Now that that’s over, here’s more boring stuff!
Improvements on the fan:
When we were experimenting with the gears in the hand-powered fan, I noticed that it was quite difficult to use as the cranking system kept jamming. We had to wait for the fan to stop moving before we could crank the handle again, which was quite annoying. Furthermore, the wind generated by the fan felt like it wasn't enough to cool myself down from the sweltering heat of Singapore.
To combat these problems, I brainstormed for some solutions that could solve it. Here are the results of my work!
Solution:
The reason (I think) the fan was not working properly was because the parts were not fitted well in the fan due to the inaccuracies that 3D printers have some times, causing it to jam. Hence, I thought of making parts that fitted better by using subtractive technologies instead, such as cutting a material down into individual gears. This makes it more accurate when designing the gears hence reducing the gap between the gears!
Another problem was that the wind generation by the fan was not enough. While we were tinkering with the fan during the practical, I noticed that the fan blades were somewhat flat. To fix the problem, increasing the angle at which the fan blades were facing would increase the airflow onto the blades and thereafter produce more wind... I think.
These fixes are not necessary, but definitely improves the useability of the fan.
Water bottle experiment:
4a: Probably the most confusing part of the practical, we had to configure the gears in a way that gave the highest gear ratio, i.e. the largest amount of torque. We were so fixated on having the largest ratio for each subsequent gear (for example, we thought the gear with 40 teeth HAD to be behind the gear with 12 teeth), which hindered our progress a ton, limiting us to worse gear configurations.
We still got it eventually though, so here it is!
And here's a pic of the gears in their optimal layout!
4b:
4c:
After doing that, we had to calculate the number of revolutions the handle had to make to make the bottle rise by 20 centimeters, where the theory was surprisingly easier than the practical.
4d:
The video of us struggling with the activity
In the end, we ended up using 50 revolutions to lift the bottle! That was really close to the calculated value, and we had an efficiency rate of 90%! Pretty respectable if I say so myself.
Looking back:
This practical really opened my eyes to the world of gears! Before this, I had practically no experience with gears and stuff, except experimenting with Lego cars here and there once in a while. Though it was somewhat boring and tiring, I enjoyed working with my group and allowed me to learn more about things I never knew I needed.
Instead of looking at things from a single perspective, this practical forced me to look at problems at a bigger scale, like that moment during the configuration of gears for the water bottle experiment.
I also have become more grateful for those who do work related to these, as I wouldn't survive a day in their jobs. The work required just to calculate and determine the most efficient gear systems would take a toll on my mental health alone, let alone fixing them together. It really makes me appreciate the fact that other people do this so that we can have so much in life, from cars to wind-up toys and more!
With that, I'm done with this blog. Not the best blogging I've done here. But thanks for reading! Here's a parting gift for the time being. Have a good day.
Walter hitting pan
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