Gears Documentation!
- shaira214
- Oct 29, 2022
- 1 min read
Updated: Nov 19, 2022
In this post, I will be giving you an introduction about gears.
I will then be describing:
The definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth.
The relationship between gear ratio (speed ratio) and output speed, between gear ratio and torque for a pair of gears.
How I can design a better hand-squeezed fan, including the sketches
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.
So, What is a Gear?
A wheel with teeth is called a gear.
Gear train is when there is 2 gears connected to each other.
There is a driver gear and a follower gear, turning the driver gear clockwise will cause the follower to turn anti-clockwise, and vice versa.
There can also be gear trains consisting of 3 gears, instead of 2. (insert pic)
The middle gear is called the idler gear, which forces the follower gear to rotate in the same direction as the driver gear.
There are 2 types of Gear chains:
Larger gear turns the smaller gear when the larger is turned.
Smaller gear turns the larger gear when the smaller is turned.
Now, I will be describing:
1. The definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth.
Gear Module refers to the size of the gear teeth.
The unit for the module is mm.
The larger a module number, the larger is the size of the teeth.
Pitch Circular Diameter is the diameter of the circle.
It is the diameter of the imaginary circle that passes through the points where two interlocking gears touch.
PCD = m x z,
- where m is the Gear module
- where z is the number of teeth
2. The relationship between gear ratio (speed ratio) and output speed, between gear ratio and torque for a pair of gears.
1: When the driver gear is larger than the follower gear, the gear ratio of the gear train is low.
Gear Ratio = Number of teeth of follower gear/Number of teeth of the driver gear
2: less speed= produces more force
The smaller the driver gear, the lesser the force needed to turn it.
when the driver gear is smaller than the follower gear, the gear ratio of the gear train is high.
Speed ratio = 1/Gear Ratio
Speed ratio is inversely proportional to Gear Ratio. If the Gear Ratio is high, Speed Ratio is low, and vice versa.
The input torque causes the driver gear to rotate, generating a tangential contact force between the 2 gears.
We can calculate the magnitude of the contact force as the input torque divided by the distance between the force and the radius of driver gear.
3. How I can design a better hand-squeezed fan, including the sketches
Video of hand-squeezed fan:
Calculations and sketches of hand-squeezed fan:
What can be improved:
Screw the fan onto the spur gear shaft to secure it to the device better instead of just attaching it together so that it does not fall off easily.
Add some cover to the fan blades so it would be safer for the user.
There was some considerations we needed to take note off:
the speed of the fan had to be fast
the speed ratio had to be as low as possible
the number of turns of the follower gear had to be as much as possible, compared to every turn of the driver gear.
Hence, we used the gear with the most number of teeth as the driver gear, and the one with least number of teeth as the follower gear.
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)
30/30=1
30/30=1
30/20=1.5
40/30=1.33
40/20=2
20/40=0.5
40/40=1
Gear ratio= 1.5x 1.33x 2x 0.5 =1.995
The photo of the actual gear layout.
Calculation of the number of revolutions required to rotate the crank handle.
2 turns of gear with handle is one turn of gear with winch
The video of the turning of the gears to lift the water bottle.
Considerations we had to take note of:
The torque had to be as high as possible, so that more force can be exerted in order to lift the bottle up.
the speed ratio had to be as high as possible
the number of turns of the follower gear had to be as low as possible, compared to every turn of the driver gear.
5. My Learning reflection on the gears activities.
Overall, I felt that this practical helped me understand a lot more on gears, gear ratio, speed ratio and also torque.
Time management is extremely crucial during practical. Halfway through, my group and I found ourselves rushing for one of the activities, as we spent too long on the bottle lifting activity. Even though we completed the work in time, I realized that it is important to manage and plan out our tasks well.
I also learnt how gears can be used to carry heavy things. For example, my group and I used gears to lift up a bottle of water, without having to use our hands, and only turning the handle. This shows that gears can be applied in the real world, and help us to carry heavy things easily. Thus, gears make a large impact on our lives!
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