Gears

Hi Everyone, this is my blog entry for GEARS !!!

In this page, I would be describe my journey learning about gears and playing with it during a practical session.  

First during the pre-pratical we did a lot of research and theory about gears and its functions. 

The definition of a gear is a wheel with "teeth". 

 

Below are the definition of gear module, pitch circular diameter and the relationship between gear module, pitch circular diameter and number of teeth

The Gear Module is like the size of a gear, and it indicates how big or small a gear is. To Calculate the gear module is to divide the pitch circular diameter which is the diameter of the gear by the total number of teeth it has.

A Pitch Circular Diameter is the diameter of the circle which passes through the centre of all the studs, wheel bolts or wheel rim holes.

 

 

 

The picture below shows exactly where the pitch diameter is

 

The formula is gear module = Pitch diameter / no. of teeth

So by this relationship when the pitch diameter increase, the gear module will increase too and vice versa. However when the no. of teeth increases, the gear module will decrease, and when the no. of teeth decreases the gear module will then increase. 

 

In conclusion, the pitch diameter and gear module are directly proportionate to each other, while the no. of teeth and the gear module are inversely proportionate to each other. 

 

 

Relationship between gear ratio (speed ratio) and output speed for a pair of gears.

Gear ratio is ratio of the input/output. Or input no. of teeth/output no.of teeth.

Speed ratio is the ratio of the output/input

 

A higher/greater gear ratio meaning a lower speed while a lower gear ratio meaning higher or greater speed produce. 

When the speed ratio is high, the output speed is high an when the speed ratio is low the output speed is low. 

 

  

Relationship between gear ratio and torque for a pair of gears.

Torque is inverse of speed. So when speed increase torque decrease and vice versa.

When gear ratio increases torque increases. This is because both gear ratio and torque is calculate by output/input. So there are both direct proportionate.

One example is a manual car. Gear 1 is to move off while gear 4 and over is for cruising. Gear one has lower speed and higher torque while gear 4 has higher speed and lower torque. 

 

 

One of the activity we did was to assemble a handheld fan. 

 

A better hand-squeezed fan can be achieve by using a big gear as the input and a very small one as the output. The reasoning is for a better hand-squeezed fan, the fan blade as to be spinning very fast to produce wind. Thus speed is more desired than torque. 

 

We build it quite fast within a couple of minutes as we had a diagram to follow by. 

 

Below is the picture of the activity that our group was tasked to do  

 

Below is the picture of the sketches of the gear location, the calculation of gear ratio and the recorded spins

Video of the fan spinning and calculation of the number of spins

 

If there is something I would want to change to increase the fan speed, is the change the output gear to a very very small gear. This will make the speed ratio of input/output as higher as possible. This is because when output (denominator) is very small the speed ratio will increase. We do not want to change the size of the input to a bigger one as it would be harder for the user to press it and cause inconvenience to the user. Another idea is to increase number of blades so more wind is produce.

Lifting water using gears

Another activity our group was tasked to do is use all the gears both simple and compound given to us to build a mechanism that will lift a 600ml water bottle filled a distance of 200mm. We are suppose to use as little force on the input gear as possible.

Picture of the activity that our group was task to do

 

 

 During the designing phrase of the mechanism, we all were thinking how to get the most amount of torque possible. Since all the gears were in 2 to 3 sizes, a simple gear train would not be effective as most of the torque generated would be cancelled out in the end and the torque in the gear would be barely above 1. So even though it is >1, it is not really effective. Thus we went straight into compound gear train. 

There were 2 different input gears to choose from (Big and small). Since we going for more torque the input gear has to be small. So we went for the smaller one. Since we learnt that more torque is output/input >1. We went with small gear to big gear, than to small gear than to big gear. We keep repeating this for our design.

 

 

 

 

 

Picture of the calculation of the gear ratio, and sketch of the gear design

Our gear ratio was calculated to be 4/3 which is 1.33333. This is greater than 1 which is a good thing as gear ratio = torque ratio. And as torque is required more than speed, So 1.33333 is good!!

 

 We came up with this finally :) 👦😆😆

Video of us turning the gear to lift the 600ml water bottle a total of 200mm or 20 cm

It took a lot of effort and strength by my group members but as a group we all gave emotional and moral support which allowed us to manage to do it !!! 😝😝😝

We were so happy that we did it as the building and constructing of the design took very long. We finish just in time too 💥💪

 

Picture of the actual gear system

As seen the the picture above, our group used all 7 gears + 1 input gear. We did a compound gear train instead of a simple one. This is because we felt that it would be more effective to use a compound gear train as it would increase the gear ratio without the need of another gear. Moreover, a compound gear is like 2 gears in one and both is turning the same direction. It can transfer the energy from a small gear to a big one quickly. 

 

We did some calculation on the number of rotation the output gear did was 3.853 as shown below.

In the video though, we saw the gear made around 3 revolutions. So the calculation and execution was accurate.

 

We felt that there were a lot of gears involve so the amount of friction between the gears were a lot. Not to mention friction between the gears and the board.

In the picture below are the solution to reduce it, to make the gear turn easier and more effectively.

My reflection on the gear practical is very fun and I learn a lot about gears along the way. Even though there where pre-practical videos to watch. It was abit boring as there were 4 videos talking about almost the same thing. But i tried my best to watch it all and manage to do so. From the pre-practical videos I learn that gear ratio is output/input and when it is greater than 1 it is more torque and when it is less then 1 it is more speed. More speed means less torque and vise versa. 👌

During the practical there was so much hands-on that to me it was much much easier to learn. I felt I took away a lot from the practical. I believe that thee skills in gears will go a lot way for me in the future. In my opinion more skills learned is always better and who knows I might use these skills for my Capstone project or even in the future.😤💪