This time, we did a competition of Drag Race. I was also solo at this time, and my goal is to build fastest robot in my class. In drag race, I need to make the fastest robot, and takes the time of distance for 3m.
In order to build the fastest robot, the gear ratio has to be close to 0. From the previous investigation of gear ratio, I learned that, when the gear ratio is close to 0, then the speed of the robot will increase.
Therefore, I first build the Gear ratio of 8:40. This gear ratio is the fastest gear ratio that I can make from my LEGO sets. However, when I loaded 8:40 gear ratio to my robot, it did not move. As I went through all the causes of this problem, I found that the power of the robot is too weak, that the gear can not afford the power to roll the wheel on the ground. My robot moved, when the wheel was floating, however as soon as it touched the ground, the motor stopped moving. It is because, the certain power is needed for wheels to roll on the ground, which has friction. And it is just that, 8:40 gear ratio could not afford that certain power.
After the fail of 8:40 gear ratio, I decided to lower my gear to second highest. The second highest gear ratio is 8:24. There is very slight change between 8:40 and 8:24 gear ratio. When I load the 8:24 gear ratio, the robot actually moved properly. After finding out the most suitable gear ratio, I tried to light my robot as light as I can. In order to make the lightest robot, I just simply changed the gear ratio and size of the wheel bigger. I did not put anything, and it is just like a standard NXT robot. My time was about 2.3 seconds, and it was fast!!!
PS: The above picture is 8:40 gear ratio.
After the experiment of Drag race, my class moved into next competition, which is Tractor Pull. In this competition, I need to build a robot, which can pull the heaviest weight. The minimum weight the robot needs to pull is 3000g, which is 3kg.
In order to build the strongest robot, the gear ratio has to be bigger. From the previous investigation of gear ratio, I learned that, when the gear ratio is bigger, then the power of the robot will increase.
Therefore, I built the gear ratio of 40:8. I can know that this gear ratio is bigger than 0, and the biggest by solving the fraction. 40/8 equals to 5, and it is definitely bigger than 0, and the biggest number. In order to give more power to my robot, I added third motor in front of my robot. By having three motors, the power of the robot increases, and makes for robot to be able to pull heavier weights. Of course, the gear ratio of three motors are all equal, as I need to balance my robot. Furthermore, I put more wheels to have friction, which eventually increases the power of my robot. There were two wheels at each front and back side. I added two more extra wheels to each side. Also, I put small wheels at back side, and big wheels at front side, in order to keep the robot stable, and not jump off. When the friction of the robot is greater, that much amount of force going to bigger surface, and makes the robot to have stronger power. My robot became huge, and seemed that it has strong power.
When I tried for competition, my robot easily pulled the weight of 3kg. The time for pulling 3kg weight is about 7.38 seconds, and it was second fastest time in my class. For the second try, I decided to pull heavier weights. My robot also easily pulled 5kg weight, and the time was 10.26 seconds. I should have tried for heavier weights.
PS: above picture is 40:8 gear ratio.
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