Tractor Pull

The tractor pull challenge is a test of strength instead of speed. The test is to see which robot can pull the most weight 50cm in the least amount of time. To do this we will need to reverse the gears on our robot due to the fact that right now they are set up for speed, not strength. To get the proper gear ratio for strength, our robot needs a larger driven gear (the one connected to the wheel) than the driving gear. This will cause the robot to move at a steady rate, but be able to pull a lot of weight.

Drag Race Challenge

The drag race challenge is a test of speed. We want to construct a robot that will be the fastest in a 3 meter race. To do this we will need to rebuild our NXT to accommodate larger gears. Once we have built the robot in a way that allows us to use large gears we can put together a set of gears (large driving and small driven) to move our NXT as fast as possible over a distance of 3 meters. I don't think the initial building or programming will be hard, but I'm not sure if we can win, I'm sure other people in our class will find ways to make their robots move incredibly fast.

Gears and Speed Investigation

In the gears and speed investigation we had to decide between two hypotheses as to which one more accurately calculates the distance that the robot will move due to its gear ratio. To do this we measure the distance the robot traveled three times, we repeated this process with a few different gear ratios. We then averaged the distances to decrease the error created during the experiment.
We then used the distances and gear ratios and using the two hypotheses to predict the speed at which the robots moves. We then compared the predicted values with the actual value and decided which of the hypotheses worked best.

We discovered that the hypothesis that works best is Hypothesis B.

Get in Gear Investigation

Today we worked on the get in gear investigation, which involved changing the gears on our NXT robot and seeing which changes caused the robot to go faster and which ones caused it to go slower. We discovered that the driving gear is the one connected directly to the motor, while the driven gear is the gear connected to that gear and the wheel.

If you were to make your driving gear bigger than your driven gear, the robot would move faster than if the gears were the same size. The reason that the robot would move faster is because the driven gear is smaller, so for every single rotation of the large driving wheel, the smaller driven wheel would rotate two or more times, causing the wheels to move faster.


The opposite is true if your robot's driven gear was bigger than the driving gear. Take what I said on the above paragraph and flip it, if the driving gear was smaller it would have to rotate at least twice (or more) times to turn the now larger driven gear just one time, this would cause the wheels to move slower than if the gears were the same size or if they driving gear was larger than the driven gear.

This was an important investigation because the fact that our robot has moved pretty slow in the past investigation despite the wheel power was at 100% was pretty frustrating, but now we know how to make it go exponentially faster, which will definitely come in handy in later investigations.

Obstacle Course Results and Conclusion

Last class we finally ran our robot on the obstacle course. After countless trial runs we were pretty frustrated, because our robot decided to do different things every time we ran it. On one run, it would go so far to the left it wouldn't even register the box of tape, yet on the next run it would work perfectly half way and then simply stop, and on some runs it did it perfectly. Finally we decided just to accept whatever happened and ran the robot for a grade. Luckily, our robot worked flawlessly until the very end where it knocked over the bottle instead of avoiding it, but we were very happy with a 9 out of 10 overall.

Programming for Obstacle Course

Today we continued the modification of our robot and the creation of our program for the Obstacle Course Challenge. First we programmed the first part of the obstacle course, beginning with a sounds sensor block. We set the threshold to 50 so that it would recognize a clap to begin the program, this went flawlessly and the clap works just fine.

Next we set up the light sensor programming, this worked as well with the smaller set of wheels, however with the larger set of wheels (which make the robot run straighter) the light sensor simply passed over the tape, we are working on fixing this problem.

The alst thing we did was modify our build so that the touch sensor was not below, but above the ultrasonic sensor. To do this we had to create our own unique assembly rig that incorporated cross beam and other building techniques to keep the touch sensor steady while remaining above and out of the ultrasonic sensor's way.

We go about halfway through our programming today, getting all the way to touching the wall, backing up and turning. I'm fairly happy with the amount of work we got done.

Chapter 6 Answers

Questions from Drew:
Define what modular is.
How can you maximize modularity?
What can make a robot move faster?
What is chassis?
What are hybrid creations?


In chapter 6 of the NXT textbook, we learn about building strategies, stud less building techniques, inertia, modularity and much more. The chapter focuses mainly on the importance of making a smaller, more compact but yet lighter-weight assembly for your robot. One of the most integral parts of building this type of light-weight robot is Modularity. Modularity is a way that you construct a robot that makes it as easy as is possible to take apart. The best way to maximize this modularity is to create subassemblies (small working parts that don't do much on their own) that when combined make up a complete and well built robot.

The next part of the chapter deals with the positioning of gears and beams and the Chassis of the robot. The chassis is the frame of the robot that the rest of the assemblies and subassemblies are built in to. The textbook states that we want the wheels or any form of gears as close to the beams as possible. We want to do this because it will keep the robot as compact as possible while reducing the spread of weight and materials. All these things together reduce the amount of friction of the robot's wheels to the ground and allow for quicker acceleration for the robot.

This chapter also states that you do not have to stick solely to studded blocks and building techniques or studless blocks and building techniques. There are certain robots that use all four of these things to effectively create what are known as hybrid creations.

Questions for Drew:
Give one example of how mass affects inertia.
Why is positioning of the load important for building strategies?
Why do we want to place gears as close to supporting beams as possible?
Define tension and compression as stated in the textbook.
What is the main structural component of a robot built with studless pieces?