Video tutorials -

• FIRST LEGO League

-

• Gears

As we are already off the season we decided to look back at the competition. First, we will take a look at the working solution for FIRST LEGO League 2017 Manhole Cover. This was generally accepted as one of the most difficult missions during the competition. We've built a single attachment to accomplish it. 

(we are releasing the video without explanations and will add the explanations later)

This video tutorial is part of the series on how to make your robot 100% precise and accurate. We accomplish the Emergency Walk mission 10 out of 10 times. The attachment works. Every time the attachment is started in successfully accomplishes the mission and this is one of the most difficult missions on FIRST LEGO League competitions ever. 

Based on feedback from many of you in this episode I would like to show you how to build an active attachment that changes the orientation of a gear wheel placed vertically to a gear wheel placed horizontally. This attachment could be used in competitions and shows a basic principle of changing the orientation. All attachments could follow the same principle. 

In this video lesson I am building a LEGO Mindstorms EV3 active attachment powered by a small gear wheel. The attachment could move up and down, it is very useful for collecting objects. It could easily be adapted and used on other robots.

We are making a parallel with Video Lesson 56 from the series and we are also showing ways to improve the stability of an axle which is most of the time neglected, but could lead to great problems.

In this episode we continue from Episode 55 and we improve the durability and stability of the attachment for a LEGO Mindstorms EV3 robot. Many times attachments are not very stable which results in gaps between parts. The goal of the video is to give basic construction ideas.

Extend the previously build attachment for the FIRST LEGO League (FLL) Nature's Fury competition so that we can move the Truck and Ambulance up and down. 

Time to lift the robot. The first approach is by using the 40 teeth gear wheels that come with the LEGO Mindstorms EV3 and NXT robotics sets. 

Build a similar mechanism to this one. Similar, but for your robot. This is the task for you. Try, give yourself half and hour or even an hour.

Connect the attachment to the box robot and find the correct number of rotations of the middle motor that would bring the robot up and forward and would attach it to the mission model.

How great is the great attachment for lifting that we built in this course? How many times can it lift the robot without making an error? How great are your attachments and how could you test them? - the answer is simple. Just try 10 times and they should work at least 9 of them as our attachment is.

Here is our solution for preventing torsion and bending of the LEGO Mindstorms EV3 axles.

How to align the wheels and how much should you push for this solution?

There were a few problems with the 40 teeth gears that we were using. Let's list some of them

The M08. AEROBIC EXERCISE is one of the very common types of mission in FIRST LEGO League robotics competitions. I think this pattern of missions was first introduced with the growing abilities of the participating students that were constantly reaching the maximum number of points. So the competition introduced mission that require a lot of time - 20-30 seconds, are time consuming and are complex. They requires a lot of moves. This here is a video tutorial on how it could be accomplished

In this tutorial, we add another mission to our current program. This mission is - hanging the Gecko from the FIRST LEGO League Animal Allies. 

We calculate the number of rotatios when a gear system is involved. The driving wheel will have to do a number of rotations for the driven wheel to rotate to a desired number of degrees. In our specific case when the driven gear wheel is rotate to about 90 degrees the legs will lift the robot.

This is a teacher's note about the math behind calculating gear ratios with for our lifting attachment. It math model we build in previous tutorials is not exactly correct and here is the explanation why.

The task in this tutorial is to execute the program 10 times and to do it yourself. If you have your attachment then use it. If you have our attachment then use it. But execute the program 10 times and make sure that it works. 

Sometimes the answer that you get by calculating seems not to be right. Is it the calculation that is wrong. Probably it is not the calculation, but something is happening with the robot. 

What should you as a teacher know when the students are trying to achieve a program and robot attachment that could reproduce their behaviour 9 out of 10 times. 

If you've done the calculation following the previous tutorials you would arrive at a result of 18.75 rotations. But this is not the correct answer. The calculation is wrong, because the math model that we've built, although kind of obvious, is not correct. When experimenting the correct number of rotations would be 37.5. This is a large difference. Two times larger. Exactly two times large. Something should be happening here - and this thing is "planetary mechanism"

Calculate the number of rotations you have to do with the motor to rotate the final small 8 teeth driving gear wheel to 1.25 rotations?

What should you do as a teacher when the students are calculating the gear ratios and number of needed rotations?

In the previous video, we found the correct answer for our task and it is 18.75, or is it?