Rubber band attachment with a flywheel - solving FLL 2014 Search Engine (part 3). Two tasks at once Pro Preview

The third part of the series the goal is to extend the robot attachment so that we could solve the second part of the FIRST LEGO League World Class mission challenge - to take the loop.

  • #106
  • 20 Sep 2015
  • 6:23

The Search Engine mission consists of two parts:

  1. push on a lever to select a color
  2. take the loop with the specified color

In the previous video - Rubber band attachment with a flywheel - solving FLL 2014 Search Engine (part 2), we finished with just pushing the lever and now we should also build an attachment for taking the loop.

The attachment is a pinless attachment build for the EV3 competition robot

  1. EV3 Competition Robot Construction

  2. Pinless attachment added below the robot

  3. Quick Pinless Attachments for LEGO EV3 Competition Robots (Part 2)

  4. Quick Pinless Attachments for LEGO EV3 Competition Robots (Part 1)

Pinless Flywheel and Rubber band attachement for LEGO Mindstorms robots

Kiril Mitov's most favourite attachment. To quote him "I had a really great fun building this attachment and recording the videos for it".

It's an attachment with a Rubber band and a Flywheel and a Gear Wheel and a Worm Gear. So much knowledge in just one small attachment. The goal of the attachment is to be able to have an active attachment without actually having a motor. So you can place that attachment and it will do the work for you instead of using a motor to power it. 

Build with LEGO Mindstorms EV3 set. 

When placing the rubber bands check out the tutorials

Placing the white rubber band is shown at at around 05:40.

Placing the red rubber band is shown at 


- In the last video of the series, we started building an attachment that was solved in the first Lego League 2014 Search Engine Mission. I didn't explain the mission well enough, this is something I will do today. And so, we are also-, we were solving part of the mission, only pushing the lever without taking the loop. In today's video, we will also take the loop, so we will extend our attachment.

Now let me first return to the mission model, and to why it was so difficult as a challenge. At the start of the round, you have the lever here. And one of the colors, in this case, red is selected. Then you must reach the mission element, push the lever. And depending on which color is selected, you must take the corresponding clue. And because of the way this mission model is constructed, it is always a different color. So now it's blue, but if I push, it will be yellow. And you must take the yellow, this will require that you have some kind of motor here for pushing the lever. And then you must also have a color sensor to detect the selected color, and to know which loop to take. Our goal is to solve this whole challenge without motors and without color sensors, because, as a requirement, you must rotate, you must have at least one rotation of the colors. So when you push, they should rotate at least once. And so, one way to solve this challenge is to see the color initially selected. Then reach the element, and then push it so gently that you get the color that you want, which is in this color-, in this case, yellow. So that was the mission, and we are gonna solve it with our attachment from previous videos, and we'll also build an extension that takes the loops. This here is the mission model, position it like this, and we program our robot. This is the attachment. So, we program the robot, it moves on the field, then it reaches the attachment-, the mission model. We push this axle here to the border, so the border is right here. And then by pushing the attachment, we have one of the levers here moving and the other here, and we actually push like this. Then we would like to when returning with the robot back to base, to automatically take the corresponding clue. And for this, we've built the following solution. First, if you would like-, initially, you see that the color is-, so let's say, yellow. Let's say that you would like to take the yellow loop. Then we extend our attachment in the following way. We add a small pin and then we add this model here from rear axles. like this. And then, let's say that we want to take the yellow loop, we reach the mission element, we trigger the attachment. And then when we return back to base we take the loop with us. This works 100% of the time. Of course, currently, our mission model is not fixed. But when it is fixed, it works every time. Again, we reach the mission model, we position, we trigger because we push on the weight of the axle here. We push on the border. And then when we return back to base, we take the loop with us. And the robot is right here. Now, I've zoomed in closer, so that you can see how the attachment works. Again, we have this model of axles here. We move with the robot, we move, we reach the attachment. Then when we reach the attachment, we position the attachment to the mission model, we trigger the attachment. And then when we return back to base, we take the loop with us. It's very important to know that the pin right here, it's a black pin, it's a friction pin, it's not frictionless. Because when we are returning, we are actually taking the loop with us. And this, of course, could slightly be modified, the whole attachment with axles. Because you can modify how long would you like to have these axles, so you can move this red pin. Or you can even change this gray axle with a shorter red one, this depends on the task, of course. Again, return-, go to your mission model and return back to base. Now we'll extend this to make it work also for the other loops.

Courses and lessons with this Tutorial

This Tutorial is used in the following courses and lessons

Image for FIRST LEGO League Competition. Attachments
  • 60
  • 347:26
  • 0
Image for Attachments with Rubber Bands
  • 12
  • 0
  • 0
  • 3d_rotation 9
Image for FIRST LEGO League Competition. Attachments
  • 60
  • 347:26
  • 0
Image for FIRST LEGO League 2014 World Class. Example solutions
  • 16
  • 0
  • 0
  • 3d_rotation 7