Turning two axles, one at a time in opposite direction with one motor and two rubber bands

With this attachment we just share an idea. The attachment was build by an FLL team called Brother in Arms and they needed a way to turn two axles in different direction, one at a time. The attachment was not used in the final robot design and construction, but presents a nice idea.

  • #102
  • 23 Aug 2015
  • 3:17


This attachment uses two parts that are not part of the EV3 or the NXT mindstorms sets. They could be found in some of the LEGO Technic sets.

Two axles in different direction, one at a time



- Previously, we did a number of videos on how we can use rubber bands to solve different challenges at the FLL competition. During the recording of these videos, the team Brother in Arms came up with a very interesting attachment. We are not sure show exactly this attachment could be used it is interesting idea that we would like to share with you.

This here is the attachment and again, it uses rubber bands right here. The purpose of the attachment is to hold it when you rotate. The gear wheel right here. For example, this here is connected to a motor. And now, when I rotate the gear wheel, only one of the axles...these two right here, one of the axles actually rotate. As you can see, currently only my left axle rotates. Now, if I turn the gear wheel in the opposite direction, only the other gear wheel...only the other axle rotates. Now why is that interesting? Because it used an interesting part, this part is not part of the Mindstorm set. It's a part of the Technic set, this one here. And there's a friction in this part that's...when you are trying to rotate them in any of the direction, it has more friction than in the other direction. And now we add the part here. You can see, we can rotate both parts but if we have our rubber band that stops the rotation of one of the gear wheels. We will achieve our result and just like this here.

Now, where can you use this? At one of the competitions, two, three years ago, I saw a team that was doing a clock with rubber bands. It was a clock mechanism and it was again, using similar parts. And probably in some if next videos, we'll build a clock. But it's an interesting attachment and you can use it for solving different missions when you need two axles, rotating one at a time in different directions.

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