How do you lift heavy objects with an attachment? In this episode we show a simple, interesting, but yet not very popular way to lift something heavy with and LEGO Mindstorms EV3 robot and without gears and motors as attachment. As a specific example we are using the Strength Exercise mission from the FIRST LEGO League 2012 competition.
- 09 Nov 2014
Many of the constructions in the LEGO world mimic the "real"/"engineering" world. But initially students need some time to come to such solutions and must see them somewhere. In this episode we are building an attachment that follows an interesting principle for lifting heavy objects. Our observation is that this are hardly ever used in competition.
Try to follow the same principle to push objects, not only lift them. If you use the attachment share with us the results and what have you achieved with it.
Instructions and rules for the use of the heavy lifting model can be found at FIRST LEGO League 2012 competiton materials
In this tutorial I'll take a look at the strength exercise from the 2012 First Lego League Challenge. In the next few minutes I'll introduce you to an interesting way to complete the mission with a detachable attachment. Now let's see how the final version of the attachment would look like.
I'd like to show you how we've come to this attachment. In the beginning there was this square frame which actually is the scissor mechanism. The main idea is that the robot will push the mechanism from one side and the model will resist from the other which will make the mechanism stretch and lift the lever which will complete the strength exercise mission from the 2012 First Lego League Challenge. What we'll do next is build on this mechanism, so that we could attach it to the robot and see what other problems we will face. I have built this frame at the back of the mechanism and I'll focus on two key features of it. First, I have this axle here which is used not only for supporting this beam but also for preventing the mechanism from falling down so it's a little bit stretched at anytime. Next, we have this rail here. So, we have these two beams at the front of the robot and they are sliding into the frame. So, in the end, the attachment looks like this. Now, if we push the robot towards the model, it will stretch and lift the weight a little bit. Unfortunately, the robot does not lift the weight all the way. This is because the mechanism is hanging at the front due to its weight. We have two solutions to this. The first one is to extend these frame beams but then the attachment will become too long and it would be hard to maneuvre through the field. Another solution is to add an extra point here where the weight will fall onto. So, I'll build it and show it to you. I have added these two wheels as pivot points for the attachment and now they are rotating. I will attach the scissor mechanism once again to the robot. and when I push it towards the model it stretches and lifts the weight all the way up. When I move it back, the attachment remains on the field. This is due to the friction between the tires and the beams. As you see, it's very difficult to rotate them. Another way to achieve this is to put a half bush between the beam and the tire.
Like this. Of course, you should also put a half bush on the outer side of the tire. I'll repeat the same thing on the other side. I put a half bush, then put the tire and finally put a half bush on the outer side. Now, when I push the mechanism towards the model, it lifts it all the way up. But when I move the robot back, the attachment remains on the construction. If you want to have no friction but still leave the attachment on the field, you could use this angled beam as a hook. I'll attach it here with this little friction pin.
Now, when I push it towards the model, the hook is flipped and when the robot returns, the attachment remains on the field. When we have the hook in place, the attachment will be left on the field. If you do not want to leave it on the field, just remove the angled beam.
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