# EV3 Phi. Extending constructions without instructions. Basic Principles. Straight Beams ProPreview

Tips and common mistakes when connecting two beams together.

• #433
• 03 May 2017
• 4:58

### Use two points of connection

Use two pins to connect two beams. The pins must not be next to each other, they must be at least one hole away from each other, in order to prevent bending.

### English

Sometimes in our courses we set a task where you should freely extend a robot construction with a few parts so that at the end you have for example a touch sensor at the front or a light sensor pointing down or probably a middle motor somewhere and we don't provide any instructions for this. So, we leave this to the students to come up with different solutions. And in this video I would like to stop at some of the principles that you should follow when freely extending a construction without following a PDF instruction. There are a lot of parts in your Mindstorms set and you can group them in different categories. Some of these categories are for example straight beams or angled beams or pins or beams with pins and you can discuss and you can use them as a group. And the first task that I would like to show you is how to connect 2 beams to each other. After you follow a number of our instructions it is very easy to understand how you connect one beam to another but what's the point of the video is to discuss how you extend one beam with another. So, you have this length but you need to for example add the touch sensor here. And now you must extend this beam with another beam. The first thing that you could do is just use a blue pin like this and then extend with the white beam. And then you can add the touch sensor. Now, that's a solution but what happens here is that the two beams rotate. One of them rotates. Why? Because we have the connection with only one pin - the blue pin. A better way and actually more correct way is to use a second pin like this. Now, this will prevent the rotation but if you apply some force at the end of the beam, it will actually move. It will bend. So, even the more correct way is to do the construction like this. For example, you can leave a number of holes between the different pins and then connect them. How many? 2, 3, 4 Leaving 10 is probably too much but don't put the pins next to each other when you extend one of the beams with another beam. Now the whole construction is much more durable and much more difficult to bend. Here is an example. We have the touch sensor, we have a beam and now we'll extend our robot. We have 3 holes at the right side of the construction of the brick and we'll use these 3 holes. We can think of them as a beam and I'll add one pin and if we leave it with one pin, you can see that it rotates. We can use a black pin and in this way we won't have a gap between the beam and the brick then we should add a second pin right here and even if we apply some force at the end of the beam, it is not rotating and it is not bending. Then we use the touch sensor and it's again the same principle. We add one pin, we add a second pin. Now, here we can use the black pins or the blue pins - the longer ones.

And this is one example for extending. We can even extend further. We can take one more beam, a number of pins

and extend even further. Now that's a stable, durable construction where the robot could move forward and if we have a touch sensor at the front, it can even detect the touch sensor pushing to a wall for example.