Tetrix FTC. Construct a ball collecting attachment - rotation axle Pro Preview

How to construct an axle with a plastic plate connected to this axle and make this plate rotate and collect balls.

  • #567
  • 11 May 2017
  • 7:16

Finding Axle

There is no such axle with the Tetrix set so we bought one. The diameter of the axle is 4mm - 4.5mm (0.16"-0.17"). We cut the axle about 200mm. 

Attaching the axle to the robot with a Coupler

We add the motor from the back of the robot to the front. We would use this motor for rotating the axle. Then coupler makes the connecting between the motor and the axle. It has a motor hub and an axle hub. The motor is connected to the motor hub, while the axle is connected to the axle hub. The size of the holes on the coupler are with different sizes. 

When attaching the coupler to the motor shaft you must fix the coupler screw on the flat part of the shaft. Check out the video to see exactly how. 




FTC PushBot Modified Robot for Collecting Balls with Plastic Plate

These are buliding instructions for the FTC robot and collecting attachments with it. We are doing small modifications of the push bot

Image for FTC PushBot Modified Robot for Collecting Balls with Plastic Plate

FTC Tetrix Ball Collecting Mechanism for PushBot

Building instructions with dimensions on the ball collecting mechanism for the FIRST Technical Challenge Push Bot

Image for FTC Tetrix Ball Collecting Mechanism for PushBot

FTC 200 mm Axle Dimensions

This is a blueprint of dimensions of the FTC 200 mm axle.

Image for FTC 200 mm Axle Dimensions


In this episode we'll stop at how do you construct an axle that you place at the front of the robot that will rotate and on this axle then we'll attach the plastic that collects the different balls. But first we need to start with this axle and how did we come up with this axle, why does it look like this, where did we find it from and how did we attach it do the robot? Here is the axle. There is no such axle in the Tetrix set so we bought one. And the diameter of this axle is important. In our case because of the different parts that we have in the set and we need to attach this axle to the parts we stopped at an axle that's 4.5 mm this is something that you can buy and in inches it's 0.17-0.16. And this axle came like 3 m. It was 3 m in length so we had to cut it. And this is the first challenge. Find such an axle and then cut it to about 20 cm. And we'll give you the specific measurements below the video so that you can have it and this is the first important part - find the axle, buy one and cut it to the dimensions that we give below the video. After you have the axle you must somehow rotate this axle. For this we'll use a motor. And we just move the motor from the back of the robot right here to the front of the robot and there are no modifications here. We just attach the robot to the front right here to this C-section. Then we use this very interesting coupler. And the idea of the coupler is that we have the motor rotating one of the hubs and from there it rotates the other hub that's called the axle hub. So, we have a motor hub and an axle hub. And they are with different sizes. So, you could see the holes here and measure them and you can see that one of the holes is larger that the other. So, we have the axle hub where we place the axle and we also the motor hub right here. Now, I'll add the motor hub to the motor. I'll take the coupler and the motor hub right here. And we attach the motor hub to the shaft of the motor. This here is the shaft of the motor and you can see that it has a flat part right here and the idea is the following: You place the hub and then we must fix the hub to the shaft and because it has a flat part we must attach and fix with the hex instrument right here. And there is a small bolt and we fix it. And while fixing we move to make sure that the bolt fixes the whole hub on the flat part. Ready. We have the coupler fixed to the motor. Next. We must fix the axle. We have the coupler attached to the motor and now using the gamepad we can rotate the whole coupler. And in the reverse direction.

The next step is to attach this axle to the coupler and this will rotate the whole axle. And this is where it gets really interesting. First, we have the axle and then we take this bronze bush. Place it on the axle. Then we have a spacer - this white spacer.

And then we have this axle set collar.

And we add the whole axle to this opening and then to the axle hub. And now we must fix the axle to the axle hub. And I'll have to rotate the hub like this. You can see right here the screw that we must rotate and we use this screw to fix the axle.

Just use the screw and

we fix the axle. Now, if we move, if we rotate, the whole axle also rotates.

Then we must also fix the other part with the set collar.

But probably I need the other instrument not this one.

And as a result we have a very cheap axle and now we can attach something on this axle to collect the balls. We have the axle but it's not perfect. And there are some slight modifications that we must do. And first we must move this coupler closer to the motor. And as you can see there is some gap right here between the coupler and the motor and we must move it closer. So, I'll just rotate the coupler

and move the whole coupler closer to the motor so that there is no gap right here. And then fix again. The next thing is that for this axle because of the shape of the axle it might be possible to fix it with the axle hub but it is always a good idea to use a tool to flatten this axle, to build this flat surface on the axle. Now, it's very difficult to see it on the camera but I hope that you can see it now and as I move, you can see that the light reflects in a different way. So, there is a very small flat surface right here and on this flat surface we can fix the screw.

And we rotate the axle. Now it looks much better.