Positioning motors on BigDaddy Competition Robot (Part 6) Pro Preview

We are showing the first way we could position the motors on the robot construction. This seems to be challenging for many robot builders and that's why we are going to do it in a few different ways in the next few video tutorials from the series.

  • #76
  • 15 Mar 2015
  • 7:07

The Robot Construction (until now)

In the previous video tutorials from the series we constructed the BIgDaddy competition robot 'front', 'rear' and 'central' frame. Now it is time to transfer power from LEGO Mindstorm Motor to the wheels of the robot. The 'rear' part has a differential and we need one motor for it. The 'front' part can turn left and right and we need another motor for it. The third motor from the Mindstorms Education/Retail Robotics Kit could be used to transfer power to any attachments that we have and for this we could use a Cardan Shaft

The Cardan Shaft

Let us take the simple case of a cardan shaft without going into much details - we would like transfer power from one axle to another and both axle are not aligned. This is where we could use a Cardan Shaft or as in German - "Kardan" (pronounced strongly)

The Positioning of the motors

While building a robot one could focus on the motors and build the whole robot around the motors. In this series we are doing it in revers. We focus on the wheels and the movement we would like to achieve. Only after that, we focus on the motors. 

Other episodes from the series:

Constructing BigDaddy Competition Robot (Part 1 - Front)

Constructing BigDaddy Competition Robot (Part 2 - Front)

Constructing BigDaddy Competition Robot (Part 3 - Front to Rear)

BigDaddy Competition Robot (Part 4 - Complex Transfer of Power in a Triangle)

BigDaddy Competition Robot (Part 5 - Power to Rear Wheels)

Courses with this episode

The episode is used in the following courses where you can find additional tasks for it to use in class

Big Daddy

Find one more way to attach the motors to this robot. Why? - experiment with different options and find advantages and disadvantages in each. Use the task in your classroom, for your team or at home to engage students in learning. 

There are 3 task from an normal, medium, hard complexities giving 1, 2, 3 points respectively

Tasks description, submission and evaluation are available to subscribed users.

Subscribe now to access the full capacity and get feedback.


- Up until now we've constructed a robot that's very stable, the BigDaddy construction, and it has a front part. It has a rear part with a differential. You can check out the previous videos. And in this episode, we will explore different ways in which we can attach the motors so that we have control over the front part of the robot and the rear part of the robot.

Continuing from last video, there are a few slight modifications for our construction, and we've improved the construction right here. There's our new gray parts and these gray parts we use them because they are just beams and we have much more beams in the construction than the other parts. And we've also add some additional modules here to make the whole construction much more stable. Having in mind that, our next step is to find a way to position the motors, here are two motors and we would like to use one of the motors to transfer power to the rear wheels and one of the motors to turn the front wheels left and right. First, I'll add the axles right here. And right here now we we're experimenting with different solutions. We could add the motors in different ways. In this video, particularly we decided to add to the motors in the following way. First, we attach the two motors together like this, and that way have motors touch. We put them in the way that we have the axles. One and the other. Now as you can see this construction would not work since the motors are attached only on the axles. We must also attach the motors to the frame of the robot. Let's remove them. One second. Now there's a frame. There are different ways, we've decided to use.. I've already prepared the module for this.

And it's a simple module with a few beams and a few pins. And if we add...

Now we have the motors. We have the frame. We should just push them and they'll attach to the pins.

One more pin is missing right here, and we're done. We have our motors attached in a way that we can transfer power to the rear wheels and transfer power to the front wheels. As a last step, we are left with a third medium motor that we used for different attachments. And if we consider that this is the front part of our robot, as mentioned, you can always think of this being the front part of the your robot but let's just for moment think that this is the front part, and probably the attachments will be somewhere around here and we need to somehow transfer power from the motor to the attachments. We have the medium motor in the inter-construction in three sets and we can add the medium motor for example here above, or here or over here, and just for the sake of the experiment we decided to add the motor right here, on the left part. And now we are going to transfer power from the motor to the attachment with this very interesting module. It's called a shaft and specifically it's a Cardan shaft and it can transfer power in a certain angle. For example, you can transfer the power when you hit the whole shaft vertically but if one of the parts is a certain angle from the other you can again transfer part of the power. And we should mention that you're always losing part of the power. For example if you go to more than 45 degrees, it's now becoming even impossible to transfer a reasonable amount of power from the motor to the end of the shaft. Let's attach this shaft on our robot.

Here it is. Technically, it would be possible to transfer power from the motor to the end of the shaft, but practically it's not a good idea. That's why in the next video we're searching for other ways to position the motors so that we could get the two driving motors, and the medium motor with the brick and position them in ways to have space.