This is the second part of LEGO Spike Prime mission and focuses on the introduction of mechanical structure. If you would like to check how to use program to control your robot, you could refer to my previous post.
Top View
The following is the top view of the robot vehicle. Since the model needs to identify an object, it uses an ultrasonic sensor, which is mounted on the front of the vehicle. Please note that the ultrasonic sensor could be replaced with a colour sensor (it should be installed in different position). However, I only have two colour sensors for this LEGO Spike Prime set. Therefore, I use an ultrasonic sensor to implement this functionality.
Some might ask why I put the ultrasonic sensor ar the right side of the vehicle. After all, according to the game demo video in the previous post, the object to be picked up is located to the left side of the vehicle. The reason is that ultrasonic sensor could not identify an object too close to it.
The attachment is installed on the left side of the vehicle. Where to put attachment is influenced by many factors, especially depends on how the designer plans to accomplish the task. In terms of this mission, the advantage of this arrangement is that the vehicle does not need to turn to pick up the object, which reduces the complexity of route planning and programming.

Bottom View
In the bottom view, we could see that two colour sensors are attached on the front of the vehicle, seating on both sides. For this mission, two colour sensors are necessary, otherwise, the program could not identify the intersection of the black lines, where the object is located.
Two big motors are used to drive wheels, while a medium motor is used to spin the side attachment. The castel wheel is attached at the rear part to keep the vehicle well balanced.

Rear Part
Since the chassis of the vehicle is very low, the ball wheel needs to be mounted at a bit higher position to keep it on the same height as the other two wheels. This model uses an I-shape 3*5 beam (gray) to help adjusting the vertical mounting position of the ball wheel.
As I mentioned before, it is much easier to build LEGO Spike Prime models. One reason is that there is no need to use complicated connectors. Using black friction preg is enough in most scenarios to connect different parts together.

Internal Structure
Now, let us remove the smart hub to see the internal structure clearer. The two big motors are mounted to a 11*15 technical frame. There is a panel fixed on the front and a beam on the rear part. They are used to tidy up the connection lines, so that those lines are stuck between the smart hub and the panel/ beam, instead of stretching out everywhere.


Sensor Installation
As I mentioned before, this model contains two colour sensors. They are connected to the 11*15 technical frame via the following connectors or parts.

After the color sensors are mounted, the ultrasonic sensor could be mounted to the pin holes of colour sensor and biscuit block through the angular beam.

Side Attachment
Finally, I will introduce the side attachment. Its structure is simple. Two angled beams (black) are connected on both sides of the medium motor. When motor spins, the beams rotate up or down. When the beams spin down, they catch the object inside and drag it moving with the vehicle. You might notice another angled beam (blue) attached at one end of the attachment. It is used to block the object from sliding out.

That is all for the introduction of mechanical structur, no complicated structure or connectors. How to design a robot vehicle is actually pretty flexible, depending on the requirement of the mission and your strategy to accomplish the mission. Practice makes perfect. Start off generating innovative models with your LEGO Spike Prime from now on and enjoy the coding and designing process.
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