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Catapult built from LEGO Mindstorms EV3/NXT (Part 3 - Automatic loading) Pro Preview

Part three of the Catapult series is about loading the catapult automatically. We use a gear system with a medium complexity along with a very interesting "clutch" developed with parts entirely from the LEGO Mindstorms NXT kits. As a result, at the end of the video, the Catapult automatically loads and fires.

  • #67
  • 18 Jan 2015
  • 11:02

Automatic Loading

A motor for loading the catapult is added to the construction shown in this and in the following video lessons of the Catapult series. Firing is achieved by using gravity force again while loading is achieved with a motor. The power from the motor is transferred to the lever by a system of gears located on different axles. In this way the orientation of the gears is changed twice and transmitted four times.

Touch Sensor

The touch sensors used in the robot are very important. We should have a way to find out if the Catapult is already loaded and when we should stop loading. Configuring the motor to use rotations or degrees is a very bad practice and we should try to avoid it. Always try to use sensors.

Additional video lessons

You could find more explanations about changing gear orientation in the following video lessons:

Active attachment for changing gears orientation

Active attachment for changing gears direction - part 2: improving durability

Active attachment for changing gears direction - part 3: moving up&down

All episodes from the series:

How to use the Ultrasonic Sensor with the Catapult built from EV3/NXT (Part 5)

Catapult build from LEGO Mindstorms EV3/NXT (Part 4 - EV3 clutch and loading)

Catapult build from LEGO Mindstorms EV3/NXT (Part 3 - Automatic loading)

Catapult build from LEGO Mindstorms EV3/NXT (Part 2 - Base)

Catapult build from LEGO Mindstorms EV3/NXT (Part 1)

Robotics Set

The current video lesson shows the robot built from LEGO Mindstorms NXT parts while the next one would use LEGO Mindstorms EV3 motors and sensors.

Building instructions for NXT Mindstorms Catapult Robot are given below. (The next lesson in the series would use EV3)

Catapult Rotating Base - LEGO Mindstorms construction for a base for a catapult

This is the initial construction of a catapult. The base on which we will place the rest of the robot. The goal of this construction is to give the catapult the ability to rotate.

NXT-G program

NXT-G program for running the Catapult robot build from the LEGO Mindstorms NXT robotics set

LEGO Mindstorms Catapult Motor and Touch Sensor

Building instructions for a LEGO Mindstorms Catapult Motor and Touch Sensor that are used for triggers for firing objects

Catapult Frame - LEGO Mindstorms construction for a frame of a catapult

This frame holds the motor and ev3 brick used in the catapult. The frame is placed on top of the rotating base and thus could be easily rotated. The brick could be both NXT and EV3

NXT-G program

NXT-G program for running the Catapult robot build from the LEGO Mindstorms NXT robotics set

Courses with this episode

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

A robot a "day" keeps the questions awake

Explore speed, distance and construction innovation for the catapult. Use the task in your classroom, for your team or at home to engage students in learning. 

There are 3 tasks with 3 complexities giving 1,2 or 3 points. 

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

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