Alectric Labs

Auto Loading Trebuchet

The Trebuchet, which is built out of the LEGO® Mindstorms NXT, is able to launch a ball a short distance about 1 to 3 feet above the floor. The device works by automatically loading a ball into one of two hatch mechanisms at an end of the arm. The Trebuchet then searches for a target and spins the arm to launch the ball.

Procedure for One Round of Operation

1. The arm is spun to ensure that the hatches are open.
2. A bar is deployed for calibration of the arm position.
3. The arm is turned until it makes contact with the bar for calibration.
4. The arm is positioned for loading.
5. A ball is loaded into the hatch mechanism.
6. The bar is deployed to close the hatch that holds the ball.
7. The arm spins towards the bar to close the hatch and lock the ball in the mechanism.
8. The bar is lowered to allow the arm to spin.
9. The entire Trebuchet turns until a target is found using the ultrasonic sensor.
10. The arm spins, both hatches open, and the ball is released.

Parts of the Trebuchet

In this picture is the arm. The arm is connected to a motor with an axle and gears. On either end of the arm is a hatch mechanism that is designed to hold the ball and release it when the arm spins quickly enough. The mechanisms have springs that hold them in their current states (open or closed).
The arm is now loaded with two balls. Also, the purpose of the light sensor is to help position the arm in a way that will not interfere with the deploying of the calibration bar.
This picture contains two motors. The motor on the top spins the arm. The motor on the bottom is connected to small wheels that are used to rotate the Trebuchet when it is searching for a target.
This is the bottom of the Trebuchet. On the left are three small wheels connected to a long axle, which is connected to a motor on the right. The three wheels are used to rotate the Trebuchet when it is searching for a target.
This is the ball loader. It can store two balls at a time and automatically loads the balls into the hatch mechanisms of the Trebuchet. The loader has a slope that the balls sit on, and when a certain gear is turned, one ball is released to roll into a hatch of the arm. The loading mechanism, at the same time, stops any more balls from being released.
One of the motors is connected to a switching mechanism. In the picture to the right, when the motor (bottom) turns clockwise, a bar with gears on it rotates and connects to a gear that deploys the bar used for calibration (right side of picture). When the motor turns counter-clokwise, the bar moves left and connects to a gear that releases a ball from the loader when turned.