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Like every mechanical engineer, at one point of our studies we were so tired/upset of everything not working or not going as intended that we wanted to shoot something.
What if we are able to make a project that converts all our frustration into something enjoyable and satisfying?
Here we present Billy, emperor of destruction, lord of the guns, ally of Nerf company.
The point of this project was to use our creativity to build a robot.
Shooting an object is a very challenging task. In previous project the idea consisted shooting a ball or a dart. We as a group think that we can do better then the average by using fly wheels hooked up to DC motors that can reach a no load of 26 000 rpm at 7,2 Volts.

The turret gun has been designed for being either a possible toy for children or a helpful balls shooter for old people and disabled people who want to play with their dogs. Hence, the gun has to be user friendly as much as possible. In order to do that we have implemented a bluetooth module to allow the user to control the gun directly from the phone. The balls chosen for this model are the Nerf soft balls with a diameter of 2.3 cm.

The gun is composed of three main elements: the “gun platform” where all the shooting and reloading mechanism is placed and the base, which is divided in in other two parts that are the main base structure and the lower base support. (see body design section).

The movements that the robot is able to performed are two:

The base can make a 360° horizontal rotation thanks to both the stepper motor and the lazy Susan bearing linked on the base (a better explanation of this mechanism is given in the chapter “BODY DESIGN”.
90° Vertical rotation made by the “gun plate” thanks to the servo motor linked on the base lateral plate and linked to a shaft which runs underneath the gun plate.
Once the turret gun is turn on, the servo motor sets the gun plate on the steady position that can be regulated by the user. By using the command “fire” the two DC motors attached to the gun plate start to run at the desired speed and by means of friction the flywheels directly linked on the motors’ shaft start to rotate. Thanks to another servo motor the reloading mechanism starts to run and it can be set up for a single shoot or for multiple shoots. It is made of a crank-connecting rod-piston system which is very simple to assemble, control and very reliable. The crank makes a 180° rotation which allows the piston to move through the cylinder and push the balls through the rotating flywheels. The balls are loaded into the cylinder by means of an automatic “Nerf balls charger” that we got when we bought the Nerf balls.”

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