Turret/Sentry - Mighty Shooter

This Project is part of my Submission for the Creato 1.0 by robu.in. The project competition is a Turret Building Competition to be built within a month starting from 21st August.

I started working on this project on 7th September 2021, and this document will provide the steps and process I went through, for completing this project.

MECHANISM

When I first heard of 'turret', it reminded me of, one of the abilities of KillJoy in the Valorant game.

So, the purpose of a turret is to shoot things. And on my behalf, I had to find a mechanism with which I can shoot things.

On the other hand, the competition rules stated that we have to build something that throws/shoots on targets precisely. With that in mind, it was necessary to have accurate geometry and a smooth mechanism, so that I could shoot things.

Post that, I kept on thinking of something that I could use as my ammo/bullet. Something small, with a mass. That could easily travel a long distance carrying along with its increasing momentum.I came up with using marble/glass balls. It is something, most of the Indian houses have. Mostly used in the old days to play with them.

Losing multiple bullets/ammo won't bother me much now, as it is commonly found in the market. And very cheap as well.

For the mechanism, I start throwing the marble ball from tunnel-shaped pipes. What I found is, using Kinetic energy to launch the marble for a longer distance would be a great idea.

So, the next day I kept thinking of a way, so that I can use a P.E. to shoot the marble. With that, the idea of using an elastic band hooked on. And, I started designing a way, so that the elastic band can be used to produce the K.E. within the barrel. And that's when I came up with this.

I used an Acrylic Sheet to carve and Superglue, to make these shapes/structures. Added many ways so that, an elastic band can be used to get the P.E. and launch the marble with that potential.

The mechanism is a kid's play. But the effort was 100% from my side. In the future, I hope to come up with an easier and better shooting mechanism. Something that would take minimal space.

BODY SETUP

Now that we have a shooting mechanism, we require a structure/body to hold the and counter the force. We know the 3rd Law of Motion - Every force has an equal and opposite reaction. This law applies practically as well. And therefore, when building a body to pull the string or/and holding the string, before the ejection, a strong structure and body are necessary.

With a strong and geometric base, the mass of the shooter will be well-balanced. Keeping in mind, that the object will be shot at an angle to get a duly proper trajectory to attain the highest distance. We know that the 45° angle has the best firing range, but I initially set up an angle of 24° in a hope of being able to change the angle in the future with the help of servos.

LOGIC and CONTROL

After setting up the body of the turret, it was time to find a way to control the elastic mechanism. Since I already had handles on both sides, I could use its help to PULL > HOLD > PASS. Here, PASS refers to ejecting the grip instantly instead of leaving the elastic slowly.

The P - H - P mechanism can be applied in different ways. Like, the usual guns that exist, Automatic and Pistol. 1st one has an auto reload-shoot system. In the latter, reload and shoot are separate.

Let us go through the 1st mechanism first-

AUTOMATIC MODE

In this mode, the bullets will be serially put, so that they can be ejected one by one, but the ejection is not limited to only one. For a rapid-firing technique, i.e. the trigger has to be pulled and ejected.

I decided to use a dual shaft motor, which will push the shaft of elastic to the end, and when it reaches there, the further force will cross the peak point, ejecting the Potential Energy formed, converting it to Kinetic Energy, and ejecting the bullet out of the barrel.

I had a 7.5 V power supply (5 x AA cells), which I used to power the motor. And as you can see in the GIF above, the motor makes one rotation only in a cycle of power supply. And, the high voltage is to move more electrons creating a greater force. This force is necessary to counter the potential of the elastic.

With proper calibration and power, it could be a sentry gun in use. As you have seen earlier, there is a bullet loading section, so every time the elastic pulls back, the bullet is loaded. And with that speed, only one bullet can be loaded and passed across the barrel. Hence, it is an auto reload-shoot system.

Next, the 2nd mechanism -

PISTOL MODE

In this mode, the reload has to be manually performed. Either using the motor or by hand. And then the shoot, after reloading of the bullet.

Here, reload refers to the building of the Potential Energy by pulling the string to the very end. In my project, I have used the servo motor, to LOCK in and EJECT the elastic.

Here, I did not use any AA power supply, with too much voltage. Just a regular 5V supply to the servo motor. And the control from my browser using Bolt IoT module.

For both the above modes, since it was a testing of the modes, I did not use strong elastic, and therefore the ejecting wasn't powerful.

CONTROL INTERFACE

As I will be using the pistol mode, to control the servo motor, I decided to use the Bolt IoT module, because it is easy and faster to write the statements. And nothing much to code as well.

I only wrote a webpage, with 3 buttons - SET, LOCK, LAUNCH

SET -

• Writes to the servo motor for 150° angle.
• Changes the color of the button to blue and all others as grey.
• Meant for a ready-to-go mood

LOCK -

• Writes to the servo motor with 180° angle
• Changes color of the button to blue and all others as grey.
• Meant for locking the shooting block. Has great pressure, as it holds the potential energy of the elastic

LAUNCH -

• Writes to the servo motor for 180° angle.
• Changes the color of the button to blue and all others as grey.
• Meant for letting go of the pressure all at once, for ejecting the shooting block.

function set(){
        set1 = 1;
        lock1 = 0;
        launch1 = 0;

        servoWrite(0,150);
}

function lock(){
        set1 = 0;
        lock1 = 1;
        launch1 = 0;

        servoWrite(0,180);
}

function launch(){
        set1 = 0;
        lock1 = 0;
        launch1 = 1;

        servoWrite(0,0);
}

The Code attachment contains the full code of the whole web interface.

TESTING

For the final prototype, I have continued with this mode, as the automatic cannot handle stronger elastic with a DC motor. I'll later use a 360° servo with a higher torque to handle the pressure.

Testing was done on different trajectory angles and with different dimensions and masses of bullets.

Below you will see the working of Pistol Mode at its full potential.

As you saw above, the pistol mode works very well. So further testing will be performed on this mode as well.

The testing will be performed 3 times for each angle and size of the ball. That is a total of 3³ = 27 times.

ANALYTICS (distance - in cm)

From the above analysis, it is determined that the best configuration for the turret is the small (S) size at an angle of 24°. It attains an average distance of 120cm on ejection.

Now you know why I chose 24° as the default angle for the trajectory. Based on the function, barrel, and the bullet (marble), the best is to have a decent angle of trajectory.

TARGET PRACTICE (Precise Shot)

Now, the main part of the competition, to record the most precise shots the turret can attain. I was asked to shoot a video of it, as Proof of Validity.

Enjoy the Show!