Tinkercad Robotics for School: Rocket Launching Mini-bot

Hello! My name is Mario. Welcome to a new lesson of "Tinkercad Robotics for School", where you can learn how to weaponize Tinkercad to create simple and fun war machines!

Probably I have been repeating this a lot, but if there is something I miss from the 80's and 90's, is the missile-shooting toys. It was awesome to see G.I.Joe, Batman, Transformers, Star Wars, and Aliens action figures and vehicles, launching spring loaded rockets against their enemies. Unsafe? Maybe. But I am an old timer raising my cane with rage against those new action figures; highly-detailed, safe and beautiful, but boring.

Well, the advantage of Tinkercad and 3D printing is that you can design your own toys and add any feature of your preference! Today's activity: we will design a small rocket-launching assault vehicle. Thanks to a micromotor, it will go forward until the front bumper hits an obstacle. In that moment, it will stop and activate another micromotor to shoot four spring-loaded missiles, one by one. The electronics are quite basic: the sensor and brain will be just one single lever switch.

Some applications for this toy are:

• Physics: study of ballistics, simple machines, rotational motion, and electrical circuits.
• Military Engineering: like it or not, this is a career that will always be on demand. Archimedes invented weapons, Leonardo Da Vinci invented weapons, Von Braun invented weapons. Even Iron Man, everybody's favorite hero, invented weapons. But we can dream that the future wars will be fought robot versus robot, saving human lives.
• Rube Goldberg machines: do you need a simple mechanism that moves forward, and then shoot to a target to activate the next step? Here is your answer!
• Robotics: the main feature of this project is the rocket launcher (the car is a plus). You can adapt it to Micro:bit, Arduino and remote controlled robots!
• Bringing impending doom to those modern action figures: let's see if their simulated firing effects are match against a burst of four ballistic rockets.

DISCLAIMER: If well this project is relatively safe, every experiment using ballistics has associated risks. Always use eyes protection. Don't aim or shoot to persons or animals. The author and Instructables.com are not accountable for any problem or legal issue derived from the execution of this activity, so replicate it under your own risk and responsibility. For more information, you can check my "Ballistic engineering for kids" instructable.

You will need the following materials.

• 1 Computer with access to Tinkercad.
• 1 3D printer. Material: PLA. I'm using a Creality Ender 3 V2.
• 4 compression springs.
• 2 x micro motor with gear box, like this. Shaft Size: 10mm x 3mm (L*D)
• 1 x 3.7V lithium polymer battery: from a broken 3Doodler 3D pen.
• 1 x slide switch SS-12F16 G4, 3 pin 2 position on/off; like this one.
• 1 x lever micro switch; like this one.
• 2 x small screws (like the ones you find in toys and calculators)
• wires
• Soldering tin
• Superglue (cyanoacrylate)
• Black rubber bands: to give traction to the wheels. I was in a rush and this was the only option in the moment, so feel free to reinvent the wheel (maybe with tires made of TPU?)
• 2 black rubber rings for plumbing.

Also, you will require the following tools:

• Pliers (for removing support material and adapting the lever of the micro switch)
• Soldering iron
• Screwdrivers
• Optional: Dremel rotary tool

I got the micro motor and the lithium battery inside a broken rechargeable 3D pen. Also, probably you will need a charger for your lithium battery. You can find it online, or create your own. To learn how to harvest valuable components from a 3D pen and create a battery charger from its board, you can check this instructable. Also, I will be recycling some ideas from one of my previous projects: the Dreadnought; so you can check it out as a reference.

First, I brought the Ruler tool to the Workplane. Then I brought three cylinders: one of 9mm diameter X 15mm high (base), a second one of 7.30mm diameter x 17mm high (where the spring will be attached), and a last one of 6mm diameter x 52mm high (rail where the spring and the rocket will slide). I aligned them and group them.

Then I added a perpendicular cylinder of 4mm diameter x 10mm length, This will be the lock that will keep the rocket on place before being shot.

I created two hole cylinders: one of diameter 10mm x 26mm high, and another one of diameter 7mm x 55mm high. I aligned them to the center and group them; and then I aligned them to the center of the porta-rocket.

This will be the hollow part of the rocket, where the porta-rocket and the spring will fit.

I brought a solid cylinder of diameter 14mm x 60mm high, and then I aligned it to the center with the porta-rocket and the hollow part.

Then, I created another perpendicular hole cylinder of 5mm diameter x 10mm length, and placed aligned to the center of the locking cylinder. Then I grouped this new hole cylinder, the previously made hollow part of the rocket, and the solid cylinder to create the basic fuselage of the rocket.

I brought a hollow box and placed it next to the lock's hole. The height had to be equal to the height of the cylinder hole, with 5 mm width x 4.8mm length. Then I rotated it, adjusted it and add more holes until I had a clear entry for the cylindrical lock of the porta-rocket.

On top of the rocket, I placed a paraboloid as nosecone.

On bottom, I added the fins. This part is very important, because the fin not only gives stability to the rocket. It's main function is to work as lever to rotate the rocket, unlocking it and consequently, launching it.

I brought to the workplane a hole model of the micromotor (previously created in my "Warhammer" instructable). Then I brought a cylinder of diameter 50mm and 5mm height. I aligned both of them to the center and group them exactly in the shaft area.

I placed the porta-rocket and the rocket, in one border of the cylinder; then I duplicated and rotated them 180 degrees and brought them to the opposite border. Then I selected the four shapes, duplicated them and rotated 90 degrees, to complete the set of four missile launchers.

I brought another cylinder, this time of diameter 50mm x 40mm height. Then I imported again the micromotor's premade shape. I centered both shapes and group them in the motor area of the micromotor. This cylinder will house the micromotor.

I brought another micromotor (solid) and placed it in the respective hole. Then I placed the launching cylinder over it and aligned both cylinders through the center.

Using a cube of 10mm x 10mm x 54mm, I created some sort of "finger". When the launcher rotates, this finger will block the path of the rocket's fin, causing the rotational motion and firing the rocket.

Then I joined this trigger to the launcher's body, using another box.

I rotated 90 degrees the whole launching set, until it was parallel to the workplane.

I needed to create a frame to place the launcher, so first I created a pin, using a cylinder of diameter 10mm x 25mm height, and another cylinder of diameter 20mm x 5mm height. I aligned them to the center and group them. Then I created one side of the frame, with a hole of 11mm diameter so the pin could pass through,; and prepared a hole of diameter 10.5mm, to place in the launcher's main cylinder.

I selected this first part of the frame and the pin, rotated them 90 degrees and placed on one side of the launcher. Then I duplicated and mirrored them, and placed on the opposite side. I grouped the main body of the launcher with the diameter 10.5mm holes, so the pins can fit on them.

For the rotatory base of the frame, I brought a diameter 70mm x 5mm high cylinder, duplicated it and placed the duplicate exactly over the original. The top cylinder was grouped with the pillars of the frame; the bottom one would be grouped with the chassis of the vehicle. To make it turn, I used the same set of holes and pin from the previous step, being this new pin shorter.

On the top base, I placed metafillets in the joints between the frame and the base, to give it more resistance to stress.

As I said at the beginning, I recycled some shapes and ideas from my previous "Warhammer's Dreadnought" instructable. In this case, I took the Dreadnought's gearbox, and removed the chimneys and joints, using hole boxes, until I got a box shape that I would use for the vehicle.

I also imported the gears, axle and cranks. Then, I assembled the gearbox and turned it flat over the workplane.

I duplicated the main body of the gearbox, and moved it to the back. Then I inserted a hole cylinder, so a second axle and pair of wheels could be placed there. Then, I grouped both gearboxes and the bottom cylinder of the frame, to create the chassis.

I took the crank and a wheel from the Beta Library of Tinkercad. Then I selected both of them and aligned to the center. I made some modifications and then, I grouped both shapes, creating the wheel for this project.

I duplicated it three times, and placed two on the front axle (gearbox), and two on the rear axle.

On the front part of the gearbox I placed a hole box of 10mm x 7mm x 21mm, to house the lever switch.

I interconnected the compartment of the lever sensor with the other compartments of the chassis, so the cables have space to pass through.

I brought a box of 30mm x 5mm x 25mm. Then I placed a little hole box of 4.10mm x 0.50mm x 7mm, so the metal lever of the lever switch can fit inside.

I personalized the plate, with some letters and numbers of my preference.

In Tinkercad, I returned to the Dashboard and duplicated the design, so I could rearrange all the pieces for a better printing; verifying that all of the components were laying over the workplane.

After rearranging the parts for printing, I exported the STL files and opened them in the slicer.
I used the following parameters:

• Printer: Creality Ender 3 V2
• Slicer: Ultimaker Cura 4.8.0
• Material: PLA
• Printing Temperature: 200°C
• Infill: 20% (wheels, chassis, and sensor plate), 50% (rockets, trigger, base, pins), 100% (axles, gears, launcher)
• Supports: Linear
• Raft: Yes
• Scale: 100%

I am attaching the STLs, so... now have fun assembling it!

The electronics are quite basic. This schematic will show you how to connect the wires and components.

When you activate the Main Switch, Motor 1 will move until the Lever Switch (sensor in the bumper) is activated. Then it will divert the electricity to Motor 2 (Rocket Launcher), stopping the car and shooting the projectiles.

Bring the Launcher and insert each spring on each cylinder. If the bottom end of the spring doesn't stay on place, add a little drop of Superglue.

Insert the micromotor on the center of the trigger cylinder.

Now, insert the micromotor's shaft in the center of the launcher.

Bring the chassis and the base frame, and use the small pin to attach them together.

Bring the other two pins and the rubber rings. Place a ring on each pin. Then, pass each pin through the frame's hole, and then, insert it in the respective hole in the launcher. The rubber rings will help the launcher to stay in place when the shooting angle is modified.

Grab the wheels, and place rubber bands in the grooves. This will give more traction.

Solder two wires to the micromotor. Then, insert its shaft in its respective gear.

Insert the micromotor in the chassis. Then, place the other gear and insert the axle. Before adding the wheels, test the direction of the movement. Don't worry about the polarity: in case you need to change the direction of the movement, you can place the axle's gear on the opposite side of the axle.

When you are happy with the result, attach the wheels.

For the back set of wheels, you only need to insert the axle and then attach the wheels.

Take two cables. Insert them into the small hole on top of the chassis, and take them out through the sensor's hole. Solder one end of each cable to each pin of the launching micromotor.

Insert the switch's lever in the little slot on the bumper plate. Then, solder the wires to each pin, following the diagram from Step 20 (Electronics). Remember: the default position of the switch is released. When it is pressed, the wheels' motor will stop, and the launcher's motor will move.

Consider these pins in the Lever Switch:

• COM: To the battery
• NO: To the launcher's motor
• NC: To the vehicle's motor

NOTE: Due to several trials and mistakes, I got the cable colors mixed. So, to recognize which wire goes to which pole of the battery, I place thermo-shrinkable tube of red color in the positive cable, and black color in the negative.

As maybe you remember, I am using recycled components from a broken rechargeable 3D pen, so I removed the plug from the board. In case you don't have a broken 3D pen, you can get a compatible socket for your battery on and electronics shop.

Insert the rechargeable battery in the respective place. Then, bring the resulting two cables.

Place the switch on the available spot and fix it with two small screws. Then, solder the positive cable (red shrinkable tube) to the corresponding positive wire (red) in the battery plug. Connect the negative wire (black) of the battery to the central pin of the switch, and connect the negative cable (black shrinkable tube) coming from the motors, to one of the available pins in the switch.

Insert a rocket into one of the launchers. When its fully inserted, rotate it until the small cylinder locks into the rocket's shaft. Do the same with the other three. Be careful when you do that. Use safety goggles.

Test the launcher. If it rotates in a way that it gets jammed, change the polarity in the motor
(invert the cables.)

Now, be ready to have ballistic fun!