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Weekend Project: Prototank

Picture of Ricardo Pires
by Ricardo Pires
Sep 29, 2018

Undoubtedly one of the coolest things about having a 3D printer is that you can print your own toys! We take it to the next level by assembling a 3D printed motorized tank, a great learning experience for both children and grownups.

Evolution

The
The "FPV ProtoTank with Turret" by Chis Tompso. Source: somerandomguy03 / Thingiverse

For this weekend’s project, we look at the ”FPV ProtoTank with Turret” by Chis Tompso. It’s a radio-controlled tank based on the Tim Clark’s “ProtoTank”. This project integrates 3D printed parts with additional electro-mechanical components that can be controlled through a radio-receiver chip. This is in contrast to the earlier version by Tim Clark, which was implemented with an Arduino controller in mind, but could also be run on a Raspberry Pi platform.

An overall attractive design is one of the key aspects of Tompso’s version, which includes a rotating turret equipped with a tilting cannon. But no cannon balls are flying off this build. Instead, the gun houses a first-person view (FPV) camera coupled to a video transmitter, through which you can observe and record the tank’s movements.

This tank also features a complete hull, which provides a comprehensive enclosure of the electronics. The vehicle is protected not only from crashes, but also from weather and terrain conditions, such as humidity or dust particles.

Technical Details

In this build, four motors are responsible for powering the wheels that in turn move a pair of caterpillar tracks. This arrangement ensures better traction even in more difficult terrains. The presence of tracks coupled to a four-wheel drive system allows for improved weight distribution, increased surface grip and precise handling even in muddy conditions.

Piloting itself is enabled by a radio receiver that directly operates the 2 servo motors responsible for the turret & gun movement. The receiver also manages two electronic speed controllers (ESCs), which in turn connect to two of the four motors.

Autonomy is enabled by a lithium-ion battery, with power being managed by a power distribution board (PDB). This connects the battery to the camera, video transmitter and ESCs.

Prototank: What You Need

Image of: Prototank: What You Need
Source: somerandomguy03 / Thingiverse

To help you with this project we list here all the parts you’ll need. They can be obtained from many different retailers, but to make your life easier we’ve linked them all to Amazon.

For 3D Printing

For Electronics

Prototank: Wiring Everything Up

Wiring schematic.
Wiring schematic. Source: somerandomguy03 / Thingiverse

Before you go about assembling everything, it’s always a good idea to first check the wiring to see if all connections have been correctly established.

The above wiring illustration is taken from Tompso’s Thingiverse page.

Essentially, the battery connects to the PDB, from which power will disseminate to the camera, video transmitter (VTX), and both ESCs. Each of the ESCs will then pass power to the motors located on the left and right of the vehicle.

Power connection from any of the ESCs to the two motors should be done in parallel. Only one of the ESCs will be electrically connected to pass power to the radio receiver. In turn, the radio receiver will connect to power the servos, and to pass the signal to them as well as to the ESCs.

Prototank: Putting It Together

Front view of the Prototank.
Front view of the Prototank. Source: somerandomguy03 / Thingiverse

To start this project, begin by downloading the the STL files for the cogwheel model, the inner and outer frames between which the cogwheels will sit, as well as the repeating unit that will form the caterpillar tracks. Initially you will need to print six cogwheels, two inner frames, and two outer frames. The cogs and frames can be mounted together using M3 bolts and nuts. Just make sure the cogs can freely rotate.

Each inner frame will house a set of two motors for each side of the tank. Once you’ve soldered some motor leads onto each of the four motors, the spindle of each motor can be fit on the hole of each cogwheel.

You’ll also need to print 66 pieces of track at 50% infill to assemble two caterpillar tracks (33 pieces per track). You’ll then join each unit in a head-to-tail fashion via 2-mm-diameter wire pins. The track pieces should freely rotate around their joint but without being too lose. This may be tricky to achieve as much is dependent on specific conditions of each print, including the differences in materials, printing parameters, and slight warping effects. To mitigate this, Tim Clark has made five different STL files available for printing the track unit. These files are dimensionally the same, except for the bore size of one of the joints. Using trial and error, you can find which track file is more appropriate for your printer, printing material and parameters.

To print the remaining parts, refer back to the Thingiverse page. The TankBody2.STL file provides one of the main parts for housing most of the electronics, and with exception of a few strategic holes designed to pass cables, it provides thorough protection of its cargo. With the help of some additional 3D printed parts, the electronic components can be appropiately stacked and accomodatedm, providing a clean layout of the internal connections.

License: The text of "Weekend Project: Prototank" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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