Making a BEAST of a 3D Printed RC TANK with Dual Speed Gearbox

In this tutorial I will show you how I built a beast of a 3D Printed RC tank or a radio-controlled tracked vehicle, featuring clean, all-black design, some cool LED lighting and a dual speed gearbox. That’s right, I specifically designed a gearbox for this tank so I can choose a lower or higher gear depending on terrain or the application that is used for, and so get either higher torque or higher speed.

You can watch the following video or read the written tutorial below.

Overview

If you follow me, you might know that some time ago I already built a 3D printed RC tank, which was cool, but a bit underpowered. That’s why now for this build I’m using 200W DC motor for each track and in combination with this gearbox, the tank has plenty of power to conquer any terrain or to have some fun doing burnouts or donuts with it.

Talking about having fun, I installed an addressable led strip for the lights, which gives endless possibilities for creating stunning light effects. For this video I made a Police lights strobe effect, which is so cool driving around with it, especially at night

As for the suspension, on each side, the tank is supported on three coil springs and shock absorbers, with two roadwheels for each of them. That allows the vehicle to run smoothly on uneven terrain and climb obstacles while maintaining good contact surface between the tracks and the terrain.

Of course, everything is 3D printed and 3D files are available for downloading, so you can build one on your own. 

For controlling the tank, I’m using a cheap commercial RC Transmitter which sends commands to it. 

At the tank, there is a suitable RC receiver which receives the commands and sends them to a microcontroller. The brain of this platform is an Atmega2560 microcontroller-based board and for easily connecting everything together I made a custom PCB which can be simply attached on top of the board. 

Nevertheless, now buckle up as I will walk you through the entire process of building this RC tank, starting from the design, 3D printing, assembling and connecting the electronics components, to programing the microcontroller.

Designing the RC Tank

I designed this tank using Onshape.

Onshape is the professional grade cloud native 3D CAD & PDM system that I use for my projects.

I recommend that mechanical engineers and product designers check out Onshape, you and your company can use Onshape Professional for free up to 6 months at https://Onshape.pro/HowtoMechatronics

The initial input parameters for the design were the DC motors, or their dimensions and the RPM. These motors are quite bulky and have 3000 RPM. That’s too high RPM for this tank, so therefore I designed this gearbox, which reduces the speed to two different values.

This gearbox works just like a manual transmission in a car works. There is a gear shifter which instead of moving it by hand, here it is moved with the help of a servo motor, and it can choose which of the two output gear sets will be engaged as final output.

The gearbox initial reduction ratio is 1.88:1, which is fixed, and then we can choose either the low gear, which has additional reduction of 2.76:1, or the high gear, which has 1:1 ration. So, in lower gear, the total reduction is 5.2 or that’s around 570RPM, and the higher gear just 1.88 speed reduction, or that’s around 1600RPM.

We will see more details how the gearbox works a bit latter in this video we will assemble it.

The next input parameter for the tank design were the RC shock absorbers that I got. They have a length of 70mm when extended, with 15mm travel. I wanted to get a bit greater vertical travel distance for the roadwheels, so I positioned them in this configuration, and got a vertical travel distance of 22mm.

In addition to that, as this is a bogie system where a pair of wheels is attached to that moving axis, the wheels can rotate around that axis and so they can make additional vertical travel. Evidently, that will provide smoother ride and better contact between the track and the surface under it.

If we take a closer look at the front roadwheels, we can notice that they connected with the idler wheel on the front to provide dynamic tension of the track. When the front roadwheels goes up, the track circumference gets smaller and so the tension loosens.

With this setup, when that happens, the idler wheel is pushed forward to tension the track. With this connection we can also tension the track statically, by adjusting this bolt and distance nut.

At the back side, we have the sprocket which is composed of three parts. It has the shaft coupler and left and right section of the sprocket connected all together with three M3 bolts.

The key dimension here on the sprocket is the pitch because it must match the pitch of the track. The pitch is 11mm here and I chose the sprocket to have 20 teeth which gave me a pitch diameter of the sprocket of around 69mm. The idea for the size of the sprocket was to be big enough so that the track stays out of the tank body.

The 11mm pitch was actually defined by the design of the track link. My goal for the track link was to be as compact as possible and to connectable with the next link with just one additional part or pin, while being strong enough to be made with a 3D printer.

On top of that, when 3D printing, I wanted to avoid any use of support material for the part, which I actually managed to achieve with this design.

For connecting the track links to each other, I planned to use pins with 2mm diameter, so I dimensioned one side to be 2.1mm, to get tight fit, and the other side 2.4mm, to get loose fit so that the track links can rotate freely.

The sprocket teeth engage with the track links at the outer cylindrical shape. The track link cylinder has 4.4mm radius, while the sprocket has 4.9mm in order to have a loose fit to work properly.

The main body where everything is connected, had to be big enough to fit the two gearboxes, and of course, to have space for the electronics and the battery. All this resulted the tank overall dimensions to be 547x397mm. That’s fairly big, bigger than the usual 3D printer’s bed, so therefore I divided the big parts into two sections, so we can print them on a 300mm bed 3D Printer. Please note that if you want to print it on a smaller 3D printer with 220mm, the model has to be divided into 4 sections. I will also provide that version in the 3D files.

For assembling the tank, we need various M3 and M4 bolts and nuts, as well as some threaded inserts and bearings. You can find a complete list of all the components needed for this project below. Of course, you can also find the 3D model and the STL files needed for 3D printing.

3D Model and STL Download Files

You can view the 3D model of this RC tank directly on your web-browser with Onshape.

You can get the 3D model of this RC tank/ robot platform , as well as the STL files for 3D Printing from Cults3D.

3D Printing

I used my Creality Ender-3 V3 Plus 3D printer for printing most of the parts for this tank.

When 3D printing, it’s important to use the Horizonal Expansion feature, or now in the new Creality Print slicer that I used, it’s called X-Y contour compensation. If we leave these settings by default, the prints outer dimensions as well as the holes are usually smaller than the original model and we might have problem assembling them.

In the Creality Print slicer I used a value of –0.07 for the X-Y contour compensation, and plus 0.07 for the X-Y hole compensations feature. Of course, you should do some test prints to see what values will give you the best results on your 3D Printer.

For 3D Printing the track links, I used rafts as build plate adhesion, because their base contact surface with the bed plate is a bit small and might not stick well if the bed adhesion on your printer is not that good.

The Creality Ender-3 V3 Plus has a build plate of 300x300mm, so I could print the main body of the tank in two parts. Even in two sections, the parts are still quite big, and push the 3D printer to its limit. But the Creality Ender-3 V3 Plus managed to handle it and it did a great job printing these big parts.

I can recommend this 3D printer to anyone looking for a large volume and fast 3D printer. It a CoreXZ 3D Printer that can reach speeds of up to 600mm/s and with its sturdy frame it provides really good printing quality. Shout-out to Creality for providing me this 3D Printer.

Check out the Creality Ender-3 V3 Plus – USA store: https://shrsl.com/4rtkk ; EU store: http://shrsl.com/4rtkm ; Amazon: https://amzn.to/3VjEoRH

Assembling RC Tank

Here are all of the 3D printed parts, so we can start assembling the tank. To be honest, there is so much 3D printing. It takes like several days to print everything, and not just time, but we also need several spools of filament.

For the track links alone, because there are 214 track links total, we need around 500g and 30 hours of 3D printing. The main body of the tank needs around 1kg of filament, if divided in two sections like here, 500g and around 12 to 18 hours for each section. Also, many of the parts need to be 3D printed with support, so we need to do spend some time cleaning.

BOM

Here’s a list of components needed for assembling this RC tank project. The list for the electronics components can be found below in the circuit diagram section of the article.

Component	Quantity	Purchase Links
RC Shock Absorbers	8	Amazon | AliExpress
Ball Bearing 686 – 6x13x5mm	18	Amazon | AliExpress
Ball Bearings 624 – 4x13x5mm	44	Amazon | AliExpress
Ball Bearing 684 4x9x4mm	6	Amazon | AliExpress
M6 Threaded Rod	300mm	Amazon | AliExpress
M6 Lock-nut	4	Amazon | AliExpress
M3 Threaded Inserts	~20	Amazon | AliExpress
M3 Grub Screw	~30	Amazon | AliExpress
M3 and M4 bolts and nuts	To be specified	Amazon | AliExpress
2mm Welding Rod	~12m	Amazon | AliExpress
M3 and M4 bolts and nuts	See list below	Amazon | AliExpress

Bolts	Nuts
M3x8mm – 10 M3x10mm – 10 M3x16mm – 20 M3x20mm – 10 M3x25mm – 10 M3x30mm – 10 M3x16mm countersunk – 20 M4x16mm – 10 M4x35mm – 20 M4x40mm – 20 M5x40mm – 2	M3 Lock-nut – 50 M4 Lock-nut – 40 M5 nut – 6

Disclosure: These are affiliate links. As an Amazon Associate I earn from qualifying purchases.

Electronics – RC Tank Circuit Diagram

let’s take a look at the electronics for the RC tank and explain how it works. The brain of this RC tank is an ATmega2560 microcontroller-based board. 

You can get the components needed for this project from the links below:

Component	Quantity	Purchase Links
DC Motor 895 – 12V 200W 3000RPM	2	Amazon | AliExpress
BTS7960 DC Motor Driver	2	Amazon | AliExpress
Servo Motor	1	Amazon | AliExpress
ATmega2560 – Arduino Mega Board	1	Amazon | AliExpress
3S LiPo Battery – minimum 3000mAh	1	Amazon | AliExpress
LiPo Battery Connectors	1	Amazon | AliExpress
Flysky FS-i6X – RC Transmitter and FS-iA6B Receiver	1	Amazon | AliExpress
WS2812b Addressable LED Strip	1m	Amazon | AliExpress
LM350 Voltage Regulator	1	Amazon | AliExpress
Trimmer Pot – 5k	1	Amazon | AliExpress
Terminal Block Connector	4	Amazon | AliExpress
Wires ~20AWG	~3m	Amazon | AliExpress
Rocker Switch	1	Amazon | AliExpress
Resistors – 1k x1 – 2k x1 – 240 x1		Amazon | AliExpress
Capacitors – 0.1uF x1 – 1uF x1 – 400uF x1		Amazon | AliExpress

Disclosure: These are affiliate links. As an Amazon Associate I earn from qualifying purchases.

Custom PCB Design

In order to keep the electronics components organized, I designed a custom PCB for the RC tank. The PCB will be compatible with the ATmega2560 microcontroller-based board to be directly mounted on top of it.

I ordered the PCB from PCBWay. Here we can simply upload the Gerber file, choose the properties of our PCB, and order it at a reasonable price.

I didn’t change any of the default properties except for the PCB color which I chose to be blue. You can find and download the Gerber from the PCBWay projects sharing community through which you can also directly order the PCB.

Finishing RC Tank Assembly

In this section I will explain how to connect everything together and complete this RC tank.

This section is still under construction.

Programming the RC Tank – Arduino Code

In this section I will explain how the Arduino code behind the RC tank works.

Please note that this section, as many other sections of this written article are still under construction. They will be done couple of days.