Lego Track Bot

What I really love about Lego's Modular System - no matter how old or new the components are, they still can be fit together.
We can also mix them up using components from one kit with some others. This project is certainly a proof of that.

Motivation

I owned an incomplete Lego's Star War Battle Droid (#8001). The Droid can be folded to fit in the small storage space.
The fun part is that we can make the Droid to draw its weapon from the shoulder by rotating the gear on its back. 

The drawback of this Battle Droid is it needed to have elastic rubber bands to hold them together, without the rubber bands it could not stand up properly, and it lost its value as collectable, and also considered incomplete.

Since the Droid is not a walkable or movable by itself, I think it will be fun to alter this Battle Droid by adding Johnny Five's (another fictional robot in the movie called "Short Circuit" released in 1986) main features: the triangle tracks and rear pivoting castor to the Droid. Then trying to make it move. 

This Lego Track Bot was designed to be an example to show how to use  Palm Arduino V3 with the Lego's components.

 Note: See more photos of my Lego Track Bot and video in Step 14.

In this project, I created a robot that combined the parts from components list below,

• Incomplete set of Star War Battle Droid (#8001),
• Treads and Hubs from RCX Mindstorm Set,
• Commonly used Technic Bricks and Plates
• Motors and motor controller.
• Sensor(s) such as IR distance sensor, etc. might be added.

Palm Arduino V3
For the details, schematic and parts for Palm Arduino V3 go here.

Lego case for Palm Arduino V3:
Bricks and Plates are already included in the Lego Parts list below.

DIY Motor Controller PCB (Photo 4) or Motor Shield

- 1 no. L293D (or SN755401) IC
- 1 no. 0.1uF Ceramic Capacitor
- 1 no. 100uF Capacitor
- Jumper Wires
- Perf. Board
- 2-Pin Right Angle Header (Motor Power Connector)
- 3-Pin Right Angle Connector (for Servo if you plan to use one, this)
- 2 nos. 2-Pin Right Angle Connector (Straight is fine too!) for motors

Tamiya Twin-Motor Gearbox (No. 97)

Lego Technic Star War Battle Droid (#8001)
I got my on ebay the one I used in this project was incompleted set and had no instruction booklet, and it was cheaper than complete or mint collectable kit

Lego Technic Bricks, Plates, and Components

All the Lego parts used in this project are from what I own. I bought them from Lego online "Pick A Brick" Shop. Some I got them from bidden on eBay.

The following Lego components are separate components from the Lego Star War Battle Droid (#8001) above.

4 nos. 1x16 Technic Brick (#3703)
4 nos. 1x12 Technic Brick (#3895)
2 nos. 1x10 Technic Brick (#2730)
4 nos. 1x8 Technic Brick (#3702)
7 nos. 1x6 Technic Brick (#3894)
7 nos. 1x4 Technic Brick (#3701)
6 nos. 1x2 Technic Brick (#3700)

10 nos.  1x2 Plate (#3023)
4 nos.    1x3 Plate (#3623)
11 nos.  1x6 Plate (#3666)
8 nos.    1x8 Plate (#3460)

2 nos. 1x2x2 Corner Plate (#242)

7 nos. 2x2 Plate (#3022)  (Note: Use two old 2x2 plate to use with Twin-motor Gearbox)

2 nos. 2x4 Technic Plate (#3709)

4 nos. 3x3 Liftarm (#32249) or 3x3 L Shape Thin (#32056)
9 nos. Liftarm 1x3 Thin (#6632)

6 nos. Bush for Cross Axle (#6590)
2 nos. 1/2 Bush (#32123)

24 nos. Connector Bush with Friction/Crossaxle (#43093)
4 nos.   Connector Peg with Friction (#2780)
4 nos.   Connector Peg with Friction 3M (#6558)
2 nos    Fric. Snap W/Cross Hole 2M (#32054)

2 nos. Connector Peg with Knob (#4274)

3 nos. Axle Joiner Inline (#6538b)
3 nos. Pin Joiner Round (#75535)


2 nos. Cross Axle 4M (#3705)
6 nos. Cross Axle 5M (#32073)
4 nos. Cross Axle 6M (#3706)
2 no.   Cross Axle 8M (#3707)

Treads and Hubs from RCX Mindstorm Set

8 nos. 16T Gear (#4019)
6 nos. Technic Sprocket Drive Wheel (#32007)
2 nos. 5" Caterpillar Tread (#680C01)

Note: These last two items could be replaced with

• Lego Technic Tank Wheels & Track for custom army vehicles for example Town Set or Indiana Jones Set, or 
• NXT Technic Mindstorm Black Treads & Hubs.

Tools

Razor Saw
X-acto Knife
Super Glue
Sugru

In this project I used the Star War Battle Droid's (#8001) torso, arms, backpack, and head, as the top parts of the Track Bot. (If you have other set that you like to use instead please feel free to do so.)

I didn't have the Star War Battle Droid (#8001) building instruction. But Lego provided the pdf instruction file on their website. So I download the file from the link here.
,
I followed the instruction to build the torso, arms, backpack, and head parts only. Since these are the parts I only needed. 

Then I measured the width of bottom of the finished torso, so I can use this measurement to build the bottom part or base of the robot to fit. I got the width of six Studs. (Stud is the Lego measurement of the Lego's components such as Bricks, Plates, etc.)

Twin-Motor Gearbox

I used Tamiya's Twin-Motor Gearbox to drive the robot because the width of the gearbox is comfortably fit inside the frame (six studs length)

I assembled the Tamiya-Twin Gearbox as C type (Low speed, 203:1 gear ratio), according to the included instruction manual. 

In order to install the gearbox to the robot's frame. I sacrificed 2 nos. 2x2 plates (#3022) by cut them up and stick them to the gearbox enclosure to be used as the connectors to the Lego components.

I installed the gearbox along the main vertical frame (1x16 Technic Brick, grey brick in Photo 1) . Because the height of the gearbox is larger than the hubs that used to drive the tracks of the Bot.

Lego parts used in this Step:

2 nos. 2x2 Plate (#3022)
2 nos. Connector Peg with Knob (#4274)
2 nos. 1x16 Technic Brick (#3703)

The details of how to modify the gearbox are shown in description text box in Photos below.

Tracks and Hubs

I chose the "Track and Hubs from RCX/NTX Mindstorm Set" because of the size that was suitable for Star War Battle Droid (#8001).

The "Track and Hubs from RCX/NTX Mindstorm" Set consisted of only two Technic Sprocket Drive Wheel (#32007). I got the extra two from eBay.

And the hubs was also suitable for the hexagonal axles of the Tamiya's Twin-Motor Gearbox (No. 97). Only a little modification on the gearbox hex. axle and hubs are required to make them work.

Here are the parts that we needed for the modification:

2 nos. Technic Sprocket Drive Wheel (#32007)
4 nos. 16T Gear (#4019)
2 nos. Connector Peg with Cross Axle (#6562)
2 nos. Hex Axles removed from the assembled Tamiya Twin-Motor Gearbox.

The details of how to modify the hubs are shown in description text box in Photo 2 to 12 below.

Vertical Frames & Base

Lego parts used in this Step:

4 nos. Connector Peg with Friction 3M (#6558)
2 nos. 1x12 Technic Bricks (#3895)
6 nos. Connector Peg with Cross Axle (#6562)
4 nos. 3x3 Liftarm (#32249) or use 3x3 L Shape Thin (#32056) instead.
2 nos. Connector Peg with Friction (#2780)
2 nos. 1x10 Technic Bricks (#2730)
2nos. 1x16 Technic Bricks (#3703)

The details of how to construct Vertical Frame & Base are shown in description text box in Photos below.

Continue on the vertical frames and base, I added two axles for the triangle sprockets (or hubs).

Lego parts used in this Step:

4 nos. Cross Axle 8M (#3707)
4 nos. Bush for Cross Axle (#6590)
2 nos.  Joiner Inline (#6538b)

4 nos. 1x3 Plate (#3623)
4 nos. 1x6 Plate (#3666)

The details are shown in description text box in Photos below.

Now it's time to secure the vertical frames together.

Lego parts used in this Step:

2 nos. Liftarm 1x3 Thin (#6632)
12 nos. Connector Bush with Friction/Crossaxle (#43093)

4 nos. 1x6 Plate (#3666)
2 nos. 1x4 Technic Brick (#3701)


The details are shown in description text box in Photos below.

This step come to the final touch of the Frames and Base.

Lego parts used in this Step:

2 nos. 1x4 Technic Brick (#3701)
2 nos. 1x2x2 Corner Plates (#2420)
1 no. 1x8 Technic Brick (#3702)


The details are shown in description text box in Photos below.

In Step 4, I did show you how to modified a pair of hubs to fit with Twin_Motor Gearbox. And in this Step, shows how to assemble the hubs and tracks.

Lego parts used in this Step:

4 nos. 16T Gear (#4019)
4 nos. Technic Sprocket Drive Wheel (#32007)
2 nos. 5" Caterpillar Treads (#680C01)

This step shows how to add the torso to the base.


Lego parts used in this Step:

Assembled Torso of Star War Battle Droid (#8001)

2 nos. 1x8 Plate (#3460)

2 nos. 2M Friction Snap W/Cross Hole (#32054)
1 no. 10M Cross Axle (#3705)
1 no. Pin Joiner Connector (#75535)

In this Step, I'm going to show you how to construct the battery compartment and the rear castor.

Lego parts used in this Step:

3 nos. 1x6 Technic Bricks (#3894)
2 nos. 2x4 Technic Plates(#3709)

4 nos. 1x2 Plates(#3023)

4 nos. Bush for Cross Axle (#6590)
2 nos. 1/2 Bush (#32123)
2 nos. Axle Pin Angle Connector (#6536)

2 nos. Tire High Narrow Ø15 X 6 (#87414)
2 nos. Hub with split axle hole (#3482)

4 nos. Connector Bush with Friction/Crossaxle (#43093)
2 nos. Liftarm 1x3 Thin (#6632)

1 no. Cross Axle 6M (#3706)
1 no. Cross Axle 4M (#3705)

Lego Parts

2 nos. 1x2 Technic Brick with two holes (#32000) or plain 1x2 Brick (#3004)
2 nos. 1x8 Technic Brick (#3702)
1 no. 1x6 Technic Brick (#3894)

2 nos. 1x2 Plates (#3023)
3 nos. 1x6 Plates (#3666)
4 nos. 2x2 Plates (#3022)

The details of how to install Palm Arduino and In situ Lego case are shown in description text box in Photos below.

Note: For the details of DIY Motors Controller, Schematic, and components, see Step 5, Palm Arduino II. 

Now the robot is ready for the test!

I test the Track Bot using the sketch below. Track Bot will do some simple movements, moves forward, turns left, moves backward, turns right, stop, forward, backward, and stop.

#define LEFT_EN 6
#define LEFT_A1 4 // Motor A1
#define LEFT_A2 5 // Motor A2

#define RIGHT_EN 9
#define RIGHT_A1 7 // Motor B1
#define RIGHT_A2 8 // Motor B2

void setup(){
  pinMode(LEFT_EN, OUTPUT);
  pinMode(LEFT_A1, OUTPUT); 
  pinMode(LEFT_A2, OUTPUT); 
  
  pinMode(RIGHT_EN, OUTPUT);
  pinMode(RIGHT_A1, OUTPUT); 
  pinMode(RIGHT_A2, OUTPUT); 
  
  digitalWrite(LEFT_EN, LOW);
  digitalWrite(RIGHT_EN, LOW);
}

void Forward(){ //Go Forward
  digitalWrite(LEFT_EN, HIGH);
  digitalWrite(LEFT_A1, HIGH);
  digitalWrite(LEFT_A2,LOW);
  
  digitalWrite(RIGHT_EN,HIGH);
  digitalWrite(RIGHT_A1, HIGH);
  digitalWrite(RIGHT_A2, LOW);
}

void Left() {
  digitalWrite(LEFT_EN, HIGH);
  digitalWrite(LEFT_A1, HIGH);
  digitalWrite(LEFT_A2,LOW);
  
  digitalWrite(RIGHT_EN, HIGH);
  digitalWrite(RIGHT_A1, LOW);
  digitalWrite(RIGHT_A2, LOW);
}

void Right() {
  digitalWrite(LEFT_EN, HIGH);
  digitalWrite(LEFT_A1, LOW);
  digitalWrite(LEFT_A2, LOW);
  
  digitalWrite(RIGHT_EN, HIGH);
  digitalWrite(RIGHT_A1, HIGH);
  digitalWrite(RIGHT_A2, LOW);
}

//Go Backward
void Backward(){
  digitalWrite(LEFT_EN, HIGH);
  digitalWrite(LEFT_A1, LOW);
  digitalWrite(LEFT_A2, HIGH);
  
  digitalWrite(RIGHT_EN,HIGH);
  digitalWrite(RIGHT_A1, LOW);
  digitalWrite(RIGHT_A2, HIGH);
}

// Stop
void Stop(){
  
  digitalWrite(LEFT_EN, LOW);
  digitalWrite(LEFT_A1, LOW);
  digitalWrite(LEFT_A2, LOW);
  
  digitalWrite(RIGHT_EN, LOW);
  digitalWrite(RIGHT_A1, LOW);
  digitalWrite(RIGHT_A2, LOW);
}

void loop(){
  
  Forward();
  delay(3000);
  
  Left();
  delay(4000);
  
  Backward();
  delay(2000);
  
  Right();
  delay(4000);
  
  Stop();
  delay(1500);
  
  Forward();
  delay(3000);
  
  Backward();
  delay(2000);
  
  Stop();
  delay(2000);
}

This is an absolutely the project that I enjoy the most!

I did a very lest modification (attached 2x2 plates to Twin-Motor Gearbox). And modified a pair of the Lego's sprockets (hubs) to fit the hex. axles of the Twin-Motor Gearbox. It's OK with me, I knew that I could easily find spare hex. axles for the Gearbox. And I could remove the Sugru and 2x2 plates out of the Gearbox with no damage done to the Gearbox at all. (That's what the Sugru is all about!) 

And I did learned something valuable, such as, how to secure Bricks and learned math. behind the Lego system. (Using Pythagoras' Theorem to solve the diagonal bracing problem.)

This project was intended to be an example to show how to use Palm Arduino V3 PCB with the Lego's components. And the project is in "work in progress" stage. It has open end, that any one who want to try out could add more stuffs into it for example,

- Add IR Sensor to make it object or obstacle avoidance.
- Add mini servo to control the arm that draw the weapon. So the robot would draw its weapon whenever there is a wall or obstacle in front of it.
- etc.

As the result of the test. I was not very happy with the result. The forwards and backward movements were OK. But the Bot were shaking instead of doing the left or right turns. I need to modify the sketch to use two motors to drive the turn instead of using one motor at the moment.

Photos and Video

Below is a gallery of photos of the finished Lego Track Bot and videos of the Track Bot.

Track Bot Test 1