Building the Mongoose Mechatronics Robot: Part 1 Chassis & Gearbox

Introduction: Building the Mongoose Mechatronics Robot: Part 1 Chassis & Gearbox

This is the first of a series of illustrated instructions for assembling the Mongoose Robot kit available from blueroomelectronics

Mongoose highlights:
  • Powerful PIC18F2525 microcontroller (32KHz to 32MHz)
  • Hardware PWM controlled SN754410 H-Bridge with thermal shutdown
  • Differential drive with powerful 114.75:1 gearbox
  • Low drag steel ball caster with steel rollers
  • Dual optical rotation sensors (108 transitions per revolution)
  • Dedicated in circuit programming / debugging connector
  • Dedicated TTL Serial port (EUSART)
  • Generous 400 hole solderless prototyping area
  • Top mounted 20pin I/O for breadboard or LCD display
  • Forward facing standoffs with 10pin I/O connector (0.1" PCB compatible)
  • 10K trimpot and high brightness LED headlight (programmable)
  • Very low center of gravity for stable operation
  • Small enough to take anywhere 115mm x 110mm x 60mm

Requires 4x AA NiMH batteries

Programmable in ASM, Swordfish BASIC SE & C18 SE

Part 1: Chassis & Gearbox
Part 2: Electrical, motors & battery holders
Part 3: Electronics, 18F2525 Controller & SN754410 H-Bridge
Part 4: Final assembly, Main driving wheels, solderless breadboard
Part 5: Programming & Testing using Swordfish BASIC SE (free) & the Junebug (PICkit2)
Part 6: Demo code LCD, PWM and Tachometer examples

  • Requires a PIC programmer, see the blueroomelectronics site for details.

Step 1: Preparing the Gearbox for the Dual Rotation Sensors

The Mongoose uses a Tamiya Double Gearbox. Part T4 requires a simple modification to allow the optical rotation sensors to monitor wheel rotation.

Simply remove by sanding or cutting away 5mm of material (plastic) from the main gearbox casing as shown in the illustration below.

Step 2: Adding the Rotation Encoders to Two Blue Gears.

The blue gears as shown below are IR transparent, so we're going to add IR opaque aluminum foil to a set of gears one for either side of the gearbox (the blue gears are all identical so any two will do)

The kit includes a small piece of self adhesive aluminum foil with a hole punched in the center.

You will need two of the blue gears as supplied with the kit.

  • Cut the foil into four pieces using the hole as the center.
  • Remove the adhesive backing from the foil only when you're ready to apply it
  • Apply two foil pieces to each gear, each foil piece should be opposite each other.
  • Carefully burnish the foil onto the gear with a toothpick or soft burnishing tool (the example below use a piece of spruce from the gearbox assembly)
  • Carefully trim away excess foul by slowly running a sharp hobby knife through the foil as show in the pictures below.

Step 3: Assembling the Axles (build 2 of Each)

You'll need to build two sets of each axle.

*more detail asap

Step 4: Chassis & Gearbox

First we'll build the Right side chassis and gearbox assembly.

  • Using a single silver 10mm self tapping screw attach the Aluminum Right side Chassis half to the Right Gearbox (T3) cover, do not tighten it yet (leave about a full turn loose).
  • Install two brass bushings into the Right Gearbox assembly (as seen in the second image)

Repeat this step for the left side chassis

Note: in the illustrations the Chassis is drawn in green for clarity (it's actually black in the kit).

Step 5: Building and Lubricating the Right Side Gearbox

This step is illustrates building the geartrain. Starting with the right side gearbox half (the brass bushings should be installed as shown in the previous step)

Lightly lubricate as you're assembling the gears
  • Lubricate and insert both the long and short axles as shown below into the brass bushings
  • add the yellow main drive gear note the notch for the set screw
  • next a blue gear
  • then a modified blue gear (from step #2)
  • a yellow crown gear goes on next
  • a silver spacer
  • add another set brass bushings

Finally you can attach the central gearbox frame with three silver 20mm Phillips screws

The left side of the gearbox is a mirror image of the right, simply repeat this step and you'll have two halves that bolt together into one finished gearbox.

Step 6: Adding the Ball Caster and Standoffs

All that's left is the ball caster assembly and standoffs

  • Photos coming soon

Step 7: Your Assembled Chassis With Gearbox Should Look Like This When Complete

This is the end of Part 1

Parts 2 to 6 to be posted soon.

Be the First to Share


    • Anything Goes Contest 2021

      Anything Goes Contest 2021
    • New Year, New Skill Student Design Challenge

      New Year, New Skill Student Design Challenge
    • Fix It Speed Challenge

      Fix It Speed Challenge



    14 years ago on Introduction

    Not a wonderful Instructable anyway, as so much is missing, but this smells a little bit like cheap tinned meat.


    Reply 14 years ago on Introduction

    This is Part 1 of this Instructable as stated in the title.. it is not a WONDERFUL Instructable, but it is good. I can't wait to see all the parts! How many parts will there be?


    Reply 14 years ago on Introduction

    I know it's "part one", but it also has phrases like "details asap" and "photos coming soon". It would have been much better to wait until the project was properly documented before it was posted, and I still smell the meat.


    Reply 14 years ago on Introduction

    True, this person should have finished everything. So basically it should be unpublished, but I cannot do that, and the pictures should be up soon, or things will get ugly. And I smell no meat.


    Reply 14 years ago on Introduction

    Don't you? Sort of like tinned pork? Or tinned ham?


    Reply 13 years ago on Introduction

    I'd say this was spam, really, since it has been 5 months since it was posted, and the promised updates have not been forthcoming. Which is odd, because surely he will sell far more of them by increasing the quality of this Instructable?


    13 years ago on Introduction

    Bill is Legendary, so don't mess with him, he can jack you up. aka Krumlink

    The next step is the circuit board assembly, it's a much different process than the mechanical so I thought it would be good to break up the process into several parts.
    The real fun begins with the programming, a free "Special Edition" of the Swordfish BASIC compiler for the PIC18Fxxxx microcontrollers is a great match for any robotics kit.
    Swordfish BASIC

    Junebug & Mongoose 002.jpg