In this this tutorial we cover the chassis assembly for our robot.
The Chassis used for the robot is a two track design, just like a tank or bulldozer. This is actually a simple and easy design for a robot since you can fully control the speed and direction of the robot with just the throttle settings for each motor, that is you need two degrees of freedom. That’s not to say rack and pinion or some other style isn’t just as simple or just as good, each design has its merits. The tracked vehicle chassis kit used here is cheap and widely available, I’ve seen them at hobby shops, toy stores, and tons of places online. It ships with a single motor and drive train, which will not meet our needs. With only a single motor, the vehicle can move in forward and reverse, but will not be able to turn. We could possibly add some sort of front wheels to do the steering like you see on old half-tracks, but that will be too complicated for this. Instead we will just use a separate double motor gearbox. This means we don’t need to fully assemble the tracked vehicle chassis kit, but I’d suggest you go ahead and do it anyway, then just replace the motor and gearbox. It isn’t very difficult, and this way you’ll have it assembled for a future project, something that only requires a “forward-reverse” functionality, I can think of lots of other applications for it, one segment of a robot arm, or the mechanism to raise and lower the blade on a bulldozer. Lets get started!
Open up the box and check that you have all the parts
start by installing the two angle brackets in the middle of the board. Do NOT use a power tool for this, the piece of wood is very soft and has pre drilled holes in it, you can just use a hand screwdriver with the supplied screws, which will self tap as you screw it in, a power drill will most likely strip out the threads as soon as you make them.
Do the same for the two little wheel mounts on the opposite side of the board.
Next assemble the plastic wheels, and axles as shown.
Now we are ready to start assembling the single motor gearbox, again the robot we are building will not actually use this gearbox, so if you don’t want to assemble it, then you can skip ahead to the next section.
Follow the included directions to assemble the switch box.
And the gearbox. You get multiple sets of instructions which allow you to choose one of several gear ratios, since we aren’t actually going to use this gearbox, it doesn’t really matter which one you choose, but I can say that in my experience with motors as small as these that when running them at low speed you won’t get much torque from them, so most applications you will end up choosing a high gear ratio, so that you can run the motor at a higher speed, and let the gearbox bring it down to the speed you want. This is highly variable depending on what you are doing though.
Next cut the piece of wire included in the kit in half, strip both ends, and cut two little pieces of the plastic tubing supplied with the kit, these are used when mounting the wires to the switch.
Now connect the the two wires to the motor, be gentle when connecting wires to the motors, the little metal tabs on the motor are not terribly strong, its not hard to rip them off the motor, then you are pretty much sunk as far using that motor again, if your lucky there will be enough of a tab to solder a wire to, but that’s not as easy as it sounds, because then your soldering iron will start melting the plastic housing of the motor ( at least that’s what I’ve heard 🙂 ). Just push the wire thorough the hole and loop it around twice, then stop messing with it. You will have an extra motor if you end up breaking one.
Once the motor is installed, you’ll want to add the plastic drive wheels, screw the gearbox down to the board, connect the switch to the battery holder, then connect the motor wires to the switch, and slide the little plastic pieces over the connections.
Finally we can assemble and install the tracks, its is easiest just to connect the rubber tracks to form a loop, then slide the track onto the drive wheels.
And that is our finished chassis. Lets take it apart and get started on the motors and drive-train assembly
Intro->SOS->Chassis Assembly->Motors & Drive-train->Arduino-Remote Control->Assembly->Ultrasonic Sensor->Final Testing