Next, it’s time to build the cyber:bot chassis. In addition to your micro:bit on a cyber:bot board, you will need the parts in the pictures below. If anything is missing, contact sales@parallax.com (888-512-1024). Set aside the bag of electronic components for now.
When you are done, you may have some pieces left over. That's okay!
(1) robot chassis
(1) rubber grommet
(2) 1″ standoffs
(2) 1/4" pan-head screws
Robot chassis, partially assembled.
(2) Parallax continuous rotation servos
(8) pan-head screws, 3/8″ #4-40
(8) Nylon core locknuts - OR - regular steel hex nuts
Parallax screwdriver
Parallax wrench
masking tape (optional)
pen (optional)
With both servos mounted, your chassis will look like this:
Note: You may mount the servos the other ways instead.
Mounting the servos with the servo shaft closer to the front of the robot is also possible. This design may cause some turning difficulty on “sticky” floor surfaces unless the front of the robot has increased weight. The benefit of mounting the servos this way is that the potentiometer hole in the servo case is more accessible (from the front of the robot). If the servos need to be re-centered, you would not need to remove them from the chassis.
You may also mount the servos with the tabs on the inside of the chassis for a narrower wheel base. This allows for the tightest turns pivoting on one wheel. But, it is easier to remove and replace the servos when they are mounted from the outside.
Throughout this tutorial you may see cyber:bot examples with different servo mounting positions.
(2) - Nylon flat-head slotted screws, 3/8″ 4-40
(2) - 1" standoffs
(1) - 5-cell battery pack with 2.1 mm center-positive plug
(1) Cotter pin
(1) tail wheel ball
(2) wheels
(2) O-ring tires
(2) screws saved when removing the servo horns
needle-nose pliers - optional, not included
CAUTION - the ends of the cotter pin may be sharp! If you have needle-nose pliers, you can bend the cotter pin ends into a circle to tuck away the points. But be aware that this makes the cotter pin more difficult to remove in the future if you ever want to do that.
The robot’s tail wheel is merely a plastic ball with a hole through the center. A cotter pin holds it to the chassis and functions as an axle for the wheel.