This Folkracer was used in Robot-SM 2016 in Gothenburg, Sweden.
The car was based on the HBX Micro Buggy bought at Teknikmagasinet
I replaced all the ballbearings and ripped out all the electronics (except the motor). I replaced the steering servo with a SG90 servo, which has only three wires, and is easy to control using PWM.
The day before the competition it looked like this
A last minute change was to add a wooden bumper all around the car, to prevent the rubber wheels from crashing into the wall.
The car uses a custom PCB board, which holds a Teensy, a tca9548apwr I2C multiplexer, and connectors for servos and IR sensors.
The schematics for the PCB is freely available on GitHub: https://github.com/NorbotNorway/KiCadTeensyFolkracePro
A HC-05 Bluetooth module can be installed into the PCB to enable Bluetooth communication between the car and a PC/mobile. This is used for troubleshooting and tweaking settings in the car.
In the front of the car are three GP2Y0E02B digital I2C sensor with 4-50cm range.
The code for the car is custom made for this PCB. The code is in the GitHub repository mentioned above, in the Arduino/folkracer folder.
The IR sensor holder was drawn in Fusion 360 and 3D printed. The base of the car is a hand-cut aluminum plate.