Firstly this 14XX 0-4-2T was the first loco I made in 3mm. It has a 3SMR chassis with Romford wheels.
The pick-ups are 33SWG phospher bronze wire attached to PCB board. Wires then transmit the current to the motor which is a Mashima with a Branchlines 40:1 gearbox. Easy to make and not that pretty but it does the job reliably. I made this model nearly ten years ago and only routine maintenance has been needed.