A simple to print 32mm gauge loco, suitable for motorising. No supports required, as the boiler has a fillet inside to support the top, and the water tank has 2 pillars, which can easily be removed by snapping them out.

The piston is designed to move up and down, driven from the axle. An eccentric cam and associated parts is included. To keep the collar on the cam, fit a couple of M3 or M4 washers either side. Extra detailing can easily be added to this fun little loco.

Motor is 3V, 24mm diameter Technobots Size D, with 0.5mm output shaft and 0.5mod worm and 30T gears. A Locoremote will fit in the tank or boiler, along with a 3.7v Li-ion battery.

Rivet detail may need cleaning up a little, as will the funnel, but otherwise, this is a simple print and build.

Motor mount has small holes to secure to chassis. easiest to use some thin brass wire pushed through the holes, as this is invisible from the outside. Bearings can be made from 3.1mm brass tubing or similar. Axles should be 3mm, and all wheels, cranks and eccentrics are designed to be a tight fit, with maybe a drop of superglue to secure. I did not fit bearings to the motor shaft chassis points, as this allows a little compensation for poor trackwork, while keeping everything nicely meshed.