Any functional crane model obviously requires a winch (or two).

Since I am not that limited in space (it’s a portal crane, after all), I used a cheap and widely available N20 gearmotor. This particular one has around 100RPM and rated 6V. I usually tend to go with 12V motor and downvoltage it to 5V, this way it quieter and still powerful enough, but that’s what I had on hand.

Renders

The motor is placed inside a 3D-printed case, and dual 3D-printed drums are installed on a 2mm steel rod (or 2mm brass tube). Rotation is transferred via 2 rubber o-rings from AliExpress.

The approach looks over-engineered, but I needed to put the drums in the middle of the design to keep it compact. That means they need to go above the motor, that means some kind of transmission. I am not sold on miniature 3D printed gears (FDM ones are too imprecise and resin ones are too brittle), so o-rings seem like a good solution. In addition, they are silent. To reduce slippage there are 2 o-rings, which makes it able to lift all the things I need (I tested it on a 40ft container with a stone inside).

A nice bonus feature of the design is a built-in torque limiter in the form of o-rings. The rubber belts start to slip long before the motor damages the plastic casing or tears the thread (and yes, it has enough torque to do that).