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 is needed. 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 (it has enough torque to do that).