The 3V mini dc motor lifts heavy loads with a 3d printed double helical gearbox. In doing so the gearbox encounters many difficulties and as a result 3V dc motor could lifts 58 kg with 125:1 gear ratio.

Youtube video link: https://www.youtube.com/watch?v=3yU7wK39-q4

Designed up this modular gearbox on fusion360 and used 20x20 sigma profiles for chassis. Thanks to sigma profiles, you can get the gear ratio you want. Of course between 3...125:1

3D printed high torque (double) helical gearbox uses a 3V 10000 RPM brushed mini DC-motor which is has very weak power and lifts heavy loads. They were all printed in PLA.

The gears rotate with a 6x6mm aluminum or PLA shaft.