I made this 3d printed high torque worm gearbox. It called also winch, hoist or crane. The gearbox uses a 775 12V 13000 RPM (100 Watt) brushed DC-motor which it has 0.074 Nm torque and 13000 rpm. This 3d printed gearbox had a gear ratio of 98:1. So the torque on the output shaft became 7.4 Nm or 75 kg*cm and the speed of the output shaft was about 132RPM with this gearbox. (in theory) I used PLA+ in all parts.

The output shaft is 20 mm in diameter and thus the maximum force the gearbox can lift is 737 newtons. (75.1 kg) Since the friction of the rope would be high, I assumed a 10% loss. but this is only valid when a rope is used. If we use the torque lever on the side, there will be no such loss I choose to go for helical gears on this one because they produce a lot less noice than regular spur gears and the forces on the teeth are transferred more gradually. The helical gears I used have a 1 mm module and a 23 degrees helix angle. I chose a low helix angle to avoid too much axial force. The pinion gear on the motor is 13 teeth and the counter gear is 34 teeth. Thus theoretically the gear ratio in the first stage is 2.61. There is also a worm gear on the same shaft. I fixed the gears here on the shaft with a cotter pin. The shaft I use here M8 threaded rod. I used 608zz roller bearing for bearing the shaft. At the same time, high axial force will occur on this shaft due to the worm gear. I fixed this shaft with 1, 2 or 3 mm spacers. I used whichever fit. The worm gear I used in this project has 40 teeth. So the gear ratio in the worm gear mechanism is 40. Here there is a really high torque increase in one stage.Output shaft has a 20 mm diameter and I used 2x6004(ORS) roller bearing to support this output shaft.I was able to test the gearbox to a torque of about 43 kg*cm.During testing none of the gears broke, they were all printed in PLA. The weak link in this design the helicel pinion gear (red one) used in the first stage on the motor shaft. This gear tend to slip under high loads, while lowering the load but this didn't occur when i performed the test where it pulled 43kg*cm of torque so it should be fine to at least this torque rating.At the first car test, the gearbox could not fully pull the car because the road was bumpy. At the same time, the rope broke. Then I went home and I do not give up:) Because I knew the gearbox could pull the car. Theoretically this was possible and as you can see in the video…I do not recommend using it in the professional field. Because you can't trust to plastic parts!Regardless, it was a very entertaining project. By the way it would be great if you make the accent out of steel :D

Below are all the parts I used in this project:

12V DC 775 Motor(100 Watt)

608zz bearing x3

6004 bearing x2

20 mm aluminium shaft

M8 threaded rod

Cotter pins

2x30—x4

3x50—x1

STL files for plastic parts: https://www.thingiverse.com/thing:4790867

Editable source files:  https://www.cgtrader.com/3d-print-models/hobby-diy/mechanical-parts/3d-printed-high-torque-gearbox-worm-gearbox-electric-hoist