This servo/gearbox is the new and improved version of my original gearbox design (https://www.hackster.io/bribro12/3d-printable-high-torque-servo-gear-reduction-0ddfe7). The original one had a gear ratio of 30:1 and the speed of the output shaft was about 715 RPM which made it difficult to tune in the right PID parameters. This new version has a gear ratio of about 162:1 which lowers the speed and increases the torque of the output shaft.
DetailsThis servo/gearbox is the new and improved version of my original gearbox design. The original one had a gear ratio of 30:1 and the speed of the output shaft was about 715 RPM which made it difficult to tune in the right PID parameters. This new version has a gear ratio of about 162:1 which lowers the speed and increases the torque of the output shaft.
I choose to go for double 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 gears rotate around a 6mm stainless steel shaft which is lubricated with bearing grease. Ideally all the gears should have some bearings, this is being considered for the next moment. Unlike my previous design I used 2 20mm bearings to support the output shaft.
The servo uses a 775 36V 9000rpm brushed DC-motor which is driven by my Universal Morion Controller (UMC). The stall torque theoretically is about 297kg/cm, I was able to test the servo to a torque of about 132kg/cm. During testing none of the gears broke, they were all printed in PLA. The weak link in this design however where the mounting tabs and the bevel gears used in the first stage on the motor shaft. These 2 gears tend to slip under high loads, like when I tried to pull the car forwards with it's handbrake on, but this didn't occur when I performed the test where it pulled 132kg/cm of torque so it should be fine to at least this torque rating.
Video:
Youtube
Thingiverse
Build instructionsStep 1
Instructions on how to build this servo can be found in the youtube video:
Files3D printable high torque servo-gearbox Version 2 20mm shaft.pdf: dimensions and hole placement for the 20mm shaft
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