Counter helical geared mechanical knee prostheric

Hi Everybody!
This project comes as a remix of Incept 3D's Leg prosthetic.

Disclaimer: This prosthetic leg design is an experimental prototype and is provided as-is for educational and developmental purposes only. It is not certified, approved, or tested for clinical, medical, or long-term use.

Description:
The Counter helical gear linkage comes as an improvement of the straight gear linkage. (Weight-activated knee with the gear meshing mechanism (Ramakrishnan and Reed, 2020), reproduced with permission from copyright 2020 by South Florida University.). Straight geared linkages provide no radial counteracting forces and are loud due to the mechanical collisions and the significant backlash between the gears‘ teeth.

Advantages:
The Counter helical gear linkage eliminates the mechanical collisions through the continuous contact points between the gears' teeth therefore providing a smooth and silent rotation. Thanks to the helical geometry, there is minimal play and twist between the upper and lower leg.The counter helical Teeth path offers parallel alignment between the axes and counteracts the radial forces, thus minimising the shearing forces applied to the outer connecting brackets. Given the size of the gears, this mechanism is able to hold a lot of weight due to the size of the gears. When sitting down, the foot reaches the ground and is also able to rotate up to 150°.

Disadvantages:

The main disadvantage of the mechanism is that the geometry is hard to model, especially the transition between the helical and the flat path. The gears‘ teeth suceptible to wear and tear due to constant plastic to plastic contact. The mechanism is voluminous posing a tripping problem during stance.
 

IMPORTANT NOTES:
ONLY BUY 2x90mm SHOULDER SCREWS for this model

PAUSE THE PRINT for the leg's inner shaft TO INSERT THE TPU DAMPERS AND M12 NUT

Bill Of Materials:

Important parts Images:

1-Shoulder screws

2- Micro Steel Deep Groove Ball Bearings 688ZZ (4PCS) - EA026

Please refer to the original Incept 3D model for the build instructions!
There are only some minor changes as the TPU parts to be glued as shown in the pictures (blue parts are out of TPU and are to be glued)

1. New hole sizes for Metric system heat threaded Inserts.
2. Main leg component is now a more avaliable M12 Screw and Nut.
3. Spring mechanism to lock the M12 Screw in place.
4. Many TPU parts to get around wide tolerances due to printing imperfections and to dampen the movement and provide a more comfortable experience.
5. Thicker and more robust foot.
6. Flexible foot on the fingers' level.
7. Different shaft lengths for different heights.