Rattling-Free Finger Joint — Involute Gears

Interlocking Involute Gear Knuckle • btHingeConstraint Motor • Raycaster Contact Points • Prosthetic Design

Involute Gear Knuckle Joint — 3D

Verts: — • Tris: — • Contacts: 0

Gear Specifications

Pitch Diameter	—
Base Circle	—
Addendum	—
Dedendum	—
Tooth Height	—
Outer Diameter	—
Center Distance	—
Contact Ratio	—

Contact Points (Raycaster)

No contacts yet. Curl the finger to engage gears.

Physics State

Constraint	btHingeConstraint
Bodies	—
Hinge Axis	Z (lateral)
Motor Target	—
Max Impulse	—

Involute Gear Theory

Involute Profile: Tooth shape traced by unwinding a taut string from the base circle. Ensures constant angular velocity ratio between meshing gears regardless of center distance variation.

Pressure Angle: Angle between the line of action and the tangent to pitch circles. Standard values: 14.5° (legacy) or 20° (modern). Higher angles = stronger teeth but more radial force.

Module (m): Pitch diameter / number of teeth. Determines tooth size. Larger module = bigger, stronger teeth.

Contact Ratio: Average number of teeth in contact. Must be > 1 for smooth motion. Typical: 1.2–1.8. Higher = quieter, smoother (rattling-free).

Prosthetic Advantage: Geared knuckles eliminate backlash and provide smooth, predictable motion. Involute profile tolerates slight misalignment, critical for 3D-printed prosthetics.

Export

Ready. Adjust gear parameters and curl the finger.