The file vendor/three.min.js is missing. Re-download it from
https://unpkg.com/three@0.152.2/build/three.min.js and place it in the
vendor/ folder.
| Rotate view | left-drag |
| Pan | right-drag |
| Zoom | scroll wheel |
| Play / pause | spacebar |
| Step 5° | . (period) |
| Chapters | ← → arrow keys |
Mechanism and kinematics follow Sclater & Chironis, Mechanisms and Mechanical Devices Sourcebook, 3rd ed. — “The Universal Joint Drive” (p. 169), “Universal Joint Relays Power 45° at Constant Speeds” (p. 301) and “Ten Universal Shaft Couplings” (pp. 330–331) — with joint kinematics cross-checked against Seherr-Thoss, Schmelz & Aucktor, Universal Joints and Driveshafts, 2nd ed. (Springer 2006), chs. 1–2. The single-joint relation used throughout is tan β = tan α·cos δ with ωout/ωin = cos δ / (1 − sin²δ·sin²α); the Rzeppa model solves each ball as the intersection of its offset inner and outer track circles.