From New Mind.
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This video traces the engineering evolution of right-angle power transmission, from the primitive pin-and-face drives of Roman watermills to the complex split-torque systems of modern aviation.
ORIGINS OF ORTHOGONAL POWER
• First conceptualized by Roman architect Vitruvius in the 1st Century BC.
• Used a "pin-and-face" design to convert horizontal water wheel rotation to vertical millstone rotation.
• Relied on animal tallow for lubrication to mitigate high sliding friction.
THE MOVE TO IRON
• Steam power torque loads caused early wooden gears to deflect or fail, necessitating grey cast iron.
• "Mortise construction" combined iron rims with wooden cogs to dampen noise and absorb shock.
• Iron gears required rigid bedplates rather than timber framing to maintain perfect alignment.
PITCH CONE GEOMETRY
• Replaces cylinders with cones that intersect exactly where the shafts intersect.
• Matches the peripheral speed of driving and driven gears at every point from heel to toe.
• Creates "line contact" instead of point contact to increase power transmission capacity.
PRECISION MANUFACTURING
• William Gleason’s 1874 Bevel Gear Planer revolutionized high-speed gear production.
• Mechanically simulated gear rolling to generate a mathematically ideal "Octoid" profile.
• Allowed bevel gears to operate at the thousands of RPM needed for internal combustion engines.
AUTOMOTIVE EVOLUTION
• Spiral Bevel gears introduced in 1913 to eliminate the "whine" of straight gears.
• Hypoid gears (1926) utilized an offset pinion to lower the driveshaft and vehicle floor.
• Extreme pressure lubricants developed to handle the sliding action of Hypoid teeth.
WORM DRIVES
• Capable of massive reduction ratios (50:1 to 100:1) in a single compact stage.
• Features "self-locking" properties where friction prevents the output from back-driving the input.
• Acts as a passive brake for safety-critical equipment like elevators.
AVIATION & SPLIT-TORQUE
• Zerol gears developed to provide spiral strength with zero spiral angle to reduce axial thrust.
• Face gear split-torque systems use a floating pinion to passively split torque 50/50.
• Allows dual engines to drive a single rotor without sensors or computer control.
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