Mechanisms
Machines & motion
Articulate, transmit and transform motion: pivots, gears, belts, cams, linkages and linear guides. The parts that actually move.
10 sections70 articles
Letting it rotate
17 articlesOne part rotating relative to another: pins, hinges, ball joints and couplings.
- Print-in-place pin joint: born already articulated
- Assembled pin joint with clevis: separate lugs and pin
- Living hinge: a thin wall that flexes
- Knuckle hinge (piano and barrel): interleaved knuckles on a shared pin
- Print-in-place captive hinge: born articulated off the printer
- Concealed cabinet hinge: the cup hinge hidden in furniture
- Friction hinge: holds at any angle
- Detent hinge: holding at defined angles
- Spring-return hinge: the hinge that closes itself
- Cross-axis flexure pivot: a pivot with no axle and no play
- Notch and cartwheel flexures: thinning down to make a pivot
- Ball joint: multi-axis articulation
- Universal joint (Cardan/Hooke): transmitting rotation between angled shafts
- CV joint: constant velocity through an angle
- Gooseneck: a ball-joint chain that holds its shape
- Embedded bushing and bearing: let the bearing spin, not the plastic
- Rolling-contact joint: surfaces that roll, no axle
Moving in a straight line
8 articlesGuides, slides and mechanisms that carry something in a straight line.
- Sliding dovetail: male and female trapezoidal rail
- Generic rail and carriage: T, slot, or tongue
- Rod and bushing (linear bearing): sliding on a smooth shaft
- Linear guide variants: V-groove, telescoping tubes, slides, and crossed rollers
- Parallel flexure stage: a linear guide with no contact or wear
- Sarrus linkage: rotation to straight translation without guides
- Scott-Russell linkage: exact straight line from a rotation
- Lead screw stage: turning rotation into linear motion, with force
Gears
10 articlesThe base of transmission: ratio, module and teeth.
- Spur gear: the foundation of it all
- Internal ring gear: teeth facing inward
- Planetary reducer: compact coaxial reduction
- Compound gear train: stages in series
- Mutilated gear: missing teeth to drive only part of a turn
- Worm drive: high reduction and self-locking
- Helical and herringbone gears: angled teeth, smooth and quiet
- The bevel family (straight, spiral, crown, hypoid): drive at 90 degrees
- Rack and pinion: rotation to linear and back
- Special gears: non-circular, cycloidal, harmonic, nutating, and differential
Flexible transmission
5 articlesCarrying rotation at a distance with belts, chains and cables.
Converting motion
6 articlesTurning rotation into reciprocation or linear motion.
- Cam and follower: any motion law from a profile
- Crank-slider: turning rotation into reciprocation
- Eccentric drive: reciprocation from an offset center
- Acme and ball screws: rotation to linear, with force
- Trammel of Archimedes: drawing an ellipse
- Scotch yoke, quick-return, and special cams: the conversions crank-slider can't cover
Couplings and clutches
5 articlesJoining shafts, or connecting and disconnecting rotation.
Stepping motion
4 articlesTurning continuous rotation into indexed steps.
One-way only
4 articlesAdvance one way, lock the other.
Bar chains (linkages)
9 articlesConvert, guide or amplify motion by connecting bars.
- Four-bar linkage: the queen of motion chains
- Scissor and lazy tongs: a lot of extension from very little
- Toggle lever: huge force near the dead point
- Bell crank: turning force through 90 degrees
- Pantograph: scaling and copying paths
- Parallelogram linkage: keeping orientation while it moves
- Approximate straight-line motion: the four-bar family (Chebyshev, Watt, Hoeken, Roberts)
- Walking legs: Klann and Jansen linkages
- Special linkages: the exact straight line (Peaucellier, Hart) and spatial motion (Bennett, Bricard)
Named gadgets
2 articlesCombining several families: showcase pieces.