This revision shows one exact declared planar construction: a fixed-length Pitman arm, fixed-length drag link and horizontal guided output pin. It does not infer wheel angle, bump steer, alignment or roadworthiness.
Pitman Arm–Drag Link Geometry Explorer
Enter Pitman-arm length, drag-link length and symmetric one-side sweep. The worksheet reports exact endpoint chord motion, arm-tip arc length and maximum link inclination for the declared guide construction.
Equation Used
- Pitman arm and drag link are rigid with ideal pin joints.
- Pitman-arm sweep is symmetric about the vertical centre position.
- The output pin is constrained to a horizontal guide passing through the two arm-tip endpoint elevations.
- Drag-link length exceeds the vertical offset throughout the declared range.
- The drawing is planar and animation phase changes only the linkage position.
- Steering-gear ratio, compliance, wheel angle, suspension travel, Ackermann geometry, alignment, wear, loads, ratings and road safety are excluded.
Removes the unsupported 15-degree bump-steer flag and vehicle-specific repair and failure claims; retains exact declared circle and rigid-link geometry only.
The steering gear swings the Pitman arm and drag link
US patent 3,868,888 describes a Pitman arm rigidly supported on the steering-gear shaft and joined to a drag link through a swivel joint, converting Pitman-arm pivoting into drag-link translation. Later steering patents retain the same steering-box, Pitman-arm and drag-link topology.
The animation uses that topology in a deliberately simplified planar construction with a horizontal output guide.
Actual steering layouts are vehicle-specific
Patented systems show longitudinal and lateral drag-link arrangements, relay arms, tie rods and steering arms. The complete linkage and suspension determine wheel motion; this page does not prescribe parts or service work.
Endpoint motion follows circle and rigid-link geometry
For a Pitman arm centred vertically and swept symmetrically by ±theta, its endpoint horizontal coordinates differ by 2L sin(theta). The full arm-tip path length is the circular arc 2L theta, with theta in radians. A fixed drag link closes exactly to the declared horizontal guide at every animation phase.
A declared geometry example
A 5.5 in arm swept ±35 degrees gives 3.15 in one-side endpoint chord, 6.31 in full endpoint span and 6.72 in arm-tip arc length. With a declared 20 in drag link and the specified endpoint-elevation guide, maximum link inclination is 2.85 degrees.
Planar output span is not wheel angle or bump steer
Wheel motion additionally depends on steering arm, knuckle, tie-rod and suspension geometry, plus compliance and joint motion. No universal 15-degree limit follows from the cited topology, so the prior bump-steer flag is removed.
Unsupported vehicle fitments, lift-kit advice, alignment corrections, wear rates, torque procedures, fatigue comparisons, failure timelines and brand claims are also removed.
Pitman-arm geometry questions
Does longer L increase declared endpoint span?
Yes, proportionally for the same sweep in this geometry.
Does this predict wheel angle?
No.
Does maximum link inclination rate bump steer?
No. It only reports the declared planar link angle.
Can this page approve steering service work?
No. Use vehicle-specific service information and qualified inspection.
Pitman-arm and drag-link references
- US 3,868,888, Vehicle steering gear assembly: steering-gear shaft, rigid Pitman arm, swivel joint and drag-link translation topology.
- EP 2,048,062, vehicle steering mechanism: steering box, Pitman arm or crank, steering arm and drag-link arrangement.
- US 2021/0197888, Steering device: ball-nut steering box swings a Pitman arm and the drag link transmits that swing to the next steering member.
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