In worm-and-roller steering, the worm moves a roller connected to the output sector and pitman arm. The calculator compares an assumed steering ratio with sector angle, output torque and pitman-arm travel.
Worm-and-roller Steering Interactive Calculator
Enter input torque, gear ratio, assumed efficiency, steering-wheel angle and pitman-arm length. Compare sector angle, output torque, ideal tangential force and the chord between arm positions.
Equation Used
- Inputs are user-supplied scenario values.
- The displayed equations are evaluated directly.
- Entered efficiencies, shares, limits and factors are not predicted.
- The visual is schematic and not dimensional.
- Strength, fatigue, wear, variation, controls and safety compliance are omitted unless explicitly calculated.
How the Worm-and-roller Steering Works
Turning the steering input moves the output sector and pitman arm. This simplified calculation uses one constant gear ratio; it does not reproduce changes in contact geometry through a real steering box.
What This Calculator Represents
Efficiency and ratio are inputs. The force result assumes a tangential load on the pitman arm. Drag-link angle, road-wheel geometry, compliance, backlash, bearing loads and steering-system strength are not calculated.
Calculation Method
Sector angle = steering-wheel angle / gear ratio. Output torque = input torque × gear ratio × entered efficiency. With torque in lb·ft and arm length in inches, ideal tangential force = 12 × output torque / arm length. Pitman chord = 2 × arm length × sin(|sector angle| / 2).
How to Read the Result
Change one input at a time to compare its effect. Apply the assumptions stated beside the equations when interpreting each result.
Assumptions and Limits
Efficiency and ratio are inputs. The force result assumes a tangential load on the pitman arm. Drag-link angle, road-wheel geometry, compliance, backlash, bearing loads and steering-system strength are not calculated.
Frequently Asked Questions
Is pitman travel the same as road-wheel movement?
No. The result is the straight-line chord between two pitman-arm positions. Road-wheel movement also depends on the drag link and steering linkage.
Does the steering ratio change through the turn?
Not in this model. The same entered ratio is used throughout the selected steering-wheel angle.
Is the drawing suitable for manufacturing?
No. It is a schematic explanation and does not specify manufacturing dimensions, tolerances or materials.
Can these results establish a safe working load?
No. Strength, fatigue, wear, operating conditions and the complete assembly must be assessed separately.
References
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
