Hiscox movement 1515 is a three-part parallel ruler whose connecting arms are equal in length and whose pivots are equally spaced on each blade. Those equalities create linked parallelogram motion that keeps the blades parallel in the ideal construction.
Three Part Parallel Ruler Interactive Calculator
Enter nominal connecting-arm length and three hypothetical mismatch magnitudes. Results are ratios only; angular error, pivot clearance, blade drift and tool accuracy are not inferred.
Equation Used
- L is a positive nominal connecting-arm length.
- Each delta_L is a nonnegative hypothetical absolute length mismatch.
- Ratios are simple dimensional comparisons, not tolerance classes or accuracy predictions.
- Pivot spacing error, clearance, blade straightness, opening angle, load and deformation are omitted.
Equal Arms and Equal Pivot Spacing
Gardner D. Hiscox describes movement 1515 as a three-part parallel ruler with all connecting arms equal in length and pivots at equal distances on each blade.
Each adjacent pair of blades and its two connecting arms forms an ideal parallelogram. The central blade extends the walking arrangement while the equal geometry preserves blade orientation.
What This Explanatory Calculator Does
The calculator compares three hypothetical absolute arm-length mismatches with an entered nominal arm length. It does not solve the deformed linkage or predict a transferred-line angle.
The visualization is a source-faithful topology sketch, not a specification for a historical or commercial ruler.
Dimensionless Mismatch Comparison
delta Lmax = max(delta LA, delta LB, delta LC)
No angular-error equation is shown because arm mismatch alone is insufficient; the answer depends on pivot geometry, opening configuration and which member differs.
Worked Ratio Example
For L = 60 mm, mismatches 0.02, 0.05 and 0.50 mm correspond to 0.033%, 0.083% and 0.833%. The largest entered mismatch is 0.500 mm.
These ratios do not mean the blades have those angular errors.
Model Boundary
- Source invariants: equal connecting-arm lengths and equal pivot spacing on each blade.
- Calculated: three mismatch-to-length ratios and the largest entered mismatch.
- Not calculated: blade angular error, line-transfer drift, pivot clearance, opening kinematics, interference, friction, blade straightness, sag, force, wear rate, tolerance grade, accuracy or suitability.
Frequently Asked Questions
Why was the angular-error output removed?
Length mismatch divided by arm length is a ratio, not a complete linkage angle solution.
What does Hiscox specify?
Equal connecting-arm lengths and equal pivot distances on each blade.
Is Case C a wear prediction?
No. All three cases are user-entered hypothetical mismatches.
Does zero mismatch prove a real ruler is exact?
No. Pivot spacing, clearance, blade shape and deformation are omitted.
Why use percentages?
They compare mismatch magnitude with nominal arm length without inventing an angle.
Can the tool set manufacturing tolerances?
No.
References
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