A drop-feed sewing machine requires coordinated horizontal advance and vertical lift so the feed dog can rise, move the work, descend and return. The retained reference calculates a selected two-axis periodic locus; it does not infer stitch length or sewing quality from guessed lever dimensions.
Feed-Dog Selected Two-Axis Locus Reference
Explore exact selected horizontal/vertical feed-dog locus geometry without inferring stitch length.
Equation Used
- Horizontal and vertical motions are sinusoidal with constant selected half-travels.
- Both axes share one cycle frequency.
- The locus is an illustrative feed-dog reference, not a stitch-length prediction.
- Exact linkage, contact, loads, slip and sewing quality are excluded.
Phase offset is a selected coordinate parameter, not a validated machine timing adjustment.
Selected orthogonal eccentric motions
The animation captures two crank pins in perpendicular slots. One yoke supplies the horizontal coordinate and the other supplies the vertical coordinate; their cross-slide intersection carries the illustrative feed dog. A selected phase offset changes the locus shape.
This is a normalized exact-coordinate reference, not a dimensionally reconstructed Singer or JUKI feed-bar assembly.
What the calculator determines
Select horizontal half-travel a, vertical half-travel b and phase offset φ. The calculator reports peak-to-peak spans 2a and 2b, the enclosed selected-locus area πab|cosφ|, and the signed entered phase.
The former stitch-length and timing-error outputs are removed.
Selected locus
x = a cosθ and y = b sin(θ + φ). Horizontal and vertical spans are 2a and 2b. The parametric locus has area A = πab|cosφ|.
Selected-input arithmetic
For a = 2.0 mm, b = 1.0 mm and φ = 0°, spans are 4.0 mm and 2.0 mm and the selected locus area is about 6.283 mm².
Intentionally partial mechanism
The two-axis locus does not determine retained fabric advance. Tooth geometry, throat-plate clearance, presser-foot force, slip, needle timing, link proportions, backlash, compliance and the exact historical linkage remain unresolved.
Questions
Is horizontal span equal to stitch length?
No.
Does phase alone predict skipped stitches?
No.
Is the illustrated cross-slide the exact historical feed bar?
No.
References & Further Reading
- Wikipedia contributors. Sewing machine. Wikipedia
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