A treadle can connect through a rod and crank to rotate a wheel, while a spring or operator motion returns the treadle. This calculator evaluates selected in-line slider-crank geometry only. It does not model a particular historic lathe, treadle lever geometry, spring return, flywheel speed or spindle speed.
Spring Lathe-Wheel Crank · Selected In-Line Slider-Crank Ledger
Explore selected in-line slider-crank stroke, rod length, obliquity and entered-travel comparison.
Equation Used
- The slider axis passes through the crank centre without offset.
- Crank and connecting rod are rigid pin-jointed links.
- The entered travel is an independent comparison value, not a derived pedal travel.
- The selected rod ratio is at least four over the available range.
- Treadle lever geometry, spring force, clearances, flywheel inertia, belt transmission, cutting load and safety are excluded.
Former required-drop and minimum-rod claims are narrowed to selected crank stroke, rod length and travel-difference arithmetic.
Selected in-line slider-crank geometry
For crank radius r and connecting-rod length L, the ideal in-line slider stroke is 2r. The selected ratio L/r fixes the rod length and the maximum rod obliquity is asin(r/L). An independently entered travel is compared arithmetically with the crank stroke.
What the calculator determines
Use it to compare crank stroke, selected rod length, maximum rod angle and entered travel difference. A real treadle requires its pivot and attachment geometry, return mechanism, clearances and force analysis.
Exact selected relationships
S=2r; L=(L/r)r; selected travel difference=T−S; phiMax=asin(r/L).
Selected-input example
At r=75 mm, L/r=4 and T=150 mm, the crank stroke and entered travel are both 150 mm, the selected rod is 300 mm long and the maximum rod angle is about 14.5°.
Not a treadle or lathe design
The entered travel is not automatically the treadle pedal travel because lever ratios and attachment locations are omitted. No spring force, flywheel inertia, cadence, belt ratio, spindle speed, cutting load or human factors are predicted.
Questions
Is 4r a minimum safe rod length?
No. The rod length is selected directly through the entered ratio; no universal minimum is asserted.
Does zero travel difference prove the mechanism fits?
No. It only matches two selected scalar distances and omits treadle geometry and clearances.
References & Further Reading
- Wikipedia contributors. Lathe. Wikipedia
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