A conventional sewing-machine treadle rocks about a pivot and drives a flywheel crank through a pitman. A belt can then transmit flywheel rotation to a driven pulley.
Treadle Mechanism Interactive Calculator
Enter foot-cycle rate, a selected speed multiplier, crank radius and toe travel. Outputs are direct kinematic arithmetic—not measured machine speed, available power or a linkage-fit decision.
Equation Used
- One entered foot cycle maps to one ideal flywheel revolution.
- The selected ratio is an ideal speed multiplier with no belt slip.
- Crank diameter is twice entered crank radius.
- Toe travel and crank diameter are compared directly even though a real treadle linkage also depends on pivot locations and pitman length.
- Force, torque, power, flywheel inertia, losses, belt tension, dynamics, ergonomics, strength and safe operating limits are omitted.
Treadle, Pitman and Flywheel
In the conventional form, a treadle oscillates about a fixed pivot. A pitman connects the treadle to an off-centre crank pin on the flywheel, converting the rocking input into flywheel rotation.
U.S. Patent 872,848 explicitly describes a pivoted treadle, a pitman connected to a flywheel arm, and belt transmission from the flywheel to a driven pulley. The interactive drawing shows the arrangement schematically; it does not specify construction dimensions.
What This Calculator Represents
The tool maps entered foot cycles one-for-one to ideal flywheel revolutions, applies an entered speed multiplier and calculates twice the entered crank radius.
It also subtracts crank diameter from entered toe travel. That signed difference is arithmetic only; linkage fit requires the actual treadle lever arms, pivot locations, pitman length and joint clearances.
Ideal Rate and Length Arithmetic
selected-ratio rate = R × ideal flywheel rate
crank-pin orbit diameter = 2r
travel difference = S - 2r
Rates are displayed in revolutions per minute under the one-cycle-per-revolution definition. r and S are millimetres. Positive travel difference means entered travel exceeds crank diameter; negative means it is smaller. Neither sign establishes linkage compatibility.
Worked Arithmetic Example
At 80 entered cycles/min, the ideal flywheel rate is 80 rpm. With selected multiplier 15, the selected-ratio rate is 1200 rpm. A 25 mm crank radius gives a 50 mm orbit diameter; entered toe travel of 70 mm gives a +20 mm difference.
Model Boundary
- Calculated: one-to-one ideal cycle rate, selected ratio multiplication, twice radius and one signed length difference.
- Not calculated: exact four-bar or rocker geometry, pitman length, dead-centre behavior, starting direction, actual shaft speed, belt slip, torque, power, flywheel energy, bearing losses, forces, fatigue, ergonomics, wear, production rate or safe setup.
Frequently Asked Questions
Does one foot cycle always produce exactly one flywheel revolution?
That is the ideal definition used here, not a measurement of every treadle machine.
Is the selected-ratio rate an actual spindle speed?
No. It omits slip, compliance, load and other losses.
Is twice crank radius the treadle travel?
No. It is the crank-pin orbit diameter.
Does a positive travel difference prove the linkage will fit?
No. Full linkage geometry is not solved.
Does the calculator predict power or operator effort?
No.
Can it approve a restoration or machine setup?
No.
References
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