Henry T. Brown's movement 83 shows two oppositely toothed ratchet arcs C, one on each side of ratchet wheel D, fast on the same rockshaft B. Reciprocating rod A rocks the shaft, and springs let each arc lift and slide on its non-driving stroke.
Considering an actuator for the reciprocating input
A linear actuator could supply the reciprocating input only after the rod travel, force, cycle rate and end positions are established. The angular comparison below does not calculate these actuator requirements.
With leverage, force is traded against travel. A bracket change that improves force can also increase required stroke, slow the output motion, or move the actuator into a poor mounting angle.
The clean way to review it is to sketch the linkage at the start, middle, and end of travel. At each position, check the line of action, required force, available clearance, and whether the actuator rod remains close to axial loading.
- Map actuator stroke to the actual output travel before choosing a model.
- Check for binding, changing leverage, and peak load near the ends of travel.
- Decide whether timed motion is acceptable or position feedback is required.
For a FIRGELLI design review, calculate the load case with the FIRGELLI actuator force calculator and plan the switching or controller arrangement with the linear actuator wiring diagram generator. If an actuator or cylinder is already installed, the linear actuator replacement finder helps keep the comparison tied to real dimensions.
Two Ratchet-arc Nearly Continuous Rotary Interactive Calculator
Enter input cycles per minute, an assumed effective arc sweep, tooth count and a separate angle comparison. Results assume ideal no-slip angular transfer—not discrete tooth pickup, spring lift, torque or continuity.
Equation Used
- Input rate means complete reciprocating cycles per minute.
- Each ideal working stroke advances the wheel by the entered effective arc angle.
- The arc-sweep/tooth-pitch result is a continuous ratio, not a guarantee of an integer tooth pickup.
- The entered angle comparison is reported only against 180 degrees and does not alter output speed.
- Geometry, tooth engagement, spring lift, backlash, missed pickup, torque, load, wear, inertia and output ripple are omitted.
Two Oppositely Toothed Arcs on One Rockshaft
Brown movement 83 places a spring-mounted ratchet-toothed arc C on each side of ratchet wheel D. Both arcs are fast on common rockshaft B and their teeth face opposite ways. Reciprocating rod A rocks the shaft.
During one direction of rockshaft motion, one arc drives while the other lifts and slides over the wheel teeth. On reversal, their roles exchange. Brown calls the result nearly continuous, but supplies no dimensions or quantified duty cycle.
What This Calculator Represents
The tool treats each entered arc sweep as an ideal wheel advance and counts two working sweeps per complete reciprocating input cycle. It also compares that sweep with the entered ideal tooth pitch.
This is not a discrete ratchet-contact simulation and does not establish uninterrupted rotation under load.
Ideal Angular-Advance Calculation
ideal advance per cycle = 2 × effective sweep
arc sweep / tooth pitch = effective sweep × N / 360°
angle difference = |entered comparison - 180°|
The entered comparison angle does not represent relative phasing of Brown's arcs because both are fast on the same rockshaft.
Worked Ideal Example
At 60 complete input cycles per minute and 90° assumed effective sweep, two ideal working strokes give 180° advance per cycle and an average 30 rpm. With 24 ideal equal teeth, one 90° sweep spans six tooth pitches.
Model Boundary
- Mechanism arrangement: reciprocating rod A, common rockshaft B, two opposed spring-lift arcs C and ratchet wheel D.
- Calculated: ideal average speed, advance per cycle and angular comparisons.
- Not calculated: exact arc profile, tooth and spring geometry, discrete pickup, lift, backlash, slip, missed teeth, velocity ripple, continuity, force, torque, wear, strength or application suitability.
Frequently Asked Questions
Are the two arcs phased independently?
No. Brown says both are fast on the same rockshaft.
Why do their teeth face opposite ways?
So one arc can drive on each direction of shaft oscillation while the other lifts and slides.
Is output truly continuous?
Brown calls it nearly continuous; this calculator does not quantify ripple or handover gaps.
Does tooth count change the ideal rpm result?
No. It changes the displayed sweep-to-pitch ratio.
Is the entered angle comparison a mechanism phase setting?
No.
Can this size springs, teeth or a drive?
No.
References
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