Compare the output step of an external Geneva with the pitch of a carousel’s stations. The calculator also reports driver engagement and dwell angles. Direct one-step-per-station indexing needs matching slot and station counts; different counts require an appropriate transmission or indexing arrangement.
Match output step to station pitch
A carousel with 12 equally spaced stations has a 30° pitch. A six-slot Geneva advances 60° per index, so a direct connection moves two stations rather than one. The two pitch values are shown separately to make that distinction clear.
Intermittent Rotary Motion Interactive Calculator
Compare external-Geneva step, engagement and dwell angles with an independently entered carousel pitch.
Equation Used
- Standard one-pin external Geneva with N equally spaced radial slots.
- Ideal crank-radius/centre-distance relation a/C=sin(pi/N).
- One engagement advances the star by one slot pitch.
- Carousel is directly coupled only when its station pitch equals the star step; otherwise a separately designed transmission is required.
- No locking-disk detail, clearance, interference, backlash, motion derivatives, load inertia, torque, stress, speed, wear, accuracy, transmission, controls or safety model.
For N slots, star step is 360/N, but driver-pin engagement spans 180−360/N degrees of input rotation and dwell spans 180+360/N. A direct star-to-carousel connection advances one station only when station count equals slot count.
External-Geneva geometry
A driver pin enters a radial slot and advances the star by one pitch. For N slots, the star step is 360/N degrees while the pin remains engaged for 180−360/N degrees of driver rotation.
The drawing uses a/C=sin(pi/N), while its slot lengths and wheel outline remain schematic. The outer carousel marks compare angular spacing; they do not add a transmission or establish physical compatibility.
Use as a geometry and compatibility check
The outputs can verify textbook phase angles and reveal whether a directly coupled star step matches carousel pitch. They cannot select an indexer, add gearing, predict process dwell time, or establish speed and capacity.
Input phase is not output step
Output step is 360/N. Input engagement is 180−360/N and input dwell is its complement, 180+360/N. Carousel pitch is 360/S.
For direct one-step-per-station motion, 360/N=360/S, so N=S. Other combinations require an explicitly designed ratio or different indexing architecture.
Six-slot example
For N=6, star step is 60 degrees, input engagement is 120 degrees and input dwell is 240 degrees. A 12-station carousel pitch is 30 degrees, so direct coupling would move two stations per Geneva index rather than one.
What the angle comparison cannot determine
Matching the two pitches establishes only the required angular advance for direct indexing. Pin, slot and locking geometry must also be compatible. Loads, inertia, clearance and settling affect practical speed and positioning accuracy, none of which is calculated here.
Questions
Why does engagement angle differ from star step?
They are rotations of different members: the driver and the star.
Can six slots directly index twelve carousel stations one at a time?
No. A 60-degree star step differs from a 30-degree station pitch.
Does dwell angle give dwell time?
Only after input speed and real settling are considered.
References & Further Reading
- Wikipedia contributors. Geneva drive. Wikipedia
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