KEVOS® MAKEOS · Mechanics
Geneva Wheel Indexing Mechanism
What crank radius and wheel size does a Geneva drive need, and how long are its index and dwell?
Geometry and timing of an external Geneva wheel with slots tangent to the roller path at entry and exit: crank radius, wheel radius, minimum slot length, driver angle for indexing, index and dwell times, and the peak speed ratio of the wheel.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Number of slots | Number of radial slots in the driven wheel (indexes per revolution of the wheel). | |
| Centre distance | mm | Distance between the driver and wheel centres. |
| Driver speed | rpm | Speed of the driving crank. |
| Roller diameter | mm | Diameter of the drive roller (sets the slot width). |
Method and formulas
- For slots tangent to the roller path: crank radius a = C sin(180° ÷ n); wheel radius to the slot mouth b = C cos(180° ÷ n).
- Driver angle while indexing = 180° − 360° ÷ n; index time = that fraction of one driver revolution.
- Peak wheel-to-driver speed ratio (roller on the centre line) = λ ÷ (1 − λ), with λ = sin(180° ÷ n).
- Minimum slot length from the mouth = a + b − C, plus the roller radius and clearance.
- Example: a 4-slot wheel on 100 mm centres needs a 70.711 mm crank and indexes in 0.25 s at 60 rpm.
Limitations
- External Geneva with radial slots; internal and spherical Geneva drives differ.
- Acceleration at roller entry is high for 3 and 4 slots; check inertia loads.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Lay out a Geneva drive for an indexing table
- Check the index and dwell times against a process cycle
- Estimate peak wheel speed for inertia loads
Who it is for
- Machine designers
- Maintenance engineers
- Automation engineers
What you get
- Crank radius and wheel radius
- Index and dwell time
- Peak wheel speed
Interpreting the result
- More slots give a smoother index but a smaller index angle per driver revolution.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 171. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
