Geneva Mechanism Simulator
Intermittent Motion • 3, 4, 6 & 8-Slot Configurations • Coupled Radius Control • 5-Phase Motion Tracking
1 Overview
The Geneva Mechanism Simulator is an interactive tool for studying the Geneva drive, which converts continuous rotation into intermittent (indexed) rotary motion. A driver disc with a pin engages radial slots in the Geneva wheel, advancing it by a precise angle each cycle. Between engagements, the driver’s embossed locking arc band slides into concave notches on the Geneva wheel, preventing any rotation during the dwell phase.
This simulator features coupled crank & wheel radius sliders with full kinematic synthesis, 5-phase motion tracking (Dwell → Engage → Drive → Exit → Lock), and real-time angular velocity/acceleration graphs across 3, 4, 6, and 8-slot configurations.
2 Getting Started
The simulator opens in Simulate mode with a 4-slot Geneva mechanism. The split canvas shows the animated mechanism on the left and a live graph on the right.
- Switch between 3, 4, 6, and 8-slot configurations using the Slots tabs.
- Adjust Crank Radius a or Wheel Radius R via sliders or type exact values into the companion text inputs (coupled by R = a/tan(π/n)).
- Adjust RPM to change the driver speed.
- Toggle SI / Imperial to switch between mm and inches for radius displays.
- Click the canvas or press Space to pause/resume. Use Arrow keys to step.
- Right-click the canvas for options: Copy Values, Reset Animation, Toggle Grid.
3 Simulate Mode
The left canvas shows the driver disc (blue) rotating with its pin (orange) and a distinct locking arc band (lighter blue embossed surface). The Geneva wheel (salmon) has radial slots and concave locking-arc notches between each slot. The animation tracks 5 phases: Dwell (locked), Engage (pin enters slot), Drive (pin pushes wheel), Exit (pin leaves slot), and Lock (locking arc seats into notch).
The right canvas displays live graphs: ω₂/ω₁ (velocity ratio — characteristic pulse), α₂/ω₁² (acceleration ratio — spikes at entry/exit), or θ₂ (staircase displacement).
4 Explore Mode
Study 12 concepts in three categories:
- Basics — Geneva anatomy, intermittent motion, slot count effects, locking arc.
- Kinematics — Indexing angle, dwell ratio, angular velocity equation, angular acceleration.
- Design & Applications — Film projectors, indexing tables, design parameters, advantages/disadvantages.
5 Practice & Quiz
Practice generates random problems on indexing angles, dwell ratios, centre distances, and velocity calculations. Quiz tests knowledge with 5 randomised questions from a 15-question pool.
6 Tips & Keyboard Shortcuts
- Watch the velocity ratio graph — it shows the characteristic pulse during the motion phase and zero during dwell.
- Compare different slot counts to see how dwell percentage increases with more slots.
- Notice how the acceleration spikes at slot entry/exit — this is the main limitation of Geneva mechanisms at high speed.
- Observe the locking arc contact — during dwell, the driver’s embossed band (lighter blue) slides into the Geneva wheel’s concave notch (highlighted), showing the secondary sliding contact that prevents backlash.
- Use the coupled radius sliders or type exact values into the companion text inputs. Crank Radius a and Wheel Radius R are linked by R = a/tan(π/n).
- Switch SI / Imperial in the mode bar to toggle between mm and inches for radius displays.
- Right-click the canvas to access Copy Values, Reset Animation, and Toggle Grid options.
- Keyboard: Space = pause/resume, Arrow Left/Right = step 2° per press.
- Try different presets to see real-world configurations, then explore how geometry affects motion.
What Is a Geneva Mechanism?
A Geneva mechanism (also called a Geneva drive or Maltese cross mechanism) converts continuous rotation of a driver disc into intermittent rotation of a driven Geneva wheel. The driver carries a pin on a rotating crank arm that periodically enters radial slots in the Geneva wheel, advancing it by a precise angle each cycle. Beyond this pin-slot connection, a secondary sliding contact exists: the driver’s embossed locking arc band mates with concave locking-arc notches on the Geneva wheel, positively locking the output during the dwell phase and eliminating backlash.
Locking Arc Contact & 5-Phase Motion
This simulator visualises the complete motion cycle as five distinct phases: Dwell (locking arc seated in concave notch — wheel stationary), Engage (pin enters the next slot), Drive (pin pushes wheel through indexing angle), Exit (pin leaves the slot), and Lock (locking arc re-engages the next notch). The concave notch regions on the Geneva wheel are shaded to show exactly where the driver’s outer arc makes sliding contact, while the embossed locking arc band on the driver is rendered in a distinct colour.
Coupled Radius Control & Kinematic Synthesis
The Crank Radius a and Wheel Radius R sliders are coupled by the kinematic constraint R = a/tan(π/n). Adjusting one automatically updates the other, along with the centre distance C = a/sin(π/n). This kinematic synthesis ensures proper pin engagement geometry, prevents pin overshoot beyond slot length, and maintains correct locking arc proportions for all 3, 4, 6, and 8-slot configurations. Slider ranges adapt dynamically to each slot count.
How Slot Count Affects Performance
The number of slots n determines the indexing angle (α = 360°/n) and the dwell percentage. A 4-slot Geneva advances 90° per cycle with 62.5% dwell time. A 6-slot Geneva advances only 60° with 75% dwell. More slots provide longer dwell periods for operations like machining, assembly, or inspection, but produce smaller indexing steps. The minimum practical slot count is 3, as fewer slots cannot geometrically accommodate the locking arc.
Kinematics & Angular Velocity
During the motion phase, the Geneva wheel angular velocity varies as ω₂/ω₁ = (M·cosφ − 1) / (1 + M² − 2M·cosφ), where M = 1/sin(π/n) is the centre distance ratio and φ is the driver angle. The velocity starts and ends at zero (guaranteed by the right-angle entry condition), with a peak of 1/(M−1) at the midpoint. The angular acceleration shows sharp spikes at slot entry and exit, which is the primary speed limitation of Geneva mechanisms.
Industrial Applications
Geneva mechanisms are found in film projectors (frame advance), rotary indexing tables (manufacturing), watch mechanisms, bottling machines, CNC tool changers, and packaging equipment. They provide precise, repeatable positioning (30–120 arc-seconds accuracy) without feedback control systems.
Who Uses This Simulator?
This tool is designed for mechanical engineering students, mechanism design learners, and instructors teaching intermittent motion mechanisms. Whether you are studying kinematic synthesis for exams, designing a rotary indexing table, exploring locking arc geometry, or demonstrating Geneva drives in a classroom, this simulator provides interactive, visual learning with real-time graphs and coupled parameter control.
Explore Related Simulators
If you found this Geneva Mechanism simulator helpful, explore our Slider-Crank Mechanism simulator, Scotch Yoke simulator, Four-Bar Linkage simulator, and Cam & Follower simulator for more hands-on practice.