Thomas R. Almond’s shaft coupling uses cranks, swivel pins and a sleeve that both slides and oscillates on a fixed post. The animation shows that construction. The name refers to the inventor, not to an almond-shaped block.
Almond Angular Shaft Coupling Interactive Calculator
Explore Almond’s crank-and-sleeve coupling. The result tiles give a separate single-Cardan speed comparison at the selected phase.
Equation Used
The result tiles model a separate single Cardan joint. Shaft angle beta sets its speed variation, which repeats twice per revolution; theta selects the input phase. These values do not describe the equal-crank Almond animation.
- Results use an ideal single-Cardan velocity relation, separately from the Almond animation.
- Shaft angle is fixed and shafts intersect at one point.
- No backlash, slot wear, compliance, or friction losses are included.
- Average speed over one revolution equals input speed.
The animation shows Almond’s sleeve-and-crank coupling. The speed equation describes a single Cardan joint, provided as a comparison at the selected input phase. It is not a validated speed-ripple calculation for Almond’s coupling.
Cranks, swivel pins and a sliding sleeve
Almond’s coupling connects shaft cranks through swivel pins engaging a sleeve on a stationary post. Turning the input crank makes the sleeve move along the post and oscillate around it. The second crank converts that combined movement into output-shaft rotation.
The 1881 patent, US236474A, describes the shafting connection and its reciprocating, oscillating slide. The name belongs to Thomas R. Almond; it does not specify the shape of an intermediate block.
The animation uses equal cranks and a symmetric arrangement with shafts turning together. Its sleeve, sliding pins and fixed post show how the motion is transferred. The illustration does not calculate contact forces, friction, wear or permissible speed.
Parts to follow
- Input crank: turns with the driving shaft.
- Output crank: turns with the driven shaft.
- Swivel-pin connections: accommodate the changing direction of the crank connections.
- Sliding sleeve: combines axial travel and angular oscillation.
- Stationary post: guides the sleeve.
What the arrangement demonstrates
This mechanism illustrates a way to transfer rotary motion through an intermediate member that both slides and oscillates. It is useful for studying how constraints combine different kinds of motion.
For a practical shaft connection, bearing arrangement, lubrication, load, speed, alignment and clearance need to be assessed from the particular design. The animation and Cardan comparison do not establish a product rating or identify a suitable coupling for a watch, instrument or motor drive.
A separate single-Cardan speed comparison
The displayed numerical results use r = cos β / (1 − sin²β sin²θ), with output speed n_out = n_in × r. This is the single-Cardan model used by the calculator. It is not the speed law of the Almond animation.
For the phase convention used here, θ = 0° gives the minimum ratio cos β and θ = 90° gives the maximum 1/cos β. The same pattern repeats after 180°. Peak-to-peak ripple, expressed as a percentage of input speed, is 100 × (1/cos β − cos β).
At zero shaft angle, the Cardan ratio is one at every phase. Increasing angle increases its variation. This ideal relationship excludes backlash, elastic deflection, friction and load-dependent effects; it does not give a permissible operating angle or torque rating.
Worked example: the Cardan comparison
Choose 60 rpm input speed and a 15° shaft angle. These are illustrative Cardan inputs, not measurements from an Almond coupling or a particular instrument.
- Minimum ratio = cos 15° = 0.965926, giving 57.96 rpm.
- Maximum ratio = 1/cos 15° = 1.035276, giving 62.12 rpm.
- Peak-to-peak ripple = 100 × (1.035276 − 0.965926) = 6.94% of input speed.
- With this phase convention, the minimum occurs at 0° and the maximum at 90°.
Changing only angle to 8° gives about 1.96% ripple; at 22° it is about 15.13%. These are kinematic results, not thresholds for acceptable feel, wear or machine performance.
Comparing shaft connections
| Arrangement | Motion-transfer elements | What this page demonstrates |
|---|---|---|
| Almond coupling | Cranks, swivel pins and a sleeve guided on a post | Combined sleeve sliding and oscillation in a symmetric example |
| Single Cardan joint | Two yokes connected by a cross | The separate ideal instantaneous speed comparison |
| Bevel gear pair | Meshing gear teeth on angled shaft axes | A different connection type; no gear-sizing calculation here |
Compare specific designs for available space, shaft geometry, load and duty. The mechanism name alone does not determine backlash, service life, cost or maximum speed.
Almond coupling questions
Does Almond refer to a lens-shaped part?
No. It is the inventor’s name. The mechanism shown here uses cranks, swivel pins and a sliding, oscillating sleeve.
Why does the sleeve move in two ways?
The shaft cranks constrain their connections to the sleeve as they turn. The sleeve can travel along its fixed post and oscillate about it, allowing both motions to occur together.
Why do the result tiles say Cardan?
They calculate a separate ideal single-Cardan speed comparison. Those numbers are not predictions of the Almond coupling shown in the animation.
Why do the two animated shafts turn together?
The drawing uses a symmetric equal-crank arrangement. It illustrates that selected geometry and does not establish the behavior of every possible shaft position or crank arrangement.
Does the formula calculate torque or wear?
No. It calculates an ideal single-Cardan velocity ratio and its variation. Loading, contact stress, friction, lubrication and durability require separate information.
Can the model diagnose a binding coupling?
No. Binding needs examination of the actual construction, alignment, engagement and loading. The ideal animation and speed comparison cannot specify clearances or a repair.
References & Further Reading
- Wikipedia contributors. Coupling. Wikipedia
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