A plunging tripod constant-velocity joint uses three trunnions and roller units running in axial tracks. This calculator provides ideal torque-radius arithmetic and entered travel ratios, not contact-load or binding predictions.
Tripod Joint Interactive Calculator
Enter torque, pitch radius, plunge, comparison travel and joint angle. Outputs are ideal force and travel comparisons under stated assumptions; they are not component ratings.
Equation Used
- Torque is represented by one equivalent tangential force at the entered pitch radius.
- The per-roller value assumes equal sharing among all three rollers.
- Plunge and travel are independent entered magnitudes; their ratio may exceed 100%.
- Thirty degrees is only the calculator input ceiling, not a binding or allowable angle.
- Track geometry, articulation kinematics, contact distribution, friction, vibration, stress, fatigue, lubrication, tolerances and ratings are omitted.
Three Trunnions, Rollers and Axial Tracks
U.S. Patent 4,932,922 describes a hollow outer part with three equally spaced longitudinal grooves and an inner part with three projecting trunnions carrying rollers, with axial plunge allowed. EP 0 009 224 likewise describes three rods spaced 120° apart, three rollers and three pairs of raceways.
What This Calculator Represents
The tool converts entered torque to an equivalent tangential force at an entered radius. It then shows an explicitly assumed equal three-way share, a direct plunge/travel ratio and distance from entered angle to the input-angle maximum.
Ideal Arithmetic
assumed equal-share force = T/(3r)
plunge/travel ratio = 100p/L
angle to input ceiling = 30°-alpha
Worked Assumption Example
At 250 N·m and 30 mm radius, equivalent tangential force is 8,333 N. An equal three-way assumption gives 2,778 N per roller. Entered plunge 35 mm over 50 mm is 70%, and 10° is 20° below the input-angle maximum.
Model Boundary
- Calculated: torque-radius equivalence and direct entered ratios.
- Assumed: equal load sharing among three rollers.
- Not calculated: actual roller forces, joint kinematics, binding, allowable angle, track contact, friction, plunge force, stress, fatigue, wear, vibration or safety.
Frequently Asked Questions
Do all three rollers always share load equally?
No.
Is 30° an allowable joint angle?
No. It is only the input ceiling.
Can plunge ratio exceed 100%?
Yes, when entered plunge exceeds entered comparison travel.
Is T/r a measured contact force?
No. It is an equivalent tangential force.
Are friction and articulation effects included?
No.
Can this calculator select a CV joint?
No.
References
- U.S. Patent 4,932,922, Tripod plunging constant velocity joint: three grooves, three trunnions, rollers and axial plunge.
- EP 0 009 224 A1, Tripod type constant velocity universal joint: three roller-supporting rods at 120°, rollers and raceways.
- U.S. Patent 6,764,407, Constant velocity joint: plunging tripod topology and torque transmission through axial tracks.
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