A sequential shift mechanism rotates a grooved drum through discrete indexed positions. Followers in the grooves translate shift forks, which move dog clutches or sliding gears axially to select successive ratios.
Sequential Shift Drum Timing Reference
Explore selected constant-speed drum-index timing without treating it as measured gearbox performance.
Equation Used
- Drum angular speed is constant during the selected index.
- The added engagement dwell is independent and occurs after drum rotation.
- The angular span is converted at the same selected drum speed.
- Dynamics, synchronization, loads, controls and durability are excluded.
The angular span is a timing reference only and is not a validated safe-overlap design value.
Drum-to-dog motion chain
Patent descriptions show a cylindrical shift drum with cam grooves, followers on shift forks, and dog clutches that engage or disengage gear trains as the drum indexes. The groove contour determines the fork sequence.
The animation uses a developed (unwrapped) cylindrical surface. The groove moves beneath a follower at fixed guide height; the follower, fork and sliding dog collar share one axial coordinate through a constant-length connector. It represents one selected ideal index event, not tooth-impact or synchronization dynamics.
What the calculator determines
Select an index angle θ, an assumed constant drum speed ω, an added engagement dwell and a selected angular groove-transition span. The calculator reports θ/ω, the sum of that interval and the dwell, the time corresponding to the selected span, and the reciprocal of the modeled interval.
The reciprocal is not a safe or achievable shift rate.
Selected timing arithmetic
For constant drum speed, tdrum = θ/ω. The selected modeled interval is tmodel = tdrum + tdwell. A selected angular span φ corresponds to tspan = φ/ω. The reciprocal reference is 1/tmodel.
Selected-input arithmetic
At θ = 60°, ω = 1,500°/s and 5 ms added dwell, drum interval is 40 ms and modeled interval is 45 ms. A 7.5° selected groove span corresponds to 5 ms, and the reciprocal interval is about 22.22 per second.
Model boundary
Constant drum speed and a separately added dwell are user-selected idealizations. The calculator does not model actuator acceleration, detent motion, lost motion, torque unloading, shaft-speed mismatch, dog-window probability, impact, synchronizers, groove force, fork deflection, lubrication, control logic or durability.
The displayed groove transition does not establish safe overlap or simultaneous engagement.
Questions
Is the reciprocal a maximum real shift rate?
No. It is only the reciprocal of the selected ideal interval.
Does angular span prove safe fork overlap?
No.
Why can gears not be skipped in the selected topology?
The drum moves through successive indexed positions and its groove sequence controls the forks.
References & Further Reading
- Wikipedia contributors. Sequential manual transmission. Wikipedia
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