In Brown movement 74, a mutilated bevel driver C alternately engages opposed output gears A and B. Each output advances intermittently, in the opposite direction to the other. Explore how the driver's toothed sector and the gear tooth counts determine the ideal angular steps.
Opposed Intermittent Bevel-Gear Calculator
Enter a declared full driver tooth count, whole teeth retained in one sector, each opposed output's tooth count and driver speed. The worksheet reports exact pitch-count arc and step geometry. It does not design bevel teeth, a dwell lock, shafts or safe speed.
Equation Used
- Driver C has one declared retained whole-tooth sector on a full Nd-tooth pitch count.
- Opposed gears A and B are identical No-tooth bevel gears and receive equal step magnitudes in opposite directions.
- The two output mesh locations are 180 degrees apart and the retained arc is less than 180 degrees.
- Module, pressure angle, cone distance, tooth form, entry relief, backlash, holding device, interference, strength, inertia, impact, lubrication, bearings, shafts, speed rating and safety are excluded.
Whole-tooth counts determine the ideal engagement sector, output step and dwell angles. The separate mechanism needed to hold an output during dwell is not modeled. Animation timing is illustrative: the driver-speed input does not change these angle-based results or playback speed.
One mutilated bevel driver alternates between opposed outputs
Brown movement 74 places opposed bevel gears A and B on either side of mutilated bevel gear C. The retained teeth on C reach the two mesh locations at different driver phases, producing intermittent output steps in opposite directions.
Brown's caption does not show a complete dwell lock. Patent and textbook sources show that a practical mutilated-gear mechanism needs a separate holding provision while teeth are out of mesh.
Alternating engagement and dwell
The arrangement shows how one rotating input can drive two outputs intermittently in opposite directions. Tooth counts determine the ideal angular steps; detailed bevel-tooth geometry and a dwell-holding mechanism are separate design requirements.
Whole-tooth sector and ideal pitch-count step
A and B have equal step magnitudes and opposite signs. The formula assumes compatible ideal bevel pitch counts and does not establish manufacturable tooth geometry.
Declared whole-tooth example
For a 48-tooth full driver pitch count with 10 whole teeth retained and two 40-tooth outputs, the retained arc is 75°, each engagement advances its output by 90°, and each output dwells for 285° of every driver revolution. A and B advance in opposite directions.
From pitch counts to a working mechanism
A pitch-count calculation describes the angular motion but does not establish load capacity or reliable entry into mesh. A working mechanism needs suitable bevel-tooth geometry, alignment and a way to hold each output while it is disengaged. The calculator does not rate operating speed, accuracy or service life.
Opposed intermittent bevel questions
Does removing teeth alone lock an output during dwell?
No.
Why must the retained sector contain whole teeth?
The calculator counts ideal tooth pitches; a fractional tooth count would not define the angular step.
Do A and B rotate in the same direction?
No. Brown explicitly describes opposite directions.
Opposed intermittent bevel references
- Brown, 507 Mechanical Movements, movement 74: historical scan and transcription showing A and B opposed around mutilated bevel driver C and stating intermittent rotary motion in opposite directions.
- US632100A, Automatic Lathe: primary patent using mutilated bevel gears for intermittent motion and a separate cam-controlled dog to lock the driven gear while out of mesh.
- Mechanisms for Intermittent Motion: engineering reference discussing mutilated gear systems with locking or holding cams during dwell.
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