Browse Publications Technical Papers 2004-01-1230

Synchronizer Design: A Mathematical and Dimensional Treatise 2004-01-1230


The manual transmission synchronizer design has been a real challenge and is usually referred to as a myth and black magic. A mathematical algorithm and dimensioning and tolerancing scheme has been developed to dispel this myth.
A unique and logical user-friendly method for designing synchronizer is devised. The knowledge that existed in the public domain is advanced to higher level to show that the design and calculations of physical parameters must go hand in hand.
The paper attempts to demonstrate the fact that the calculations of synchronizer physical parameters should be supported by scrupulously dimensioning and tolerancing the components design to achieve the intended functional objective.
A mathematical algorithm is developed which facilitates establishing the sleeve and blocker ring pointing angle relationship with the synchronizer size, coefficient of friction, cone torque, and index torque. The relationship is presented graphically in a unique manner identifying the clash and hard shift zones. As such, it allows sizing the synchronizer and selection of the parameters for a given application for comfortable shiftability between the two extremes of clash and hard shift.
Synchronization episode is separated in to the following six distinct events:
  • Event I
    Strut contacts blocker ring
  • Event II
    End of strut loading, strut out of detent
  • Event III
    Sleeve point hits ring point, ring clocked
  • Event IV
    Sleeve chamfer passes through ring chamfer
  • Event V
    Sleeve tooth point contacts clutching tooth point
  • Event VI
    Sleeve tooth chamfer passes through gear clutching tooth chamfer
Arithmetic stack and calculations are utilized to iteratively dimension and tolerance the components for each event so functional harmony is achieved in concert with the selected physical parameters. Event charts are presented with illustrations and necessary stack for dimensioning and tolerancing the synchronizer components. The components that play significant role in each event are identified and related to specific physical parameter.


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