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Helical splines for linear motion (Bendix Drive)

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  • Helical splines for linear motion (Bendix Drive)

    For a given diameter of shaft: when
    planning a helical spline in an application
    with the objective of providing linear motion,
    what considerations influence the number of

    For instance, to enable the pinon gear of a
    Bendix Drive on a starter motor to advance
    along the armature shaft, engage with a ring
    gear and then retract back to its initial

    In general terms, will a greater spline count
    produce more bearing surface for smoother
    travel at the expense of reduced torsional
    strength and increased mfg cost?

    The back story here is that a change-up p/n
    for a replacement pinion for an old ('70s)
    Bendix for a Tecumseh (Toro) starter turns
    out to have 7 helical splines, instead of 6.

    Looks right with the correct gear tooth count
    and slips right onto the armature like it
    should, just doesn't engage w/ the helical
    portion of the shaft.

    Sourced from a local Tecumseh rep, though
    with the company long departed, I suppose
    all parts now are aftermarket. Looking online,
    I have not come across a single instance
    where spline count is given in the description
    of parts purported to fit.

    For a fixed shaft size, by the 70's and beyond
    one would think there would have been some
    standard settled on, obviating the need to
    mess with spline counts.

    Last edited by EddyCurr; 11-29-2014, 12:12 PM.