Quattro in gear textbook

[Wallace White <wallace@remdesign.com>]

As I was reading up on gear design in Shigley & Mischke's _Mechanical
Engineering Design_, Fifth Edition, I came across Problem 13-18,
concerning an automobile with three differentials. The figure, showing
the ur-q drivetrain, has the caption, "The Audi 'Quattro concept,'
showing the three differentials which provide permanent all-wheel drive.
(By Permission, Audi of America, Inc., Troy, Michigan.)"

The text explains the system of three differentials and then asks:

(a) Explain why this concept may allow greater acceleration.

(b) Suppose either the center or the rear differential, or both, can be
locked for certain road conditions. Would either or both of these
actions provide greater traction? Why?

(c) Suppose the center differential were of a torque-sensing
arrangement... [Just kidding!]

- Wallace
  '87 5kcstq 160k