Review of Chassis Design: Principles and Analysis
by "The Flying Lady"
The periodical of the Rolls-Royce
Owners' Club (RROC/USA)
July/August 2002 issue
For the Rolls-Royce or Bentley enthusiast this important book has a very special
place, for the vast majority of the material has been taken directly from the
previously unpublished writings of Maurice Olley.
Born in Yorkshire England, Olley (1889-1972) grew up on the great Holyhead Road
running through Wales. He describes his early impressions of a time when
England was dominated by the steam engine. The idea of internal combustion took
hold in France and Germany more quickly than in England, where it was first
generally accepted as power for motorcycles. Still, young Olley developed a
lifelong passion for the motorcar and had that goal firmly in mind during his
educational years. His first real job out of school was working in France for
Henry Royce, first as a tool designer. The remainder of his life was devoted to
automobiles, first with Rolls-Royce both in England and in Springfield, MA, and
finally with General Motors where he went on to be head of R & D at the
Chevrolet Division. After his retirement in the early 1960s Olley wrote a
series of monographs, covering his life's work in the field of chassis design.
By the late '60s the material was well on the way to publication when a very
tight lid was suddenly placed on the project. The legal staff at GM, in view of
the enormous litigation issues then raging around the "Corvair Affair" had
decided it would be prudent to keep all suspension development information
in-house and protected. We owe the authors of this new book a great debt of
gratitude that finally, after more than thirty years under wraps, the Olley
monographs have been released, and permission granted for their publication.
Keeping in mind the genesis-and also the purpose-of the book, it is best to
think of it as a textbook. Olley wrote his notes for peers, for practicing
engineers; he presupposes familiarity with principles and jargon. Almost every
page is filled with geometric diagrams, illustrations, and mathematical
progressions. Front and rear endpapers contain the symbols used throughout the
work in developing the mathematical solutions. It is a true look into the world
of automotive suspension design and despite the enormous body of data
presented, the book is honest in its conclusion that even with all that has
become understood and quantified, the subject remains probably the most complex
field in automotive engineering. Even today, just as with new aviation
products, much of the design effort in automotive suspensions can only be
carried out during actual testing.
This work not only looks like a textbook, but one would expect that it will
indeed be adopted for exactly that purpose. Any new student of automotive
chassis design would do well to start his or her education with an appreciation
and understanding of how suspension systems have reached their present
development and I cannot imagine a better source than this single book. As the
authors point out, today much of the mathematical effort, and even some of the
qualitative understanding, can be sidestepped by solving chassis problems
(suspension linkage for example) using one of the computer programs now
available. But blind reliance upon a computer program can, and has, produced
gross and expensive errors. I should think that the serious student of chassis
design would insist upon first working his way through the graphical approach
used by Maurice Olley, developed at a time when the only computer aid at his
disposal consisted of the logarithmic scales on his slide rule.
And although the book is primarily aimed at engineers in industry and
advanced-level users it is still recommended reading for the rest of us who
neither aspire to a future in automotive engineering (some among us have long
since developed a gentle but realistic appreciation of our personal
limitations), nor wish to run through the mathematical equations just for the
fun of it. It is perfectly legitimate to scan over the more difficult
mathematics, accepting that they are correct as written, and instead focus
one's attention on the diagrams/illustrations and the qualitative conclusions,
each of which are skillfully explained.
Of particular value to the RROC reader is the sweeping nature of Olley's
writing. He first started serious suspension experiments at GM in 1930, and
includes all the early effort in his writing. During the mid-1920s a serious
problem with front wheel shimmy had been studied by W. A. Robotham at
Rolls-Royce using a bump rig. From about 1911 Rolls-Royce had always tested
every chassis on a dynamometer by setting the rear wheels on 4-ft steel drums.
Later the same idea was used for chassis fatigue testing by using an automobile
engine to turn the drums, and this was the basis of the first bump rig. Maurice
Olley took the idea with him to GM and began his own test program, seeking the
solutions to front wheel shimmy and caster wobble. This was at a time when
virtually all automobiles being produced used solid front axles and leaf
springs. The eventual result of Olley's efforts was the development of the
so-called flat-ride at GM and the adoption of independent front suspension in
all GM products. The story of how that happened is explained in this book and
it must be said that it was largely the effort of one man. I can still remember
my grandfather raving about the ride of those first Cadillacs to benefit from
the change: "It's like floating down the road, no matter whether you're sitting
in front or back." Now at last I know how they achieved it and have also
learned who was the driving force. Have you ever wondered why ifs is so
superior to a fixed front axle? It is not just a matter of reducing the
unsprung mass, as many believe. You will find answers to many questions you
hadn't even imagined. The book contains 619 core pages and almost none of it is
redundant. Starting with fundamental concepts the work then moves on to a
consideration of a wide range of specific problem areas which are encountered
in chassis design.
Throughout the book, the authors have included italic text to help the reader
understand the concepts and to adjust for changes in modern SAE sign
convention. Olley assumes an audience of engineers and does not explain such
basic terms as "Ackermann angles." The authors' notes are particularly helpful
in that regard and they include additional information at the end of each
section as well as in appendix form. Even so, the non-technical reader may find
a short review of basic engineering terms to be helpful. A bending load can
visualized by a bar fixed at each end and loaded in the middle, a torsion load
is a twisting force, a tension load is one that would tend to stretch a part,
while a compression load will do the opposite. Stress, in engineering talk
refers to the internal force in a member resulting from an external load and
strain is the deformation of the material or structural member that the
internal stress may cause. A force acting at right angles to an axis is called
a normal force. These and other terms are used throughout the book and their
exact meanings are essential to grasping the material.
One cannot come away from this book without gaining a greater appreciation of
this complex subject. You will also come to have a great respect for Maurice
Olley, one of the original pioneers in chassis design, and for the Millikens
who carry on that tradition today (for more on the work of Milliken Research
Associates go to http://www.millikenresearch.com
where you will also find errata for this book posted). I, for one, have already
decided to also order a copy of their SAE best-seller Race Car Vehicle
Dynamics.
-James Pate
The Flying Lady
The periodical of the Rolls-Royce
Owners' Club (USA)
* * *
Recipient of a 2001 Golden Quill and IAMC Silver Medal