Review of Chassis Design: Principles and Analysis
by "Flutenews"
The magazine of the
Vauxhall Owners Club 1903 to 1957
January 2004
Maurice Olley was one of the outstanding automobile engineers of the twentieth
century, who made invaluable contributions to the understanding of vehicle ride
and handling, and to the development of car suspension during the 30's, 40's
and 50's. He was born in Scarborough, North Yorkshire, in 1889, and from the
age of four grew up in North Wales. His career as an automobile engineer
started when he worked for Henry Royce, both in Derby and at Royce's winter
retreat in the south of France, and for ten years from 1920 he was Chief
Engineer at the Rolls-Royce factory in Springfield, Massachusetts, USA.
In 1930 he joined Cadillac in Detroit, working on vehicle suspension and ride,
and during the ensuing years was responsible for introducing independent front
suspension on all General Motors cars. He also spent time from 1936 onwards in
England, introducing the Dubonnet IFS on to the Vauxhall models.
A few years after "officially" retiring from GM in 1955, Olley returned to
Chevrolet on an informal basis and proceeded to write a series of monographs
describing his lifetime's work in chassis engineering. These were acquired by
Bill Milliken and were being readied for publication in 1969 when General
Motors decided that in view of the litigation issues to which the Chevrolet
Corvair had been subjected from 1963 to 1968, it would not be prudent to
publish such information on vehicle handling, and the project was stopped.
Thirty years later, father and son Bill and Doug Milliken, who are themselves
eminent vehicle dynamicists, and the authors of "Race Car Vehicle Dynamics",
again approached GM, and this time permission to publish was granted.
Bill Milliken had worked in association with Maurice Olley from 1952 until
Olley's death in 1972, and together with colleagues at the Cornell Aeronautical
Laboratories had been the first to apply some of the principles and techniques
used in aeronautical engineering to the analysis of road vehicle stability and
transient handling, in a project sponsored by General Motors.
"Chassis Design - Principles and Analysis" contains over six hundred pages, and
covers all aspects of vehicle suspension, ride and handling. As a textbook, it
develops the subject matter from first principles, supported by a vast number
of easily understood diagrams; the authors have also added their own
explanatory notes in places to clarify some aspects and to aid understanding.
Those of us for whom school is but a distant memory may prefer to skip through
much of the mathematics, but the erudite manner in which Olley discusses the
conclusions drawn from his theoretical and practical work makes fascinating
reading for anyone interested in how and why motor cars behave in the way that
they do. Any young engineer starting work in this field, with arrays of
computer aided design and data acquisition packages at his disposal, would be
well advised to first study the contents of this book, to obtain a tangible
feel for the subject and to help to avoid some of the "rubbish in - rubbish
out" pitfalls of the electronic age.
This is not just a textbook however. Sections are devoted to Olley's
reminiscences, descriptions of early motoring in Britain and his views on the
future. It even includes four rather "Thurberesque" cartoons drawn by Olley. In
short, it forms a comprehensive review of the accomplishments of an engineer
described by the authors as a "creative and inspired individual" whose work
"has had a positive effect on the ride and handling of every car on the road".
For owners of late pre- and early post-war Vauxhalls, the information on
Dubonnet suspension should be particularly interesting, including a practical
analysis of the "caster wobble" exhibited by a Chevrolet fitted with Dubonnet
IFS. The book makes clear distinctions between wheel fight, shimmy, (which
cannot occur with IFS) and caster wobble, (which can). In fact the book states
that "nose-wheel shimmy" on aircraft is actually an example of caster wobble.
To this I could also add the wheel wobble of some early generation supermarket
trolleys!
As the owner of the LM 14-40 once owned by Brian Frank, I was particularly
interested in wheel wobble. In correspondence with "Flutenews" about twelve
years ago, Mr Frank suggested reducing the camber angle (!) and increasing the
caster angle, (perhaps the intuitive thing to do, to increase the
self-centring), to cure wheel wobble, but finished up fitting a steering damper
between the track-rod and the axle.
In the book Olley states that, on the Chevrolet, increasing the caster increased
the violence of the wobble, but had little effect on the frequency, and that
caster wobble can be damped out by decreasing the caster or by a small
increase in king-pin friction - friction applied elsewhere in the steering
linkage is less effective and more liable to spoil the handling. On my car, the
damper certainly made the steering feel dead, but when I removed it, the first
bump in the road hit at about 15mph set off a violent wobble. I then fitted
some wedges, tapering from 3/16ins to 1/16ins over a 4ins length, between the
springs and the axle, so as to reduce the caster angle (as described on page
29a of Supplement No 2 to the 14-40 HP Vauxhall Chassis Shop Manual, kindly
sent to me by fellow VOC member and 14-40 owner Alan Livingstone).
The result is steering which feels decidedly "lively", with plenty of feedback,
but despite severe provocation from badly surfaced local roads the wobble has
not returned.
"Chassis Design - Principles and Analysis" (ISBN 0-7680-0826-3) is published by
Society of Automotive Engineers Inc., Warrendale, PA 15096-0001, USA, and is
available in UK from Professional Engineering Publishing Ltd, Bury St. Edmunds,
IP32 6BW. at £62.00 (with a discount for Institution of Mechanical Engineers
members).
-Brian Shilton
Flutenews
The magazine of the
Vauxhall Owners Club 1903 to 1957