Post by NoddyPost by Keithr0Post by NoddyPost by Keithr0Torsion BEAM suspension (also known as twist beam) is not torsion
BAR suspension.
It is *exactly* the same principal as any torsion bar suspension
system with the exception that a torsion bar system usually links the
two wheels of an axle together mechanically and relies on the flex of
the link to supply the spring medium, as opposed to a torsion bar
system where each wheel is usually sprung independently of each other.
The big difference is that, in torsion bar suspension, the torsion
element actually provide the suspension, in a torsion beam suspension
the actual suspension is provided by coil springs, and the torsion
element is simply an anti-roll car of a sort.
Pretty much. As I said, they're little more than an extension of your
average sway bar, and like *you* said they're a cheap and nasty
suspension system. They do nothing particularly well, other than make
cheap cars cheaper.
The point I was objecting to was the claim that the system used in the
crappy little MG ZS had to wait for "computer modelling" to be invented
before it could exist, which is complete and utter bullshit :)
Ah, poor desperate Darren, lost your street cred and are now desperately
seeking some. Sorry, not here Darren, you're just a *confirmed* bullshitter!
It took me a while to find a relevant book on the topic but let me quote
a pertinent paragraph from it here;
The optimization of a compound-beam design, where the trailing
arms must be laterally and torsionally elastic as well, cannot
be achieved by manual techniques and depends heavily upon
finite element stress analysis (see chapter 6) of the complete
welded assembly. The selection of the geometry for bump steer,
roll steer, roll camber, deflection steer and the roll-centre
height also requires the use of advanced, dynamic computer
modelling.
The above paragraph is from the book;
Chassis And Suspension Engineering
Road and Track Theory and Practice
By Geoffrey Howard 1987
I have the 1989 reprint so I've had it for quite a while.
Now, in the above cited text, chapter 6 is referenced. What is chapter 6
all about? Well, the title is "Computer aids and design techniques".
I'll cite a few pertinent paragraphs on the first page of the chapter;
Although the first use of computers in suspension
design and development dates back 20 years, rapid and
recent advances in graphic displays, measurement
techniques and processing time are putting a new
emphasis and value on the results of interactive studies.
Today, the visual display unit linked to a powerful,
high speed computer running advanced, dynamic suspension
and vehicle models are the basic tools of the
suspension-design trade.
Computer aids in suspension design eliminate much of
the guesswork, empirical measurement and practically all
the tedious calculations that were required previously
to determine safe stress levels and acceptable durability
standards as the preliminary stages to a new system
design. Carefully-developed programmes allow the
thousands of simultaneous equations of dynamic movement
to be solved rapidly, and advanced computer graphics are
used regularly to simulate actual parts in action under
strain, showing differences in stress levels, by keyed
colour graduations, like a thermal-image picture of heat
radiation. Three-dimensional representations also act as
valuable visual aids to the experienced eye of a
component engineer working on a new design, with
light-source angle of view and magnification all under
keyboard control.
This kind of computer-aided design (cad) is currently
being integrated with computer-aided manufacture (cam)
into a new operating science known as computer-integrated
engineering (cie). It is having dramatic effects on the
whole process of creating new vehicles and components,
and updating existing models.
Stress analysis for both the supporting elements of
the integral body/chassis unit and each component part
of the suspension system is performed with impressive
accuracy by a mesh of finite elements (fe) built up into
a framework of several thousand, finely-detailed,
interlinked struts forming triangles, squares and
rectangles. From the first application of fe programmes,
used to handle only discrete parts of a full system, new
tools have been developed that can simulate the
considerably more complex models required to represent
authentic dynamic behaviour.
Early fe work was limited originally to stress and
strain calculations by the inability of the computer
systems to handle the non-linear events and relatively
large displacements typical of vehicle suspensions under
dynamic loads. Setting up representative mathematical
equations of motion for the interrelated parts was too
complex and time consuming for the skills and abilities
of the engineering department staffs. However, with the
new generation computers came automated and
user-friendly programming interfaces that eliminated
the tedium and lowered the threshold of acceptance by
traditional mechanical engineers.
As I said in a previous post, my first experience of fe stress analysis
suspension modelling work was at the GM Development Labs in Fishermans
Bend. It was on a Camira which had a *ram* under the left front wheel
and the ram was pumping the suspension as if the car were running on a
corrugated outback road and the results of the effects displayed as a
wireframe graphic on a large monochrome monitor. At the time I was
amazed to see just how far and wide the vibrations travelled throughout
the car body. At the time what I was seeing was cutting edge technology,
the colour displays, mentioned in the text above, yet to appear.
So Darren, in all his ignorance, can shout from the treetops that what I
said was bullshit but, unlike him, I have the proof right here at my
fingertips. I have another text on the same topic but I have yet to
locate that but this will suffice.
BTW, the software used by the engineers was this and is referenced in
the book, obviously a much earlier version
https://en.wikipedia.org/wiki/MSC_Adams
The original creator of the software was a company called Mechanical
Dynamics Inc. and they were taken over/bought by MSC in 2002.
https://en.wikipedia.org/wiki/MSC_Software
--
Xeno
Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)