sold to a private firm was its Ride
Dynamics and Brakes unit, which
became BWI Group. Julian Buckley
finds out what BWI has to offer
carmakers by way of new part
technology, while also examining the
company’s production set up.
Under GM, Delphi was of the world’s largest
automotive part manufacturers. After being
made a fully-independent company in 1999,
the company faced an uncertain future,
leading to a filing for Chapter 11 bankruptcy
protection in 2005. In an effort to cut costs and refocus on
core activities, a series of plant closures followed; in 2006,
Delphi closed 21 of its 29 remaining US plants. As part
of this restructuring, various non-core parts production
businesses were sold off, including battery production
(sold to Johnson Controls, 2006), brake hoses (Harco
Manufacturing, 2007), and wheel bearings (Kyklos, 2008).
These were followed with the March 2009 announcement
that the Ride Dynamics and Brakes unit would be sold to
China’s BWI Group.
Beijing West Industries Group is made up of three
separate investment entities; Shougang Corporation (51%),
Beijing’s Fangshan District (25%) and Bao’an Investment
Development (24%). Shougang, one of China’s largest steel
producers, is said to view the purchase as route to product
diversification, while retaining steel production as its core
business. Bao’an Investment is held by Tempo Group, a
company which has been providing after-market parts in the
US for over a decade.
While Delphi had almost exclusively supplied GM, BWI
Group has no such ties to a parent company. Tim Schlangen,
MR Mounts Engineering Manager, sees the sale, finalized in
November 2009, as an opportunity to market former Delphi
products to carmakers of any size and in any region. Of
particular interest will be BWI’s magneto rheological (MR)
engine mounts, the latest addition to the company’s range of
premium car parts that will first feature on the Porsche 911
GT3.
Although there are a range of powertrain mounts,
Schlangen says the new product is specifically designed for
use as an engine mount: “There could be up to five different
types of (powertrain) mounts depending on what type of
vehicle it is, the setup, but the ones we are producing now
are for the motor.” Delphi was one of the first companies
to address the problem of engine mount optimization, and
was the first to introduce glycol-filled mounts that could be
tuned to control one main vibration frequency. The latest
MR mounts have almost completely eliminated the need to
compromise mount behaviour, in allowing mount stiffness
to be tuned to control powertrain frequencies in real time.
Mount technology
The key element to the MR mounts is the MR fluid. Iron
particles suspended in a base liquid are located within a
sealed cavity in the rubber body of the mount. When a
magnetic field is applied by a coil, the particles become
aligned, increasing the sheer stress and resistance to flow.
The stronger the magnetic field, the higher the dynamic
rate (or stiffness). Further to this, closed loop feedback
provides direct measurement of the fluid pressure, ensuring
real-time compensation for changing conditions and as the
components age. According to Alan Lee, Director of Sales,
Marketing and Planning at BWI, the importance of the
technology represented by the fluid cannot be understated.
“The fluid and its properties, that’s one of the key intellectual
property assets that has been developed by BWI.”
Schlangen says that the fluid in the MR mounts has been
researched intensively over the past six years, chiefly to
ensure that there is a minimal amount of fluid breakdown.
“We have virtually eliminated the properties that would
cause this to happen, and with the software, if you do
something that has changed, you can change the current
level and get back to where you need to be.
“We test fluids and compounds offline to make sure they
meet performance specification, because once they have
been built up, there’s a lot of value in the end part. We try
to get stations involved in testing those parts and then we
have testing as a sub-assembly, the bottom can (which is a
diecast part) and the stamped top part, we crimp that, then
run it through our performance sector to make sure it meets
customer specification for the specific vehicle.”
Benefits represented by the MR mounts go far beyond that
of the standard equivalent, according to Schlangen: “There
are two types of passive mounts. A conventional mount
uses a metal bracket and a piece of rubber, while a hydraulic
mount has fluid in it, in a track, with a rubber main spring.
These can be tuned to a vehicle. Then there are active
mounts, MR mounts, that we control with the changing
of the sheer strength of the fluid, driving the rubber main
spring.”
Schlangen continues: “About 1,000 times per second, the
system looks at what the vehicle body is doing in terms of
roll and pitch, what the wheel is doing, throttle position,
brake, gear selection, together with internal and external
temperatures. From this data, we can determine what the
vehicle is going through, millisecond by millisecond, and
calculate precisely what needs to be done using the onboard
CPU.”
The rubber main spring is also a critical element to the
MR engine mount. Of particular importance is the material’s
durability and how it interacts with the fluid. Schlangen
says that the on-site lab at the company’s Dayton, Ohio
headquarters has carried out extensive research into rubber
compounding and formulation, ultimately delivering
the best rubber material for the control and isolation of
powertrain vibration. A further two suppliers are being used
to develop new, ‘outside the box’ formulations.
Benefits of the MR mounts include improvements in
powertrain isolation, vehicle stability and traction. While
sound and vibration can be reduced, the mounts offer
brand-specific tuning, with the opportunity to incorporate
driver-initiated settings, linked to other active systems such
as dampers and a sports exhaust system.
Variations on a theme
Schlangen points out that owing to the variety of engines
and powertrain combinations, no two mounts are the
same, which leads to individual development costs for each
application – costs generally assumed by BWI. “As you
change engines and powertrains, they fit into a completely
different space. So if I have two different powertrains on the
same vehicle, the chassis is probably the same, but the engine
side is probably not. So I have a lot of part pieces to make
the same base component. Then my end of test changes
because the engine specs would be different.”
Carmakers also have difficulties in outlining part
specification at the development stage. “(Part) specifications
are tough to write, because car manufacturers are not exactly
sure what to ask. We keep running into the same situation,
where they say ‘We know what that does’, then they put it
on the vehicle and realize they have no idea how to specify
what you’re able to do.” In order to solve such problems, BWI
can take the vehicle in-house to develop a mount solution.
This can take place at the Dayton HQ, or at either of the
company’s technical centres in France or Poland.
When it comes to part installation, Schlangen says the
mounts must be applied on the chassis (a process
known as ‘decking’) in preparation for marriage of the
powertrain and body. Beyond managing engine vibration,
the mounts must also be able to handle the stress of being
the point at which the body and powertrain meet. In a sense,
the mounts serve the same purpose as cartilage in a human
joint.
The magneto rheological development featured in BWI’s
engine mounts has also been used in its range of shock
absorbers, this in addition to the existing air-levelling
shocks and the range of MagnaRide shocks and struts that
will feature in the new Ferrari 458 Italia. Tim Schlangen
is adamant that replacing standard springs with such
technology is not simply reinventing the wheel. “From a
damper control standpoint, the difference between an MR
shock and a passive shock is astounding. The MR fluid
allows us to draw force velocity curves that we just could not
do with passive mounts. When (sufficient) pressure is put
on any given corner of the car, a spring would not be able to
handle the forces involved, there the MR system could easily
do this.”
In operation, the stiffness of the dampers is altered by
varying the strength of the electric current passing through
the liquid; the fluid rearranging itself to stiffen or relax the
level of body control. “The current actually changes the
effective viscosity of the liquid,” says Schlangen. “We use a
DC current measuring between five and 25V. It’s a low-level
current, not like a starter.”
Braking ground
In addition to engine mounts and shock absorbers, BWI
also produces braking systems for a variety of carmakers.
In China alone, the company supplies both national and
transplant companies including BYD and GM.
Within brakes, there are two well-defined areas of
technology, foundation braking systems, which includes
production of rotors, callipers, boosters and master
cylinders, together with control systems, which covers
development and implementation of ABS and electronic
stability control systems.
Alan Lee explains that the vast majority of rotors are
cast, then finished in a post-cast machining process. “The
rotors have to have specific diameters and surface finishes.
They also have to be very well balanced or you will feel that
throughout the vehicle - even our fine suspension parts will
not stop that type of vibration!”
Other cast components used by BWI in its braking
systems include the callipers, master cylinder and ABS
body – the latter may also be made from aluminium in an
extrusion process, this in an effort to reduce overall weight.
To provide consistent, reliable braking, cooling of the
brake discs is vital. Schlangen says that there are various
methods that can be used to keep rotors in peak condition,
even under heavy use. “Rotors use some quite complex
geometries to assist in cooling. While the rear brakes might
be solid (steel), the front rotors will probably be veined, and
some of the veined systems are quite complex.” Techniques
used to cool rotors can vary, with some companies using
veined or crossed rotors, while another technique use body
geometry to provide a constant flow of air to the rotor.
Says Lee: “Combine the two areas and we can deliver the
whole corner unit. Bearing, brake, calliper, damper and
spring or strut. Between the two areas, we’re capable of
engineering and providing the complete unit.”
In light of this option, how do manufacturers prefer
to receive the components, as individual parts or as a
completed module? Schlangen: “I think that depends on
how a company partitions the work. In areas where labour
is more expensive, companies prefer us to supply the
subassemblies. In places like China, where labour is relatively
inexpensive, they are just as happy to put separate parts
together inside the production plant.”
Test for success
This has implications for safety and testing, as Lee explains.
“From our standpoint, what we like about delivering
modules is that we have complete control over the output
of that part. It’s no longer a case of ‘how did it get bolted
together’ or ‘does this line up’. When delivering modules we
can address any problems in-house, so we do like it for those
reasons.
Lee goes on to explain that in the case of ‘pulsation’
braking systems, such as those that feature ABS, it is critical
that tolerances are maintained. Like the full corner module,
if BWI is producing and assembling the parts, the company
can guarantee the tolerances, which is virtually impossible
to do if separate companies are supplying individual brake
system components.
In the case of the manufacturer assembling parts that
have passed BWI’s in-house testing criteria, does the
manufacturer assume liability for the failure?
“We first test our components in the lab, comparing
our results with the manufacturer’s requirements,” says
Schlangen. “Then we have a document that outlines our
testing and their testing. The car company can then carry
out durability tests, after which we receive the parts, together
with related feedback, and we can test internally before the
parts are put on the vehicle.”
Sounds time consuming – and it is. According to Lee,
development of a powertrain mount can be between 18 and
36 months. For dampers it is never less than 12 months,
while brake development times can be anywhere from nine
months to two years, depending on customer requirements.
According to Schlangen, manufacturers include a series
of tests on the production line to make sure that the parts
are applied to the vehicle correctly, consisting of a roller test,
where the wheels are spun up to a certain speed and have
to stop using a pre-defined pedal force, testing the traction
control and the ABS units. “There are checks at every level
and step of production, because being a safety part, there is
no room for error.”
Further, each part is marked in inventory, so if there is
a problem, it can be traced back through the production
process to uncover where the fault occurred in the internal
production process.
“Over the past five or ten years, a lot of (part)
manufacturers have been introducing traceability that allows
you to get back to a time of day, shift and batch. We used to
hold this information internally, but now a lot of customers
are now asking for that information.”
BWI uses a combination of paper labels, laser marking
and part stamping to mark each component. Each of the
stations in the production process is connected, which
allows management of each of the processes and overall
finished part quality.
“The electric
booster masters, they
have labels, while the
powertrain mount has
a paper label on it,”
says Schlangen. “We’ve
spent some time on
this and it works very
well. There’s a check
valve on the booster
which is marked
using a non-contrast
barcode, read by a
red laser. There’s no
contrast to it, so it measures the height of the bars, allowing
us to read the part numbers of each check valve. There are
four of them together, they’re all the same colour, but when
they go through this non-contrast system, we can identify
each component. What the customer likes is that they don’t
see a label, they’re black. So we have some simple systems,
such as standard labels, and some very complex systems,
such as this non-contrast bar code.”
Design for Environment
As with most companies producing parts for consumption
by automotive manufacturers, BWI must address concerns
surrounding the impact its production facilities have on the
local environment.
“We’ve done business around the world, while at the
same time being conscious of the local environmental
requirements,” says Alan Lee. In addition, the company has
its own internal standards, which outline how operations
must be completed. “We have to go through special
treatments of waste water and air quality checks, as well as
measuring all other outputs. We’re not doing anything that’s
really dirty these days, as we don’t make brake linings or
pads any more.”
Tim Schlangen adds: “There’s actually a part of our design
process called DFE (Design for Environment). We have a
checklist of items, materials, that we look at for recyclability,
so the reusability of a part is taken into account before the
part goes into production.”
