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Friction Materials
Their Use and Applications
Introduction
Friction materials as a whole have changed as much as horse power
and torque ratings have changed in the past few years. Listed below
is a short informational guide to friction material. Each engine,
driver, and driving condition is unique. D&W can customize clutches
by plate load, torque capacity, and application to optimize your
clutch service. D&W has solved problems for U.P.S., local BFI, and
Waste Management locations by switching them to a kevlar and ceramic
button combination unit, which U.P.S. now demands at the OE level.
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Kevlar/Aramid

The kevlar/aramid fiber material that D&W utilizes is developed and
manufactured in the U.S.. When used in the proper applications, it
can outlast other friction materials two to five times. Kevlar
provides the pulling capabilities of ceramic button materials along
with the smooth engagement properties of an organic facing. By its
nature, Kevlar allows for smooth clutch engagement which allows for
prolonged life of universal joints, differential gears, and other
drive line components.The major cost benefit savings of kevlar,
aside from less downtime, is that all of the friction wear surfaces
will show little or no wear compared to clutches using other
friction materials. A truck originally equipped with a kevlar
clutch, and kevlar replacement units, may never need the flywheel
replaced!
Ceramic
Ceramic button-style clutch facings are very durable and have the
unique ability to grab better as it heats. Organic facings tend to
fade as they heat. A ceramic button clutch is appropriate for
hard-working applications and has traditionally held up to
expectations. However, there are downsides to ceramic material.
First, this clutch is either in or it’s out; there is no soft
engagement. Second, it is as hard as the material that it mates
against, which means that the pressure plate, center plate, and
flywheel wear at the same rate as the ceramic facing. This high rate
of wear often means that the flywheel will wear out well before the
engine or truck does. Therefore, there is an additional expense
associated with using a ceramic button clutch. For those customers
who work their trucks the hardest and carry the heaviest loads, the
ceramic friction clutch is still the best choice because it handles
the heat better than any other friction material. D&W offers ceramic
buttons made by SK Wellman and Miba, OE suppliers, which are made in
western Europe. Ceramic button clutches are the preferred and
recommended choice for dump trucks, refuse vehicles, off-road
equipment, and heavy hauling in mountainous terrain such as logging
and coal hauling.
Fibertuff
Fibertuff is a product designed to give the wear of a ceramic
facing, yet have the engagement and disengagement qualities of an
organic material. Fibertuff is a product of Canada and is intended
to wear against its mating surfaces like organic material. Used
primarily in the stamped steel and 14”cast units, this product
offers greater life than organic material with many of the same
qualities that organic friction has traditionally offered.
Around-town delivery trucks and mid-range applications find that
this product works best.
Carbotic
Carbotic, recently introduced by the manufacturer of Fibertuff, was
designed to offer super smooth engagement, like both the organic and
kevlar materials. In addition to smooth engagement, this product has
excellent service longevity and the ability to handle high horse
power and high torque requirements like the ceramic button, but
without the harsh wear of the mating surfaces. This product is best
utilized in heavy hauling vehicles such as quarry dump trucks which
encounter steep grades where clutch slippage and high heat
generation are probable. We have also used it in tractor pulls and
truck racing vehicles.
Organic
The basic organic disc has been in the industry for 50 plus years
and has evolved considerably due to engine alterations as well as
environmental issues. Organic facings were originally made with
asbestos, but as health issues arose concerning the use of asbestos,
it was phased out of the industry. Facings were then made of
fiberglass and brass as its main ingredients. Varying ingredients by
different manufacturers have caused brand loyalties to exist among
rebuilders. D&W primarily uses FMC facings from the U.S. who also
supplies Eaton Corp. An organic facing should be used in engines
with low to medium horse power and torque where the clutch must be
engaged and disengaged many times a day. This type of clutch is one
of the smoothest engaging clutches in the industry today. Its
downside is its short life span.
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