Belt drives are the most widely used
method of flexible power transmission. Improvements in materials and
methods of manufacture have allowed the introduction of new belts
with much broader application capabilities.
Belt drives basically fit into four
types: flat,V,V-ribbed, and synchronous. Although each of these basic
belt types are more suitable in specific application areas, most
applications can be successfully designed with more than one type of
belt.
Flat belts, one of the earliest forms
of flexible power transmission, are generally more suited to high
speed, low-horsepower applications. At low speeds and high loads,
flat-belt drives usually become too large to be cost-effective.
V belts are the most commonly used
today, and they are the only belts that can be used on variable pitch
and variable speed drives. V-ribbed belts are described by some as
guided flat belts. Their thinner cross section makes them suitable
for operation on smaller diameters at higher speeds.
Synchronous (timing) belts are
specifically designed as alternatives to roller chains and gears on
drives, which require exact speed ratios and synchronization between
the driver and driven machines. They are also widely used today in
low-maintenance, energy-efficient applications.
FLAT BELTS
Flat belts are still widely used for
power transmission. Their thin, flexible cross section allows them to
operate over small diameters and, in some cases, at very high speeds.
Many different sizes and constructions
are available for a wide variety of uses. Flat belts are made either
of fully molded or woven construction and may or may not have a
tensile member.
One significant disadvantage of flat
belts is that they depend entirely on friction in order to transmit
power. Thus they require higher belt tension to do the same work,
which results in higher shaft and bearing loads. The need for higher
tension may cause more belt stretch, causing the belt to slip more
easily than V belts.
V BELTS
The problems of high tension with flat
belts led to the development of V belts. Unlike flat belts, which
depend only on friction, V belts have deep V-shaped cross sections
that wedge into the sheave groove to provide added horsepower
capacity.
Because of the wedging action, V belts
are highly stable and can operate at tensions considerably lower than
those needed by flat belts.Thus,V-belt drives can be more compact and
allow for smaller shafts and bearings.
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