Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

Chapter 2 Indirect Power Transfer Devices 73
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Flat Belts
Flat belts are an old design that has only limited use today. The belt was
originally made flat primarily because the only available durable belt
material was leather. In the late 18 th and early 19 th centuries, it was used
extensively in just about every facility that required moving rotating power
from one place to another. There are examples running in museums and
some period villages, but for the most part flat belts are obsolete. Leather
flat belts suffered from relatively short life and moderate efficiency.
Having said all that, they are still available for low power devices with
the belts now being made of more durable urethane rubber, sometimes
reinforced with nylon, kevlar, or polyester tension members. They
require good alignment between the driveR and driveN pulleys and the
pulleys themselves are not actually flat, but slightly convex. While they
do work, there are better belt styles to use for most applications. They are
found in some vacuum cleaners because they are resistant to dirt buildup.
O-Ring Belts
O-ring belts are used in some applications mostly because they are
extremely cheap. They too suffer from moderate efficiency, but their cost
is so low that they are used in toys and low power devices like VCRs etc.
They are a good choice in their power range, but require proper tension
and alignment for good life and efficiency.
V-Belts
V-belts get their name from the shape of a cross section of the belt, which
is similar to a V with the bottom chopped flat. Their design relies on friction,
just like flat belts and O-ring belts, but they have the advantage that
the V shape jams in a matching V shaped groove in the pulley. This
increases the friction force because of the steep angle of the V and therefore
increases the transmittable torque under the same tension as is
required for flat or O-ring belts. V-belts are also very quiet, allow some
misalignment, and are surprisingly efficient. They are a good choice for
power levels from fractional to tens of horsepower. Their only draw-