Engineering a notched belt can be a balancing act between versatility, tensile cord support, and stress distribution. Precisely formed and spaced notches help to evenly distribute tension forces as the belt bends, thereby helping to prevent undercord cracking and extending belt lifestyle.
Like their synchronous belt cousins, V-belts have undergone tremendous technological development since their invention by John Gates in 1917. New synthetic rubber compounds, cover materials, construction methods, tensile cord advancements, and cross-section V Belt profiles have led to an often confusing selection of V-belts that are highly application particular and deliver vastly different degrees of performance.
Unlike smooth belts, which rely solely on friction and can track and slide off pulleys, V-belts have sidewalls that fit into corresponding sheave grooves, offering additional surface and greater stability. As belts 
operate, belt pressure applies a wedging force perpendicular to their tops, pressing their sidewalls against the sides of the sheave grooves, which multiplies frictional forces that permit the drive to transmit higher loads. How a V-belt fits in to the groove of the sheave while operating under pressure impacts its performance.
V-belts are made from rubber or synthetic rubber stocks, so they have the versatility to bend around the sheaves in drive systems. Fabric materials of various kinds may cover the stock material to supply a layer of safety and reinforcement.
V-belts are manufactured in various industry regular cross-sections, or profiles
The classical V-belt profile goes back to industry standards developed in the 1930s. Belts produced with this profile come in a number of sizes (A, B, C, D, Electronic) and lengths, and so are widely used to displace V-belts in older, existing applications.
They are accustomed to replace belts on industrial machinery manufactured in other areas of the world.
All of the V-belt types noted over are usually available from manufacturers in “notched” or “cogged” versions. Notches reduce bending stress, enabling the belt to wrap easier around little diameter pulleys and permitting better high temperature dissipation. Excessive warmth is a major contributor to premature belt failure.
Wrapped belts have an increased resistance to oils and severe temperatures. They can be used as friction clutches during set up.
Raw edge type v-belts are more efficient, generate less heat, enable smaller pulley diameters, boost power ratings, and provide longer life.
V-belts appear to be relatively benign and basic devices. Just measure the best width and circumference, discover another belt with the same measurements, and slap it on the drive. There’s only one problem: that strategy is about as wrong as you can get.