Engineering a notched belt can be a balancing act among flexibility, tensile cord support, and stress distribution. Precisely formed and spaced notches help to evenly distribute stress forces as the belt bends, thereby helping to prevent undercord cracking and extending belt existence.
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 strategies, tensile cord advancements, and cross-section profiles have resulted in an often confusing selection of V-belts that are highly application specific and deliver vastly different degrees of performance.
Unlike flat belts, which rely solely on friction and can track and slip off pulleys, V-belts have sidewalls that fit into corresponding sheave grooves, providing additional surface and greater stability. As belts operate, belt tension applies a wedging force perpendicular to their tops, pushing their sidewalls against the sides of the sheave grooves, which multiplies frictional forces that allow the drive to transmit higher loads. How a V-belt fits in to the groove of the sheave while operating under tension impacts its performance.
V-belts are produced from rubber or synthetic rubber stocks, so they possess the V Belt flexibility to bend around the sheaves in drive systems. Fabric materials of varied types may cover the stock material to supply a layer of protection and reinforcement.
V-belts are manufactured in a variety of industry regular cross-sections, or profiles
The classical V-belt profile dates back to industry standards developed in the 1930s. Belts manufactured with this profile come in a number of sizes (A, B, C, D, E) and lengths, and so are widely used to replace V-belts in old, existing applications.
They are accustomed to replace belts on commercial machinery manufactured in other areas of the world.
All the V-belt types noted above are usually available from producers in “notched” or “cogged” variations. Notches reduce bending stress, enabling the belt to wrap easier around little diameter pulleys and allowing better temperature dissipation. Excessive high temperature is a significant contributor to premature belt failing.
Wrapped belts have a higher level of resistance to oils and extreme temps. They can be utilized as friction clutches during set up.
Raw 
edge type v-belts are more efficient, generate less heat, enable smaller pulley diameters, increase power ratings, and offer longer life.
V-belts appear to be relatively benign and basic devices. Just measure the top width and circumference, find another belt with the same sizes, and slap it on the drive. There’s only one problem: that approach is approximately as wrong as you can get.