Engineering a notched belt is definitely a balancing act between 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 life.

Like their synchronous belt cousins, V Belt 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 profiles have led to an often confusing selection of V-belts that are extremely application particular and deliver vastly different degrees of performance.
Unlike smooth belts, which rely solely on friction and can track and slip off pulleys, V-belts have sidewalls that match corresponding sheave grooves, providing additional surface area and greater stability. As belts operate, belt pressure applies a wedging push perpendicular to their tops, pressing 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 working under pressure impacts its performance.
V-belts are produced from rubber or synthetic rubber stocks, so they possess the flexibility to bend around the sheaves in drive systems. Fabric materials of varied types may cover the share 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 dates back to industry standards developed in the 1930s. Belts produced with this profile come in a number of sizes (A, B, C, D, E) and lengths, and are widely used to displace V-belts in old, existing applications.
They are accustomed to replace belts on industrial machinery manufactured in other areas of the world.
All the V-belt types noted above are usually available from manufacturers in “notched” or “cogged” versions. Notches reduce bending stress, allowing the belt to wrap more easily around little diameter pulleys and allowing better heat dissipation. Excessive warmth is a major contributor to premature belt failure.

Wrapped belts have an increased level of resistance to oils and extreme temps. They can be used as friction clutches during start up.
Raw edge type v-belts are better, generate less heat, enable smaller pulley diameters, increase power ratings, and offer longer life.
V-belts appear to be relatively benign and simple pieces of equipment. Just measure the best width and circumference, discover another belt with the same sizes, and slap it on the drive. There’s only one problem: that strategy is about as wrong as you can get.