Engineering a notched belt is a balancing act among 
flexibility, tensile cord support, and tension distribution. Precisely designed and spaced notches help to evenly distribute stress forces as the belt bends, thereby assisting to prevent undercord cracking and extending belt life.
Like their synchronous belt cousins, V-belts have undergone tremendous technological development since their invention by John Gates in 1917. New synthetic rubber substances, cover materials, construction methods, tensile cord advancements, and cross-section profiles have resulted in an often confusing selection of V-belts that are highly application specific and deliver V Belt vastly different degrees of performance.
Unlike toned belts, which rely solely on friction and may track and slip off pulleys, V-belts possess sidewalls that fit into corresponding sheave grooves, providing additional surface and greater stability. As belts operate, belt stress applies a wedging pressure perpendicular with their tops, pushing their sidewalls against the sides of the sheave grooves, which multiplies frictional forces that permit the drive to transmit higher loads. What sort of V-belt fits in to the groove of the sheave while operating under stress impacts its performance.
V-belts are made from rubber or synthetic rubber stocks, so they possess the flexibility to bend around the sheaves in drive systems. Fabric materials of various kinds may cover the stock material to supply a layer of protection and reinforcement.
V-belts are manufactured in various industry standard cross-sections, or profiles
The classical V-belt profile dates back to industry standards created in the 1930s. Belts produced with this profile come in several sizes (A, B, C, D, Electronic) and lengths, and are widely used to replace V-belts in old, existing applications.
They are used to replace belts on industrial machinery manufactured in other areas of the world.
All the V-belt types noted over are usually available from producers in “notched” or “cogged” variations. Notches reduce bending tension, allowing the belt to wrap easier around little diameter pulleys and allowing better high temperature dissipation. Excessive high temperature is a significant contributor to premature belt failure.
Wrapped belts have an increased level of resistance to oils and extreme temperature ranges. They can be utilized as friction clutches during set up.
Raw edge type v-belts are more efficient, generate less heat, allow for smaller pulley diameters, boost power ratings, and provide longer life.
V-belts look like relatively benign and basic pieces of equipment. Just measure the best width and circumference, find another belt with the same dimensions, and slap it on the drive. There’s only one problem: that strategy is approximately as wrong as you can get.