Engineering a notched belt can be a balancing act between flexibility, tensile cord support, and tension distribution. Precisely designed and spaced notches help evenly distribute tension forces as the belt bends, thereby assisting 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 substances, 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 particular and deliver vastly different levels of performance.
Unlike flat belts, which rely solely on friction and will track and slide off pulleys, V-belts have sidewalls that match corresponding sheave grooves, offering additional surface area and greater stability. As belts operate, belt stress applies a wedging drive perpendicular with 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 into 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 versatility to bend around the sheaves in drive systems. Fabric materials of various types may cover the share material to supply a layer of protection 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 manufactured with this profile come in a number of sizes (A, B, C, D, Electronic) and lengths, and are widely used to replace V-belts in older, existing applications.
They are used to replace belts on commercial machinery manufactured in other areas of the world.
All of the V-belt types noted above are typically available from manufacturers in “notched” or “V Belt cogged” variations. Notches reduce bending tension, permitting the belt to wrap more easily around small diameter pulleys and allowing better heat dissipation. Excessive warmth is a significant contributor to premature belt failing.
Wrapped belts have a higher level of 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, increase power ratings, and offer longer life.
V-belts look like relatively benign and basic pieces of equipment. 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 strategy is about as wrong as possible get.