Engineering a notched belt is certainly a balancing act among flexibility, tensile cord support, and stress distribution. Precisely shaped and spaced notches help evenly distribute stress forces as the belt bends, thereby assisting 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 substances, 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 levels of performance.
Unlike toned belts, which rely solely on friction and may track and slide off pulleys, V-belts have sidewalls that match corresponding sheave grooves, offering additional surface area and greater balance. As belts operate, belt pressure applies a wedging pressure 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 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 a variety of 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 several sizes (A, B, C, D, Electronic) and lengths, and so are widely used to replace V-belts in older, existing applications.
They are used to replace belts on commercial machinery manufactured in other parts of the world.
All the V-belt types noted above are typically available from manufacturers in “notched” or “cogged” versions. Notches reduce bending stress, allowing the belt to wrap easier around small diameter pulleys and permitting better warmth dissipation. Excessive temperature is a significant contributor to v belt china premature belt failing.
Wrapped belts have an increased level of resistance to oils and intense temperature ranges. They can be used as friction clutches during start up.
Raw edge type v-belts are more efficient, generate less heat, allow for smaller pulley diameters, increase power ratings, and provide longer life.
V-belts appear to be relatively benign and basic devices. 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 possible get.