is larger than the largest pulley diameter, but less than three times the sum of both pulleys. Optimal speed range is . V-belts need larger pulleys for their thicker cross-section than flat belts. For high-power requirements, two or more V-belts can be joined side-by-side in an arrangement called a multi-V, running on matching multi-groove sheaves. This is known as a multiple-V-belt drive (or sometimes a "classical V-belt drive"). V-belts may be homogeneously rubber or polymer throughout, or there may be fibers embedded in the rubber or polymer for strength and reinforcement. The fibers may be of textile materials such as cotton, polyamide (such as Nylon) or polyester or, for greatest strength, of steel or aramid (such as Technora, Twaron or Kevlar). When an endless belt does not fit the need, jointed and link V-belts may be employed. Most models offer the same power and speed ratings as equivalently-sized endless belts and do not require special pulleys to operate. A link v-belt is a number of polyurethane/polyester composite links held together, either by themselves, such as Fenner Drives' PowerTwist, or Nu-T-Link (with metal studs). These provide easy installation and superior environmental resistance compared to rubber belts and are length-adjustable by disassembling and removing links when needed. V-belt history Trade journal coverage of V-belts in automobiles from 1916 mentioned leather as the belt material, and mentioned that the V angle was not yet well standardized. The endless rubber V-belt was developed in 1917 by Charles C. Gates of the Gates Rubber Company. Multiple-V-belt drive was first arranged a few years later by Walter Geist of the Allis-Chalmers corporation, who was inspired to replace the single rope of multi-groove-sheave rope drives with multiple V-belts running parallel. Geist filed for a patent in 1925, and Allis-Chalmers began marketing the drive under the "Texrope" brand; the patent was granted in 1928 (). The "Texrope" brand still exists, although it has changed ownership and no longer refers to multiple-V-belt drive alone. Multi-groove belts A multi-groove, V-Ribbed, or polygroove belt is made up of usually between 3 and 24 "V" shaped sections alongside each other. This gives a thinner belt for the same drive surface, thus it is more flexible, although often wider. The added flexibility offers an improved efficiency, as less energy is wasted in the internal friction of continually bending the belt. In practice this gain of efficiency causes a reduced heating effect on the