What is the difference V belts 4l vs b belt?

Answer 1

The specification of "4L" indicates that the V-Belt is 1/2 inch wide at the top. This is the same as the specification "A" in terms of width, and in fact "A" specification belts are often interchangable with "4L" specification belts in terms of size - however, the composition of the belts and the effective duty rating may nonetheless be different. The "4L" belts are designated as light duty industrial or lawn and garden, and are often found on lawn tractors. They are typically 5/16 in cross section (height), as compared to the 11/32 inches to 13/32 inches for the "A" specification. On the other hand, the "B" specification V-Belt is a larger belt in both dimensions than the "4L" (this was the premise of the question). It is 21/32 inches in width by 7/32 inches in height. It is not interchangable with either the "A" or the "4L" belts. However, it is roughly the size of the "5L" belts, which is the same width (or sometimes 20/32 inches), but slightly less height - 11/32 inches. The specifications relate to design stress placed on the belts (i.e. the horsepower of the drive motor, the requirements of the driven device, the pulley ratios, etc.). Although many people use the "4L" in place of the "A", or use the "5L" in place of the "B", I cannot imagine doing so merely to save a buck or two (literally). Bottom line, it is my recommendation that one stick with whatever the manufacturer specifies for the product. Otherwise, the manufacturer will likely have a good defense to any failures associated with the subject system (i.e. when the belt fails and your widget breaks or you get injured by a flying belt that is not strong enough for the job).