D2 there is less of a distance (and therefore less addition of length) until its approaches zero. On the other hand, in a crossed belt drive the sum rather than the difference of radii is the basis for computation for length. So the wider the small drive increases, the belt length is higher. V-belt profiles Metric v-belt profiles (note pulley angles are reduced for small radius pulleys): * Common pulley design is to have a higher angle of the first part of the opening, above the so-called "pitch line". E.g. the pitch line for SPZ could be 8.5mm from the bottom of the "V". In other words, 0-8.5mm is 34° and 38° from 8.5 and above See also Belt-drive turntable Belt-driven bicycle Belt track Conveyor belt Gilmer belt Lariat chain – a science exhibit showing the effects when a belt is run "too fast" Roller chain Timing belt (camshaft) References External links Belt Passing Frequency Vibration Calculator | RITEC | Library & Tools Chinese inventions Mechanical power transmission