Unusual types of gramophone records Unusual types of gramophone records The overwhelming majority of records manufactured have been of certain sizes (7, 10, or 12 inches), playback speeds (33, 45, or 78 RPM), and appearance (round black discs). However, since the commercial adoption of the gramophone record (called a phonograph record in the U.S., where both cylinder records and disc records were invented), a wide variety of records have also been produced that do not fall into these categories, and they have served a variety of purposes. The most common diameter sizes for gramophone records are 12-inch, 10-inch, and 7-inch. Early American shellac records were
Gear inches 60 gear inches and pedalled similar to an ordinary with a 60-inch wheel. Thus on a bicycle geared at 72 gear inches one revolution of the pedals advances the bicycle the distance that a 72-inch wheel would in one revolution. Gear inches express gear ratios in terms of the diameter of an equivalent directly driven wheel, and is calculated as follows: This formula assumes that any hub gear is in direct drive. A further factor is needed for other gears (many online gear calculators have these factors built in for common hub gears). For simplicity, 'gear inches' is normally rounded