Derailleur gears several standards in use, and in each the product of the derailleur's actuation ratio and the length of cable pulled must equal the pitch of the rear sprockets. The following standards exist. Some rear derailleurs, especially for mountain bikes, incorporate a clutch to keep the lower length of chain in sufficient tension to prevent the chain from striking the bottom of the chain stay, called "chain slap", and which can damage the chain stay. Clutches are also helpful in preventing the chain from derailing from the chain ring on systems without a front derailleur. The front derailleur only has to
French fry vending machine The unit uses a specially-designed dispenser to prevent the potatoes from being crushed or broken. As of September 2015, only the single prototype is available, which is housed at Wageningen University. Orders are placed using a touchscreen, and a fork and salt are provided separately in a box. French fry vending machine A French fry vending machine is a vending machine that dispenses hot French fries, also known as chips. The first known french fry vending machine was developed circa 1982 by the defunct Precision Fry Foods Pty Ltd. in Australia. A few companies have developed and manufactured French fry