Derailleur gears operates the lever while pedalling, the change in cable tension moves the chain-guide from side to side, "derailing" the chain onto different sprockets. For more information about the choice of particular gear ratios and sprocket sizes, see Bicycle gearing. "Derailleur" is a French word, spelled "dérailleur" in French, derived from the derailment of a train from its tracks. Its first recorded use was 1930. At least one notable bicycle industry author has attempted to promote the anglicized spelling of "derailer". As of 2013, however, neither Merriam-Webster nor the Oxford English Dictionary has an entry for "derailer". Various derailleur systems were
Dwell mechanism backwards. The cams in this application are usually phased 90 degrees apart allowing a pause in the up/down movement of the dog while it is being moved forwards/backwards. A separate adjustable sliding block or link is used to control the amount of forwards/backwards movement of the dog. Industrial applications include loading or unloading parts, or transporting a part to a machine and holding it in place for a manufacturing process. Other applications include assembly lines, package machinery, machine tools etc. Dwell mechanism A dwell mechanism (either a linkage or cam-follower type) is an intermittent motion mechanism that alternates forward and