vandalism question this page seems to get an unusually high incidence of vandalism normally a page has to be either a featured article or a very public and controversial topic to be vandalized this regularly any hypotheses about why this page is so regularly attacked talk pretty sure pulley is british slang for handjob i've heard it a few places across the web i'm assuming that's it's consistently vandalized theory of operation i added a theory of operation section and used two of the pulley system images from the original article i have removed the simplest compound pulley image because its practical implementation is not different from the diagram which is the case for the other two they are different from the diagrams i also removed the historical images of pulleys because it didn't seem to add much without an explanation maybe it could go back in under a history section how about the diameter of the wheel doesn't that have something to do with the force necessary to lift an object preceding unsigned comment added by talk contribs nope nothing the forces on either side of the pulley are the same regardless of the radius of the wheel okay actually that's for a theoretical pulley a real pulley will suffer some slight amount of friction between the fibers of the rope as it goes around the pulley a larger diameter pulley will deform the rope less resulting in slightly less friction but that is a miniscule effect compared to the normal forces used on the pulley talk bicycle chain pulley is it correct or incorrect to call the non driven wheels in a modern bicycle rear derailleur pulleys the chain is kept in place by its side plates and small near teeth in the pulley rather than by fitting in a groove this particular application also involves no mechanical advantagejust tension adjustment are there other applications where chains and wheels function as cables and pulleys in the context of the six simple machines yes a derailleur would be considered a pulley specifically a class pulley with a mechanical advantage of the fact that the groove is on the chain rather than on the wheel is a minor variant the definition of something as a simple machine is based on how the force is transformed as the force does work any situation where the force is being carried through tension and where the direction is changed would probably count as a pulley talk sheldon brown had these entries in his glossary idler an idler is a pulley or roller that does not produce any mechanical advantage nor transmit power to a shaft idlers are used to lead a chain around a bend as in short wheelbase recumbents or to take up slack in a drive chain as in a tandem chain tensioner or the pulleys in a derailer chain pulleys most rear derailers use two pulleys in a spring loaded cage to regulate the tension of the chain as it runs over different sized sprockets the upper pulley is called the jockey pulley the lower one is the tension pulley jockey pulley the upper pulley on a rear derailer this is the pulley that actually guides the chain from one sprocket to another shimano jockey pulleys are designed with a centeron mechanism that allows a small amount of sidewards motion to compensate for imprecise index adjustment additional information needed i think information should be added to this article to recognize a sheave as a type of pulley i'm probably not the right person to add this but i do know that they are commonly used in oceanic applications suspended from an a frame on a ship and also for oil drilling tired angel regarding pict