Derailleur gears by 13 drive-train. Most road bicycles have two chainrings, and touring bicycles commonly have three. The rear derailleur serves double duty: moving the chain between rear sprockets and taking up chain slack caused by moving to a smaller sprocket at the rear or a smaller chainring by the front derailleur. In order to accomplish this second task, it is positioned in the path of the bottom, slack portion of chain. Sometimes the rear-derailleurs are re-purposed as chain tensioners for single-speed bicycles that cannot adjust chain tension by a different method. Although variations exist, as noted below, most rear derailleurs have
Word sort words. Spelling or word study notebooks may be used to record, collect, and organize information about words and spelling patterns learned from the word sort. To complement the many 'hands on' activities students use for sorting words, digitized word sorts provide an efficient way for teachers to deliver spelling pattern differentiation. A variety of these are ready-made, including wordsortwizard.com. Research has shown that students who experience significant difficulty with spelling follow the same developmental course as other students, but do so at a slower pace. In such cases, it is critical to provide word sort words at the appropriate developmental