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A herringbone gear, a specific type of double helical gear, is a special type of gear that is a side to side (not face to face) combination of two helical gears of opposite hands.〔(Herringbone gears ) 〕 From the top, each helical groove of this gear looks like the letter V, and many together form a herringbone pattern (resembling the bones of a fish such as a herring). Unlike helical gears, herringbone gears do not produce an additional axial load. Like helical gears, they have the advantage of transferring power smoothly because more than two teeth will be in mesh at any moment in time. Their advantage over the helical gears is that the side-thrust of one half is balanced by that of the other half. This means that herringbone gears can be used in torque gearboxes without requiring a substantial thrust bearing. Because of this herringbone gears were an important step in the introduction of the steam turbine to marine propulsion. Precision herringbone gears are more difficult to manufacture than equivalent spur or helical gears and consequently are more expensive. They are used in heavy machinery. Where the oppositely angled teeth meet in the middle of a herringbone gear, the alignment may be such that tooth tip meets tooth tip, or the alignment may be staggered, so that tooth tip meets tooth trough. The latter alignment is the unique defining characteristic of a Wuest type herringbone gear, named after its inventor. == Benefits == Since a herringbone gear is non-linear in the teeth the gears won't slip out from grabbing one another if the axle or another force moves the gears up and down. This is also a benefit with machinery that needs very straight movement, because a herringbone gear is designed to 'self center' and is much less likely to skip a tooth or fall out of place. With some gears sets that use herringbone gears; an axle can be lost and the gear will stay in place, a herringbone planetary gear system. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Herringbone gear」の詳細全文を読む スポンサード リンク
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