的法则 for transmission shafting传动轴 is that the deflection should not exceed 0.0005L, where L is the shaft length between supports; although greater stiffness may be desired需要.
变形的允许值很小，也许是因为每种特定的情况都有其独特性。旧时后的检验法则表示就算需要更高的强度变形也不能超过轴长的0.0008倍。
Preferably较好的, on transmission shafts, the pulleys and gears should be located close to bearings轴承 in order to minimize最小化 moments. If journal bearings径向轴承 with “thick film” lubrication润滑 are used, the deflection偏向 across the bearing width轴承宽度 should be only a small fraction部分 of the oil-film thickness油膜厚度; if the slope斜坡 is excessive过多 here, there will be “binding粘合” in the journal轴颈. A self-aligning bearing球面轴承 may eliminate消除 this trouble if the deflection is otherwise acceptable.
传动轴的较好的设计是将齿轮和滑轮放在靠近轴承的地方。如果使用的是涂有润滑油的径向轴承那么轴承宽度方向的偏向只能是油膜厚度的一小部分。如果斜坡过多那么就要在轴颈上涂上粘合剂。但是当变形在可接受范围内时球面轴承可以消除这种问题。
On machine tools, rigidity硬度 is a special concern because of its relation to accuracy准确性. If a shaft supports a gear, deflection is more of a consideration than if it carries a V-belt pulley皮带轮.
在机械工具中，硬度被特别关注。因为他反应了其精度。装了齿轮的轴比装了皮带轮的轴更加强调偏差。
The center of mass质心 of symmetric匀称的, rotating旋转 body does not coincide with与一致 its center of rotation. This is because (a) it is impossible from a practical实际 viewpoint to get the mass uniformly distributed分布式 about the geometric几何学 center of the body and (b) the shaft on which the body rotates deflects under load, thus moving the center of mass away from the true axis, which passes through通过 the center line of the bearings.
均与的旋转体的质心与其旋转中心不重合。因为从实际情况看，质量是不可能按照其几何形状均匀分布的。因此将质心移动离开其轴心，
Rotation循环 may begin about the geometric axis几何中心, but at some speed, the centrifugal force离心力 of the displaced取代 center of mass质心 will equal the deflecting forces偏转力 on the shaft; the shaft with its attached附加的 bodies will then vibrate震动 violently猛烈的, since the centrifugal force changes its direction方向 as the shaft turns. This speed is termed术语是 the critical speed临界转速. Above the critical speed, a smooth-running state光滑运行状态 of equilibrium平衡 is again reached when the body is then rotating旋转 virtually事实上 about its mass center质心 (centrifugal forces离心力 balance).
循环也许会绕着几何中心进行。但是在某些速度的情况下，被取代了的质心的离心力会与轴上的偏心力平衡，带着附加物件的轴将会猛烈的震动。知道离心力方向改变成与转动方向一致。这个速度被称为是临界转速。在此速度时，工件将会再次达到平衡的光滑运行状态。
High-speed turbines高速涡轮机 often operate运转 above the critical speed临界转速. Additional附加的 critical speeds, higher than the first, are successively相继的 attained得到, but the amplitudes振幅 of the corresponding相应的 vibrations震动 progressively逐渐的 decrease.
高速涡轮机经常在临界转速运转。更加高的附加的临界转速也常常被运用。但是相应的震动的振幅也就逐渐的减少。
Many shafts supported by three or more bearings, which means that the problem is statically静态的 indeterminate不确定的. Texts on strength of materials材料强度 give methods of solving such problems. The design effort设计工作 should be in keeping with与。。相关联 the economics经济学 of a given situation. For example, if one line shaft supported by three or more bearings is needed, it probably would be cheaper to make conservative assumptions保守假设 as to moments and design it as though it were determinate. The extra cost of an oversize shaft may be less than the extra cost of an elaborate复杂的 design analysis.
许多的轴承上装了三个甚至三个以上的齿轮，也 就意味着，这
个问题是不确定的。材料强度手册给出了解决这个问题的方法。设计工作应该随时与经济情况相联系。例如，如果需要在轴上加上三个或者以上的齿轮时，去直接买设计好了的比设计一个复杂的设计分析还要省钱。
In addition to除了 gears, belts皮带 and chains链条 are in widespread use. Belts and chains represent代表了 the major types of flexible灵活的 power transmission能量传输 elements. Fig.8.1 shows a typical典型的 industrial application应用 of these elements combined with a gear-type speed reducer减速装置. This application illustrates阐明 where belts, gear drives, and chains are each used to best advantage.
除了齿轮，皮带，链条也是广泛的运用。它们代表了绝大部分的灵活能量传输机构。他展示了这些包含了减速装置的元素的典型的运用。这个运用阐明了皮带，齿轮和链条的每个的优点。
Rotary旋转 power能量 is usually developed by the electric motor电动机, but motors typically典型的 operate运行 at too high a speed and deliver传送 too low a torque转矩 to be appropriate for适合于 the final drive application最终执行应用程序. For a given power transmission, the torque is increased in proportion to成比例 the amount that rotational转动的 speed is reduced.
电动机一般输出旋转能量，但是典型的电动机进行高速的运转，并且输出低速的转矩来适应最终执行应用程序。经过一个能量转换器来成比例的增加转矩和减少转速。
So some speed reduction减速 is often desirable令人满意的. In general, belt drives皮带传动 are applied where the rotational speeds转速 are relatively相当 high, as on the first stage of speed reduction减速 from an electric motor or engine. A smaller driving pulley皮带轮 is attached to附属于 the motor shaft电机轴, while a larger diameter直径 pulley is attached to a parallel平行的 shaft that operates操作 at a correspondingly相应的 lower speed. Pulleys皮带轮 for belt drives皮带传动 are also called sheaves捆绑. The linear speed线速度 of a belt is usually 10-30m/s, which results in导致 relatively相对的 low tensile forces拉力 in the belt.
一部分减速是比较令人满意。一般皮带轮适用于将高速运动转变成为低速运动。连丽如电动机和马达的第一步减速过程。皮带轮是附属于电机轴同时一个大直径的皮带轮附属于一平行的在相应的低速运行的轴。
These are four main belt types: flat, round, V, and synchronous同步的同时的. Flat and round belts may be used for long center distances between the pulleys in a belt drive. On the other hand, V and synchronous belts are employed for负责 limited shorter center distance. Excluding除了 synchronous belts, there is some slip滑到 between the belt and the pulley, which is usually made of cast iron铸铁 or steel.
以下是四个主要的皮带形式：平皮带，圆形皮带，v型和同步皮