Radial driveshaft
8.
The purpose of a radial driveshaft is to transmit the drive from the internal gearbox to an accessory unit or the external gearbox. It also serves to transmit the high torque from the starter to rotate the high pressure system for engine starting purposes. The driveshaft may be direct drive or via an intermediate gearbox (para. 14).

9.
To minimize the effect of the driveshaft passing through the compressor duct and disrupting the airflow, it is housed within the compressor support structure. On by-pass engines, the driveshaft is either housed in the outlet guide vanes or in a hollow streamlined radial fairing across the low pressure compressor duct.

9.為了盡量減小傳動軸通過壓氣機流道和阻礙空氣流的影響，它被安裝在壓氣機支承結構里面。在內外涵發動機上，傳動軸既可以安排在出口導向葉片之中，也可安排在穿過低壓壓氣機流道的、空心的流線型徑向整流罩之中。
10.為了減少對空氣流的干擾，要求傳動軸的直徑盡可能小。直徑越小，為了提供同樣的功率，軸就應當轉動得越快。但是這又增加了內部應力，并產生了更大的動力學問題，即引起振動。一根長的徑向傳動軸通常要在其中部位置安裝一個滾棒軸承,以保證其平穩運轉。這樣就允許用直徑小于1.5英寸的軸達到約25000轉／分的轉速而不會遇到嚴重的振動問題。

Fig. 7-3 An internal gearbox.
rotate to provide the same power. However, this raises the internal stress and gives greater dynamic problems which result in vibration. A long radial driveshaft usually requires a roller bearing situated halfway along its length to give smooth running. This allows a rotational speed of approximately 25,000
r.p.m. to be achieved with a shaft diameter of less than 1.5 inch without encountering serious vibration problems.
Direct drive
11. In some early engines, a radial driveshaft was used to drive each, or in some instances a pair, of accessory units. Although this allowed each
Accessory drives

accessory unit to be located in any desirable location around the engine and decreased the power transmitted through individual gears, it necessitated a large internal gearbox. Additionally, numerous radial driveshafts had to be incorporated within the design. This led to an excessive amount of time required for disassembly and assembly of the engine for maintenance purposes.
12. In some instances the direct drive method may be used in conjunction with the external gearbox system when it is impractical to take a drive from a particular area of the engine to the external gearbox. For example, fig. 7-1 shows a turbo-propeller engine
中間齒輪箱

14.在不可能直接將徑向傳動軸與外部齒輪箱連接的時候，就要使用中間齒輪箱。為了解決這個問題，中間齒輪箱可安裝在高壓壓氣機機匣上，并通過傘齒輪來改變通向外部齒輪箱的傳動方向。這種布置的例子見圖7-1由上至下的第3圖所示。
16．外部齒輪箱的總體布置由很多因素決定。為了減少飛機飛行中的阻力，減小迎風面積非常重要。因此齒輪箱“封裝”在發動機的周圍，從前面看，呈香蕉形狀。為了維護方便，齒輪箱通常位于發動機的
下部，以方便地勤人員接近。但是直升機的安裝設計則通常要求將齒輪箱安排在發動機上部才易于接近。

15．外部齒輪箱包括各附件的傳動裝置，來自起動機的傳動裝置，為各個附件裝置提供安裝座。而且，為了維護的目的，它還有通過齒輪箱用手轉動發動機的機構。圖7-4示出了那些可以在外部齒輪箱上看到的典型附件裝置。
Accessory drives

which requires accessories specific to the propeller 'shear-neck', which is designed to fail and thus reduction drive, but has the external gearbox located protect the other drives. This feature is not included away from this area to receive the drive from the for primary engine accessory units, such as the oil
外部齒輪箱
 
18．如果某個附件裝置損壞而使轉動受阻，就有可能由于齒輪系牙齒被剪切而引起外部齒輪箱內部的進一步損壞。為了防止發生二次損壞，在傳動軸上，用機械加工方法加工出了一個稱之為“剪力頸”的薄弱部位，這個部位的破壞可以保護其他傳動機構。但是這種特點并不用于主要的發動機附件裝置，例
如滑油泵，因為它們對于發動機的運轉至為重要，任何故障都要求將發動機立即停機。
compressor shaft.
Gear train drive
13. When space permits, the drive may be taken to the external gearbox via a gear train (fig. 7-1). This involves the use of spur gears, sometimes incorpo-rating a centrifugal breather (Part 8). However, it is rare to find this type of drive system in current use.
Intermediate gearbox
14. Intermediate gearboxes are employed when it is not possible to directly align the radial driveshaft with the external gearbox. To overcome this problem an intermediate gearbox is mounted on the high pressure compressor case and re-directs the drive, through bevel gears, to the external gearbox. An example of this layout is shown in fig. 7-1.
External gearbox
15.
The external gearbox contains the drives for the accessories, the drive from the starter and provides a mounting face for each accessory unit. Provision is also made for hand turning the engine, via the gearbox, for maintenance purposes. Fig. 7-4 shows the accessory units that are typically found on an external gearbox.
　
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