**4.3 Quill shafts**

Below we describe assemblies used in systems that allow some torsion in the split torque shafts (Smirnov, 1990; Cocking, 1986) in order to minimize the difference in torque split between paths. These systems achieve their goal in several ways:


The use of such elements in the design adds weight and makes both initial assembly and maintenance more complex, thereby losing to some degree the advantages of split torque gearboxes. Described below are the most representative types of quill shaft.

## **4.3.1 Conventional quill shafts**

Conventional quill shaft design involves assembly on three different shafts (Fig. 12). The

Fig. 12. Conventional assembly of a quill shaft

(66) defines a first gear rotation shaft A1 and the second gear (68) defines a second gear rotation shaft A2. The axes AG, A1 and A2 are preferably located transversally to the pivot axis Ap. The first gear (66) and the second gear (68) engage an output gear (70). The output gear (70) defines an output rotation shaft A0 and is rotationally connected to the translational driveshaft (44) and the rotor driveshaft (46) to power, respectively, the

The assembly transmits torque from the pinion (64), which operates at very high revolutions, to the output shaft (44 -46) via two paths. The pivot system works as follows: since the input pinion (64) meshes with two gears (66) and (68), the pivoted engine arrangement permits the input pinion (64) to float until gear loads between the input gear (64), the first gear (66) and the second gear (68) are balanced. Irrespective of gear teeth errors or gearbox shaft misalignments,

Below we describe assemblies used in systems that allow some torsion in the split torque shafts (Smirnov, 1990; Cocking, 1986) in order to minimize the difference in torque split

 Conventional systems (Kish, 1993a) assemble intermediate shafts with some torsional flexibility so that angular deviation produced between the input and output pinions

 Other systems are based on elastomeric elements in the shaft (Isabelle et al., 1992, Kish & Webb, 1992) or materials with a lower elastic modulus (Southcott, 1999), such as an idler pinion constructed of nylon or a similar material (Southcott, 1999). This solution is

Yet other systems operate on the basis of spring elements (Gmirya & Vinayak, 2004).

The use of such elements in the design adds weight and makes both initial assembly and maintenance more complex, thereby losing to some degree the advantages of split torque

Conventional quill shaft design involves assembly on three different shafts (Fig. 12). The

translational propulsion system and the rotor system".

**4.3 Quill shafts** 

**4.3.1 Conventional quill shafts** 

Fig. 12. Conventional assembly of a quill shaft

the input pinion will float and split torque between the two gears.

between paths. These systems achieve their goal in several ways:

not explored here because the torque transmitted is reduced.

gearboxes. Described below are the most representative types of quill shaft.

adjusts the torque transmitted via the two paths.

input shaft (1) is assembled with two separate bearings (2) and the input gear (3).The output shaft (4) is assembled with two separate bearings (5) and, in this case, two output pinions (6). The quill shaft is a third shaft (7) that connects the other two shafts. Due to a lower polar moment of inertia, it admits torsional flexibility, resulting in a small angular deviation between the input and output shafts. The value of the angular deviation is proportional to the transmitted torque; thus, if one path transmits more torque than the other, the angular deviation is greater, allowing the shaft that transmits less torque to increase its load.
