DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
A SHAFT IN A PROPULSION SHAFTING SYSTEM FOR SIMULATION PURPOSE

Applicant:
Mazagon Dock Shipbuilders Limited
A company Incorporated in India under the Companies Act, 1956
Under Ministry of Defence,
(A Govt. of India Undertaking)
Having address:
Dockyard Road, Mazagon,
Mumbai - 400010, Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
This patent application claims priority from Indian Provisional Application 201821042947 filed on November 15, 2018.

TECHNICAL FIELD
The present subject matter described herein, in general, relates to a shaft in a propulsion shafting system for simulation purpose.

BACKGROUND
Generally, in shipbuilding a propulsion shafting system is deployed for transferring power from main engine to a propeller shaft. The propulsion shafting system is designed to support the propeller shaft by forward and aftward stern tube bearings and A-bracket bearings.
The propeller shaft is required to be aligned. Although the actual shaft alignment is carried out in dry dock, a pre-aligned shaft line axis is established by carrying out sighting on a slipway. Further, post establishment of the pre-aligned shaft line axis, an A-bracket is welded to a stern region of the marine vessel by controlled welding. However during launching, the pre-aligned shaft line axis is expected to be disturbed due to buoyancy forces acting on a the marine vessel.
OBJECT OF INVENTION
One object of the present subject matter is to develop a dummy shaft as a temporary replacement of an actual propelling shaft in a propulsion shafting system for post launch objectives to be met.
Another object of the present subject matter is to minimize an effect of launch induced deflections on shaft line reference axis by utilizing the dummy shaft.
Another object of the present subject matter is to reduce time required in dry docking period by welding support brackets on a slipway.
Another object of the present subject matter is to reduce manpower required for machining, re-welding and re-alignment activities to be done in dry dock during the shaft line installation post launching of a marine vessel.
Another object of the present subject matter is to reduce cost required for manufacturing of the shaft by avoiding rework activities.

SUMMARY
Before the present shaft in a propulsion shafting system 100 for simulation purpose is described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a technology being implemented in the shaft in a propulsion shafting system 100 for simulation purpose. The aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
In one implementation, a shaft in a propulsion shafting system 100 for simulation purpose is disclosed. The shaft may comprise a pipe section configured to be stiffened with one or more stiffeners mounted on said pipe section along its length. Further, at least one sleeve may be configured to be inserted on said stiffened pipe at a location of a support bracket to generate a dummy shaft for simulation purpose.
In another implementation, a ring assembly may be inserted between said at least one sleeve and a stern boss. The ring assembly may be configured to form a leak proof stern boss assembly. Further, said stiffened pipe section is configured to provide said propelling shaft of a predetermined size and strength. Further, said one or more stiffeners may be plurality of bars provided on said pipe section to provide the predetermined strength to said pipe section. Further, said at least one sleeve may be configured to be inserted to provide a smooth mating surface at said support bracket. Further, said dummy shaft may be configured to be supported with plurality of supports. The said plurality of supports may be one or more fixed supports and one more roller supports. Further, said dummy shaft may be configured as a temporary replacement of an actual propelling shaft for simulation purpose.
In yet another implementation, a method for generating a shaft in a propulsion shafting system for simulation purpose. The method may comprise procuring a pipe section of a predetermined size. Further, the method may comprise stiffening said pipe section along its length by mounting one or more stiffeners to generate a stiffened pipe section of a predetermined size and a predetermined strength. Further, the method may comprise inserting at least one sleeve on said stiffened pipe section at a location of a support bracket. Further, the method may comprise inserting a ring assembly between said at least one sleeve and a stern boss for a leak proof stern boss assembly, to generate a dummy shaft. Further, the method may comprise supporting said dummy shaft with a plurality of supports forming one or more fixed supports and one more roller supports. Further, the method may comprise configuring said dummy shaft as a temporary replacement of an actual propelling shaft for simulation purpose.

BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawings:
The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.
Figure 1A illustrates a schematic diagram of a conventional process showing pre-alignment disturbance during conventional launching of a marine vessel.
Figure 1B illustrates a schematic diagram of a conventional process showing pre-alignment disturbance during pontoon assisted launching of a marine vessel.
Figure 1C illustrates a schematic diagram showing elements of a propulsion shafting system 100, in accordance with an embodiment of the present subject matter.
Figure 2 illustrates a schematic diagram of C fixed support 201 for a dummy shaft 700, in accordance with an embodiment of the present subject matter.
Figure 3 illustrates a schematic diagram of an end support 301 for a dummy shaft 700, in accordance with an embodiment of the present subject matter.
Figure 4 illustrates a schematic diagram of stiffeners 401 mounted on a dummy shaft 700, in accordance with an embodiment of the present subject matter.
Figure 5 illustrates a schematic diagram of a sleeve 501 inserted on a dummy shaft 700, in accordance with an embodiment of the present subject matter.
Figure 6 illustrates a schematic diagram of a ring assembly 601 inserted on a dummy shaft 700, in accordance with an embodiment of the present subject matter.
Figure 7 illustrates a schematic diagram of a dummy shaft 700, in accordance with an embodiment of the present subject matter.
Figure 8 illustrates a shaft deflection curve for a propulsion shafting system 100, in accordance with an embodiment of the present subject matter.
Figure 9 illustrates a curve for stresses acting on a dummy shaft 700 in a propulsion shafting system 100, in accordance with an embodiment of the present subject matter.
Figure 10 illustrates a plot for stresses acting on fixed bracket supports 201 in a propulsion shafting system 100, in accordance with an embodiment of the present subject matter.
Figure 11 illustrates a plot for stresses acting on an end support 301 in a propulsion shafting system 100, in accordance with an embodiment of the present subject matter.
Figure 12 illustrates a shaft deflection curve of a dummy shaft 700 during launching in a propulsion shafting system 100, in accordance with an embodiment of the present subject matter.
Figure 13 illustrates a method 1300 for generating a shaft in a propulsion shafting system 100 for simulation purpose, in accordance with an embodiment of the present subject matter.
The figures depicts an embodiment of the present disclosure for purpose of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structure and method illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION
Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words “comprising”, “generating", “receiving”, “forming” and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, shaft in a propulsion shafting system 100 for simulation purpose are now described. The disclosed embodiments of a shaft in a propulsion shafting system 100 for simulation purpose are merely exemplary of the disclosure, which may be embodied in various forms.
Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure of a propelling shaft in a propulsion shafting system 100 for simulation purpose is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.
Conventionally, a propeller shaft is required to be aligned. Although the actual shaft alignment is carried out in dry dock, a pre-aligned shaft line axis may be established by carrying out sighting on a slipway. Further, post establishment of the pre-aligned shaft line axis, an A-bracket may be welded to a stern region of the marine vessel by controlled welding. However during launching, the pre-aligned shaft line axis may be expected to be disturbed due to buoyancy forces acting on a hull of a marine vessel. The pre-aligned shaft line axis established on the slipway may show a banana shape when it is docked. Further, the A-bracket and stern boss axis may be off centred with reference to the pre-aligned condition due to the heavy loads imposed on the hull during launching. The hull may be deflected to banana shape due to the launching induced forces, thereby causing deflection in the pre-aligned shaft line axis. Further, in case of large deflection, the A-bracket and stern tube may be eccentric beyond tolerance limit, thereby creating a need for rework. In addition, to re-establish the shaft line axis, rework may be carried out by machining the A-bracket, the stern tube and the main engine seat. The rework activity may require at least eight months of dry docking activity. Thus, the establishment of the shaft line axis and the installation of the support bracket on the slipway may be challenging. Further, the rework activity may require installation of new propelling shaft, thereby increasing overall production cost.
The present subject matter overcomes the above problems in the conventional art. The present subject matter discloses a dummy shaft introduced as a temporary replacement of an actual propelling shaft for minimizing the effect of the deflections on the shaft line. The dummy shaft may comprise a pipe section. The pipe section may be stiffened by one or more stiffeners to generate a stiffened pipe section of a predetermined strength. Further, at least one sleeve may be inserted on the stiffened pipe section to provide a smooth mating surface at a location of bearing surfaces of support brackets. Furthermore, a ring assembly may be inserted on pipe section covered by stern boss to form a leak proof stern boss assembly. Thus, the dummy shaft may be generated. Further, the dummy shaft may be supported with one or more roller supports and one or more fixed supports.
The present subject matter does away with the rework activity to reduce launch induced deflections and the process of welding bracket supports during dry-dock. The present subject matter thereby provides an improved shaft as a replacement of an actual propelling shaft for simulation purpose during pre-launch, to reduce the launch induced deflections in the shaft line axis.
Figure 1A:
Referring now to figure 1A, a schematic diagram of a conventional process showing pre-alignment disturbance during conventional launching of a marine vessel is illustrated.
The figure 1 A reflects that the pre-aligned shaft line axis established on the slipway may be disturbed. A marine vessel such as a ship and the like may gradually attain buoyancy from an aft during launching. Further, a load imposed on a hull from a dock that acts as point support may be gradually replaced by the buoyancy force acting on the hull. The buoyancy may vary uniformly from the aft to forward of the marine vessel at any point of time during its travel. The buoyancy moment and weight moment about the fore poppet may equalize, thereby leading to stern lift. During this point of stern lift, the hull may take a banana shape resulting in a deflection of the hull. The deflection of the hull may further induce a deflection in the pre-aligned shaft line axis. Further, the A-bracket and stern boss axis may be off-centered with reference to the pre-aligned condition. The figure 1A shows a deflection in the pre-aligned shaft line axis in the banana shape.
Figure 1B:
Referring now to Figure 1B, a schematic diagram of a conventional process showing pre-alignment disturbance during pontoon assisted launching of a marine vessel is illustrated.
The figure 1B shows a deflection in the shaft line axis during pontoon assisted launching of a marine vessel. Further, the deflection in the shaft line axis in case of pontoon assisted launching may be greater than the conventional launching due to an additional buoyancy force acting on the shaft line created by an aft pontoon. The deflections from the pre-alignment condition may require dry-docking of the marine vessel for machining various elements of propulsion system like A-bracket, stem boss and even engine seat to establish the shaft line axis again. The dry-docking may result in re-work, additional time consumption, wastage of manpower and consumables.
Figure 1C:
Referring now to Figure 1C, a schematic diagram showing elements of a propulsion shafting system 100 is illustrated in accordance with an embodiment of the present subject matter.
The propulsion shafting system 100 for a marine vessel may comprise a propeller 101, an A-bracket with bearing 102, a stern boss 103 with stern tube bearings, intermediate bearings 104 housed in plummer block, a thrust block 105 with thrust bearing, an actual propeller shaft 106, a reduction gear 107, an engine 108. Further, the actual propeller shaft 106 may be required to be aligned in accordance with shaft line axis 109. The alignment activity of the actual propeller shaft 106 may require extreme precision due to its length and to minimize transmission losses. Although the actual propeller shaft alignment may be carried out in the dry dock, a pre-aligned shaft line axis may be established by carrying out the sighting on the slipway. Further, post establishment of the shaft line axis, an A-bracket 102 may be welded to the stern region of the marine vessel by controlled welding. However, during launching, the pre-aligned shaft line axis may be disturbed due to the buoyancy forces acting on a hull of the marine vessel, thereby generating a need for a dummy shaft 700 for simulation purpose. The dummy shaft 700 may be utilized as a replacement of the actual propelling shaft 106 for pre-launch testing.
Figure 2:
Referring now to figure 2, a schematic diagram of C fixed support 201 for a dummy shaft 700 is illustrated in accordance with an embodiment of the present subject matter. The figure 2 discloses lock supports for the dummy shaft 700. The dummy shaft 700 may be locked inside a hull of a marine vessel at two locations with the fixed C-support 201.
Figure 3:
Referring now to figure 3, a schematic diagram of an end support 301 for a dummy shaft 700 is illustrated in accordance with an embodiment of the present subject matter. The figure 3 discloses lock supports for the dummy shaft 700. The dummy shaft 700 may be locked inside a hull of a marine vessel at one location with an end support 301. The end support 301 may be provided at the end of the dummy shaft 700.
Figure 4:
Referring now to Figure 4, a schematic diagram of stiffeners 401 mounted on a dummy shaft 700 is illustrated in accordance with an embodiment of the present subject matter.
In one exemplary embodiment, a length of the dummy shaft 700 to be installed may be 20m. Further, a section modulus of a pipe section 704 may be less than that required for an actual propelling shaft 106 disclosed in the propulsion shafting system 100. In order to achieve the predetermined strength, the pipe section 704 may be stiffened based on design calculations to provide a stiffened pipe section 400. The pipe section 704 may be longitudinally stiffened by one or more stiffeners 401. In one embodiment, the one or more stiffeners 401 may be one or more flat bars. In one embodiment, the pipe section 704 may be stiffened by 16 flat bars. Further, a size of the one or more flat bars may be 35 X 10 on a periphery of a 12 m pipe section. The stiffening of the pipe section 704 may provide additional strength equivalent to a pipe section of 60 mm thickness in case of the actual propelling shaft 106.
Figure 5:
Referring now to figure 5, a schematic diagram of a sleeve 501 inserted on a dummy shaft 700 is illustrated in accordance with an embodiment of the present subject matter.
The figure 5 depicts at least one sleeve 501 inserted on the stiffened pipe section 400 as demonstrated in figure 4 of the present subject matter. The at least one sleeve 501 may be introduced in order to provide a smooth mating surface at a location of a support bracket on the stiffened pipe section 400. In one embodiment, the thickness of the at least one sleeve 501 may be 5mm.
Figure 6:
Referring now to figure 6, a schematic diagram of a ring assembly 601 inserted on a dummy shaft 700 is illustrated, in accordance with an embodiment of the present subject matter.
The figure 6 shows a ring assembly 601 inserted on a pipe section 704. In one embodiment, the ring assembly 601 may comprise a blanking O-ring assembly. It is to be noted that, there may be a gap between the at least one sleeve outside diameter and a stern boss diameter due to said at least sleeve 501 introduced in the stiffened pipe section 400 as disclosed in figure 5. In one embodiment the gap may be 8mm. The gap may lead to water seepage inside the hull. The ring assembly 601 may be inserted to provide a leak proof stern boss assembly. Figure 7:
Referring now to Figure 7, a schematic diagram of a dummy shaft 700 is illustrated, in accordance with an embodiment of the present subject matter.
In one embodiment, the factors considered for designing an actual propeller shaft 106 may be one or more of:
Launch weight is 3000 tonnes
Maximum stem drop due to thermal stresses is 80 mm.
The actual propelling shaft is considered as an indeterminate beam with A-bracket support, stern boss support and fixed supports 702 inside the hull.
The actual propelling shaft undergoes only bending moment and no torsional moment.
In one embodiment, an outside diameter of the actual propelling shaft 106 in the propulsion shafting system 100 may be within the stern boss inside diameter (D, b), as the actual propelling shaft 106 may be passing through the stern boss. In one exemplary embodiment, the stern boss inside diameter D, b may be 708 mm. Further, the outside diameter (D0) of the actual propelling shaft 106 may be approximated to be 660 mm. Further, a material of the actual propelling shaft 106 in the propulsion shafting system 100 may be carbon steel. In addition, a bending moment of the actual propelling shaft 106 in the propulsion shafting system 100 may be computed. A maximum buoyancy force during the stern lift may be taken from theoretical launching calculations to obtain the maximum bending moment value during afloat condition from an FE software.
In the embodiment, a section modulus of the actual propelling shaft 106 in the propulsion shafting system 100 may be computed further. The section modulus may be computed by following equations (1) and (2).
M/ l = s/ y……………………………………………………………………(1)
z = l/y…………………………………………………………………………(2)
In the embodiment, an inside diameter of the actual propelling shaft 106 in the propulsion shafting system 100 may be computed further to withstand the estimated bending moment in afloat condition. In the exemplary embodiment, the inside diameter of the actual propelling shaft (D,) derived from the calculations is 535 mm.
In the embodiment, a thickness of the actual propelling shaft 106 in the propulsion shafting system 100 may be computed further. In the exemplary embodiment, the thickness of the actual propelling shaft 106 to achieve the desired section modulus is 62.5mm.
It is to be noted that the utilization of the actual propelling shaft 106 in the propulsion shafting system 100 with the above required dimensions may be costly, thereby generating a need to develop the dummy shaft 700 as a temporary replacement of the actual propelling shaft 106 for pre-launch testing.
The figure 7 depicts the dummy shaft 700 for utilization in the propulsion shafting system 100 for simulation purpose. The dummy shaft 700 may be shown as an indeterminate beam with one or more roller supports 701 and one or more fixed supports 702. In one embodiment, the dummy shaft 700 may be provided with two roller supports 701 and three fixed or welded supports 702. The dummy shaft (700) may be configured as a replacement of the actual propelling shaft 106 for pre-launch testing in the propulsion shafting system 100. The dummy shaft 700 may used for alignment of a shaft line axis to minimize deflections in the shaft line axis before installing an actual propelling shaft 106 which may be costly.
Further, in one embodiment, in order to predict Von Mises stresses and deflections on the dummy shaft 700 and their supports at the time of launching, a Finite Element (FE) Analysis may be performed. The actual propelling shaft 106 may be modelled to form a dummy shaft 700. The dummy shaft 700 may be analyzed as an indeterminate beam of a pipe section 704 with roller supports 701 at A-bracket, and stern boss and three fixed supports 702 inside the hull. Further, the dummy shaft 700 along with one or more stiffeners 401 is modelled and then meshed with the quadrilateral elements of size 20 using a HyperMesh module. The material property of carbon steel is assigned to the assembly of the one or more stiffeners. For the one or more stiffeners 401, PSHELL elements may be assigned. The dummy shaft 700 assembly with one or more stiffeners 401 is modelled as a single entity and then simulated as a static problem with the estimated loads on said assembly. The FE analysis may be further performed using a Radioss solver for discretization. The boundary conditions may be as follows:
A-bracket: X=0,Y=0,Z=2mm,Mx=0,My=0,M,=0
Stern boss: X=0,Y=0,Z=2mm,Mx=0,My=0,M,=0
Fixed ends: X=0,Y=0,Z=0,Mx=0,My=0,Mz=0
Axial Load (Fa) =-258 KN
Buoyancy (Fe) = 73 KN
In one exemplary embodiment, the following equations (3), (4) and (5) of statics may be used for the calculation of Von Mises stresses and deflection:
[F] = [K][X]…………………………………………………………………………..(3)
e = x/L………………………………………………………………………………...(4)
s = eE…………………………………………………………………………………(5)
Figure 8:
Referring now to Figure 8, wherein a shaft deflection curve for a propulsion shafting system 100 is illustrated, in accordance with an embodiment of the present subject matter.
In one exemplary embodiment, the finite element analysis may be provided for a static condition during a stem lift. The result of the analysis show a relative deflection of 21.7 mm in the pre-aligned shaft line axis between the stem boss and the A-bracket. The displacement curve is shown in figure 8.
Figure 9:
Referring now to Figure 9, wherein a curve for stresses acting on a dummy shaft 700 in a propulsion shafting system 100 is illustrated, in accordance with an embodiment of the present subject matter.
In one exemplary embodiment, the maximum Von Mises stress acting on the dummy shaft 700 as shown in Figure 9 is about 150 N/mm2. The stresses may be dominant in the vicinity of the A-bracket and the stern boss. However, they are instantaneous and below the elastic limit. Therefore, the dummy shaft 700 may be expected to spring back even after stem lift.
In the embodiment, the FE Analysis may be performed for the Fixed Supports 701. It is to be noted that the fixed supports 701 may be provided to the dummy shaft 700 inside the hull for transferring a load from the dummy shaft 700 to the bottom of the hull. The fixed supports 701 may be required to be tested to withstand buoyancy and drag forces acting on the dummy shaft 700. In one exemplary embodiment, the finite element analysis for the fixed supports 701 may be performed to ascertain the Von Mises stresses.
Figure 10:
Referring now to Figure 10, wherein a plot for stresses acting on fixed bracket supports 201 in a propulsion shafting system 100 is illustrated, in accordance with an embodiment of the present subject matter.
Two intermediate bracket supports may be provided just outside the stern tube. A static FE analysis may be performed on the bracket that is welded to the bottom of the marine vessel. All the degrees of freedom may be constrained and the load may be applied on the semi-circular face of the bracket. In one exemplary embodiment, the maximum von Mises stress acting on the bracket is 13.8 N/mm2. The plot showing the von Mises stress is shown in Figure 10.
Figure 11:
Referring now to Figure 11, wherein a plot for stresses acting on an end support 301 in a propulsion shafting system 100 is illustrated, in accordance with an embodiment of the present subject matter.
The end support 301 may be provided at the terminating end of the shaft line to take the buoyancy and axial loads. In one exemplary embodiment, the end support 301 may be a hollow cylindrical steel section of length 1.2m fabricated in two halves that are bolted together. Predominantly, the maximum bending moment may be acting on the top half of the support. Further, a provision may also given to arrest the axial movement of the shaft. The FE analysis may be further performed by considering only the bending moment acting on the bottom half. The FE analysis shows a maximum bending stress of 181 N/mm2 as shown in Figure 11. Therefore, six (6) carbon steel bolts of 50mm diameter that can withstand 30 N/mm2 of stress each are used as it is well within the limiting yield stress of 325 N/mm2.
Figure 12:
Referring now to Figure 12, wherein a shaft deflection curve of a dummy shaft 700 during launching in a propulsion shafting system 100 is illustrated, in accordance with an embodiment of the present subject matter.
In one exemplary embodiment, deflection calculations may be performed using a shaft designer software. The dummy shaft 700 may be modeled in the shaft designer software to predict the shaft deflections. The inputs may be a hull deflection value and a buoyancy force at the time of stem lift. The deflection curve obtained from the software is shown in Figure 12.
From the curve it may be evident that the absolute shaft deflection in the vicinity of A-bracket is 56 mm and at the locking end it is 33.75 mm. Therefore the relative shaft deflection obtained at A-bracket is 22.3 mm which is comparable with the deflection obtained from HyperMesh viz. 21.7 mm. The relative deflection values obtained at various locations are as follows:
A-bracket: 22.3 mm
Stem boss: 14 mm
Final locking support: 2.5 mm
In one embodiment, a physical measurement of launching induced deflection using one or more strain gauges may be performed. Before launching, the one or more strain gauges may be installed on the dummy shaft 700 to measure the deflection in shaft line. In one exemplary embodiment, twenty four strain gauges are placed on each shaft.
The one or more strain gauges may be placed near the stern boss, A-bracket and at the proximity of the end support 301 to measure the hull deflection in the vicinity of shaft line up to the end support 301. The measurements may be taken onboard during launching with the help of loggers.
Further, the relative deflections in horizontal (RH) and vertical directions (RV) at A-bracket obtained from the physical measurements taken onboard using the strain gauges are shown below in Table 1:
Table 1
In one exemplary embodiment, the observations from the strain gauge readings are as follows:
The relative vertical deflection in the port and starboard shaft at A-bracket during stern lift is 8.24mm and 8.12mm upwards. The values may indicate a banana shape of the hull formed during stern lift.
The relative horizontal deflection during stern lift is 34 mm in starboard shaft and 32 mm in port shaft. The values may indicate the effect of the bending moment on the hull and they are likely to cause a permanent deviation in the pre-aligned shaft line axis.
The relative vertical and horizontal deflection between A-bracket and stem boss obtained from strain gauge readings are 8.25mm and 26.54 mm respectively.
The resultant deflection obtained from the above readings is 27.8mm. The deflection value is in accordance agreement with the predicted values. A comparison matrix is shown below in Table 2.

Table 2
Further, in the afloat condition, when the ship is fully buoyant, the relative vertical deflection between A-bracket and stern boss in port and starboard shaft is very minimal to the range of 2.78 mm and 2.66 mm respectively.
The relative horizontal deflection noted is 12.67 mm and 12.09 mm respectively for port and starboard shaft. The residual deflection may be attributed to the uneven weight distribution resulting in the heel and trim of the vessel. The deflection is well within the tolerance limit and may be further expected to reduce when it is dry docked in the absence of hydrostatic and hydrodynamic forces.
Further, the final deflection in the pre-aligned shaft line axis obtained post dry docking of the vessel are shown below in Table 3:

Table 3
The above values are well within allowable tolerances. However, from the above results, it may be observed that the introduction of the dummy shaft 700 may yield satisfactory results by reducing the shaft line deflections leaving enough tolerance for the final alignment of the actual propelling shaft 106 in dry dock. It is to be noted from the physical measurements taken onboard that the relative horizontal deflection in way of A-bracket is 3.25mm which lies well within the tolerance limit of 7mm thereby leaving enough tolerance for the final alignment of the actual propelling shaft 106. Further, the alignment of the A bracket bearing and stern tube bearings may be smoothly done by using resin chock without too much machining. In addition, the eight months of dry docking period and manhours may be saved.
Figure 13:
Referring now to figure 13. The figure 13 illustrates a method 1300 for generating a shaft in a propulsion shafting system 100 for simulation purpose, is disclosed in accordance with an embodiment of the present subject matter.
The order in which the method 1300 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method 1300 or alternate methods. Additionally, individual blocks may be deleted from the method 1300 without departing from the spirit and scope of the subject matter described herein. Furthermore, the method 1300 can be implemented in any suitable hardware, software, firmware, or combination thereof. However, for ease of explanation, in the embodiments described below, the method 1300 may be considered to be implemented in the above described system 100.
At block 13.1, a pipe section 704 of a predetermined size may be procured.
At block 13.2, said pipe section 704 may be mounted with one or more stiffeners 401 along its length. The one or more stiffeners 401 may be configured to generate a stiffened pipe section 400 of a predetermined size and strength. Further, the one more stiffeners 401 may increase a section modulus of said pipe section 704. In one embodiment, said one or more stiffeners 401 may be plurality of bars mounted on said pipe section 704.
At block 13.3, at least one sleeve 501 may be inserted on said stiffened pipe section 400 with said one or more stiffeners 401. Further, the at least one sleeve 501 may be configured to provide a smooth mating surface at a support bracket on the pipe section 704.
At block 13.4, a ring assembly 601 may be inserted between said at least one sleeve 501 and a stern boss to form a leak proof stern boss assembly. In one embodiment, said ring assembly 601 may comprise a blanking O-ring assembly. Further, a dummy shaft 700 may be generated.
At block 13.5, a plurality of supports may be provided to said dummy shaft 700. In one embodiment, the plurality of supports may comprise one or more roller supports 701 and one or more fixed supports 702. The one or more roller supports 701 may comprise a first roller support at the A-bracket and a second roller support at the stern boss. Further, the one or more fixed supports 702 may comprise a first and a second C-support 201 at two locations and one end support 301 at an end of the dummy shaft 700.
At block 13.6, said dummy shaft 700 may be configured as a temporary replacement of an actual propelling shaft 106 for simulation purpose during pre-launch. The dummy shaft 700 may be easy to manufacture and further reduces a cost of rework activity for minimizing launch induced deflections in shaft line axis.
Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
Some embodiments of the shaft in a propulsion shafting system 100 for simulation purpose enable reduction in time required for dry-docking period by welding supports bracket on a slipway.
Some embodiments of the shaft in a propulsion shafting system 100 for simulation purpose enable minimization of an effect of launch induced deflections on shaft line reference axis by introducing a dummy shaft as a replacement of an actual propelling shaft for simulation purpose during pre-launching.
Some embodiments of the shaft in a propulsion shafting system 100 for simulation purpose enable reduction in cost required for manufacturing pipes for the actual propelling shaft.
Some embodiments of the shaft in a propulsion shafting system 100 for simulation purpose enable reduction in manpower required for machining, re-welding and re-alignment activities in launching the propelling shaft.
Although implementations for a shaft in a propulsion shafting system 100 for simulation purpose have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementations of a shaft in a propulsion shafting system 100 for simulation purpose.
,CLAIMS:
1. A shaft in a propulsion shafting system (100) for simulation purpose comprising:
a pipe section (704) configured to be stiffened with one or more stiffeners (401) mounted on said pipe section (704) along its length; and
at least one sleeve (501) configured to be inserted on said stiffened pipe section (400) at a location of a support bracket to generate a dummy shaft (700) for simulation purpose.

2. The shaft in the propulsion shafting system (100) for simulation purpose as claimed in claim 1, wherein a ring assembly (601) is inserted between said at least one sleeve (501) and a stern boss, to form a leak proof stern boss assembly.

3. The shaft in the propulsion shafting system (100) for simulation purpose as claimed in claim 1, wherein said stiffened pipe section (400) is configured to provide said dummy shaft (700) of a predetermined size and strength.

4. The shaft in the propulsion shafting system (100) for simulation purpose as claimed in claim 1, wherein said one or more stiffeners (401) are plurality of bars provided on said pipe section (704) to provide the predetermined strength to said pipe section (704).

5. The shaft in the propulsion shafting system (100) for simulation purpose as claimed in claim 1, wherein said at least one sleeve (501) is configured to be inserted to provide a smooth mating surface at said support bracket.

6. The shaft in the propulsion shafting system (100) for simulation purpose as claimed in claim 1, wherein said dummy shaft (700) is configured to be supported with plurality of supports, and wherein said plurality of supports are one or more roller supports (701) and one more fixed supports (702).

7. The shaft in the propulsion shafting system (100) for simulation purpose as claimed in claim 1, wherein said dummy shaft (700) is configured as a temporary replacement of an actual propelling shaft (106) for simulation purpose.

8. A method (1300) for generating a shaft in a propulsion shafting system (100) for simulation purpose, the method (1300) comprising the steps of:
• procuring a pipe section (704) of a predetermined size;
• stiffening said pipe section (704) along its length by mounting one or more stiffeners (401) to generate stiffened pipe section of a predetermined size and a predetermined strength;
• inserting at least one sleeve (501) on said stiffened pipe section (400) at a location of a support bracket;
• inserting a ring assembly (601) between said at least one sleeve (501) and a stern boss for a leak proof stern boss assembly, to generate a dummy shaft (700);
• supporting said dummy shaft (700) with a plurality of supports forming one or more roller supports (701) and one more fixed supports (702); and
• configuring said dummy shaft (700) as a temporary replacement of an actual propelling shaft (106) for simulation purpose.