INTRODUCTION  
       [0001]     This invention relates to a support structure for use with auxiliary machinery in a sea going vessel. More particularly the invention relates to a support structure to support auxiliary machinery used in a multi hulled passenger and vehicle carrying sea going vessel.  
       BACKGROUND OF THE INVENTION  
       [0002]     Sea going vessels are usually propelled by large diesel engines that are housed within the hull of the vessel to drive one or more propulsion systems at the stern of the vessel via drive shafts that are located in housings that extend from the engine or engines. Such vessels also have a requirement for auxiliary machinery, that is machinery that is driven off the internal combustion engines or turbines to power generators, pumps and a variety of other componentry that is conventional in vessels of this kind.  
         [0003]     Because this auxiliary machinery is driven by, for example, diesel engines and there is a considerable transfer of force from the diesel engines to the auxiliary machinery and this force requires a substantial support structure there is a need for means to reduce or eliminate vibration which is highly undesirable as it can resonate through the hull of the vessel. One means of reducing vibration is to further increase the size of the support structure and this can be a particular problem where the ship is constructed of aluminium in order to obtain light weight. The support structure that is thus used to support auxiliary machinery usually limits access to the machinery especially access to the machinery services that are frequently located on the underside of the machinery such as electrical cabling, cooling water and fuel supplies. Furthermore, access to the mounting bolts and the machines themselves can be difficult because of the substantial nature of the support structure.  
         [0004]     On high speed light weight craft engine rooms are usually congested because the need for high speed results in very large power units and thus physically large engines and associated transmission systems. In multi hulled vessels this is a particular problem due to the narrowness of the hulls and yet the need for an engine room that can house a power unit of substantial size.  
         [0005]     It is these issues that have brought about the present invention.  
       SUMMARY OF THE INVENTION  
       [0006]     According to the present invention there is provided a support structure for auxiliary machinery of a sea going vessel, the support structure comprising a trussed frame supporting a mounting plate at an elevated height above the bottom or deck of the vessel, the mounting plate being adapted to support auxiliary machinery, the trussed frame comprising beams arranged in triangles along the sides and ends of the frame, whereby the frame elevates the machinery and provides ready access to the underside of the machinery.  
         [0007]     Preferably the beams are constructed in aluminium.  
         [0008]     Preferably the beams have a rectangular or square cross section. Alternatively the beams may be of circular or similar cross section.  
         [0009]     In another embodiment a diagonal bracing beam is removed from either end of the frame to make way for a girder joining the plate or frame to the frame of the vessel on each side of the vessel.  
         [0010]     Vibrational damping mounts may be positioned between the frame and the plate or at the joins between the beams of the truss. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0011]     The prior art and an embodiment of this invention will now be described by way of example only with reference to the accompanying drawings in which:  
         [0012]      FIG. 1  is a perspective view of a typical conventional installation of auxiliary machinery;  
         [0013]      FIG. 2  is a perspective view of an installation of auxiliary machinery in accordance with an embodiment of this invention;  
         [0014]      FIG. 3  is a cross sectional view taken through the engine room illustrating the association of the auxiliary machinery with the main engine;  
         [0015]      FIG. 4  is a plan view of the engine room; and  
         [0016]      FIG. 5  is a partial perspective view showing the support for auxiliary machinery in association with the frame of the vessel. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     A conventional installation of auxiliary machinery M is shown in  FIG. 1  in which the auxiliary machinery M is supported in an elevated configuration by a pair of spaced girders G 1  and G 2  via flexible mounts F positioned at each corner of the machinery. The auxiliary machinery M spans the two girders which are welded to project in a parallel array upwardly from the bottom plating P of the vessel V. A series of interconnecting webs W join the girders G 1  and G 2  and lateral support webs W 2  extend from the sides of the girders to the plating P. A series of access holes H are provided along the girders and the webs to provide access to the underside of the auxiliary machinery M. However this is a cumbersome arrangement with very difficult and limited access that has proved unsatisfactory in practice.  
         [0018]     In the embodiment shown in FIGS.  2  to  5 , a trussed frame  10  is used to support a rectangular horizontal plate  11  which in turn supports the auxiliary machinery M via flexible mounts F mounted at each corner of the machinery. The trussed frame  10  not only provides support for the auxiliary machinery but also acts to elevate the machinery above the level of the main engine E as shown in  FIGS. 3 and 4 .  
         [0019]     The trussed frame  10  comprises elongate aluminium beams that are fastened to one another to define a triangular array with the upper plate  11  and bottom plating (not shown) of the vessel V. As shown in  FIG. 3  which is a cross section through the engine room, the main engines E 1  and E 2  are supported on vertical girders G 3  and G 4  with the main output shafts S 1  and S 2  extending rearwardly at a level below the floor plate  15  which is the working level of the vessel. The auxiliary machinery M is supported so that the base of the machine is level with the floor plate  15  and the aluminium trussed frame  10  supports the auxiliary machinery M through connection to the side frame  20  of the vessel V and the girders that support the main engines. As shown in  FIG. 4  in plan the auxiliary machinery M is positioned away from the main engines E 1  and E 2  at a level above the output shafts S 1  and S 2  thereby providing easy access both to the machines themselves and to the space underneath the machines due to the open structure of the trussed frame  10 .  
         [0020]     The trussed frame  10  has two triangular frames  12  and  13  along the longer sides and a single triangular frame  14  across the ends. The frames  12  and  13  comprise vertical uprights  18  joined by a diagonal bracing beam  17 . A diagonal bracing beam  19  joins the frame at the end of the structure. All the beams are mounted to extend in a vertical plane. The trussed frame can support the plate in a free standing manner or, in the embodiment shown in  FIG. 5 , the ships side frames  20  are connected to the rectangular support plate  11  via elongate beams  21  and  22  that can be connected to the plate  11  via flexible mounts  23  and  24 . The opposite ends of the beams  21 ,  22  are firmly secured to the side frame  20  of the vessel V. The beams  21  and  22  can be on both or one side of the plate  11 . In this embodiment the diagonal beam  19  across the ends of the frame  10  are removed but the sides of the rectangular plate  11  are supported by the triangular trussed frame  10  structure as described above. This drawing also shows how the trussed structure  10  is firmly secured through bolting or welding to the deck D that extends laterally across the sides of the vessel V.  
         [0021]     The triangular trussed structure provides ready access underneath the plate  11  and thus allows maintenance and access to the associated service lines that could be electrical cable, water piping or fuel supply lines. It also allows maintenance and access to the main output shaft  51  where this may pass close by  
         [0022]     The use of trussed frames  10  to support the auxiliary machinery M is particularly desirable in multi hulled vessels that operate at high speed. The auxiliary machinery M can be positioned where it is readily accessible and there is ready access to the underside of the machinery for service purposes. The use of a trussed frame provides the required degree of support and rigidity in a light weight structure that does not substantially obstruct access within the engine room.  
         [0023]     The beams that make up the truss structure  10  are either of rectangular of square cross section though it is understood that they could also be of circular or other cross section. It is further understood although, not shown that vibrational dampers can be positioned within the truss elements where they are secured to the floor of the vessel, to each other and the support plate  11 . In a preferred embodiment all the structural members are made of aluminium.  
         [0024]     In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
A support structure for auxiliary machinery in a seagoing vessel, the support structure comprising a trussed frame supporting a mounting plate at an elevated height above the bottom or deck of the vessel, the mounting plate being adapted to support auxiliary machinery, the trussed frame comprising beams arranged in triangles along the sides and ends of the frame, whereby the frame elevates the machinery and provides ready access to the underside of the machinery.