Patent Publication Number: US-2016236527-A1

Title: Amphibian

Description:
The present invention relates to an amphibian and, in particular, to an amphibian having a three wheel configuration. 
     A number of road wheel and seating arrangement layouts have been proposed and built for amphibians. The most popular layout, as for road vehicles, is to have four wheels and sit-in seating provided across the amphibian in one or more rows. This convention provides stability and ease of communication respectively. However, it also sets constraints on the dimensions, weight, performance and manoeuvrability of the amphibian. 
     Two wheeled amphibians are also known, for example, from Buchanan (GB 2,254,831). The size of hull needed to ensure flotation on water gives a bloated appearance to the amphibian, reduces stability and manoeuvrability on road, and hinders access to mechanical parts for servicing. Indeed, such amphibians tend to be compromised both on land and on water. For example, Buchanan provides extensible bellows on both sides of his amphibian body, to act as stabilizers at low speed on water. 
     Three wheeled road vehicles are known, the convention being to have a single front wheel and two driven rear wheels. This allows a small turning circle, and uninterrupted space for passengers and/or goods at the rear of the vehicle. However, this layout is notoriously unstable on land. On the other hand, the three wheeled Morgan sports cars, which had two wheels at the front and one at the back, are remembered with affection over fifty years after going out of production. 
     Three wheeled amphibians are known, for example from Grzech (U.S. Pat. No. 5,690,046), who uses a single front wheel. The two rear wheels are covered on water by complex hinged panels, which may stop working if damaged in collisions or if their mechanisms were clogged by water, or by fine debris, e.g. sand. Salt water may of course lead to corrosion. It is noted that Grzech does not provide a full description of the operation of these covers. Grzech shows hinged panels which are hinged in one dimension, but need to be hinged in two dimensions. 
     Baker (WO 99/24273) discloses a three wheeled amphibian whose wheels, including a single rear wheel, are not retractable. The glazing, roof, and doors of Baker&#39;s amphibian add weight, cost, and complexity, and enclose the driver and passengers in a conventional sit-in vehicle architecture. Similarly, the driver and passenger sit side-by-side, meaning that the driver is offset from the amphibian centre line. This in turn necessitates handed steering, which increases complexity of production in a small and fragmented niche market. When only the driver is aboard, there are potential problems in amphibian handling due to offset weight distribution. The side-by-side front seating also sets a minimum width for the amphibian. 
     A further amphibian is disclosed by Maguire (U.S. Pat. No. 6,505,694). Essentially, this is a snowmobile adapted to float. It has two front wheels and a rear endless track drive mounted on the centre line of the amphibian. Marine propulsion is effected by the track drive which is retractable within the bodywork when the amphibian is on water. Marine propulsion by track drives has been found to be painfully slow even with exposed tracks; retracted tracks are even less efficient. Maguire&#39;s amphibian is also compromised by these tracks on hard surfaces. Track drives limit speed and manoeuvrability on metalled roads. A hard track made of steel will damage the road, a soft track will be damaged by the road. Maguire&#39;s amphibian will stress its track particularly badly when turning, as shear loads in opposite directions will be applied to opposite ends of each cleat or lag. 
     The present invention provides an amphibian as set forth in the appended claims. 
     In a first aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheel stations, two of the three wheel stations being front wheel stations provided one on each side of and in the front half of the amphibian, and the third wheel station being a rear wheel station provided in a central region in the rear half of the amphibian; 
     at least one wheel provided at each wheel station, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least two impellers or propellers provided one on each side of the rear wheel station. 
     In a second aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheel stations, two of the three wheel stations being front wheel stations provided one on each side of and in the front half of the amphibian, and the third wheel station being a rear wheel station provided in a central region in the rear half of the amphibian; 
     at least one wheel provided at each wheel station, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least one impeller or propeller, wherein: 
     the land propulsion means is independent of the marine propulsion means. 
     In a third aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     at least three wheels arranged in a three wheeled vehicle configuration, two of the wheels being front wheels provided one on each side of and in the front half of the amphibian, and a third wheel being a rear wheel provided in a central region in the rear half of the amphibian, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least one impeller or propeller, wherein: 
     the land propulsion means is independent of the marine propulsion means. 
     In a fourth aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheels, two of the wheels being front wheels provided one on each side of and in the front half of the amphibian, and the third wheel being a rear wheel provided in a central region in the rear half of the amphibian, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least one impeller or propeller, wherein: 
     the land propulsion means is independent of the marine propulsion means. 
     In a fifth aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheel stations, two of the three wheel stations being front wheel stations provided one on each side of and in the front half of the amphibian, and the third wheel station being a rear wheel station provided in a central region in the rear half of the amphibian; 
     at least one wheel provided at each wheel station, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     a prime mover which in the land mode of the amphibian provides direct or indirect drive to at least one of the wheels; 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least two impellers or propellers provided one on each side of the rear wheel station. 
     In a sixth aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheels, two of the three wheels being front wheels provided one on each side of and in the front half of the amphibian, and the third wheel being a rear wheel provided in a central region in the rear half of the amphibian, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least two impellers or propellers provided one on each side of the rear wheel station. 
     In a seventh aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheels, two of the three wheels being front wheels provided one on each side of and in the front half of the amphibian, and the third wheel being a rear wheel provided in a central region in the rear half of the amphibian, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least one impeller or propeller, wherein: 
     the land propulsion means is independent of the marine propulsion means. 
     In an eighth aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheel stations, two of the three wheel stations being front wheel stations provided one on each side of and in the front half of the amphibian, and the third wheel station being a rear wheel station provided in a central region in the rear half of the amphibian; 
     at least one wheel provided at each wheel station, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; and 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least one impeller or propeller, wherein: 
     the marine propulsion means is driven independently of the land propulsion means. 
     In a ninth aspect, the present invention provides an amphibian for use in land and marine modes comprising: 
     a planing hull; 
     three wheel stations, two of the three wheel stations being front wheel stations provided one on each side of and in the front half of the amphibian, and the third wheel station being a rear wheel station provided in a central region in the rear half of the amphibian; 
     at least one wheel provided at each wheel station, each wheel being movable between a protracted land mode position and a retracted marine mode position; 
     land propulsion means to propel the amphibian on land in the land mode, the land propulsion means comprising at least one of the wheels; 
     marine propulsion means to propel the amphibian on water in the marine mode, the marine propulsion means comprising at least one impeller or propeller; and 
     a prime mover, wherein: 
     the marine propulsion means is driven by the prime mover independently of the land propulsion means. 
     In a tenth aspect, the present invention provides an amphibian comprising at least three retractable wheels, at least two of the retractable wheels being retractable about an axis substantially parallel to, or offset by an angle α of up to 40 degrees from, a longitudinal axis of the amphibian, and at least one of the retractable wheels being retractable about an axis substantially parallel to, or offset by an angle β of up to 40 degrees from, a transverse axis of the amphibian. 
     Thus, an amphibian is provided with good handling on water and inherent stability on land. It is capable of operation on land and on water with minimal operational compromise on either medium. 
     The applicant has combined the benefits of two spaced apart wheels at the front of the amphibian and a central wheel at the rear to optimise on land performance, but which is counter-intuitive to optimising performance on water due to the inherent track width at the front of the amphibian, with a narrowing pointed hull at the front provided between the front wheels, which hull becomes wider rearwards along its length to optimise on water performance, but which hull is counter-intuitive to optimising on land performance due to the shape of the hull suggesting a single central front wheel and two spaced apart wheels at the rear. 
     The present invention provides, in a further aspect, a powertrain for an amphibian as set forth in the appended claims. This provides a compact layout of a powertrain for an amphibian. 
     For the avoidance of doubt, reference herein to a rider or a driver means the person controlling the amphibian. 
     Grzech describes a centrally mounted water jet unit, which ejects water between the two rear wheels. The disclosed water jet unit would be incompatible with a single rear wheel, for packaging reasons. 
     Baker describes an amphibian propelled in water by vanes attached to the rear wheel. The rear wheel must remain immersed in order to thrust the amphibian forward. This increases the drag of the amphibian in water, since half of the wheel and tyre are always under the water when the amphibian is operated in marine mode. 
     Grzech provides for retraction of a single front wheel by long-travel hydraulic suspension forks, with road steering disconnection by splines on the forks. This design is not readily adaptable to a pair of front wheels. 
     Baker uses water skis which can be rotated beneath the front wheels to allow planing on water. This prevents the amphibian from leaning into turns on water, reducing possible cornering speed. 
     Both Grzech (with articulated wheel covers) and Baker (with mudguards rotating to become water skis) teach covering of wheels over water. The mechanisms necessary to move such covers can be difficult to maintain. Mechanisms and, where used, electric motors are exposed to a number of aggressive substances such as salt water and sand, which are liable to erode, clog, corrode, or distort moving parts. The operation of the covers may also be adversely affected by distortion of the covers and/or their mechanisms resulting from collisions, even with minor obstacles such as rocks under water. Furthermore, the covers may be visible on the outside of the amphibian, and thus will need a class “A” finish for marketing reasons. Such a high gloss finish will be very vulnerable to scratching and chipping, leading to rapid deterioration in the appearance of the amphibian. 
     Surprisingly, the present applicant has found in trials of prototype amphibians that such covers are not necessary to ensure good marine handling. Furthermore, exposed wheels have the advantage that the tyres can act as fenders. The tyres are especially effective in absorbing minor bumps if the wheels are retracted at an angle to the vertical. 
    
    
     
       Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view from above of an amphibian according to a first embodiment of the present invention, with the wheels protracted for use in land mode; 
         FIG. 2  is a perspective view from below of the amphibian of  FIG. 1 ; 
         FIG. 3  is a front elevation view of the amphibian of  FIG. 1 ; 
         FIG. 4  is a side elevation view of the amphibian of  FIG. 1 ; 
         FIG. 5  is a rear end elevation view of the amphibian of  FIG. 1 ; 
         FIG. 6  is a top plan view of the amphibian of  FIG. 1 ; 
         FIG. 7  is a bottom plan view of the amphibian of  FIG. 1 ; 
         FIG. 8  is the same perspective view of the amphibian of  FIG. 1 , but with the wheels retracted for use in marine mode; 
         FIGS. 9 to 14  correspond to the views shown in  FIGS. 2 to 7  save that the views shown in  FIGS. 9 to 14  show the amphibian with the wheels retracted for use in marine mode; 
         FIG. 15  is a perspective view from above of an amphibian according to a second embodiment of the present invention, with the wheels protracted for use in land mode; 
         FIG. 16  is a perspective view from below of the amphibian of  FIG. 15 ; 
         FIG. 17  is a front elevation view of the amphibian of  FIG. 15 ; 
         FIG. 18  is a side elevation view of the amphibian of  FIG. 15 ; 
         FIG. 19  is a rear end elevation view of the amphibian of  FIG. 15 ; 
         FIG. 20  is a top plan view of the amphibian of  FIG. 15 ; 
         FIG. 21  is a bottom plan view of the amphibian of  FIG. 15 ; 
         FIG. 22  is the same front perspective view of the amphibian of  FIG. 15 , but with the wheels retracted for use in marine mode; 
         FIGS. 23 to 28  correspond to the views shown in  FIGS. 16 to 21  save that the views shown in  FIGS. 23 to 28  show the amphibian with the wheels retracted for use in marine mode; 
         FIG. 29  is a schematic perspective view from above of a rolling chassis of the amphibian of  FIGS. 1 to 28 ; 
         FIG. 30  is a schematic perspective view from above of a powertrain layout and retractable rear wheel suspension assembly of the amphibian of  FIGS. 1 to 28 ; 
         FIG. 31  is a schematic top plan view of the powertrain layout of  FIG. 30 ; 
         FIG. 32  is a schematic side elevation view of the powertrain layout of  FIG. 30 ; 
         FIG. 33  is a schematic side elevation view of an amphibian according to a third embodiment of the present invention, in a land mode operation state; 
         FIG. 34  is a schematic side elevation view of the amphibian of  FIG. 33 , in a marine mode operation state; 
         FIG. 35  is a schematic underneath plan view of the amphibian of  FIG. 33 , in a land mode operation state; 
         FIG. 36  is a schematic rear elevation view of the amphibian of  FIG. 33 , in a land mode operation state; 
         FIG. 37  is a schematic underneath plan view of an amphibian and powertrain layout according to a fourth embodiment of the present invention; 
         FIG. 38  is a schematic simplified partial-cross-sectional view of an amphibian according a fifth embodiment of the present invention; 
         FIG. 39  is a schematic partial-front view of an amphibian according to a sixth embodiment of the present invention, showing a wheel in a protracted vehicle-supporting position; 
         FIG. 40  is a schematic partial-front view of an amphibian according to  FIG. 39 , showing a wheel in a retracted position; 
         FIG. 41A  is a schematic simplified partial cross-sectional view of an amphibian according to the present invention, having a step-down drive; 
         FIG. 41B  is a schematic partial cross-sectional view of the step-down drive of  FIG. 41A ; 
         FIGS. 42A and 42B  are schematic cross-sectional plan views of portions of hulls of amphibians; 
         FIG. 43  is a rear perspective view of a seventh embodiment of amphibian according to the present invention; 
         FIG. 44  is a schematic top plan view of an eighth embodiment of amphibian according to the present invention; and 
         FIG. 45  is a schematic side elevation view of the amphibian of  FIG. 44 . 
     
    
    
     Referring first to  FIGS. 1 to 7 , there can be seen an amphibian  10  in its land mode having a forward bow end  12  and a rear stern end  14 . 
     The amphibian  10  has three wheel receiving stations  50 ,  52 ,  54 . Two are front wheel stations  50 ,  52  provided one on either side at the front of the amphibian  10 , while the third is a rear wheel station  54  provided in a central region at the rear of the amphibian  10 . At least one road wheel  51 ,  53 ,  55  is provided at each wheel station  50 ,  52 ,  54 . Each wheel  51 ,  53 ,  55  is connected to the remainder of the amphibian  10  by any suitable wheel suspension system which includes a wheel retraction mechanism for moving the wheels  51 ,  53 ,  55  between a lowered state for land use and a raised state for marine use. The front wheels  51  and  53  are steerable and handlebars  60  are provided to enable steering of these wheels. Alternatively, a steering wheel may be employed in place of handlebars. The rear wheel  55  is driven to propel the amphibian  10  on land. Alternatively, or in addition, one or both front wheels  51 ,  53  may be driven (i.e. the amphibian may be one, two, three or all wheel drive). Jet drive units  72 ,  74  (see  FIG. 2 ) provide propulsion in marine use. 
     The structure of the amphibian  10  comprises an upper deck section  30  and a lower hull section  40 . The upper deck structure  30  is sealed to the lower hull section  40  around a peripheral planar edge  35  which is above the water line when the amphibian  10  is fully displaced in water. The complete upper deck section  30  is detachable from the lower hull section  40  as a single unit, and/or as separate panels. This permits ease of access to internal components of the amphibian  10  for servicing, etc. 
     Air inlet openings (not shown) provide an entry for cooling air (which may or may not be fan-assisted) for use by the cooling systems of the amphibian  10 . Air entrained via these inlets is eventually exhausted via outlets (not shown). Between the air inlets and air outlets, a dorade system is installed to prevent the ingress of water. The dorade system facilitates righting of the amphibian on water by use of a labyrinthine air inlet passage system to prevent the ingress of water should the amphibian  10  be inverted in use in the marine mode. 
     Sit-astride seating  34  is provided for a driver and passengers of the amphibian  10 . Step through openings (not shown) may be provided in the sit-astride seating  34  to aid a rider/driver and/or passenger(s) getting on and off the amphibian  10 . Footwell areas  36 ,  38  are provided one on either side of the sit-astride seating  34 , each shrouded by bodywork positioned laterally outside of the footwell areas  36 ,  38  to provide protection. These footwell areas  36 ,  38  may be provided with means to bail automatically any water shipped in use of the amphibian  10 . 
     Front wheel arches  31 ,  32  and rear wheel arch  33  are provided so as to afford protection from spray. An instrument panel  62  is provided ahead of the steering controls to convey relevant parameters of the amphibian  10  to the rider/driver. Additionally, rear view mirrors (not shown) may be provided as a visual aid to the rider/driver. Furthermore, navigation lights may also be provided within or on the upper deck structure  30  in accordance with the local legislative requirements. 
     The upper deck structure  30  forms an integral part of the entire structure of the amphibian  10 . It is a structural component and not merely cladding. Typically it will take the form of a composite structure (e.g. glass fibres or carbon fibres set in resin) although any suitable manufacturing method may be employed. Where localised areas of strength are required in the upper deck structure  30 , extra layers or mats of fibres may be laid down during manufacture. The deck  30  will be formed with localised reinforced areas in order to provide a complete force transmitting path extending around the amphibian  10  in a complete circle in a plane orthogonal to a longitudinal axis of the amphibian  10 , in order to provide resistance to torsional loads on the amphibian  10 . 
     Referring in particular now to  FIGS. 2 to 4 and 7 , the underside of the hull  40  can be seen extending from the front bow section  12  to the rear stern section  14 . Starting from the planar interface  35  with the upper deck section  30 , there is a wall  41  extending around a periphery of the amphibian  10  down to a lower hull surface  42 . The overall displacement of the hull  40  provides stability when the amphibian  10  is operated at high speed in marine mode, in particular because of the volume of hull  40  spaced laterally from the centre line of the amphibian  10 . As such, when cornering sharply, for example, an increase in righting force is experienced as the angle of lean increases. The bodywork provided laterally of the footwell areas  36 ,  38  in particular provide righting forces spaced from the amphibian  10  centre line. Any or all such hull volumes can be provided with buoyancy inserts to give residual buoyancy. 
     It will be appreciated that no cutouts are provided in the hull  40  in the region of the front wheel stations  50 ,  52 . Indeed, with reference in particular to  FIG. 14 , it will be appreciated that the only discontinuities  46 ,  48  and  49  in the hull are those provided at the rear of the hull  40  to accommodate the rear wheel station  54  and jet drives  72 ,  74 . These discontinuities  46 ,  48  and  49  have little effect on the performance of the hull  40 . As such, it has been possible to avoid the use of any cover device to reconstruct the lines of the hull  40  when the wheel assemblies are retracted for use in marine mode. 
     A vee-hull section  44  is formed in the central lower surface  42  of the hull  40  and this can form or be provided with a keel which runs from the bow  12  along the length of the amphibian  10 . Strakes or other hydrodynamic aids (not shown) may be integrated in or provided on the hull  40 . At the rear of the hull  40 , water intake areas  46 ,  48  are incorporated for the jet drive marine propulsion units  72 ,  74  of the amphibian  10 . In addition, a recess  49  is provided to accommodate the rear wheel  55 . 
     The design of the hull  40  is critical in determining the performance achieved when the amphibian  10  is operated in the marine mode. The present applicant has spent considerable time and effort in the design of the hull  40  which has resulted in a rather surprising shape as compared to that usually expected for a planing water craft or amphibian. The hull  40  comprises a narrow uninterrupted (no cutouts) bow section  43  having a dead rise angle of substantially 23 degrees along its length, followed by a widening rearward section  45  having a dead rise angle of substantially 18 degrees along its length. This compares with traditional planing hulls which start at the bow section with a very steep dead rise angle and these dead rise angles become more shallow along the length of the hull towards the stern, typically ending at 5 degrees or less of dead rise angle. Prior art amphibians have hulls provided with substantial cutouts or discontinuities to accommodate retractable wheel and suspension assemblies, these cutouts or discontinuities being provided with hull covers or entire slidable panels to reconstruct the lines of the hull for use of the amphibian in marine mode. 
     Since the sit-on seating  34  of the amphibian  10  is arranged longitudinally, the amphibian  10  is narrower than a passenger car. Aligning the engine longitudinally along the amphibian gives a body shape which is narrower in beam and deeper. Rather than adopting the flat planing hull common in the prior art, the applicant has adopted a greater dead rise angle for the agile marine handling this provides, accepting that this gives a need for a suspension with a lot of travel to give adequate ground clearance on land. 
     Whereas before amphibians such as that of Grzech strove to keep the track width of the wheels within the beam of the amphibian, the applicant has realised that better land mode operation can be achieved if the track width of the front wheels  51 ,  53  of the amphibian  10  amphibian is greater than the beam of the hull  40 . The approach adopted by the applicant does mean that wheels must be retracted through a large angle in order to be clear of the amphibian waterline in marine use, but the strategy does provide for a amphibian capable both on land and on water. 
     Even with the small footprint of the hull  40  of the amphibian  10 , the hull design  40  is capable of propelling the amphibian  10  up onto the plane with little difficulty in fast time periods. Furthermore, on-water performance of the amphibian  10  is not compromised and adequate ground clearance is available when operating the amphibian  10  in land mode. 
     The amphibian  10  has an overall length in the range of from 3.600 m to 4.200 m, more preferably in the range of 3.800 m to 4.050 m, most preferably of substantially 3.950 m, an overall width in the range of from 1.730 m to 2.000 m, more preferably in the range of 1.800 m to 1.900 m, most preferably of substantially 1.850 m, and an overall height in the range of from 1.200 m to 2.000 m, more preferably in the range of 1.300 m to 1.500 m, most preferably of substantially 1.400 m. The wheelbase length of the amphibian  10  is in the range of from 2.300 m to 3.700 m, more preferably in the range of 2.400 m to 3.000 m, most preferably substantially 2.580 m and the track width of the front wheels  51 ,  53  is in the range of from 1.400 m to 1.900 m, more preferably in the range of 1.600 to 1.700, most preferably substantially 1.655 m. The length of the hull  40  is in the range of from 3.000 m to 4.200 m, more preferably in the range of 3.300 m to 3.900 m, most preferably substantially 3.600 m. The maximum beam of the hull  40  is in the range of from 1.100 m to 2.000 m, more preferably in the range of 1.200 m to 1.600 m, most preferably substantially 1.380 m, and beam of the hull  40  between the front wheels  51 ,  53  in the front region  43  is less than the track width. 
     Referring now to  FIGS. 8 to 14 , these Figures correspond to the views shown in  FIGS. 1 to 7  respectively, save that each shows the amphibian  10  with its wheels retracted for use in marine mode. 
     Referring next to  FIGS. 15 to 28 , there is shown a second embodiment of amphibian  10  according to the present invention. This second embodiment is broadly similar to the first, save that it is a smaller scale version and comprises a ‘mudguard’ type design of wheel arch for front wheel arches  31 ′,  32 ′. Like reference numerals designate like components throughout. The hull  40  comprises a narrow uninterrupted (no cutouts) bow section  43  having a dead rise angle of substantially 16 degrees along its length, followed by a widening rearward section  45  having a dead rise angle of substantially 12 degrees along its length. 
     The amphibian  10  has an overall length in the range of from 2.700 m to 3.800 m, more preferably in the range of 3.000 m to 3.600 m, most preferably of substantially 3.323 m, an overall width in the range of from 1.200 m to 1.800 m, more preferably in the range of 1.400 m to 1.700 m, most preferably of substantially 1.600 m, and an overall height in the range of from 1.100 m to 1.700 m, more preferably in the range of 1.300 m to 1.500 m, most preferably of substantially 1.400 m. The wheelbase length of the amphibian  10  is in the range of from 1.500 m to 3.000 m, more preferably in the range of 1.900 m to 2.600 m, most preferably substantially 2.330 m and the track width of the front wheels  51 ,  53  is in the range of from 1.000 m to 1.800 m, more preferably in the range of 1.200 m to 1.600 m, most preferably substantially 1.430 m. The length of the hull  40  is in the range of from 2.400 m to 3.600 m, more preferably in the range of 2.700 m to 3.300 m, most preferably substantially 3.000 m. The maximum beam of the hull  40  is in the range of from 0.900 m to 1.500 m, more preferably in the range of 1.050 m to 1.350 m, most preferably substantially 1.200 m, and beam of the hull  40  between the front wheels  51 ,  53  in the front region  43  is less than the track width. 
     Referring now to  FIG. 29 , there is illustrated, schematically, a rolling chassis showing certain internal components of the amphibian  10 . A prime mover  80  can be seen which is a multi-cylinder internal combustion engine. Alternatively, any prime mover  80  such as electric, hydraulic, pneumatic, hybrid or otherwise may be beneficially employed. Wheel suspension and retraction assemblies, powertrain, driveline and transmission components can be seen, and these are more fully described below with reference also to  FIGS. 30 to 32 . 
     The powertrain comprises an output shaft  81  leading drive from the engine  80  via a torsional damper  82  to a driveshaft  83 . Driveshaft  83  provides drive, via a forward-neutral-reverse gearbox  85 , continuously variable transmission (CVT)  90  (see pulleys  91 ,  92 ) and reduction drive  86 , to a land mode output shaft  94 . Land mode output shaft  94  relays drive via a bevel gear set (not shown) located in the rear wheel hub  413  to the rear wheel  55  during land use of the amphibian  10 . Driveshaft  83  also provides drive, via a belt drive system  100 , to two marine mode output shafts  102 ,  104 . Belt drive system  100  comprises an input/driver toothed wheel  102 , two output/driven toothed wheels  104 ,  106  and a toothed belt  108 . Marine mode output shafts  102 ,  104  relay drive to the jet drive units  72 ,  74  during marine (and, optionally, land) use of the amphibian  10 . The jet drive units  72 ,  74  may be permanently connected to the engine  80  to be driven thereby at all times, whilst the rear wheel  55  is driven (connected to the engine  80 ) only in its lowered (protracted) land use position. The forward-neutral-reverse gearbox  85 , CVT transmission  90 , reduction drive  86  and belt drive system  100  could of course be replaced in other embodiments by a conventional automatic gearbox or a manual gearbox, or other powertrain and/or transmission systems and arrangements, as required. 
     Steering input is from handlebars  60 . Various mechanisms may be used to transfer movement from the handlebars  60  to front steered wheels  51 ,  53 . For example, the applicant&#39;s co-pending application published as US 2006/0178,058 A1 discloses a steering system for a small amphibian with handlebars, wherein road steering is automatically disengaged as the retractable suspension is retracted for use of the amphibian on water. However, this is essentially a cam-operated steering system, without gearing. If steering loads are sufficiently high that gearing and power assistance are required, a steering system according to the applicant&#39;s patent GB 2,400,082B may be used. This patent discloses an adaptation of a power-assisted rack and pinion automotive steering system to an amphibian, arranged such that the power assistance also applies to marine steering. This is helpful in damping out the water feedback forces on the jet steering nozzle or nozzles which might otherwise cause painful and/or irritating feedback to the rider through the steering control. 
     The seating  34  in the amphibian  10  is provided substantially above the amphibian powertrain, with the handlebars  60  located in the front half of the length of the amphibian. This gives a good driving position for both marine and land use. 
     The front left-hand wheel suspension and retraction assembly  64  (the front right-hand, partially shown, corresponds) and rear wheel suspension and retraction assembly  400  are also shown in  FIG. 29 . Spring and damper assemblies are provided for each of wheels  51 ,  53 ,  55 . Retraction actuators  65  and  430  retract and extend these wheel suspensions from their lowered positions (as is shown in  FIG. 29 ) to their raised positions, while spring and damper units  66  and  402 ,  404  cater for normal suspension movement. Where actuator rams  65  and  430  are hydraulic, hydraulic fluid may be provided by a pump (not shown) powered by the engine  80 . 
     A fuller description of the rear assembly follows immediately below (with reference to  FIG. 30 ) and, of the front assemblies, follows later (with reference to  FIGS. 38 to 42B ). However, it is to be noted that these are only examples of retractable suspensions which may be used. 
     Referring to  FIG. 30 , the retractable rear suspension  400  can be seen to comprise a coil spring  402  and a telescopic damper or shock absorber  404 . First and second ends of damper  404  are pivoted to the amphibian  10  at pivots  406  and  408  respectively. Pivot  408  is mounted on a cross beam  410  which is part of a trailing arm assembly comprising two front angled arms  411  and two rear angled arms  412 , one each provided on either side of rear wheel  55 , and a forward trailing arm  414 . In normal bump and rebound movement, the trailing arm assembly will pivot around the pivot  416  at the front of the trailing arm assembly, compressing and extending spring  402  and damper  404  to give conventional damped suspension movement. 
     Upper pivot mounting  406  is mounted to retraction arm  420 , which is in turn mounted at pivot  422  to bracket  424 , which is firmly mounted to the frame (not shown) of the amphibian  10 . A retraction ram  430  is mounted to bracket  424  at pivot mount  426 , and to retraction arm  420  at pivot point  428 . When ram  430  is actuated to retract, arm  420  is rotated forwards, pulling damper  404  forward and up. This in turn lifts arms  412  and thus the rear wheel  55  and trailing arm assembly until the rear wheel  55  is fully retracted. This movement is reversed for protraction of the wheel  55  when the amphibian  10  returns to land. 
     This mechanism is essentially a simplified version of the retractable suspension disclosed in the applicant&#39;s co-pending application published as US 2006/0234,567A1, and shares its advantages in that off-the-shelf coil springs and telescopic damper valves may be used to tune and adjust the ride and handling of the amphibian  10  as required. 
     Although a hydraulic ram is shown as the actuator for the retractable suspension, other actuators powered by compressed air or electricity could be used instead, as required. 
     It will be appreciated that the above wheel suspension and retraction assembly mechanisms described above are given by way of example only, and any suitable alternative may be beneficially employed. Alternative mechanisms which may be used or adapted for suspension and retraction are described the applicant&#39;s patents and patent applications, such as U.S. Re. 36,901; U.S. Pat. No. 6,886,83782; U.S. Pat. No. 6,945,832B2; U.S. Pat. No. 6,994,358B2; WO 04/039,613A1; U.S. Pat. No. 7,234,982B2; and US 2006/0,234,567A1, for example. 
     The powertrain components illustrated in  FIGS. 29 to 32 , i.e. the engine  80  and transmission are built up on a frame platform which is then connected to the hull  40 . This gives considerable advantage for ease of manufacture. Indeed it is envisaged that a chassis could be constructed with a frame supporting all of the wheel suspension components, the wheel steering mechanism, the wheel retraction mechanism, the engine and the transmission. This would considerably aid construction and repair. This is illustrated in  FIG. 29  where a rolling chassis of the amphibian can be seen stripped of the surrounding hull and deck sections. In  FIG. 29  there can be seen the engine, the transmission as well as the suspension assemblies for the front and rear wheels, all mounted to a common supporting structure. 
     A radiator (not shown) located at the front of the amphibian will cool the amphibian&#39;s engine, at least in land use. The amphibian&#39;s engine can also be cooled by a water/water heat exchanger (not shown) in marine use, with water being drawn from beneath the amphibian to cool water used by the engine cooling system. 
     Referring next to  FIGS. 33 to 36 , there is shown an amphibian  310  according to a third embodiment of the present invention. The amphibian  310  may include any or all of the features described above, in any combination, with the following particular features. 
     The amphibian  310  comprises a body  312  joined to a hull  314  at joint line  313 , hence being a buoyant vessel, having a pair of front wheels  320  and a single rear wheel  322 . It can be seen from  FIG. 36  in particular that hull  314  has a vee-shaped cross-section, to enable both planing and good handling on water. 
     The amphibian  310  includes a prime mover  316 , which may be an internal combustion engine or a similar power source, to provide power through a transmission  318  to the rear wheel  322 . Alternatively, the prime mover may power the front wheels  320  only, or may power the front wheels  320  and rear wheel  322 . 
     The front wheels  320  are connected to the body  312  by suspension  324 , and covered by mudguards  326 . These guards may be fixed to the body or to the wheel suspensions by brackets (not shown). The rear wheel  322  is connected to the body  312  by a trailing arm  328 , which provides suspension for the rear wheel. The trailing arm may be double-sided as shown, or single-sided. 
     The rear wheel  322  and front wheels  320  are retractable by means of retraction mechanisms. The retraction mechanisms for the front wheels may be as described in U.S. Pat. No. Re. 36,901, which is incorporated herein by reference. The front wheel retraction mechanisms acts on the suspension mechanisms to allow retraction and protraction of the wheels  320 . 
     The front wheel retraction mechanisms are operable to raise the front wheels  320  by rotation about axes substantially parallel to a longitudinal axis of the body. Such axes are substantially horizontal when the amphibian is level. The front wheels  320  are retractable above the waterline when the amphibian is in a water mode. 
     The rear wheel retraction mechanism is operable to raise the rear wheel  322  substantially vertically upwardly into the body  312 . The rear wheel  322  is retractable above the waterline when the amphibian is in a marine mode. One or more struts according to U.S. Pat. No. 6,886,837 B2 may be used to retract and protract arm  328 . 
     The front wheels  320  can be steered to provide amphibian steering. Amphibian steering is controlled by handlebars  334  linked to the front wheels  320 . Alternatively, the handlebars may be linked to the rear wheel  322 , or to both the front wheels  320  and rear wheel  322 . A seat  332  is located on the body  312  to support a rider of the amphibian  310 , in a position facing forwardly and within reach of the handlebars  334 . The seat  332  and body  312  allow the rider to sit along a central longitudinal axis of the amphibian  310 , with the rider&#39;s legs on either side of the body  312 . The driver is thus sitting astride the body. Preferably, the seat  332  is dimensioned to allow a passenger who can sit directly behind the driver on the seat  332 . The passenger would also sit centrally on the amphibian  310 , astride the body  312 . 
       FIGS. 33 and 34  show that the body  330  is provided with a front fender  336  at a front end of the amphibian, and a rear fender  338  at a rear end of the amphibian. Headlights  340  for use on land and marine lights  342  for use on water are provided at the front end of the amphibian. A combination tail light unit  348  is provided at the rear end of the amphibian. This may incorporate a CHMSL (Centre High Mounted Stop Light), where this is required by legislation. 
     Rear view mirrors  346  and a windscreen  344  are provided on the body  312 . Left and right footwells  350 ,  352  are provided on the body  312 , for the rider and passenger to rest their feet. The footwells have drains  354 . 
     With reference to  FIGS. 33 and 35 , a hull  314  is formed on the underside of the body  312 . The prime mover provides power to a marine propulsion unit. The marine propulsion unit may be a water jet unit  360 , or any other form of marine propulsion. The water jet unit  360  is preferably positioned on a central longitudinal axis of the amphibian  310 . The water jet unit  360  is preferably positioned forward of the rear wheel. The water jet unit has a jet intake  362 , for drawing water into the jet unit; a driveshaft  364  from transmission  318 ; an impeller section  366 ; and a jet nozzle  368 , through which water is expelled to provide propulsion. 
     At least one deflector  370  may be provided in order to divert accelerated water from the jet nozzle  368  away from the rear wheel  322  when the rear wheel is in a protracted position. This will occur when the amphibian first enters the water, when the water jet unit will provide propulsion and the rear wheel  322  is yet to be retracted. The deflectors  370  form a chevron shape in plan view with the apex facing the jet nozzle  368 , in order to divert water either side of the rear wheel  322 . 
     The deflectors  370  are located directly behind the jet nozzle  368 , and are attached to the trailing arm  328 . Hence, when the rear wheel  322  is fully retracted, the deflectors  370  are clear of water expelled from the jet nozzle  368 . Ducts  372  and  374  may be provided to deflect water rearwards. The exits from these ducts may be in the sides of the body, as shown, or more productively, in the transom. Alternatively, upstanding and substantially vertical walls (not shown) may be joined to the outer edges of trailing arm  328 , to deflect water rearwards along both sides of rear wheel  322 . 
       FIG. 34  shows the amphibian  310  in a marine mode. The front wheels  320  have been retracted by rotation above the waterline. The rear wheel  322  has also been retracted above the waterline. The wheels  320 ,  322  comprises tyres  376 ,  378  around their periphery. The front tyres  376  can act as fenders when the wheels are retracted, to absorb minor impacts to the amphibian on water. 
     The rear wheel  322  is not provided with any cover on an underside when retracted. The underside of the rear wheel  322  is therefore exposed to water in the retracted position. The front wheels  320  are similarly not provided with a cover, and so are exposed to water when the wheels  320  are retracted. 
     It may be found convenient for rear wheel  322  and tyre  378  to be exposed above the rear bodywork when retracted, as shown in  FIG. 34 . However, this requires a gap in the bodywork, which may give rise to excess spray on wet roads. 
       FIG. 36  shows a lid  380  which may be connected to trailing arm  328  by a linkage (not shown) to lift it out of the way as the wheel is retracted. Unlike the linkages described above with reference to prior art, this linkage could be very simple—possibly just a straight prop—and would be well above the water line, and thus relatively immune to the hazards of a marine environment. 
     Alternatively, a “mud flap” type spray guard (not shown) could be mounted to hull  314  near to rear fender  338 . This could be retracted automatically on water by a linkage to the trailing arm. In this case, however, the linkage may be partly located below the water line; and would therefore have to be designed carefully to ensure durability. 
     Area  382  behind seat  332  may be used to provide either an open, or a closed and waterproof storage area (not shown). It could also be used to provide a fuel filler neck and opening (not shown), depending on the location of the amphibian fuel tank (not shown). 
     A fourth embodiment of an amphibian  910  and powertrain according to the present invention will now described, with reference to  FIG. 37 . The amphibian  910  may include any or all of the features described above, in any combination, with the following particular features. 
     The amphibian  910  is a light weight version of the amphibian  310 , and is intended to carry one person, being the rider. The amphibian  910  comprises a body  930  being a buoyant vessel, and has two front wheels  920  and a single rear wheel  922 . The front wheels  920  and rear wheel  922  are retractable by means of retraction mechanisms (not shown). 
     The rider sits on a seat astride the body  930  of the amphibian  910 , with the rider&#39;s legs on either side at least part of the body  930 . The seat is aligned with a central longitudinal axis of the body  930 . The seat and body  930  may be configured to support only one person, i.e. the seat is dimensioned only to support the rider and not a passenger. 
     The amphibian  910  in a land mode may be front wheel drive only. The rear wheel  922  is not driven in the embodiment shown in  FIG. 37 . 
     In a water mode, a water jet unit  960  can propel the amphibian  910 . The water jet unit  960  has a jet intake for drawing water into the jet unit. The water is expelled from a jet nozzle to provide propulsion. The water jet unit  960  and/or nozzle may be spaced apart from a central longitudinal axis of the amphibian  910 . Alternatively, the water jet unit  960  and/or nozzle may be located on a central longitudinal axis of the amphibian  910 . 
     Alternatively, the water jet unit may have two nozzles located either side of the rear wheel. The two nozzles may be connected to a single water jet unit, or may be connected one each to two separate water jet units. 
     A prime mover  916  and transmission  918  are located between the front wheels and the rear wheel. Transmission  918  may be a continuously variable transmission (CVT). The prime mover  916  may be a transversely mounted internal combustion engine. Thus, the crankshaft axis extends sideways. The prime mover  916  is connected to the front wheels by a forwardly extending driveshaft  921  to a differential  923 , the differential  923  being linked to the wheels in a known manner. 
     The transmission  918  is connected to the water jet unit  960  by a jet driveshaft  961 . The jet driveshaft  961  extends rearwardly of the transmission  918 . Since the driveshaft  921  and jet driveshaft  961  extend in opposite directions, there is no interference between the two driveshafts. The driveshaft  921  and jet driveshaft  961  extend substantially parallel to the longitudinal axis of the body. This drivetrain arrangement thus offers packaging advantages, as it places the land drive train at the opposite end of the amphibian to the marine drive train, so that they do not conflict with each other spatially. 
     Front wheel drive may result in difficulties in leaving water on muddy banks, due to rearward weight transfer. However, the amphibian  110  may leave water on prepared, hard surface slipways. The front wheel drive brings an unexpected advantage, in that it offers a familiar “feel” to riders who have become accustomed to driven front wheels in road cars. 
     Pontoons  973  extend either side of the rear wheel  922 . The pontoons  973  are buoyant to improve the buoyancy of the amphibian. The water jet unit  960  may be located in one of the pontoons  973 . An output nozzle of the water jet unit may extend from one of the pontoons. In the embodiment of two nozzles, one nozzle may extend from each pontoon. The two nozzles may be connected to a single water jet unit. Alternatively, each nozzle may be connected to a separate water jet unit. One water jet unit may be located in each pontoon. 
     The water jet unit(s)  960  and/or output nozzle(s) may be located adjacent to the pontoon(s). 
     The water jet unit  960  may be located substantially alongside the rear wheel  922 . The water jet unit  960  extends substantially parallel to the plane of the rear wheel  922 . Alternatively, the water jet unit  960  may be located substantially ahead of the rear wheel  922 , or substantially rearward of the rear wheel  922 . 
     The wheels  920 ,  922  are connected to the body  930  by means of suspension (not shown). The suspension may be arranged to allow the body  930  to lean from side-to-side, i.e. about a longitudinal axis of the body. The body  930  can lean inwardly into corners in a similar manner to a conventional motorcycle. The ability of the body  930  to lean improves the cornering ability of the amphibian  910  on land. 
     The amphibian  910  may be provided with lights, a registration plate and any other means necessary to allow it to be road legal. 
     Referring next to  FIGS. 38 to 42B , there are shown amphibians  1001  according to fifth and sixth embodiments of the present invention. The amphibian  1001  may include any or all of the features described above, in any combination, with the following particular features. 
     Amphibians should be well-suited for transporting occupants on both land and water equally efficiently. However, it will be understood from the prior art that most amphibians are more suited for transporting occupants on either land or water, rather than both. 
     In order to provide good speed and manoeuvrability on land, suspension arms, drive shafts and wheels are often located at lower regions of the amphibian, often protruding directly from a hull section of the amphibian and/or parts of the amphibian that would be submerged during use on water. Further, even though retractable suspension has been described in the prior art, the suspension, drive shaft and/or wheel—in the retracted position—is often left exposed to water, when in use on water. Further, cut-out portions or other abnormalities to the shape of the hull may be provided in the hull section of the amphibian to accommodate the suspension apparatus, drive shaft or wheel, when the wheel is in either of the retracted or protracted, vehicle-supporting positions. The protracted position would be with the wheels in place for use of the amphibian on land. Whilst the prior art designs provide hulls that are buoyant and water-tight, a significant disadvantage is also found in that they often have cut-outs, abnormalities, and/or parts of the suspension apparatus, drive shaft or wheel that are submerged and/or simply contactable by water—even when retracted—in use of the amphibian on water. This clearly alters the hydrodynamics of the hull section of the amphibian, making the amphibian perform less-well on water—especially if the cut-outs, abnormalities, and/or parts of the suspension apparatus, drive shaft or wheel are located in the planing surface of the hull. In particular, large cut-outs for locating retracted wheels can have a great impact on the speed and manoeuvrability of the amphibian in use on water. For example, the amphibian may tend to “dig-in” at the back of an open wheel arch when turning on water. 
     The present invention addresses the above-mentioned disadvantages of the prior art. 
     The present invention provides, in a further aspect, an amphibian for use on land and water, comprising: 
     a hull having a planing surface which contacts water when the amphibian is planing on water; 
     at least one retractable suspension apparatus which is movable from a vehicle supporting position to a retracted position; wherein 
     the retractable suspension apparatus comprises for each wheel upper and lower suspension arms that are pivotably connected at inboard ends to a support structure within the hull and are pivotably connected at outboard ends with a suspension upright, the upper suspension arm being pivotably connected to the suspension upright by a first, upper pivot connection and the lower suspension arm being pivotably connected to the suspension upright by a second, lower pivot connection; 
     the suspension upright extends from the second connection, in a direction away from the first connection to a wheel hub mount location at which the wheel hub is rotatably mounted on the suspension upright at a location remote from the first and second pivot connections; 
     the suspension upright when deployed in land use extends externally of the hull across an outer face and/or a side face of the planing surface; and 
     the lower suspension arm remains above a top of the planing surface throughout use of the amphibian on land. 
     Preferably, the suspension arms extend from within the hull over an outer edge of the hull. 
     Most preferably, the wheel hub is located a distance from the second connection at least equivalent to the distance between first and second connections. Further, the hub may be located at least around 5 cm, 10 cm, 15 cm or 20 cm from the second connection. 
     Preferably, the wheel hub is rotatably mounted on the suspension upright at a distal end of the suspension upright. 
     The wheel hub is, preferably, driven to rotate by a transmission relaying drive from a prime mover of the amphibian. The transmission may have a step-down drive section in which drive is taken from a location at or above the lower pivot point and is relayed along or alongside the suspension upright to the driven wheel hub. 
     Alternatively, the wheel hub may be driven by a hub motor. Preferably, the hub motor is a hydraulic motor or an electric motor. 
     Most preferably, the hull is a vee hull. 
     The amphibian may comprise a spring and damper assembly connected between one of the suspension arms and the support structure. 
     Preferably, the amphibian comprises a retractable and extendable actuator operable to move the retractable suspension apparatus from the vehicle supporting position to the retracted position and vice versa. Further preferably, the actuator is also operable to vary ground clearance by varying the suspension height. 
     The support structure, preferably, comprises a rotatable support arm which is pivotally mounted at one end to a fixed part of the support structure and to which is pivotally connected the actuator, the actuator being pivotally connected at one end to the support arm and being pivotally connected at the other end to a fixed part of the support structure, a/the spring and damper assembly being pivotally connected at one end to the rotatable support arm and at the other end to the lower suspension arm. 
     According to a further aspect, the invention provides an amphibian for use on land and water, comprising: 
     a vehicle body comprising a hull section without cut-outs in a planing surface thereof, the planing surface for contacting water when in use on water; and 
     at least one retractable suspension apparatus which is movable from a vehicle-supporting position to a retracted position; 
     wherein, the at least one retractable suspension apparatus is connected to the vehicle body to locate the at least one retractable suspension apparatus externally of the hull section, in a vehicle-supporting position, and has an elongate suspension upright which extends from above the planing surface to a wheel mount location, such that no cut-out is required in the planing surface to accommodate the at least one retractable suspension apparatus in retracted and vehicle supporting positions. 
     Preferably, the at least one retractable suspension apparatus is connected to the vehicle body above the hull section, or above the planing surface. 
     Preferably, the planing surface is directly contactable with water, when in use on water. 
     Advantageously, the amphibian of the present invention substantially reduces, or removes totally, the necessity to have cut-outs, abnormalities, and/or parts of the suspension apparatus, drive shaft or wheel in the planing surface or that are submerged and/or simply contactable by water—even when retracted—in use of the amphibian on water. Accordingly, the hydrodynamics of the hull are improved. 
     An embodiment of the invention is provided by an amphibian for use on land and water, comprising at least one retractable suspension apparatus which is movable from a vehicle supporting position to a retracted position, the retractable suspension apparatus comprising, in a vehicle supporting position, upper and lower suspension arms operably-connected to a suspension upright, the suspension upright for receiving one or more wheels, wherein the suspension upright comprises a step-down drive for receiving an input drive from a relative higher location and providing an output drive to a relative lower location. The step-down drive may be integral with the suspension upright or may be provided in addition to the suspension upright. When the step-down drive is provided in addition to the suspension upright, the step-down-drive may be located alongside the suspension upright and operably-connected thereto. The step-down drive may be a geared apparatus, or a chain, a belt or a shaft driven apparatus. The retractable suspension apparatus may comprise a wishbone-type suspension. 
     A simplified view of part of an amphibian is shown in  FIG. 38 , in which the amphibian is, generally, indicated by reference  1001 . The amphibian  1001  includes a hull section  1002 , a vehicle body  1003  and a suspension apparatus  1004 , including a wheel  1005 . In this particular embodiment, the demarcation between the hull section  1002  and the vehicle body  1003  is shown by the dotted line indicated by reference  1006 . Most preferably, the hull  1002  provides a planing surface for contacting water when the amphibian  1001  is planing. The amphibian  1001  includes a regular hull  1002  having a ‘V’ (vee) shape, for aiding manoeuvrability. The vehicle body  1003  includes any feature of the amphibian which is not defined in relation to the hull section  1002  or the suspension apparatus  1004 . Accordingly, a suspension support structure  1011  is provided as part of the vehicle body  1003 , and is provided to receive parts of the suspension apparatus  1004 . The support structure  1011  may be directly connected to an internal surface of the hull  1002 . The support structure  1011  may also comprise part of a vehicle frame (not shown). Reference  1070  indicates a possible water level on the hull  1002 , below which portions of the hull  1002  form a planing surface. However, it will be understood by those skilled in the art that the size and shape of the planing surface depends upon, at least, the size of hull and the speed at which the amphibian  1001  is travelling on water. 
     As shown in  FIG. 38 , the suspension apparatus  1004  includes a suspension upright  1007 , also known as a king pin, and first and second lateral suspension arms  1008  and  1009 . The suspension upright  1007  is approximately transverse to the suspension arms  1008 ,  1009 , in a vertical plane. An upper lateral suspension arm  1008  is connected to the vehicle body  1003  at a first end, and to the suspension upright  1007  at a second end. Both connections are pivotal connections allowing the respective parts of the suspension apparatus  1004  to move. The lower suspension arm  1009  is also connected to the vehicle body  1003  and to the suspension upright  1007 . Again, the connections are pivotal connections, allowing respective movement of the suspension apparatus  1004 . By way of example, the suspension apparatus  1004  can move in a vertical plane to the ground and a horizontal plane to the ground, as shown by arrows indicated by references  1013  and  1014 , respectively, when moving between vehicle supporting and retracted positions of the apparatus  1004 . As can be seen from  FIG. 1 , the suspension upright  1007  includes an extended suspension upright  1007 A which extends from the connection of the lower lateral suspension arm  1009  in an opposite direction to the upper lateral suspension arm  1008 . A hub  1010  for receiving a wheel  1005  is located at or around a distal end of the extended suspension upright  1007 A, in a location that is remote from the suspension arm connections. Advantageously, provision of an extended suspension upright  1007 A allows the suspension apparatus  1004  to be connected to the amphibian  1001 , such that, no cut-out is required in the submerged surface—or planing surface—to accommodate the at least one retractable suspension apparatus in retracted or in vehicle supporting positions. 
     As can be seen from  FIG. 38 , the suspension upright  1007 , when deployed in land use, extends externally of the hull  1002  across an outer face  1002 A and/or a side face  1002 A of the planing surface. 
       FIGS. 39 and 40  show a sixth embodiment of amphibian according to the present invention. Like reference numerals have been used to identify common features with the fifth embodiment, which features will not be discussed further here in detail. In particular, the differences between these two embodiments will be described. 
     The amphibian  1001  includes a hull  1002 , a vehicle body  1003 , a suspension apparatus  1004  and a wheel  1005 . Also provided are a suspension support structure  1011 —which is connected directly with the vehicle body  1003 —and a steering apparatus  1012 . 
     The suspension apparatus  1004  comprises a suspension upright  1020 , also known as a king pin, an upper lateral suspension arm  1021  and a lower lateral suspension arm  1022 . In particular, the upper and lower lateral suspension arms  1021 ,  1022  are wishbone-type suspension arms. The upper suspension arm  1021  is operably-connected to the suspension upright  1020  at a relative upper region of the suspension upright, when compared to the relative lower connection of the lateral suspension arm  1022  and the suspension upright  1020 . Accordingly, an upper pivotal connection  1023  is provided between the upper suspension arm  1021  and the suspension upright  1020 . Further, a lower pivotal connection  1024  is provided between the lower suspension arm  1022  and the suspension upright  1020 . At opposed ends of the suspension arms  1021 ,  1022 , one or more pivotal connections  1025  is/are provided between the upper suspension arm  1021  and an upper part of the support structure  1011  and one or more pivotal connections  1026  (and/or  1033 ) is/are provided between the lower suspension arm  1022  and a lower part of the support structure  1011 . An anti-roll bar  1027  is also provided to link the suspension apparatus  1004  to a second suspension apparatus (not shown) which would be located opposite the first apparatus  1004 . 
     As shown in  FIG. 40 , in particular, the suspension apparatus  1004  includes a retraction ram  1028 , for moving the suspension apparatus  1004 —and wheel  1005 —from the vehicle-supporting position to the retracted position. By way of example,  FIG. 39  shows the suspension apparatus  1004  and wheel  1005  in a vehicle-supporting position. Further,  FIG. 40  shows the suspension apparatus  1004  and wheel  1005  in a retracted position. A first, upper end of the retraction ram  1028  is connected to an arm  1030 , which forms part of the support structure  1011 . The second, lower end is connected to the vehicle body  1003 . 
     Also, as shown in  FIG. 40  in particular, a damper and spring assembly  1029  is provided to allow the upper and lower suspension arms  1021 ,  1022  and suspension upright  1020  to operate as a conventional suspension. A first end of the damper and spring assembly  1029  is connected to the arm  1030  and the second end of the damper and spring assembly  1029  is connected to the lower suspension arm  1022 . The arm  1030  is pivoted at an opposite end to the connections with the retraction ram  1028  and the damper and spring assembly  1029 , and provides a pivot point  1033 , which is common with at least one of the pivotal connections  1026 , around which the wheel  1005  and parts of the suspension apparatus  1004  can rotate between vehicle supporting and retracted positions. 
     In order to allow the suspension apparatus  1004  to move from a vehicle-supporting position to a retracted position, both the upper and lower suspension arms  1021 ,  1022  are provided with a pivot point along their length, to allow the suspension arms  1021 ,  1022  to be moved between retracted and protracted positions. The upper suspension arm is pivotal around the pivot point(s)  1025 , provided at the junction of the suspension arm  1021  and the support structure  1011 . The lower suspension arm  1022  is pivotal around pivot point(s)  1026 ,  1033 , provided at the junction of the lower suspension arm  1022  and the support structure  1011 . In particular, a part of the lower suspension arm  1022  is rigidly connected with the arm  1030  so that they are movable together. Further, a drop link  1031  is provided between the anti-roll bar  1027  and the lower suspension arm  1022 , to provide increased rigidity and strength. 
       FIG. 40  shows, in particular, outer faces  1002 A and/or side faces  1002 A of the planing surface across which the suspension upright  1020  extends, when deployed for land use. The suspension apparatus of  FIGS. 39 and 40  show a front-wheel only of an amphibian  1001 . However, the suspension apparatus  1004  may be used on any of the wheels of an amphibian  1001 . In particular, although the amphibian  1001  shown in  FIGS. 39 and 40  has no drive going to the wheel  1005 , the wheel  1005  may be a driven wheel. Further, in order to drive that wheel  1005 , a step-down drive (not shown) may be provided as an integral structure with the suspension upright or in addition to the suspension upright. As known by those skilled in the art, a step-down drive is capable of receiving an input drive from a relative higher location and producing an output drive to a relative lower location. Alternatively, the wheel hub  1010  may include one or more hydraulic motors (not shown), or one or more electric motors or electric hubs (not shown). 
     By way of an alternative, the retraction ram  1028  or the damper and spring assembly  1029  may be manually adjusted for varying the ground clearance of the amphibian  1001 . 
     Although the suspension apparatus  1004  shown in  FIGS. 39 and 40  is drive-less, that suspension apparatus  1004  includes apparatus  1012  used for steering the amphibian  1001 . The steering apparatus  1012  includes an arm  1036  which is operably connected, at connection  1032 , to the suspension upright  1020  in a mid-region of the suspension upright  1020 , preferably between the connections  1023  and  1024 . The other end of the arm  1031  is connected to input steering means, for example, handle bars or a steering wheel (not shown). 
       FIGS. 38, 39 and 40  show only one suspension apparatus  1004  and wheel  1005  attached to the vehicle body  1003 . However, it will be understood that any number of wheels could be used, in particular  3  wheels, and an appropriate number of suspension apparatuses  1004 . Further, the wheels  1005  may be driven or drive-less. 
       FIG. 41A  shows an embodiment of the present invention which is similar to that shown in  FIG. 38 . Accordingly, like references have been utilised for common features and only the differences will be discussed. In particular, the suspension upright  1007  and extended suspension upright  1007 A include a step-down drive  1060 . As shown in  FIG. 41B  in particular, the step-down drive includes an upper input end  1061  and a lower output end  1062 , when the suspension apparatus  1004  is in its vehicle-supporting position. A cog  1063  is provided at each end  1061 ,  1062  and is linked by a chain  1064 , so that when either cog  1064  is moved, corresponding rotation of the other cog  1063  is provided. The cog  1063  at the input end  1061  is driven by a shaft  1065 , itself driven directly or indirectly by a prime mover, as exemplified by an engine  1066 . One or more universal joints  1067  or equivalents are used to connect the engine  1066 , shaft  1065  and cog  1063 . The cog  1063  at the output end  1062  drives the wheel hub  1010  and the wheel  1005 . Accordingly, an input drive from a prime mover is stepped-down to a lower height with respect to the ground the amphibian is standing on to drive one or more wheels. 
       FIG. 42A  shows a hull of an amphibian according to the present invention. The hull is shaped to provide good hydro-dynamics. Further, no cut-out or other abnormalities, and/or parts of the suspension apparatus, drive shaft or wheel would be submerged and/or contactable by water, when the amphibian has the suspension apparatus  1004  retracted, for use on water. By contrast,  FIG. 42B  shows a hull of an amphibian in which cut-outs  1050  are provided to locate the suspension apparatuses and/or wheels in a retracted position thereof. Accordingly, a hull shown in  FIG. 42A  has better hydro-dynamics than a hull shown in  FIG. 42B . 
     Referring next to  FIG. 43 , there is shown an amphibian  1110  according to a seventh embodiment of the present invention. The amphibian  1110  may include any or all of the features described above, in any combination, with the following particular features. 
     A number of suspension layouts for amphibians have been proposed. Such suspension layouts allow sprung and damped movement of the wheels when the amphibian is on land, and retraction of the wheels for use of the vehicle on water. The suspension is generally inboard of the wheel, for example as known from US 2005/0034646 to Royle. This has the disadvantage that the width of the hull between the wheels is restricted for a given width of the amphibian, as at least a lower suspension arm must project through the plane of the hull to support the wheel in protracted land mode. Space must also be allowed for suspension rebound travel. An example of this restriction may be seen from the applicant&#39;s co-pending application published as US 2007/0,006,788 A1. 
     The present invention provides an amphibian according to claim  149 . Thus, the width of the hull is not restricted by the suspension. 
       FIG. 43  shows an amphibian  1110  according to the present invention. The amphibian  1110  comprises a hull  1112  being a buoyant vessel, and having a pair of rear wheels  1120  in close proximity (i.e. adjacent to each other) arranged as effectively one wheel. The closely spaced pair of wheels are located on the central longitudinal axis of the amphibian. 
     The hull  1112  is V-shaped in vertical cross-section. The amphibian  1110  also has two or more front wheels (not shown). 
     The amphibian  1110  includes a motor (not shown) or a similar power source to provide power through a transmission to the rear wheels  1120 . Alternatively, the motor may power the front wheels only, or may power the front wheels and rear wheels. 
     The rear wheels  1120  are connected to the hull  1112  by a suspension assembly  1122 . The suspension assembly  1122  comprises a pair of trailing arms  1124 , extending rearwardly from the hull  1112 . The trailing arms are rotatably connected to a chassis of the vehicle (within and supporting the hull  1112 ) at pivots (not shown). 
     The rear wheels  1120  are rotatably mounted to inboard sides of the trailing arms  1124 , each wheel rotating about its own axis. The wheels  1120  are rotatably mounted to distal ends of the arms  1124 , distal to the pivots, by mounts  1126 . The mounts  1126  allow rotation of the wheels  1122  about their common rotational axis X-X. The mounts  1126  are compliantly secured on trailing arms  1124  and allow relative movement between the wheels  1120  and arms  1124  about a substantially horizontal axis, parallel to a longitudinal axis of the hull, in order to allow the hull  1112  to roll in use on land, but to maintain good tyre contact with the ground. Although tyres of a substantially square tread cross-section are shown in the figures, tyres of a more rounded cross-section as used on motorcycles, may be used instead. The mounts  1126  may each comprise a ball joint. 
     The two rear wheels  1120  are preferably connected by an axle (not shown). The axle assists in keeping the wheels  1120  parallel. Alternatively, the pair of wheels may not be connected by an axle. 
     Each trailing arm  1124  is spring-mounted to the vehicle, preferably by torsion bars (not shown) provided at or adjacent to the pivots. A separate torsion bar is preferably provided for each arm  1124 . The torsion bars extend laterally towards the centre of the hull  1112 . 
     The wheels  1120  may be driven via a shaft acting through a differential (not shown) in the axle. The differential may be in the centre of the axle, or may be offset to one side. 
     Alternatively, the wheels  1122  may each be driven by a belt or a chain. The belt or chain may be located partially or wholly inside one or each arm  1124 . Alternatively, a driven toothed wheel or sprocket may be provided at the centre of axle. 
     The amphibian  1110  may be powered on water by one or more jet drives  1140 . The or each jet drive has one or more jet nozzles through which water is expelled to provide propulsion. The jet nozzles may be located between the wheels  1120 . 
     The suspension  1122  is provided with a retraction mechanism, in order to retract the wheels  1120  for use of the amphibian  1110  on water. The retraction mechanism may comprise cranked torsion bars (not shown). Each torsion bar comprises an aligned portion substantially aligned with the pivots, and defining a rotational axis of the torsion bar. 
     Each torsion bar further comprises a cranked portion perpendicular to the axis of the torsion bar. The cranked portion is at or near an inboard end of each torsion bar. 
     An actuator may be attached to each cranked portion. Contraction or extension of the actuators can be used to control retraction or deployment of the wheels  1120 . Alternatively, a single actuator may be connected to a cranked portion of the torsion bars of both of the pair of wheels  1120  (the single actuator could act on a bar connecting the cranked portions). 
     Preferably, each arm is connected to its own laterally outwardly extending bar, each outwardly extending bar having a cranked portion, the two cranked portions connected by a connecting strut extending laterally. 
     Alternatively, the retraction mechanism may be in the form of one or more hydraulic struts (not shown). The hydraulic struts may be connected between the arms  1124  or axle and the hull  1112 . The hydraulic struts may act both as dampers and also as hydraulic actuators to retract and deploy the wheels. Suitable hydraulic struts are known from publication US 2003/0047899. 
     The hull  1112  has recesses  1136 , for receiving the arms  1124 . The recesses  1136  are shaped to allow retraction of the wheels. 
     In a retracted position, the wheels  1120  may be within the length of the hull  1112 . The hull  1112  extends over and beyond the wheels  1120  in their retracted position. This location of the wheels improves spray control when the amphibian is planing on water, and the wheels are in the retracted position. 
     The above description relates to the use of the suspension assembly  1122  on rear wheels of an amphibian. Alternatively, the same or similar suspension assembly  1122  may be used for the front wheels of an amphibian. The arms  1124  may extend rearwardly and support front wheels as described above. Alternatively, the arms  1124  may extend forwardly, such that the supported front wheels are forward of the pivots. The rear wheels  1120  may be supported on forwardly extending arms. The features described above would be the same or reversed as would be clear to a person skilled in the art. 
     The amphibian may have a total of three wheels, in the form of a pair of front wheels and a single rear wheel. The amphibian may have four wheels, being a front pair of wheels and a rear pair of wheels provided adjacent one another in close proximity. One or both of the front and rear pair of wheels may have a suspension assembly as described. The amphibian may have more than four wheels, for example, the amphibian may have six wheels (e.g. three pairs of two wheels). 
     Referring next to  FIGS. 44 and 45 , there is shown an amphibian  1210  according to an eighth embodiment of the present invention. The amphibian  1210  may include any or all of the features described above, in any combination, with the following particular features. 
     Amphibians have been proposed and produced in various formats. Although amphibian bicycles have been proposed, the smallest engine driven amphibians have been motorcycles. Lehrberger (DE 19831324C2), Gong (U.S. Pat. No. 6,540,569), and Buchanan (GB 2,254,831) all disclose designs for amphibian motorcycles. But none of these designs have been manufactured or sold. There is clearly room for improvement over this prior art. 
     Amphibians are dual purpose vehicles, and must therefore be equally usable on land as they are on water. Different classes of vehicle generate different expectations in the potential buyer&#39;s mind. Motorcycles are generally sold on a sleek image, with an implicit promise of fast acceleration and fast, steeply leaning cornering. The three machines described above, however, are heavy, wide, and bulbous in shape. 
     The addition to a motorcycle of equipment needed for travel on water leads to a large increase in weight; particularly where twin marine jet drives are used. The casings of these jets are usually castings; which makes them very heavy. This weight will blunt performance on road, and reduce roadholding capability on corners. The width of the motorcycle must also be increased compared to the convention for a purely road machine, to provide both buoyancy and stability on water. But this increased width limits the angle through which the machine can be leaned on corners on road. The additional weight and width will make the motorcycle feel cumbersome on road. If the machine falls over, either due to a skid or through impact when parked, it will be very difficult to return it to the upright riding position. It is clearly preferable for a vehicle which is too heavy to be lifted by the rider to be self-stable. Finally, the bloated appearance of an amphibious motorcycle&#39;s bulbous bodywork will limit its market appeal. 
     It is necessary, therefore, is to address these problems with an amphibian which will provide adequate performance on water without unacceptable compromises in use on land. Implicit in this equation is the avoidance of a mismatch between expectation and delivery. If at the same time, the utility of the amphibian is increased, a still more attractive package may be developed. 
     The use of twin jet drives in amphibians is known, not least from the prior art cited above. The advantage of twin jets is that the amphibian can rise rapidly onto the plane on water—perhaps one or two seconds faster than an equivalent machine with a single jet drive. The drawbacks of twin jets are in the weight of the driveline, cost, and packaging; and a reduction in top speed on water due to the increased pumping losses through the additional jet drive. The top speed might, for example, be reduced by four knots for a compact amphibian. 
     So the choice of single or twin jets is not a matter of either doing the same job as well as the other; but a more conscious decision based on the market sector at which the amphibian is aimed. The ultimate high performance amphibian will use a single jet drive, but may be regarded as more difficult to ride; but a twin jet machine will be easier to ride, less ultimately fast but more relaxing. Although twin jets may be assumed to be heavier than a single jet drive, the applicant has established a surprising result occurs when comparing the two layouts. To provide equivalent performance from twin jets as from one jet, the twin jets will be specified as being of smaller diameter than the equivalent single jet. This reduces the tip speed of the jet blades compared to the single jet drive; which makes the twin jets less liable to cavitation at speed. It is also found that as forces at the tips of the blades go up as the square of the rotational speed, a smaller jet can be built more lightly than a single jet, because it is of smaller diameter. Hence, twin jets may in themselves be lighter than a single jet drive; and may still be lighter overall, even when a more complex transmission is necessarily specified than for a single jet drive. 
     Other options to consider in managing the customer&#39;s expectations would include performance available on land. One option here is to offer less power on land than on water, as described in the applicant&#39;s U.S. Pat. No. 7,207,851B1. Another option in managing expectations is to amend the layout of the vehicle; particularly in making it more stable than a motorcycle by providing more wheels. This in turn would also increase the carrying capacity of the vehicle, both in volume and in weight. So the overall package would move away from ultimate performance towards utility. It is considered that the market for ultimate performance amphibians is small—as for “supercars” on road; but greater market success can be obtained with a slightly slower, but much more usable, amphibian. 
     It is considered that a combination of three wheel stations  1220 ,  1222 ,  1224  with twin jet marine drives  1230 ,  1232  (each having an intake  1234  and outlet  1236 ) provides an ideal combination of accessible marine performance, failsafe road stability, and carrying capacity. Front and rear retractable wheel suspension assemblies  1260 ,  1280  are provided. These characteristics may be combined with ride on seating  1240 , which provides best visibility in all directions; and being aligned with the longitudinal centre line X-X of the amphibian  1210 , gives good lateral weight distribution, even when there is only the rider on the amphibian. 
     The increase in load carrying area brought about by the increase in the number of wheels is considered to be more than adequate compensation for the concomitant increase in amphibian weight. Where three wheels are used, the use of two front wheels offers good stability on road, while twin jet drives  1230 ,  1232  can be easily packaged either side of the single rear wheel. This is in contrast to U.S. Pat. No. 5,690,046 to Grzech, where the single front wheel requires complex retraction arrangements and the twin rear wheels only allow use of a single jet drive. 
     Referring now to  FIGS. 1 to 4  and  FIG. 6 , amphibian  10  can be seen to comprise a longitudinal axis L-L running from a front bow end  12  to a rear stern end  14  of the amphibian  10 , which longitudinal axis can be any longitudinal axis spaced laterally or vertically, as indicated by the arrows. Indeed the longitudinal axis may lie in or out of the horizontal plane of the amphibian, i.e. may be inclined to the horizontal. In addition, amphibian  10  can be seen to comprise a transverse axis T-T running from a left port side to a right starboard side of the amphibian  10 , which transverse axis can be any transverse axis spaced laterally or vertically, as indicated by the arrows. Indeed the transverse axis may lie in or out of the horizontal plane of the amphibian, i.e. may be inclined to the horizontal. 
     The amphibian can be seen to comprise at least three retractable wheels  51 ,  53 ,  55 , at least two of the retractable wheels  51 ,  53  being retractable about an axis substantially parallel to, or offset by an angle α of up to 40 degrees from, the longitudinal axis L-L of the amphibian  10 . At least one of the retractable wheels, the third retractable wheel  55  is retractable about an axis substantially parallel to, or offset by an angle β of up to 40 degrees from, a transverse axis T-T of the amphibian. 
     Preferably the angle α is any angle in the range of from 0 degrees to 40 degrees, more preferably from 0 degrees to 30 degrees, even more preferably from 0 degrees to 20 degrees, and preferably from 0 degrees to 15 degrees. Preferably the angle β is any angle in the range of from 0 degrees to 40 degrees, more preferably from 0 degrees to 30 degrees, even more preferably from 0 degrees to 20 degrees, and preferably from 0 degrees to 15 degrees. 
     It will be appreciated that the axis of wheel retraction parallel to, or offset from, the longitudinal axis L-L of the amphibian may spaced laterally or vertically from the longitudinal axis L-L. Similarly, the axis of retraction parallel to, or offset from, the transverse axis T-T of the amphibian may be spaced laterally or vertically from the transverse axis T-T. 
     Although several embodiments of amphibian have been described above, any one or more or all of the features described (and/or claimed in the appended claims) may be provided in isolation or in various combinations in any of the embodiments. As such, any one or more these features may be removed, substituted and/or added to any of the feature combinations described and/or claimed. For the avoidance of doubt, any of the features of any embodiment may be combined with any other feature from any of the embodiments. 
     Whilst in certain of the above embodiments a single internal combustion engine is used to both drive a road wheel in land mode operation and also to power the jet drive(s) in marine mode, separate engines could be provided, one for the road wheel(s) and another for the jet drive(s). Indeed, the engines may not be internal combustion engines, but may instead take the form of any primer mover (electric, hydraulic, pneumatic, hybrid, or otherwise, as required). Also the jet drive(s) could be replaced by a propeller(s) or any other marine propulsion means. 
     It will be appreciated that the present invention is not limited to handlebar steering; a steering wheel may be beneficially employed. Amphibians according to the present invention may be rear wheel drive, front wheel drive or all wheel drive. Indeed, the amphibians may be one wheel drive, two wheel drive or three wheel drive. To supplement the three wheel configuration of the present invention, stabilising devices may be beneficially employed. One form of stabilising device may take the form of two wheels or skids provided in the rear half of the amphibian, preferably spaced laterally from the longitudinal centre line of the amphibian. These stabilising devices may be retractable and deployed only in certain operating conditions (e.g. when learning to operate the amphibian for the first time). 
     Whilst preferred embodiments of the present invention have been described above and illustrated in the drawings, these are by way of example only and non-limiting. It will be appreciated by those skilled in the art that many alternatives are possible within the ambit of the invention, as set out in the appended claims.