US 3205852 A
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Description (OCR text may contain errors)
Sept. 14, 1965 B. M. SHEPARD CONVEYOR BOTTOM BOAT Filed Dec. 17, 1964 INVENTOR Berger M. Shepard BY M ATTORNEY 1 a k m m ZGENT the vessel and the water at high speeds. :vehicles roll forward over the water, although this is not zontally as possible.
optimum conditions. :from the floating to the planing conditions, the prior the belt at this point.
United States Patent 3,205,352 CONVEYOR BGTTOM BOAT Berger M. Shepard, 10409 Naglee Road,
Silver Spring, Md. 7 Filed Dec. 17, 1964, Ser. No. 419,252 6 Claims. (Cl. 115-63) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
This invention relates to the art of marine propulsion. More particularly, the invention relates to a boat or vehicle designed for traveling on water at a high rate of speed, the vehicle being supported when under way on a runner belt or endless track which extends under the hull and provides the propelling force as well as support therefor.
The present invention is an improvement in vehicles of this type and particularly in those of the type disclosed by Heroult in U.S. Patent No. 855,510, issued June 4, 1907 or MacCallum, U.S. Patent No. 1,545,342, issued July 7, 1925. As disclosed in these patents, a boat of the type here under consideration consists of a hull capable of sustaining the weight of the vessel by ordinary displacement when at rest, and a broad endless track extending beneath the hull. The endless track is supported by suitable rollers disposed in a transverse direction, and serves to spread the load to insure that, because of the inertia of the water, the vehicle will rise up onto the surface of the Water when it is under way. The main advantage of thebelt is to minimize the effect of skin friction between In effect, these strictly true in practice since the belt must actually travel backward with respect to the water.
There are two fundamental problems in the construction and operation ofa vehicle of this type. First, in order to provide maximum lift and thrust and minimum drag at all speeds of the boat, including the low speeds where support is partially by displacement and partially by the inertia effect of the water, it is necessary that the belt enter and travel through the water as nearly hori- In the prior art structures, the forward belt supporting roller Will be at least partially submerged when the boat is at rest and, in the planing condition, will become tangent to the water surface only under Accordingly, during the transition structures exhibit substantial drag.
Even after the planing condition is reached in the prior boats, they still do not operate satisfactorily, since their structure is fixed and inflexible. The angle of attack 'of vehicles of this type increases to a maximum as the 'vehicle starts out and decreases thereafter to a value proportional to the square of the velocity. The prior structures, being fixed, cannot compensate for this variation. Y
The second problem encountered in the art is in preventing the water from clinging to the belt at the rear of the vehicle and introducing an additional drag factor because of the surface contact energy between the water and Heroult suggests the use of passages through the belt through which air may pass to break the suction. This solution is not satisfactory, however, since an unnecessarily complicated belt is required. Note that flaps must be provided to close the openings when the belt is in contact with the water.
Accordingly, it is an object of this invention to provide a high speed, endless-track water vehicle having 3,25,352 Patented Sept. 14, 1965 means to vary the angle of entrance of the track into contact with the water, whereby one of the problems of the prior art structures is obviated.
It is another object of the invention to provide an endless-track water Vehicle in which improved means are provided for freeing the track from the adhesion of the water at the stern.
The objects of the invention are accomplished by providing a structure in which the forward roller for the belt, which may also serve as the drive roller, has its axis positioned so that the roller is above the surface of water in substantially all stages of the boats operation. The drive roller axis is also positioned substantially forward of the first of the main supporting roller of the belt, and between these two rollers, an adjusting roller is provided which is movable in a substantially vertical direction to vary the entrance angle of the belt.
At the rear of the vessel, the belt passes over a relatively small roller and extends back toward the front of the vessel at the top of the main supporting rollers, while remaining under the hull. The relatively small diameter of the rear roller has the advantage of providing a high centrifugal force on the water clinging to the belt, thereby breaking the adhesion between the water and the belt.
Other objects, advantages and new features of the present invention will become apparent from a reading of the following detailed description when taken with the accompanying drawings wherein:
FIGURE 1 is a side view, partially in section, of the boat of the present invention;
FIGURE 2 is a diagrammatic showing of the configuration of the belt while the vehicle is under way; and
FIGURE 3 is a front view of the vehicle.
Referring now to FIGURE 1, the vehicle or boat according to the invention is generally indicated at 10. Boat 10 consists of the hull 11 which, in the illustrated embodiment, is of conventional open-top construction. The boat may be provided with a suitable windshield 12.
In order to support the boat 10 on the surface of the water in the manner described above, the hull is provided with suitable supporting structure for the endless track or belt 13. This supporting structure comprises a plurality of supporting rollers 14 which extend transversely under the hull and are about as long as the hull is Wide. Each of the supporting rollers 14 is journaled for rotation in a journal block 16 guided for vertical sliding movement in a channeled frame 17 which is rigidly attached to the hull 11. Heavy, shock absorbing coil springs 18 are provided within the channel frames 17 and hear at one end on the journal block 16 and at the other end against the fixed portion of the hull. The springs 18 perform the dual functions of providing for shock absorption when the vehicle is traversing rough water and to allow the rollers and the belt to assume a curved relationship with respect to the water as indicated in FIGURE 2, which curve is the natural affect of the hydraulic forces on the belt when the boat is under Way. The belt will also be forced into a concave form between each of the supporting rollers, but this effect is not shown.
All the supporting rollers are of relatively small diameter. At the stern, this small radius provides the high centrifugal force which serves to break the adhesion of the water to the belt. A blade 38 supported from hull 11 by means of a suitable bracket 39 may also be provided here to prevent the belt from carrying water forward on its return trip above the rollers. This blade will be very effective at slow speeds when the centrifugal force of the back roller is low.
At the bow, the belt 13 passes over a transversely disposed drive roller 19. Drive roller 19 is of substantially larger diameter than the other rollers in order to provide a large bearing area between belt 13 and the roller to prevent or minimize slip. Drive roller 19 has a shaft 20 which is journaled in the depending support portions 21 of hull 11. As stated above, the vertical posltion of the axis of this roller is chosen to place the roller itself above the surface of the water at all stages of the boats operation. On the outboard end of shaft 20 is a drive pulley 22, which receives driving power from a belt or chain 23, in turn from a sprocket 24. It will be understood that a suitable power source, such as an internal combustion engine, is contained within hull 11 and serves to drive sprocket 24.
As indicated above provision is made for varying the angle of entry of the belt 13 into the water. This function is served by a transversely disposed adjustable roller 26 which is supported in depending relation from hull 11 by means of a lever 27. Lever 27 has a first leg 28, roller 26 being journaled in one end thereof as shown and a second roller 29 for tensioning the belt being attached to the opposite end thereof. Belt tensioning roller 29 i journaled, in a manner similar to the main supporting rollers, in a channeled frame 30 fixedly attached to leg 28 of lever 27. Extending upwardly from leg 28 is a leg 31 which is journaled at 32 in hull 11. Connected to the free upper end of leg 31 is a hydraulic motor assembly 33 fixed at 34 to hull 11 and responsive to suitable controls within the hull to adjust the position of rollers 26 and 29. This construction automatically compensates for the increase and decrease in the length of belt travel between the drive roller and supporting rollers when roller 26 is adjusted. It will be understood that similar structure is provided on the opposite side of the hull and acts simultaneously with the adjusting structure on the side shown. A suitable fender or protective cover 36 may be provided to protect the mechanism.
Steering may be accomplished by means of a rudder 37 at the stern, controlled by suitable means within the hull 11. Alternatively, and especially if the vehicle is intended to be used as an amphibious vehicle, a use to which it is well adapted, the single track shown may be separated into two tracks by providing a double roller assembly, additional tension and position controlling means, and a separate drive means for each of the two tracks so that the device may be steered in the manner of a conventional endless-track land vehicle.
FIGURE 2 has been provided to aid in the explanation of the operation of the present invention. This figure shows the configuration adopted by the belt and roller when the vehicle is under way and in the planing condition. The problem of the entrance of the belt into contact with the water is illustrated in FIGURE 2 by the vector diagram under the first of the main supporting rollers for the belt. This is intended to be the point of entrance of the belt into contact with the water when the boat is planing at a certain speed. Vector R is the normal to the belt at the point of entry with the water. Vector R is the projection of R on the vertical and is representative of the lift provided by the reaction of the belt with the water at this point. R is the projection of R on the horizontal, the drag component. It should be readily apparent that in order to provide maximum lift and minimum drag, which would be the optimum conditions of operation, R should be made as close to vertical as possible, thus minimizing R and maximizing R Heroult states in the above identified patent that the more use of the belt supporting system is sufiicient to provide a solution to this problem, stating that with the belt support there is substantially no depression of the forward roller into the water and that the forward roller may therefore be of quite small radius. This may be true after the planing condition has been established, but at low speeds the forward roller in Heroult will be at least partially submerged. Thus, a very large forward roller is indicated in order to minimize the effect of partial immersion of the roller. A large roller, however, is difficult to fabricate and difiicult to support and operate. Applicants structure provides the effect of a large roller, while efiiciently utilizing the space at the forward portion of the boat.
When the boat is at rest in the water, drive roller 19 is quite close to the water surface and the lower portion of the belt will lie under the surface. At this time adjusting roller 26 is raised to its uppermost position to reduce the angle between that portion of the belt between drive roller 19 and the adjustable roller 26, this being the portion which first engages the water. As the speed increases, the boat rises and the initial line of contact with the water moves backward along the belt until it lies somewhere along that portion of the belt between the adjustable roller 26 and the first of the main supporting rollers 14. As the boat rises, the water above the lower portion of the belt spills out the sides. Roller 26 is now lowered to improve the angle between the belt and the water under these new conditions. The belt adjustment must also take into account the angle of attack of the vehicle, since this varies withspeed as noted above. In this manner, the optimum entrance angle is provided at all times.
Thrust is provided by the boundary layer effect due to the adhesion between the belt and the water at the beltwater interface. The vehicle is operative with a smooth belt, but a rough belt or a belt provided with transverse ribs or grooves as suggested by Heroult or MacCallum would probably be more effective. An auxiliary outboard propeller drive might be used to assist in getting the boat into the planing condition.
It should be apparent from the foregoing that a construction for an endless belt vehicle has been described which provides distinct advantages over the prior art. A useful solution to the belt entrance problem has been provided as well as an eflicient alternative to the problem of freeing the belt from the adhesion of the water at the stern. Moreover, the boat may be made amphibious, with obvious military applications.
Obviously there are modifications and variations which may be made by those skilled in the art. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than is herein specifically described.
What is claimed is:
1. A boat of the class described comprising a hull capable of floating said boat by displacement,
endless track means disposed under said hull for supporting said hull completely above the surface of the water when under way,
and means for varying the angle of entrance of the track means into contact with the water.
2. A boat as recited in claim 1 wherein said endless track means comprises a runner belt,
a plurality of rollers for supporting said belt, said rollers being connected to said hull and journaled for rotation about axes extending transversely under said hull,
a drive roller in contact with said belt and driven by an englne Within said hull, the axis of said drive roller being parallel to the axes of said supporting rollers, positioned substantially above the surface of the water and substantially forward of the forwardmost of said supporting rollers.
3. A boat as recited in claim 2 wherein said means for varying the angle of contact of the track means with the water comprises a roller coupled to said hull for adjustable movement substantially vertically with respect to the water surface, said roller contacting said belt at a point between the drive roller and said forwardmost supporting roller and movable to vary the angle between that portion of the belt extending between said adjustable roller and said forwardmost supporting roller and that portion thereof extending rearwardly from said forwardmost supporting roller.
4. A boat as recited in claim 3 wherein said adjustable roller is pivotally mounted on said hull, the structure of the pivotal mounting comprising a lever pivotally attached to said hull, said adjustable roller being journaled at one free end of said lever, and
a hydraulic motor connected to said lever for controlling the position of said adjustable roller.
5. A boat as recited in claim, 4 wherein a belt tensioning roller is provided,
said lever having a leg extending rearwardly and up' wardly from said adjustable roller to the opposite side of the return portion of the belt,
said belt tensioning roller being yieldably journaled in the end portion of said leg,
aftermost supporting roller has a short radius of curvature whereby high centrifugal forces are generated to break the adhesion between the belt and the water.
References Cited by the Examiner UNITED STATES PATENTS 2,091,958 9/37 Braga ll5.5
15 MILTON BUCHLER, Primary Examiner.