Bravo drive propeller shaft bearing carrier
A propeller drive system for V-hull and catamaran racing vessels including an offshore racing cleaver propeller run on a long, thick propeller shaft coupled with a Bravo Unit Drive Motor at, and above, the water's surface through a tightly fitted bearing carrier.
Research and development of this invention and Application have not been federally sponsored, and no rights are given under any Federal program.
CROSS-REFERENCE TO RELATED APPLICATIONSNONE
REFERENCE TO A MICROFICHE APPENDIXNOT APPLICABLE
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates to sterndriven marine vessels, in general, and to an improved propeller drive system for V-hull and catamaran racing and/or pleasure vessels, in particular.
2. Description of the Related Art
As will be appreciated by those skilled in the art, the Bravo Drive form of propulsion developed for high performance marine vessels would be more attractive for use in the Offshore Racing Circuit were it not for the fact that while it may increase a vessel's speed, it also tends to fail quickly. My analyses and testings have shown that this premature failure results from a high frequency harmonic caused by propeller slippage—which also makes it more difficult for the operator to stabilize a vessel's path of direction. At high speeds, such failure could very well lead to the possibility of crashes, injuries and deaths; at the very least, it could result in significant vessel and component damage.
As will also be appreciated, these problems can become all the worse as the propeller shaft is sought to be raised from below the water line in an attempt to enhance higher performance and obtain higher speed from the vessel. This follows because it is accompanied by even higher slippage and greater vibration.
As will become clear from the following description, the improved propeller drive system of this invention allows a racing vessel to run approximately 10 miles per hour faster, without failure or damage to the propeller. A reduction of slippage from the 14-16 percent common to the Bravo Drive down to approximately 4 percent also will be understood to result, significantly decreasing propeller vibration.
SUMMARY OF THE INVENTIONTo understand the advance of the present invention, it must first be appreciated that the original development of the Bravo Drive by Mercury Marine utilized a propeller intended to run submerged below the water line. In trying to increase the vessel's speed toward 80, 90 and 100 miles per hour, the installation was changed to run the propeller on the surface, utilizing a different Mirage or Maximus propeller. However, with one blade of these propellers being out of the water at any instant of time, these propellers became unevenly loaded, with the impact in its striking the water then eventually damaging the shaft to breakage—with the resulting loss of the propeller. My analysis showed that with these propellers being of a 30 inch pitch, running them in the water produced a slippage of between 14 and 16 percent; and it was this harmonic vibration which threw the propeller out of balance and eventually over time destroyed the entire drive. Substituting, instead, a propeller intended to be run on the surface seemed to be an possible solution as its increased blade area would bring the slippage down, leading to less harmonic vibration. But this suffered disadvantages of its own: a) first of all, in increasing the cost from the Bravo Drive of approximately $8,000.00 to one of $35,000.00 if a Mercury Marine #6 Drive were used instead; and b) secondly, such a substitute drive would require a significant increase in horsepower to reach the same vessel speeds. The result would then be that a 36 foot boat with a #6 Drive would cost approximately $400,000.00, as compared to $250,000.00 for the Bravo Drive vessel. However, even so, #6 Drives are not user friendly to many vessels, at least due in part to their mass and weight.
As will be seen from the description that follows, the present invention sets out a new and improved propeller shaft and bearing carrier for a Bravo Drive. This will be appreciated to allow the vessel to use an offshore racing cleaver propeller of a type meant to run on the surface. Being of a design whose blades leave and enter the water more smoothly, the resultant slippage and vibration are reduced. Being more massive, a longer invention, to fit the shaft is used as well.
BRIEF DESCRIPTION OF THE DRAWINGSThese and other features of the invention will be more clearly understood from a consideration of the following description, taken in connection with the accompanying drawings, in which:
Referring to the Drawings, the propeller shaft 10 of
While Applicant does not wish to be restricted to any particular set of dimensions, the following dimensions for the propeller shaft 10 of
The propeller shaft 10 may be manufactured of chrome finished, heat treated stainless steel. Preferably, it is of a length of substantially 18.400 inches, and of a girth at its widest part of substantially 2.350 inches. At its splined first end 15, the shaft 10 is of a diameter of substantially 1.125 inches, and at its threaded end 16 where the cleaver propeller 12 rides, the propeller shaft 10 is of a diameter of substantially 1.000 inches. With these dimensions, the shaft 10 is of a length and girth to ride to a height of 2-½ inches above the water through which the boat is propelled.
Dimension 2o5 in
As will be appreciated by those skilled in the art, the teachings of the present invention allow a designer to run more horsepower than the Bravo Drive was designed for, although not as much as with the Mercury Racing Six Drive. The invention also will be seen to allow one to run the vessel at higher speeds than with the prior constructed Bravo Drive, yet without its slippage and possible drive failures. Although less able to reach the speeds of the Mercury Racing Six Drive, the teachings of the invention allow a significant savings as associated with the latter's increased cost—and thus effectively fills a gap between the Bravo Drive and the Racing Six Drive.
While there have been described what are considered to be preferred embodiments of the present invention, it will be readily understood by those skilled in the art that modifications can be made without departing from the scope of the teachings herein. For at least such reason, therefore, resort should be had to the claims appended hereto for a true understanding of the invention.
Claims
1. In a stern-mounted propulsion system for a marine vessel of the type having a Bravo Unit Drive Motor, a bearing carrier at an output end of said motor, a propeller shaft coupled to said motor via said bearing carrier and having a splined first end and a threaded second end, and an offshore racing cleaver propeller on said threaded second end, the improvement comprising a bearing carrier to securely fit and support said propeller shaft when being of a length and girth to ride above the surface of the water through which the vessel is propelled.
2. The improvement of claim 1 wherein said bearing carrier securely fits and supports said propeller shaft when being of a length and girth to ride to a height of 2-½ inches above the surface of the water through which the marine vessel is propelled.
3. The improvement of claim 1 wherein said bearing carrier through which said propeller shaft couples includes an apertured front end of a diameter to receive said threaded end of said propeller shaft and an apertured rear end of a diameter to receive said splined end of said shaft.
4. The improvement of claim 3 wherein the aperture of said apertured front end is of a diameter of substantially 2.900 inches and wherein the aperture of said apertured rear end is of a diameter of substantially 3.865 inches.
5. The improvement of claim 4 wherein said apertured front end is of a diameter of substantially 4.305 inches and wherein said apertured rear end is of a diameter of substantially 4.283 inches.
6. The improvement of claim 5 wherein said bearing carrier is of a length between said front and rear apertured ends of substantially 4.900 inches.
7. The improvement of claim 6 wherein said bearing carrier is composed of hard anodized, billeted aircraft 2024 aluminum.
Type: Application
Filed: Mar 17, 2005
Publication Date: Sep 21, 2006
Inventor: Rolf Papke (Brick, NJ)
Application Number: 11/081,944
International Classification: B63H 20/14 (20060101);