US 3229296 A
Description (OCR text may contain errors)
Jan. 11, 1966 o E. SAAR] 3,229,296
SUBMARINE-TYPE WHIP ANTENNA DESIGNED FOR FULLY LOADED AND DEFLECTED CONDITION Filed Jan. 10, 1964 frfi 2 INVENTOR. OLIVER SAARI United States Patent Office 3,220,295 Patented Jan. 11, 1966 3,229,296 SUBMARlNE-TYPE WHIP ANTENNA DESIGNED FOR FULLY LOADED AND DEFLECTED CON- DITIGN Oliver E. Saari, Eimhurst, 112., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Jan. 10, 1964, Ser. No. 337,111 Ciaims. (Cl. 343-709) This invention relates to whip antennas and more particulariy to a whip antenna which is under constant stress when in a fully loaded and deflected condition.
Due to the numerous whip antenna failures resulting from high submarine speeds through the water, it was necessary to develop a method for determining antenna configurations, bending moments, drag forces and stresses. Most of the failures have been traced to either excessive bending stress or to fatigue due to excessive cycles of stress. The stress failures, which are more common, usually cause the antenna to break at or near the base in the area of maximum bending stress while the fatigue failures usually occur near the top of the antenna due to vibration.
An antenna which will be under substantially constant stress when in a fully loaded and deflected condition solved the failure problem and resulted in the lightest of antennas. Where there is no constant stress the antenna is unnaessarily bulky. In this case, the whip antenna will be no stronger than its weakest portion which is the most highly stressed portion. Stronger portions, therefore, will not increase the reliability of the total whip. In fact, they decrease it due to the fact that the excess material carried by the stronger-than-necessary section increase the drag loading. This load is transferred to the lower weaker portions of the antenna, thus reducing the overall whip strength.
It was discovered that neither a cylindrical rod nor a straight taper are ideal for a slender body of minimum weight, but that a double taper gives a minimum of failures.
In a whip antenna, as the tip of the whip deflects more in the direction of the fiuid flow of the media, the loading changes. The drag load gradually diminishes while the skin friction drag load increases. As the skin friction drag load increases, the whip is deflected into a more streamlined silhouette. This in turn decreases the area exposed to the stream and decreases the initial load and the silhouette becomes less streamlined. Naturaliy there is some dynamic balance between the drag load and the skin friction drag load. The forces generated by the drag load and skin friction drag load on a whip antenna act along the entire length of the antenna and may be called a distributive load. Therefore, the dynamic forces present at any given cross-sectional area of the whip antenna along its length is the summation of all the forces generated by the drag load and the skin friction load present from the point of the cross-sectional area to the unattached end of the antenna. Also, gravity may have some effect at some conditions of speed and media.
An object of this invention is to provide whip antenna having a dynamic balance resulting in a minimum of failures.
The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing.
The sole figure of the drawing shows a double taper whip antenna. The amount of taper is exaggerated in the drawing so that the individual portions can be more readily seen. Referring to the drawing there is shown a long straight slender double taper whip body 2, having a base 4 which is a cylindrical barrel having a constant diameter. Beginning at the top of the base 4 the whip body has a tapered rod portion 6. At the end of the rod portion 6 there is a second tapered end portion 8. The rod portion 6 and end portion 8 are both frustums. The tapers are gradual with no steps.
The transistion between the base, rod portion and end portion are continuous and smooth with no sharp edges.
The base end of the whip antenna is chamfered as shown at 10 while the tip of the end portion has a break edge 12 of 0.2 to 0.3 inch radius.
The length of the base 4 is in excess of one inch and less than four inches and preferably two or three inches. The taper of the rod portion 6 is at least double the taper of the end portion 8 and preferably in excess of three times as great but less than seven times as great. The length of the end portion 8 is four or more times as long as the rod portion 6 and preferably six to eight times.
The material for the whip antenna may be any of the known materials for whip antennas. Titanium (7 percent aluminum-4 percent molybdenum; alpha-beta structure) is the preferred material.
A protective coating on the whip antenna may be used. The purpose of the coating is to protect the whip material from nicks, scratches and other physical damages. The reliability of the antenna is improved by the elimination or reduction in severity of these faults. Since the loading of these members is spasmodic and at times high, failure is accelerated by severe nicks because of the resulting high stress concentration. Most whip antenna materials are suihciently resistant to corrosion of the elements that a protection against this phenomena is unnecessary.
The effect of a coating wouid not increase the strength of the assembly, but it would cause an additional drag load due to a larger area exposed to the stream velocity.
For the basis of example only and in no way intending to prescribe limitations, the following sample dimensions for the whip antenna are disclosed:
Base three inches long and 0.6 inch in diameter. Rod portion 19 inches long and a taper of 0.0079 inch per inch.
End portion 122 inches long and a taper of 0.00235 inch per inch.
A second example of dimensions which are illustrative only and in no way limiting are:
Base two inches long and 0.62 inch diameter.
Rod portion fifteen inches long and having a special shape as indicated in the table below.
Diameters at one-inch intervals:
Inches- Diameter 0 .620 1 .605 2 .592 3 .580 4 .568 5 .556 6 .544 7 .533 8 .522 9 .511 10 .500 11 .490 12 .480 13 .470 14 .460 15 .450
End portion 123 inches long and a taper of 0.0023 inch per inch.
Weight of 2.61 pounds.
The invention is not restricted to the exemplified embodiments described. The whip antenna may be solid or tubular. The cross-section need not be circular but may be of any desired cross-sectional shape. Consequently, any changes or modifications to the above described embodiments may occur to those skilled in the art without departing from the spirit of the invention which is intended to only be limited by the scope of the appended claims.
skin friction load as the antenna moves through a liquid medium and free from constant failures that plague submarines.
2. An antenna as defined in claim 1 wherein:
the base is at least one inch long; and
the end portion is at least four times as long as the mid portion.
3. An antenna as defined in claim 1 wherein:
the base is two to three inches long; and
the end portion is six to eight times as long as the mid \portion.
4. An antenna as defined in claim 1 wherein:
the taper of the mid portion is three to seven times as great as the end portion; and
the length Olf the base is 2 to 3 inches long.
5. A long slender continuously smooth antenna for submarines comprising:
means configured to produce substantially constant stress when said antenna is in its fully loaded and deflected condition due to the forces generated by the drag load and the skin friction load resulting from said antenna moving through a liquid medium, said means comprising;
a base two to three inches long having a constant cross-sectional dimension;
a tapered mid portion adjacent to the base;
a tapered end portion adjacent to, and being six to eight times longer than the mid portion; and
said mid portion having a taper three to seven times greater than the end portion taper.
6. An antenna as defined in claim wherein:
the end portion .is at least six times longer than the mid portion; and
the taper of the mid portion is at least three times the taper of the end portion.
7. An antenna as defined in claim 6 wherein:
the end portion and mid portion are both frustums in shape.
8. An antenna as defined in claim 6 wherein:
the antenna is made of titanium 7 percent aluminum- 4 percent molybdenum). 9. An antenna as defined in claim 6 wherein: said base portion being 3 inches long and 0.6 inch in diameter; said tapered mid-portion being 19 inches long and having a taper of 0.0079 inch per inch; and said end portion being 122 inches long and having a taper 0.00235 inch per inch. 10. An antenna as defined in claim 6 wherein: said base portion being 2 inches long and 0.62 inch in diameter; said mid-portion being 15 inches long and having a special shape as indicatedin the table below Inches: Diameter 0 .620 1 .605 2 .592 3 .580 4 .568 5 .556 6 .544 7 .533 8 .522 9 .511 10- .500 11 .490 12 .480 13 .470 14 .460 15 .450 and;
said end portion being 123 inches long and having a taper of 0.0023 inch per inch.
References ited by the Examiner UNITED STATES PATENTS 2,668,187 2/1954 Von Wald et al 343-900 2,808,278 10/1957 Snyder 343900 3,003,149 10/1961 Grashow 343900 FOREIGN PATENTS 1,087,190 8/1960 Germany.
660,913 11/1951 .Great Britain.
OTHER REFERENCES Allen: Mechanical Design Analysis for \Vhip-Type Antenna, SCTM 381(14), March 1961, pp. l16 relied on.
- HERMAN KARL SAALBACH, Primary Examiner.
R. F. HUNT, Assistant Examiner.