US2374261A - Propeller snare - Google Patents

Description

Apri! 24, 1945. B. A AMES A 2,3749261 PROPELLER SNARE Filed sept. 5, 1941 Parenied api. 24, 1945 omiso STATES PATENT lorifice PROPELLER SNARE Blanche Ames Ames, North Easton, Mass. Application September 5, 1941, Serial No. 409,679

2 Claims.

This invention relates to propeller snares by which hostile airplanes in flight may be destroyed or brought down.

Snares for the purpose of stopping airplanes have heretofore been proposed consisting of wires, cables or similar strands suspended in the air, with the object of becoming entangled with or injuring the propeller or other parts of an airplane which may encounter them. Such straight strands are comparatively taut since they are held under considerable tension by their own weight and possess the inertia of their Whole mass and therefore they do not yield readily to a sharp blow from a rapidly revolving propeller.

The principal object of the present invention is to provide snares of this general class in which the strands are so suspended that they will present to an airplane. propeller lengths of strand suciently slack and free from tension and intertia to yield readily to the blow of a propeller without being cut or broken, whereby the strand will be caught by and ensnare the revolving propeller blades and become wound around the propeller shaft. The strand mass thus wound on the propeller shaft acts as a brake which stalls the engine and prevents restarting. If the strand is of inflammable material or treated with an innammable material, the wound mass may be ignited by friction and cause damage by overheating the propeller shaft. The strand may also carry explosive material, which after being wound into a sufficient mass around the propeller shaft and being exploded by heat will injure the bearings, lubrication system or other surrounding parts. And further the strand may also carry abrasive materials damaging to the propeller shaft, and if an explosive material is also used the explosion will blow abrasives into the neighboring parts.

More specically, a, snare embodying this in`- vention comprises a braking strand of string, cord, rope or slender wire formed into a series of slack lengths which in effect float freely in the air substantially without tension. Such slack lengths may be formed and supported in many ways. For example, the slack lengths of the main or braking strand may be supported in the form of loops or coils from a second or supporting strand to which the main strand may be attached by string or elastic threads or adhesive strands or clips or knotting or any other suitable means at a number f spaced intervals so that the lengths of the braking strand between the points of attachment to the supporting strand form the desired loops or coils. Or, two or more braking strands may be connected together at intervals by rings or in other suitable ways, and the lengths between such points of connection may be spread and held in the form of loops byspanners of light, frangible material. Or, the braking strand may be in the form of a coil helically wound around a supporting strand or around a core containing a supporting strand. f

Certain embodiments of the invention are illustrated in the accompanying drawing in which:

IFig. 1 shows an airplane approaching a snare embodying one form of the invention;

Fig. 2 shows a loop of the braking strand caught by the blade of a propeller of an airplane and drawn down to the hub thereof;

Fig. 3 shows a braking strand wound ina coiledmass around the shaft of the airplane propeller;

Fig. 4 shows on an enlarged scale a portion of a snare of the form illustrated in Fig. l;

Figs. 5, 6, '7 and 9 show parts of other embodiments of the invention; and

Fig. 8 is an enlarged view of a detail of the einf bodiment shown in Fig. 7.

The snare embodying this invention may be suspended in the air from a balloon, parachute, kite or the like, or from supporting cables stretched generally horizontally to form a barrier or a network. In any case, the snare is preferably attached to the balloon or other support by 'a frangible. connection which will lbreak when the snare is caught by a propeller, as described below.

Thesnare shown in Figs. 1 and 4 includes a balloon Ill from which the-snare is suspended, The snare consists of a braking strand I of string, cord, rope or light wire, and a supporting strand l2 of any suitable material. The strand l l is attached to the strand I2 at spaced intervals l5 by ties or fasteners I6. The lengths of the strand ll between the points I5 are substantially longer than the spacing of the pointsv l5 on the supporting strand and thus form slack loops Vl which oat or hang freely without substantial tension in the air. It is recommended that the slack loops Il be made at least three times as long as the corresponding lengths of the supporting strand between the points l5.

When a blade IB of a rapidly revolving propeller i9 encounters the snare, it will usually cut or break the supporting strand l2, but the main or braking strand made of slack loops Il will yield suiiiciently to avoid being cut, will be drawn down to the hub of the propeller and will be wound into a dense coil 20 around the propeller shaft 2 l. As the coil increases in size, the wound mass will brake the motor and stall it or slow it down materially so that the plane 22 will lose headway and crash.

In the embodiment shown in Fig. 5, the braking .strand 23 is coiled around a core 24 made up of a float freely in the air without substantial tensionl and upon being caught by the propeller of anairplane will be drawn toward the' hub' and wound about the propeller shaft as' before.

Figs. '7 and 8 illustrate an embodiment ofk the invention which includes two connected to each other atintervals, preferably by some form of tie which-ineiect forms ajslip noose. As herein shown such attachingmeans consists of a double ring- 3flbest shown in Fig.- 8, one strand passing through one ring-and the other strand. passing through the other ring. rIfhe two strands 30 are spread or separatedinto loops betweenA the points of connection at the ringsby spanners or spreaders 32 made of light,` frangible material. andl having rings 33 which guide the strands at the ends of the spanners. When a propeller blade strikes a snare of., this form, the relativel'yrweak spanners will collapse, thuspermitting the unsupported loops ofthe strands to 4yield without being cut or broken andthe two strands will then be drawn byl therevolvingpr peller toward the hub and then wound around the propeller shaft. More than two strandsmay be used ifdesired to'l insure that if one should be broken there are others' which will be pulledv in upon the propeller shaft.

Fig'. 9 shows the braking strand 35 in the form of a helicalcoil wound around a cor'e. The core maybe merely a supportingA strand, but preferably, posite structure including a supporting strand 3'! enclosed in a paper cover 36 which may be' made of a paper ribbon orstrip" rolledleng'thwis'e in. the forml of a' paper tube around the s'u'ppor't' ing strand or' helically twisted or Wrappedin the form of a paper tube4 around the' supporting strand. The braking strandinay be wound on' the core inan open coil asillustra'ted or in a closed coil. A' greater'len'gth' of slack brakngstrand for any given section of the snare ispr'ov'ided by a' closed coil. When the core' is ruptured' by a pr'opeller blade and the b'rakingstran'd is' caught' by the propeller the' coils of the braking strand quickly pay out endwise from the corefofa' considerable length and then tighten` o'n` the core so that the whole' snare (coil and'core)l -is ready' to be wound on the propeller shaft and duicklyto build upa large mass: of material onf th'e propeller shaft; The papertube'l 36 may also serve as a wrapper' to enclose inil'arnrriable'l or,A explosive or abrasive materials, or any combination of them,l and it is advisable to make the tube of oiled" or otherwise waterproofed paper' in' order' to' keep said' materials dry and also to preserve the'slip'- periness' of the paper tube it'self"arid so' facilitate the pulling of theL coils olf the: corel A sna'r'e of braking strands" 30' and as shown in' the drawing, it a corr'ithe kind shown in Fig. 9 is complete in itself and may be used alone or it may be supported by a second supporting strand in any desired manner, for example, as shown in Figs. 1, 5 or 6.

In view of variable conditions, and in order to insure against failure, any of the forms of snares may be made with a multiplicity of braking strands so that if one be broken another will act to brake the motor. Furthermore, streamers may be attached to l, points to increase the'thickness of the wound mass around the shaft more quickly,

As suggested above, the braking strands may v be treated with suitable inflammable or explosive orabrasive materials or be wound in spirals around a` core of cotton so treated (Fig. 5). The inflammable and explosive materials may be of yany well-known pyrotechnic composition, such as those having a red phosphorus-potassium chlorate base, or the'like, and the abrasive material may comprise emery, carborundurn, high carbon steel,` etc., in granular form. Such materials' will be rendered active by the heat generated by friction at the point where the strandfmassis-forced by the propeller shaft against the front plate of the engine.

The' amount of slack most advantageously pro# vided' in' thebraking strands depends' upon the conditions to be met, such asl the length of the propeller blades, thickness ofthe propeller hub, speed-of rotation, andthe speed of travel.- When the: propeller blade strikes a loop orV coil the sup-l porting strands will break so there'willl be no" delay in supplying enough braking strand t'o' for-m an efficient mass toV` be wound ony the propeller shaft. The. movement of the braking strand along the blade to' ther hub 'usually takes placeduringionethird toV one-half! of a revolution, depending.. on thefspeed ofthe propeller and slipperlne'ssvof the blade-and strand. In order tov yield to the blow of the propeller enough slack strand must be immediately available to prevent' severing the strand. urtherm'ore,l the strand must be long enough to form a complete brake when wound up' on the' propeller shaft. The length'v of the strands: andi the amount of the slack mayfthus be varied to suit thecond-itions mostlikely. to be encountered.

While the' invention ha'sibeen' describeclf as applicable for defense against airplanes, itis not limited thereto and might beusedagainst'- other propeller'v impelled instrumentalities' 'or revolving shaftsV such as submarines', torpedoes; and the like.

Iclaim:

l. A propeller' snare comprising a` supporting. strand,an ensnaring. strand, and a'V core' around which said en'snaring strand is coiled,` said ensnaring strandl and core beingY connected att intervals to said supporting strand to form a series of slack lengths o'r loops substantially freelf'r'orn' 2. A` propeller snare comprising-'- af supporting strand, an' ensna'ringl stra-rid; an'dfbreakable' means connec'tingv said ens'n'aringf strand to said' sup# porting straii'd at intervals? to" form 4 a Series of slack' l'o'ops substantiallyv freel from tension,the lengths' ofsaidY lo'o'p's' being" severaly times'f asi long' a's the corresponding: lengths o'f the" supporting strfandbetween-the breakablefconnectingl-means BLANCHE AMES AMES.

the brakingstrands at spaced

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