Abstract:
Devices and means to suspend scaled flying crafts during test and training flights, in a controlled environment space with a cable/string from a high point in the space, consisting of an electrical slack sensor on the cable/string and a radio controlled electrical system to automatically adjust the slack in the cable/string with the help of an electrically driven winch, permitting the flying craft to fly safely and freely under its own power.

Description:
CROSS REFERENCE 
     This application is a continuation in part of Ser. No. 07/707,593 filed May 30, 1991, now abandoned. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     Flying crafts such as hovering crafts, helicopters and other flying craft&#39;s scaled models are tested to study their flying qualities and control characteristics. A controlled environment space for their flight which enables them to be tethered to a safety cable/string without such cable/string affecting their free flight is a useful device. No such device exists except by an operator physically holding a cable/string tied to the flying craft and controlling the same by visually observing the flight of the craft. This means requires an operator and his ability to quickly pull or let loose the cable/string as the flying craft moves around and up and down in its flight. Other means also exist for tooting helicopters, which consist of a ground based stand with movable fan fold extendable arms which extend in and out and rise up or down as the helicopters strapped to the arm maneuvers in flight. Helicopter&#39;s area of movement is restricted by the size of arm and the area covered by a circle with a radius corresponding to the length of the arm. This invention provides another and a superior method to suspend flying crafts giving them a larger volume of space for their flight and a freer flight during test and training flights. 
     2. Description of Prior Art 
     National Advisory Committee for Aeronautics, Technical Note 3630, March, 1956, FIG. 2, Indoor test setup used in the flight testing of hovering models. 
     SUMMARY OF INVENTION 
     Devices and means to suspend scaled flying crafts during test and training flights, in a controlled environment space with a cable/string from a high point in the space, consisting of an electrical slack sensor on the cable/string and a radio controlled electrical system to automatically adjust the slack in the cable/string with the help of an electrically driven winch, permitting the flying craft to fly safely and freely under its own power. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1. Flying craft suspended from the high point with a cable/string equipped with a device to automatically detect and then automatically adjust the slack in the cable/string from which the flying craft is suspended. 
     FIG. 2. The electrical slack sensor that automatically detects slack in the cable/string. 
     FIG. 3. How the electrical slack sensor operates as the flying craft moves up or down in its flight. 
     FIG. 4. A light weight rigid frame for use on flying crafts for which no suitable tether point is available on top of the craft. 
     FIGS. 5A, 5B, 5C. A cable/string to flying craft tether means allowing craft to freely rotate without at the same time winding up the cable/string. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Flying crafts such as hovering crafts, helicopters and other flying craft&#39;s scaled models are tested to study their flying qualities and control characteristics. A controlled environment space for their flight which enables them to be tethered to a safety cable/string without such cable/string affecting their free flight is a useful device. No such device exists except by an operator physically holding a cable/string tied to the flying craft and controlling the same by visually observing the flight of the craft. This means requires an operator and his ability to quickly pull or let loose the cable/string as the flying craft moves around and up and down in its flight. Other means also exist for testing helicopter, which consist of a ground based stand with movable fan fold extendable arms which extend in and out and rise up or down as the helicopter strapped to the arm maneuvers in flight. Helicopter&#39;s area of movement is restricted by the size of arm and the area covered by a circle with a radius corresponding to the length of the arm. This invention provides another and a superior method to suspend flying crafts giving them a larger volume of space for their flight and a freer flight daring test and training flights. 
     REFERENCE FIG. 1 
     A controlled environment space in the form of a building or other suitable structure is used for test and training flights of the flying crafts.(1) The flying craft is suspended with a thin light weight cable/string from a high point in the space.(2) The total length of the cable/string is such that at its full extension or deployment, the flying craft is protected from impacting or crashing into the floor or the surroundings of the space. The cable/string is wound on a winch attached to the high point, such that winding the winch in different direction would lower or raise the cable/string end and the flying craft attached to it.(3) 
     The cable/string end attachment to the craft is attached by means of a spherical ball bearing mechanism such that it would allow the craft to freely rotate without winding up the cable/string itself. (4) 
     The winding of the winch is controlled by an electrical motor, which itself is activated by commands received by a radio receiver attached to the motor.(5) 
     The string from which the flying craft is hung is equipped with an electrical slack sensor that senses the slack of the cable/string at a point of the cable/string close to where it is attached to the flying craft. (6) 
     When the slack sensor detects too much or too little slack, it conveys its output to an electrical circuit consisting of a radio transmitter and the radio receiver. The transmitter radiates forward or reverse commands to the radio receiver which drives the electrical motor connected to the winch at the high point. When the slack sensor detects correct amount of slack, No command or Stop command is radiated by the transmitter. The electrical motor is connected to the winch which pulls the cable/string end and therefore the hanging flying craft up or down.(5) 
     The radio transmitter is hung from the same cable/string approximately a few feet above from where the electrical slack sensor is connected.(7) This does not affect the modal flying craft in its flight. 
     This enables the flying craft to move up or down in the controlled environment space with the qualities of a very near free flying craft even though it is tethered to this cable/string from central location on top of the flying craft.(8) 
     REFERENCE FIG. 2 
     The electrical slack sensor consists of a thin/slender hollow glass/other suitable material tube with an elbow bent in the middle, and containing small amount of mercury and electrical contacts so that the when the position of the tube changes, the mercury makes contact with different electrical contacts. (9) 
     If the tube is in nearly vertical position, the mercury remains at the bottom, indicating that the tube position is vertical and that there is no slack in the cable/string.(10) If the tube is in nearly horizontal position, that is up to 45 degrees on either side of the horizontal, the mercury settles in the elbow bent in the center of the tube indicating that there is the right amount of slack.(11) If the tube is in nearly upside down vertical position, mercury settles at the top end of the tube, indicating that there is too much slack in the cable/string from which the tube is connected.(12) 
     The glass tube has electrical contacts inside it at three locations that are connected to wires which are carried to a few feet above the electrical slack sensor along the cable/string and connected to a radio transmitter.(13) 
     Thus, this device just described acts as a electrical slack sensor to keep the slack in the cable/string from which the flying craft is hanging just right to make the flying craft free flying. 
     REFERENCE FIG. 3 
     The electrical slack sensor is attached at the lower end with a very short, few inches, of cable/string to the spherical ball bearing which then is tied to the top of the flying craft.(14) The sensor from the upper and is attached to a long cable/string which is connected to a winch at the high point.(15) Therefore when the flying craft is hanging straight down under its own weight without being flown, both the cables/strings, the short one and the long one are tight and the sensor is in vertical straight position. (16) When the craft is lifted up a little, less than the length of the short string, either by hand or when flying under its own power, then the short string will assume nearly horizontal position resembling a stretched out horizontal S shape.(17) If the craft is further lifted up then it will partially be touching and lifting the weight of the glass tube itself.(18) If the craft is further lifted up the glass tube will tilt further assuming inverted vertical position, then the tube will be fully touching the craft and the weight of the tube will be wholly supported by the craft.(19) Therefore the glass tube assumes different positions or rotates when the craft lifts up varying amounts from its fully hung position. A craft flying under its own power would lift up rotating the glass tube as indicated above. The rotating glass tube will cause the mercury to settle in one of three positions and cause forward/reverse/stop commands to be issued to the winch via the electrical slack sensor and the electrical circuit. 
     REFERENCE FIG. 4 
     For flying crafts that do not have an accessible location on the top for hooking to cable/string, a light weight rigid frame is attached at the bottom or other accessible part of it. Horizontal members of the frame extend to both sides of the craft.(20) Then other members, possibly two or three, go up and around encircling the craft away from the moving parts to a common point on the top.(21) At that point on the top of the frame is attached the cable/string with a electrical slack sensor connected to the cable/string and the winch motor. The cable/string is lowered or raised based on slack detected by its electrical slack sensor.(22) 
     REFER TO FIG. 5 
     The spherical ball bearing mechanism consists of an internal sphere.(23) It is connected at one end to the cable/string.(24) An outer larger hollow sphere with a circular opening at one end encloses the internal sphere with the circular opening accommodating the cable/string attached to the internal sphere.(25) Another cable/string is connected to the other end of the hollow sphere directly opposite the opening.(26) The two spheres are separated by a space occupied with small spherical balls and touching them, providing a freely moving spherical ball bearing mechanism.(27) The small spherical balls rest in multiple shallow uniform depressions either on the outside surface of the internal spherical ball or on the inside surface of the outer hollow sphere.(28) The outer hollow sphere is thus free to rotate and ride the spherical balls, in relation to the internal sphere. A cross section across lines X--X of FIG. 5 (29) and cross section across Y--Y of FIG. 5 (30) shows the arrangement of the small balls in the mechanism. 
     This mechanism will let one cable/string and rotate independently and freely from the cable/string at the other end of this spherical ball bearing mechanism even when the axes of the two cables are not perfectly aligned to each other in a straight line.