Abstract:
A clocking bar includes a rod and an indicator located along a length of the rod, wherein the indicator has a pair of indication components with a predetermined spacing therebetween. The bar also includes a hole one locator located along the length of the rod, and a rear hole locator located along the length of the rod. The clocking bar is configured to identify a stack bolt hole one from among a plurality of bolt holes on a rotor through use of a relationship between physical features of the rotor.

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to gas turbine engines and, more particularly, to a tooling device in the form of a clocking bar that facilitates the identification of the stack bolt hole one on an unclocked rotor wheel. 
     Clocking of blades on rotating rotors or wheels is common in gas turbine engines, especially on modern rotors. Clocking generally refers to the relative positioning of two rows of blades or airfoils with respect to each other, wherein such blade positioning can affect the efficiency of the gas turbine. However, some rotors have blades that are not clocked, for example, those on older compressor rotors or wheels. As such, these unclocked rotors have an unknown or random relationship between the bolt hole pattern in the rotor and the dovetail slots formed in the rotor to accommodate the blades or airfoils. Typically the number of dovetail slots is not evenly divisible by the number of bolt holes. Thus, the distance from each bolt hole to the nearest dovetail slot differs between bolt holes and dovetails. Such randomly clocked wheels sometimes result in unfavorable aerodynamic consequences that may lead to component damage within the engine. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a clocking bar includes a rod; an indicator located along a length of the rod, wherein the indicator has a pair of indication components with a predetermined spacing therebetween; a hole one locator located along the length of the rod; and a rear hole locator located along the length of the rod, wherein the clocking bar is configured to identify a stack bolt hole one from among a plurality of bolt holes on a rotor through use of a relationship between physical features of the rotor. 
     According to another aspect of the invention, a method for identifying a stack bolt hole one from among a plurality of bolt holes on an unclocked rotor includes placing a clocking bar on a forward face of the unclocked rotor such that a hole one locator that is part of the clocking bar is within one of the plurality of bolt holes, and inspecting an indicator portion of the clocking bar to determine if the bolt hole that the hole one locator is within is the stack bolt hole one on the unclocked rotor, wherein the bolt hole that the hole one locator is within is the stack bolt hole one of the unclocked rotor when the indicator portion of the clocking bar indicates that a particular relationship between physical features of the unclocked rotor has occurred. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a clocking bar according to an aspect of the invention; 
         FIG. 2  is a perspective view of the clocking bar of  FIG. 1  in the process of being inserted within a pair of bolt holes on a front face of a unclocked rotor used within a gas turbine engine; 
         FIG. 3  is a perspective view of the clocking bar of  FIG. 1  inserted within the pair of bolt holes on the front face of the unclocked rotor; and 
         FIG. 4  is a front view of an indicator portion of the clocking bar of  FIG. 1  illustrating a relationship between a dovetail slot of the rotor and a centerline of the rotor. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , an embodiment of a tooling device in the form of a clocking bar  100  in accordance with an aspect of the invention includes a rod  102  that may be generally rectangular in shape or other suitable shapes. The rod  102 , which may comprise aluminum or other suitable material, may have at least one handle, here a pair of handles  104 , formed from plastic or other suitable material located on one side (e.g., a top or upper side) of the rod  102 . Located on an opposite side (e.g., a lower or bottom side) of the rod  102  is a hole one locator  106  which may be generally cylindrical in shape (to match the corresponding cylindrical holes in the rotor as described and illustrated hereinafter) and may also be made of aluminum or other suitable material. Also located on the bottom side of the rod  102  is a rear hole locator  108 , which may comprise an octagon-shaped post made from aluminum or other suitable material. The hole one locator  106  and the rear hole locator  108  may each be spaced equidistantly from the center of the rod  102 . A pair of pins  110 , in the form of, e.g., dowels and formed from, e.g., steel, may be spaced equidistantly apart and are located on the bottom side of the rod  102  so as to protrude downward therefrom. At one end of the rod  102  is located an indicator  112 , which is illustrated in more detail in  FIG. 4  and which is also located on the underside of the rod  102 . As described in more detail hereinafter, the indicator  112  is utilized to provide a visual indication of whether the clocking bar  100  has located the stack bolt hole one on an unclocked rotor. A stand-off pad  114  is located on the bottom side of the rod  102  and at the other end of the rod  102  opposite the indicator  112 . 
     Referring to  FIG. 2 , there illustrated is a portion of the rod  102  having the hole one locator  106  and the rear hole locator  108  in the process of each being inserted into a corresponding bolt hole  120  on a rotor or wheel  122  of, e.g., a compressor of a gas turbine engine. The illustrated rotor  122  may comprise one stage of a plurality of stages within the compressor. The rotor  122  may have a plurality (e.g., 15) of such bolt holes  120  spaced apart, e.g., equidistantly, on a front surface  124  of the rotor  122 . The hole one locator  106  is placed within one of the bolt holes  120  and the rear hole locator  108  is placed within another one of the bolt holes  120  that is located on the rotor front surface  124 . The bolt hole  120  that the rear hole locator  108  is placed within is approximately 168 degrees opposite the bolt hole  120  that the hole one locator  106  is placed within. The bolt holes that the hole one locator  106  and, thus, the rear hole locator  108  are placed within may be selected at random by the user of the clocking bar  100 . If the clocking bar  100  is placed incorrectly on the rotor  122  (e.g., not in proper alignment with a pair of bolt holes  120 ), the dowel pins  110  will physically contact a boss  126  on the rotor  122 , thereby indicating to the user of the bar  100  an incorrect placement thereof. Otherwise, if the clocking bar  100  is placed correctly on the rotor  122 , the dowel pins  110  contact no part of the rotor  122  and both the indicator  112  and the stand-off pad  114  rest on a surface  128  of the outer periphery of the rotor  122 .  FIG. 3  illustrates the clocking bar  100  correctly placed on the rotor  122 . 
     Referring to  FIG. 4 , there illustrated in greater detail is the clocking bar  100  placed on the rotor  122  with the indicator  112  lined up with both one of the dovetail slots  130  of the rotor  122  and the centerline created between the center of the rotor  122  and the center of the bolt hole  120  being checked to see if it comprises the stack bolt hole one. A pair of depressions  132 ,  134  in the shape of semi-circular cutouts is formed along an edge  136  of the indicator  112 . The depression  134  is in the form of a relief cut and has a vertical surface (“Surface X”) rising upwards in  FIG. 4  from a right hand edge of the relief cut  134 . The distance between the depression  132  and Surface X is at a predetermined spacing therebetween depending primarily upon the particular stage of the, e.g., compressor, that the clocking bar  100  is intended for use with. It is envisioned that different sized stages will require different sized clocking bars  100 , including indicators  112  with different spacings between the depression  132  and Surface X in order to properly identify the stack bolt hole one on an unclocked rotor. 
     In accordance with an embodiment of the invention, the user of the clocking bar  100  performs a visual inspection of the indicator  112  to determine if the bolt hole  120  that the hole one locator  106  is located within comprises the stack bolt hole one of the unclocked rotor  122 . The stack bolt hole one of the unclocked rotor  122  is identified when the leading edge of a dovetail slot  130  lies within the depression  132  on the indicator  112 . 
     If the stack bolt hole one is not identified with the then-current position of the clocking bar  100  on the rotor  122 , the clocking bar  100  is moved to locate the hole one locator  106  within another bolt hole  120  on the rotor and the visual inspection of the indicator  112  of the clocking bar  100  is again performed. This process of placing the clocking bar  100  in different bolt holes  120  is repeated until the stack bolt hole one on the rotor  122  is located. Typically, since the leading edge of a dovetail slot lies within one of the depressions  132  for only one bolt hole  120  on the rotor  122 , only one of the plurality of bolt holes  120  on the rotor  122  can be the stack bolt hole one. 
     The clocking bar  100  of embodiments of the invention allows for manufacturing and repair shops to quickly determine, using a relatively low cost tooling device, the stack bolt hole one on rotors or wheels that have an unknown bolt hole to dovetail slot relationship. This allows an unclocked or randomly broached rotor to be provided with clocked blades. The clocking bar thus eliminates relatively longer and more costly metrology work that normally would be required to identify the stack bolt hole one on an unclocked rotor. Also, by allowing a previously unclocked rotor to become clocked, the cost of having to replace the entire unclocked rotor with a clocked rotor is eliminated. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.