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Text Box: DESIGN REQUIREMENTS 1.      The design must be portable and operable by a single crewmember, including a depth of no more than 12 inches and a diameter not to exceed 18 inches. 2.      The design must fit into the smaller window of the piston cylinder, although it may be assembled once all parts have been passed through the designated opening. 3.      The total assembled design weight goal is no more than 60 pounds, with each unassembled component being of reasonable weight for individual human transport.

Text Box: 4.      Any necessary engagements with the water break assembly must be currently available and no new holes may be drilled or tapped. 5.      The device must be capable of removing the material of the choke ring. The cutting tool must also be able to sustain one full removal cycle of the choke ring. 6. The design must not damage the surrounding brake assembly, including the mating choke ring threads.  The group must impose limits, whether mechanical or electrical, to control the destruction of the choke ring. 

 

 

 

 

 

 

 

 

 

 

 

 

Text Box: The guidance system will allow the user to make up to forty wedge-shaped cuts into the choke ring as illustrated in Figure 2.  The exact pattern of these cuts was determined by an ANSYS finite element analysis as explained in Section 4.2.  In this analysis, it was concluded that four wedge-shaped cuts are sufficient for the design.  Each wedge is created with two intersecting cuts.  These cut depths do not penetrate through the entire choke ring thickness in order to prevent thread damage.  Likewise, the lengths of the cuts do not extend the entire length of the choke ring in order to prevent damaging the rear-mating water brake cylinder.  For this reason, the cut wedges remain attached at the rear inner lip of the choke ring. Text Box: It was concluded that a reciprocating cutting approach would be the most viable solution for cracked choke ring removal.  Upon investigating reciprocating saws, the 13-Amp Super Sawzall with rotating handle by Milwaukee Tools was chosen as the ideal tool for this cutting task.  The orientation of the Sawzall’s power components in relation to the blade is ideal for use within the spatial constraints of the piston cylinder.  The Sawzall’s rotating handle is an added benefit, allowing the stationary tool operator to cut in a variety of different directions. Using a reciprocating saw, the choke ring removal procedure is as follows.  The Sawzall will be mounted to a rigid guidance system.  The tool operator will need to transport the guidance system components through the slotted window into the piston cylinder.  Once in the cylinder, the components will be assembled and mounted via the threaded holes of the water brake cylinder.  The operator will then make a specified number of wedge-shaped cuts into the cracked choke ring.  Next, the operator will remove the mounted system and attach the standard torque wrench via the remaining thru holes of the choke ring.  The cheater bar will be attached to the torque wrench and the choke ring will be removed via standard procedure.

 

 

 

 

 

Text Box: The rigid shoe rail rigidly mounts the Sawzall in the correct orientation while allowing for sliding motion required for cutting.  The entire assembled system facilitates accurate cutting and also acts as a mechanical stop in order to prevent thread damage.  The mechanical stop allows the Sawzall to safely cut within 1/8-inch of the mating threads.  As manufactured, the Sawzall has an adjustable and removable shoe guide.  A pivoting shoe guard is attached to the front portion of the shoe guide.  The standard shoe guard was removed and replaced by a rigid aluminum shoe guard.  The designed shoe guard slides within the shoe rail during cutting.  A shoe guard block was also designed to provide an attachment point between the redesigned shoe guard and standard shoe guide using standard 0.25 inch aluminum bolts.  The direct attachment of the shoe guide to the aluminum shoe guard is prevented by the pre-manufactured design of the shoe guide.  As depicted, the shoe rail has two 0.25-inch thru holes at each end, through which the shoe rail is attached to inner circumferential holes of the mount using 0.25-inch aluminum bolts.  .  The mount system utilizes the cavity formed by the removal of the Jet and Annulus rings per the established choke ring removal procedure.  Within this cavity, a circular outer mount is secured to the water brake cylinder.  The design of this mount is shown in Figure 3.  Through the outer circumferential holes, standard aluminum bolts will secure the mount to the existing threaded holes of water brake cylinder in eight locations.  The inner circumferential threaded holes are utilized to secure the shoe rail, depending on the location of a particular wedge cut. 

  Text Box: The Sawzall is designed to be hand guided during cutting.  However, the precision required by the mating surfaces of the choke ring necessitated the design of a rigid mounted guided system.  All rigid guidance was designed using 6061 aluminum.  This material was chosen for its light weight, high strength and machinability.  The mount system utilizes the cavity formed by the removal of the Jet and Annulus rings per the established choke ring removal procedure.  Within this cavity, a circular outer mount is secured to the water brake cylinder.  The design of this mount is shown in Figure 3.  Through the outer circumferential holes, standard aluminum bolts will secure the mount to the existing threaded holes of water brake cylinder in eight locations.  The inner circumferential threaded holes are utilized to secure the shoe rail, depending on the location of a particular wedge cut. 

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