ISS CHAMP

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*Note: This text was originally posted in the ISS CHAMP Overview.pdf file, and is shown here for reference. Please see the PDF file for additional illustrations. The ISS CHAMP operates on a quarter turn cam principle and combines: - Reliable connections to the hand rail and seat track - Effective use of material - A one-print setup - One handed installation and removal Description The CHAMP contains an internal cam-shaped cavity which is designed to fit the section of the hand rail. During installation the CHAMP is slid on to the hand rail and then rotated ¼ turn around the hand rail. During this rotation, the rounded ends of the hand rail follow the cam-shaped edges of the cavity. As the CHAMP nears the locked position, the C shaped body is pried apart by the hand rail, producing a powerful clamping force. Simultaneously, a spring loaded locking latch is pushed aside by the hand rail. Once the CHAMP is in the locked position the locking latch no longer obstructed by the hand rail, and it slides back into position, preventing further rotation of the CHAMP. During removal, the locking latch is released by means of a user accessible release tab which is recessed in the CHAMP Body to prevent accidental disconnection. Once the release tab is engaged the CHAMP is again free to rotate about the hand rail. This rotation is in the same direction as the motion of the release tab, making removal a single, one handed action. Development Process Development of the CHAMP started out as a simple foam core 2D cut mockup, and progressed through iteration of the clip design, testing of the internal mass reduction features and design of internal features for reliable 3D printing. Total Material Usage ABS Material Usage per unit is approximately 102g assuming 100% infill. - CHAMP Body 93.62g - Locking Latch 8.09g The CHAMP Body overall scale is maximized for strength within the given constraints of the ISS 3D printing build envelope and envelope requirements. Mass is then reduced using an internal set of spherical voids, arranged in a tetrahedral grid pattern. This pattern is only possible with 3D printing and it can be further optimized to achieve the ideal strength to weight ratio. Alternatively, the submitted design can be printed with reduced infill percentages to save material. Number of Prints Required Only one print is required to produce a CHAMP. Ease of Attachment Attachment of the CHAMP to the hand rail can be accomplished with a single, one handed action. Push the CHAMP Assembly on to the Hand Rail and ¼ turn to lock. Ease of Removal Removal of the CHAMP from the hand rail can be accomplished with a single, one handed action. Push the release tab on the Locking Latch and ¼ turn to remove. See Installation and Removal Video: http://youtu.be/M_AJeg-gwY0 Stability of Attachment Slippage along Hand Rail Length High clamping force is generated by the cam design during installation, preventing slippage along the hand rail. The rounded retention recesses are sized to 0.758” for the maximum tolerance width of the Hand Rail. The end-to-end distance is sized at 1.335” to clamp the minimum tolerance length of the Hand Rail. The cam is designed in a parametric model and can be adjusted to dial in required holding force. Rotation about Hand Rail. Once the locking latch is engaged, rotation about the Hand Rail would require either a fracture of CHAMP Body or the head of Locking Latch. Inadvertent Disconnect Since the release tab on the Locking Latch is recessed below the exterior surface of the CHAMP Body, protected by an opening sized for a finger, and located toward the wall of ISS, an inadvertent disconnect is unlikely. Impact resistance The design is extremely resistant to impact since the shock of an impact is converted into slight motion of the clamp. The clamp is designed to flex slightly under impact and return to nominal position rather than attempting to remain perfectly rigid. Seat Track Connection The Seat Track Stud is installed by sliding it in from one end, dropping the stepped washer into the retention hole and tightening the nut. The Seat Track Connection has the following features to maximize strength: - One end of the track is closed off - All corners are fully radiused - Internally, the flanges are solid and the internal shell wall is radiused toward the interior body - Depending on the length of the stud hardware, the entire profile could be more deeply recessed into the body of the clamp. Sharp Edge Human Factors All sharp edge criteria are met after initial assembly is complete. Overall Envelope The completed CHAMP assembly measures as follows when in the installed state: X: 2.320” by Y: 3.031” by Z: 2.320” A 1.00” offset from the hand rail is permitted in the X-Y plane, normal to the hand rail axis. The CHAMP Body extends to 0.950” offset. A 5.00” length is permitted along the Z length of the hand rail axis. The CHAMP Assembly extends 2.320” in this direction. Multiple Parts Assembly Assembly is completed by hand without the use of additional tools. The Locking Latch clips in to the CHAMP Body in a two-step, non-reversible process. See Assembly Video for the completed functional prototype: http://youtu.be/9G7WYuB-Czs Build Orientation Build Layers are to be oriented normal to the axis of the hand rail for both the CHAMP Body and the Locking Latch. CAD File submission High and lower resolution STL, STEP and Native Solidworks 2014