Overview
The main purpose of our system is to provide a hull that is sturdy while still protecting the electronics from water and allowing for easy access to the inside without shutting down the computer. This is accomplished by a cantilevered rack to hold the electronics, and an acrylic hull that uses bore seals to provide a water tight seal with the rear end cap.
The rack is cantilevered off of the rear end cap so that the hull can be removed without moving or cutting power to any of the electronics onboard. The rack must also provide a surface for the hull collars to rest on as they slide on to seal the hull. Several aspects of this rack were improved upon from the Proteus rack design in order to help improve cooling in the hull, and make servicing the hull less necessary and more convenient.
Rack Structure
The main structure of the rack is consists of four aluminum L-beams mounted together to form bulkheads of open rectangles. This allows for both heat and air flow through the rack. This structure is held together by both 8-32 and 4-40 screws. All of the parts for the rack were machined in-house, saving time and money on outsourcing. The entire rack is then mounted to the rear end cap with nine #8-32 screws through the top and side bulkheads to provide a sturdy platform to support the hull and keep stress off of the bore seal.
Guides
The acrylic guides are mounted to both the top and bottom horizontal bulkheads with 4-40 screws. These guides allow the hull to slide on easily and support the end of the hull that is not inside the bore seal. The aluminum hull collars slide on these guides so that the acrylic hull will not get scratched and impeded the view of the downward facing camera.
Wire Routing
The four point rack system leaves more room on top for wire routing than the three point structure used in Proteus. The connector wires are run along the length of one of the four L-beams, then up or down to the correct port on a board. Most wires between boards are run straight from one to another, but longer paths follow the same pattern as the connector wires: up or down to the most convienient L-beam, then forward and down/up to the correct board. To facilitate this routing, holes were drilled in all four L-beams where wires need to descend/ascend and in a regular hole pattern.
Board and Camera mounting
Aft Section:
The Merge, Distro, Serial and Depth boards are mounted in the aft section in 1/8” slots in the vertical bulkheads.
Middle Section:
This section is devoted to the downward facing camera and two fans, one pointed backwards to blow over the distro board, and one pointed forwards to blow over the computer.
Front section:
The computer is mounted on a tray, which slides into the 1/8” slots in the front pair of bulkheads. The 3DM-GX1 mounts to a plate which is bolted directly to the L-beams in the front section. The slots in the vertical bulkheads are 1/8” wide and will be padded with thin self-adhesive rubber padding to provide a tight fit for the boards (See Figure 4). Stability of the boards will then be guaranteed by fastening 1/8” plexiglass panels on both sides of the rack which will be mounted to the vertical bulkheads and will be laser-cut to accommodate for the connectors on the boards.
Side Panels
Stability of the boards that are in slots is ensured by attaching 1/8” plexiglass panels on both sides of the rack mounted to the vertical bulkheads. These panels are lasercut to accommodate for the connectors on the boards and labled with engraving.
Heat
To deal with heat issues, the fans will push hot air through the hull to the end caps where it will be cooled by the conductive properties of the aluminum end cap and any additional heat sinks. The fans will then move the cooled air back to warmer areas of the hull. Order of magnitude simulations were done to determine whether or not the fans would be sufficient to cool down the hull.
