The UHPV consists of a front endcap assembly, hull assembly, and rear endcap assembly.
Front Endcap Assembly
- Viewport system: Seals sapphire viewport to endcap.
- Endcap: The hull collar seals into the beveled endcap. When the hull slides over rack, slot in projection fits over the holddown block.
Hull Assembly
- Two hull collars glued onto a 15.75” long, 7” in diameter acrylic hull.
- Hull Collars contain double bore seals for #262 o-rings.
- Slots in hull collars fit both 8-32 screws and 3/16” pins
Rear Endcap Assembly
- Endcap seals to hull collar.
- Pins keep endcap attached to hull collar.
- Tapped holes on inside attach to rack bulkhead.
- MCBH6, MCBH8 and MCBH10 connectors interface to external devices and power.
- Depth sensor screwed into the endcap.
- Triangle braces attached into the back of the endcap cantilever the hull and rack.
Hull Sealing
The difficulty in 2006-2007 with face seals and acrylic collars caused us to move to bore seals in aluminum sealing collars. There are potential drawbacks to these choices: aluminum is heavier than acrylic, and bore seals are more difficult to engage and disengage than face seals. The first was considered a worthwhile sacrifice for better structure, especially since aluminum is more thermally conductive than acrylic and would thus help decrease overheating. The second was of more concern: the double bore seal endcaps of the 2004-2006 vehicle, the Seamonkey, can take several people to pry off. However, people at Wood’s Hole Oceanographic institute suggested that a 15 degree bevel of the lip of the endcap could solve this problem.
The 15 degree bevel may have helped to some extent, but it is still nearly impossible to engage the upper hull in the rear endcap without a tremendous amount of force. The solution to this is copious amounts of o-ring grease, only using the back of the two o-rings, and using three screws in the holes originally intended for pins to crank down the pressure vessel until the o-ring seals. This is not as much of an issue for the front endcap, because it is not removed frequently.
Another problem associated with bore seals not encountered with face seals is that they cannot be rotated easily once engaged. Because of this (and because it is nearly impossible to line the hull on the present vehicle up exactly) it was important that the design be at least somewhat rotationally independent.
Hull Collar Design
30 degrees in each direction was decided as a reasonable amount of independence, so there are three 60 degree slots in the sealing collars to match with the three holes on the front and rear endcaps. In order to have a larger surface area for epoxy, there is a slot for the hull to epoxy into the endcap. The hull collars are epoxied to the hull rotated 180 degrees from eachother.
