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Hi David. Another good video of a psub. I always enjoy them with the sound
of the bubbles and the water going over the windows/dome.
On the directionality issue.....
as Jon mentioned, the K boats use a " block V seal " where the shaft exits
the pressure hull to rotate the side motors. A hydrophone pick-up could be
rotated much the same way. These seals are pretty basic and in use on most of
the boats with good success.
Another method could be to use a
linear actuator powered by air, hydraulic, or electrical.
Because the unit isn't large and there's not much resistance, the mechanism
could be small, say 1/4 inch.
My personal preference for thru-hulls is to have a valve
on every hole, but it's still possible to have a rotating shaft penetrate the
hull AND a valve to isolate the hole should it leak. It would take a little more
to fabricate, but the design will allow for complete isolation of that hole if
it leaked.
Again, I'm not using this method for my motors/dive planes or my
rudders, but I do plan on using it as part of my drop weight assembly as a
back-up for the hydraulic release mechanism. It seems like it will be
fairly easy to build.
What I'm proposing is the same basic design with the block V seal,
shaft, shoulder, etc. but this assembly will be mounted in a tube section and
threaded into a welded thru-hull on the outside of the sub. The interior part of
the thru-hull will have a ball valve on it like all my other thru-hulls.
To rotate the shaft with the block V seal, a rod with a socket is inserted
into the open ball valve and the socket grabs the hex nut welded onto the shaft
end. In this way the inserted rod/socket can be pulled out and the ball valve
closed if the block V seal assembly were to start leaking because of wear or a
collision or what ever.
In my application, I'll be using it to drop the emergency drop weight, as a
manual back-up to the hydraulic mechanism. A small hand pump and hydraulic
cylinder will be used as the primary means to rotate the drop weight pin or
shaft. If the hydraulic mechanism jams or fails for some reason, I will still be
able to open the ball valve to expose the pin/shaft holding the drop weight,
insert the rod/socket into the valve and turn the pin/shaft manually.
The small "periscope video camera" in my hatch will use the same device but
without the hydraulics.
The video camera will be mounted on a rotating plate mounted inside a small
chamber with a plexi dome so should remain dry but just in case it gets smashed
or leaks, that chamber can be isolated from the cabin with the ball valve.
I've got some preliminary sketches for both these designs but like most
things, changes in the actual device will happen when I actually start
fabrication. This is one of the few areas where close tolerance machining is
required so my son-in-law will be involved in the fabrication. ( he owns a
machine shop )
Frank D.
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