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Hi Brent. Just a random thought......I think the hinged idea may be
problematic. If the tolerance is close enough to assure proper alignment, it may
be so tight that it can "jam" after a little wear or temperature change. Most
poppet valves use a central shaft moving up and down in a sleeve, spring loaded
to keep it closed, and a linkage arm that depresses the disk from above. The
disk stays in the middle, and the linkage arm and associated mechanism doesn't
require any close tolerances. To achieve a smooth exterior surface, you could
put the sleeve, shaft, and spring on the inside of the valve, and the linkage
arm could pull the disk down from the bottom, rather than push it from above.
The disk and seat can be made from plastic, fiberglass, or stainless. It
doesn't need to hold any high pressure so it wouldn't need to be that
strong. The mounting for the sleeve would need to be stainless, and the shaft
also, but very little needs to be "close tolerance" work. The shaft and bushing
are "off the shelf" parts. The disk and seat can be machined from plastic ( or
stainless ) with a doughnut type gasket set onto the seat.The disk
simply pushes up against the rubber gasket with spring pressure. Making the
gasket soft and wide ( 1 inch ) would make a little sand not a problem.
I don't have the computer skills to draw this so.....Picture your same
design, with a shaft attached to the center of the disk. The shaft extends down
from the disk center, through a bushing mounted on a "T" shaped piece, that's
attached to the underside of the MBT hole. A spring on the shaft pushes the
disk up onto the seat. The shaft goes through the bushing and has a linkage
"L" on the bottom end that when pulled, opens the valve by pulling the disk
down. With the disk being smooth, very little sand can collect on it's surface,
and the doughnut gasket points down so no sand will get on it. Any sand or grit
that goes in there will simply be washed away by the water as it goes through
the valve. The whole valve assembly mounts directly onto the MBT hole with small
bolts/gasket so can be removed from above for maintenance/repair.
Because I'm not a machinist, I don't
approach design with the idea that I can use a machined part. I like to
just buy stainless tube and rod that fits together, and weld on whatever else is
needed.
Like my motor mounts and rudder swivels. I got some 1-1/2 inch stainless
bar stock, some stainless tube that fits close, and welded stuff on there to
hold the parts, welded some more stuff to bolt it onto the hull, drilled a hole
for a grease fitting, and it works fine. The only close tolerance part is the
tube and bar stock.
If I'm down in Mexico or somewhere and I need a repair, having a mechanism
that requires machining could put an end to the dive operation. By using "off
the shelf" parts I should be able to repair/replace pretty much any part of the
sub right there in the field without having to "make" a complicated piece in a
shop. Spare parts and extra stock items like tube, bar, and sheet can be carried
along in the truck. A small portable generator/welder and a few basic power
tools ( saw, grinder, drill, etc.) and field repairs should be pretty easy. I
want to keep this thing as simple as possible, with the ability to fix it where
ever I am. Frank D. |