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Brent, I didn’t reply fully to your previous post. The
lands could be fewer/further apart but I wouldn’t make them taller.
You want them to be depressed in the low durometer gasket material but you don’t
want too much deformation of the gasket as it will speed its
deterioration/shorten its life. R/Jay Respectfully, Jay K. Jeffries Andros Is., Bahamas As scarce as the truth is, the supply has always been in excess of
the demand. -Josh Billings From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of ShellyDalg@aol.com 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.
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