Brent,
Just a comment on your MBT valve. If you alter the depth
of the eat area so that when it is open it has a larger gap it would
help. With valves you should have ¼ x diameter lift opening for the same
area as the hole.
Yours appears to only have about ¼ inch opening. What is
the ratio of vertical gap to diameter in your drawing? It is what we call
design review. Hope it helps. Hugh.
.
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Sent: 13 January 2009 17:30
To: PSUBSorg
Subject: RE: [PSUBS-MAILIST] MBT valve
Hey Jay,
That assembly looks like it will work well to me,
and doesn't look to hard to manufacture, install, or maintain. It's good to see
some of your CAD work. It's basically along the lines of what I was
thinking of doing when I first started to think about large venting options and
from what I was thinking Vances mushroom vents might look like. Having
the closure spring inside the pneumatic actuator simplifies things for use both.
I like the sealing grooves you used. I had thought at first that the mushroom
vents would be partly above the MBT's to let all the air out of the tanks and
mount them. But both are assemblies are basically hidden, and yet still let
most of the air out. Your blue components, namely the piston and the
piston land, I think might be able to be made out of UHMW plastic or the
like, or even acrylic for that matter. But I like UHMW for it's ease of
machining, much cheaper then SS, it's light so that helps in keeping the weight
down (since these are mounted higher up in the subs), and it's very corrosion
resistant as far as I'm aware of.
I can see how I could blend your assembly with
mine by using your type of upper rubber gasket and grooved plunger/piston, and
then just use a SS or UHMW retaining ring to hold the gasket in place
basically in the same way you've secured the gasket on
yours. The main reason I switched over my thinking from a piston to a
hinged plunger assembly was that the top of my MBT's are right next to the
knuckle curvature of the steel heads, and my MBT's are not even close to flat
on top, unless I modify them.
"Want to mount the complete valve assembly on the tank
surface so that if there is give between the hull and the tank surface, closing
tolerances and alignment will not be affected."
This point I believe is a good one, and this is why I
left as much thickness to my plunger land as I did. I could even add some
additional thickness to the underside of the FRP tank shell to beef things up
in that area if need be. I can see how that might be good for your
assembly as well, not for making it seal better like mine, but primarily for
keeping the FRP tank rigid over time. Also I hope to have less trouble
with my assembly from any flexing or alignment issues by using a good large
soft O-ring(s) or gasket.
Your mentioning having the complete valve assembly on
the tanks surface to better deal with alignment issues, gave me an idea of how
I could do that with my basic hinge type assembly, and not have to weld the two
SS tabs onto the pressure hulls steel heads. I would need to add about a
1/4" of FRP to the bottom of the upper area of the MBT's to beef it up to
handle this new configuration. So that means it's back to the salt mines
to work up another assembly model. ;)' Thank goodness for soft office
chairs.
From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] MBT valve
Date: Sun, 11 Jan 2009 03:23:15 -0500
Brent
& Vance,
Thanks
for taking the lead with the illustration of a MBT valve. I have taken
the liberty to play with the design some, see the 3 images at http://flickr.com/photos/bottomgun
in the MBT Vent Valve group. I believe if you have a FLICKR account, you
can view the images at a higher resolution.
Some
thoughts:
1. Want to minimize
number of moving parts
2. Want to minimize
the number of hinge points
3. Want to mount the
complete valve assembly on the tank surface so that if there is give between
the hull and the tank surface, closing tolerances and alignment will not be
affected.
4. Want seating
surfaces to mate square on to insure complete closing of valve
5. Seating surface
material should be above the valve disk so sand or other matter doesn’t
settle on it and allow air to leak
6. Seating material
should be a soft elastic material
7. Operating cylinder
should fail in the valve closed position (some cylinders have springs installed
and air pressure operates against the spring below the piston, not sure if
Bimba has this capability)
Bimba
cylinders, 3-D models in various formats are available on their web site:
http://www.bimba.com/
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