<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1480260351346_4982"><span>Sean,</span></div><div id="yui_3_16_0_1_1480260351346_4982" dir="ltr"><span>I agree completely except the operating pressure is </span> not as high as you suggest. I know for a fact Gamma ran at 1,100 psi from the maintenance records. You do make a point that I missed. Without a bladder, I could leak oil into the water when relieving the pressure while surfacing. I was considering an accumulator either a piston or rubber bladder type, but they are very heavy. I would like to figure out how to use this idea with a water pressure tank with bladder for the light weight. </div><div id="yui_3_16_0_1_1480260351346_4982" dir="ltr">Maybe this is not the way to go, but an interesting brain exercise. </div><div id="yui_3_16_0_1_1480260351346_4982" dir="ltr">I do have a small hyd pump that is pretty light and makes 1,100 ps,i it is just such a pain in the butt. Mind you with external batteries and external pump it will not be as bad.</div> <div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"><font size="2" face="Arial"> On Sunday, November 27, 2016 7:38 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv8499684973"><div>
<div class="yiv8499684973moz-cite-prefix">Hank, what sort of total oil volume are
you considering? The immediate problem I see is the loss of
pressure in your HP supply, given the necessary operating pressure
of the hydraulic system. Regulating a cylinder at e.g. 4000 psi
down to 2000 for drive pressure is still not going to last very
long, and you also have the problem of pressure increase in the
receive tank if it is not vented reducing your total available
delta-P (i.e. you have a drop in pressure on the drive side
combined with an increase in pressure on the receive side - it may
not take long to become ineffective). If that isn't an issue for
you, then there's no reason it wouldn't work. You are essentially
powering your system from a precharged accumulator, and draining
into another one at lesser charge pressure. I would incorporate a
check valve between the supply accumulator and the control valve,
so that pressure pulses are not transmitted upstream and no
sponginess is evident. You might also want to take a concept from
commercial gas charged accumulator designs and incorporate some
sort of bladder inside each pressure vessel to physically separate
the oil from the charge gas. If you insist on using air (I still
prefer nitrogen), this would prevent the mixing of high pressure
oxygen with oil, and also allow you to vent the receive tank to
the water without worrying about oil contamination in either
direction. It also makes the system insensitive to vessel
attitude. Then your pumbing becomes simple - one tank is charged
and one is vented, and when all the fluid is moved to the receive
side, you just switch the direction.<br clear="none">
<br clear="none">
Such a system gets its energy input from the compressor that
charges the HP air or nitrogen source, versus having an on-board
hydraulic pump drawing energy from the batteries. The advantage
of the former is that the energy input is decoupled from the
vessel and need not be carried, but you only achieve constant
power for as long as you can maintain constant precharge pressure,
which will be a function of the pressure setting and the
respective volumes of both the hydraulic system and the HP gas
source. The advantage of the latter is the ability to run
continuously without having to switch directions, and that energy
storage in batteries is probably more efficent than energy storage
in compressed gas.<br clear="none">
<br clear="none">
Sean<br clear="none">
<br clear="none">
<br clear="none">
On 2016-11-27 05:47, hank pronk via Personal_Submersibles wrote:<br clear="none">
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<div id="yiv8499684973yui_3_16_0_1_1480249331941_4890"><span>Alan,</span></div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480249331941_4890"><span id="yiv8499684973yui_3_16_0_1_1480249331941_5254">Think of it as a
hydraulic system, not an air system. The arm is identical
in every way except it is powered by air pushing the oil
instead of a pump. It would not be spongy because the
cylinders are full of oil. The air never leaves
the pressurized oil tank. </span> When the valve is
activated, the oil moves as if it had a pump. Instead of the
oil returning to the pump reservoir, it is sent to a holding
tank that is a HP bottle. The air in the receiving tank
compresses as the oil flows into it. Nothing is vented, it
can not vent because I need to maintain a balance between the
two tanks for buoyancy. As the oil leaves the pressure tank,
the tank gets lighter. At the same time the receiving tank
gets heavier, so they are balanced. </div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480249331941_4890">I am not
worried about space, it is weight I am thinking about and
complexity. Of coarse if you were doing construction with the
arm it would need to be electric. But to grab one gold bar it
can be air driven. Air drive saves battery power also.
Having said all that, it may have a problem I have not
expected, so speak up and save me some trouble anyone. </div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480249331941_4890"> I don't see
a problem with a motor submerged in WD40, my vertical
thrusters are full of it. I could use something else as long
as it has a low enough viscosity for the motor to run. </div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480249331941_4890">Hank</div>
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<div class="yiv8499684973yqt3551329935" id="yiv8499684973yqtfd85605"><div dir="ltr"><font size="2" face="Arial"> On Saturday,
November 26, 2016 8:03 PM, Alan James via
Personal_Submersibles
<a rel="nofollow" shape="rect" class="yiv8499684973moz-txt-link-rfc2396E" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></a> wrote:<br clear="none">
</font></div>
<br clear="none">
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<div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;">
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480187447224_5856"><span id="yiv8499684973yui_3_16_0_1_1480187447224_5900">Hi Hank,<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5884">
Wouldn't you have to exhaust the air as in a
pneumatic system?<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5885">
Also air would have to displace the volume of
oil in the cylinder<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5886">
as the piston moves in & out, so there
would be marginal benefits<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5887">
over a pneumatic system. It would also be
spongy like a pneumatic <br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5888">
cylinder because any bouncing force on the
cylinder would compress the air<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5889">
that is the source for the movement.<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5890">
You were talking about saving space with this
idea, but if compressed<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5891">
air was a good form of power we would have
pneumatic thrusters <br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5892">
instead of batteries & electric motors..<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5893">
I once did the maths on how much energy was
stored in a dive tank;<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5894">
can't remember the result, but there was at
least 3 x more energy in<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5895">
a battery of an equivalent size.<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5896">
WD40 as hydraulic oil? It is flammable with a
reasonably low flash point.<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5897">
Also at that viscosity you would be more prone
to leaks wouldn't you?<br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5898">
<a rel="nofollow" shape="rect" class="yiv8499684973moz-txt-link-freetext" target="_blank" href="https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf">https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf</a><br clear="none" id="yiv8499684973yui_3_16_0_1_1480187447224_5899">
Cheers Alan</span></div>
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<div class="yiv8499684973yqt5393059757" id="yiv8499684973yqt26177">
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<font id="yiv8499684973yui_3_16_0_1_1480187447224_5710" size="2" face="Arial"> </font>
<hr size="1"> <b><span style="font-weight:bold;">From:</span></b>
hank pronk via Personal_Submersibles
<a rel="nofollow" shape="rect" class="yiv8499684973moz-txt-link-rfc2396E" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></a><br clear="none">
<b><span style="font-weight:bold;">To:</span></b>
Personal Submersibles General Discussion
<a rel="nofollow" shape="rect" class="yiv8499684973moz-txt-link-rfc2396E" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></a>
<br clear="none">
<b><span style="font-weight:bold;">Sent:</span></b>
Sunday, November 27, 2016 4:59 AM<br clear="none">
<b><span style="font-weight:bold;">Subject:</span></b>
Re: [PSUBS-MAILIST] Hydraulic idea<br clear="none">
</div>
<div class="yiv8499684973y_msg_container" id="yiv8499684973yui_3_16_0_1_1480187447224_5717"><br clear="none">
<div id="yiv8499684973">
<div id="yiv8499684973yui_3_16_0_1_1480187447224_5716">
<div id="yiv8499684973yui_3_16_0_1_1480187447224_5715" style="color:rgb(0, 0, 0);font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;background-color:rgb(255, 255, 255);">
<div id="yiv8499684973yui_3_16_0_1_1480175087437_3060"><span>Sean,</span></div>
<div id="yiv8499684973yui_3_16_0_1_1480175087437_3060"><span id="yiv8499684973yui_3_16_0_1_1480175087437_3181">The receiving tank
will take the full depth
pressure and be large </span>enough
to take all the oil without
building up excess air pressure,
no need to vent off, since it is
only receiving oil and
displacing air. I need a
balance with two tanks to
maintain neutral buoyancy.</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480175087437_3060">I
am not worried about oxidation
of the oil because the oil is
not going through a pump and the
flow rate is so small. I
ordered air cylinders for the
manipulator with a 5\8 rod to
reduce the back pressure.
Gamma's manipulator operated at
1,100 psi when the sub was at
1,000 feed of depth. The arm
will loose power, but I don't
expect that to be an issue,
because the oil tank will be
powered from a separate bottle
of air. </div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480175087437_3060">I
have to work with what I have to
keep the cost in check, so I can
modify an open centre valve by
blocking the final pressure port
drain. I also have some HP
tanks. If it does not work out
easily, I have a few electric
pumps I can use. </div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480175087437_3060"><br clear="none">
</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480175087437_3060">If
I go electric, I intend to
submerge the motor pump unit in
the oil reservoir with a bladder
top to compensate. That means I
will use WD40 as hydraulic
fluid.</div>
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<div class="yiv8499684973yqt2382799783" id="yiv8499684973yqt36000">
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480187447224_5719"><font id="yiv8499684973yui_3_16_0_1_1480187447224_5718" size="2" face="Arial">
On Saturday, November
26, 2016 6:25 AM, Sean
T. Stevenson via
Personal_Submersibles
<a rel="nofollow" shape="rect" class="yiv8499684973moz-txt-link-rfc2396E" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></a>
wrote:<br clear="none">
</font></div>
<br clear="none">
<br clear="none">
<div class="yiv8499684973y_msg_container" id="yiv8499684973yui_3_16_0_1_1480187447224_5803">
<div id="yiv8499684973">
<div id="yiv8499684973yui_3_16_0_1_1480187447224_5802">
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480187447224_5801">How
do you intend to
control the
pressure on the
receive tank? Just
vent it through a
check valve to the
water? You need to
design carefully
to prevent
contamination in
either direction.</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480187447224_5804">I
wouldn't use air
as the drive gas
under high
pressures, in
order to prevent
oxidation of the
oil. Charge with
nitrogen if you
intend to do this.</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480187447224_5805">To
generate the same
drive capability
as a hydraulic
pump, you are
talking about very
high precharge
pressure -
approaching the
pressure at which
HP bottled gas is
supplied, unless
you can source
e.g. 6000 psi
nitrogen and
regulate it down
to 2500-5000
depending on your
manipulator
requirements. In
any case, if your
cylinders are
single acting, or
even dual acting
with a single rod,
you have to
contend with the
force from the
ambient water
pressure, so your
receive tank
pressure needs to
be this at
minimum, and with
a pressure
reservoir source
instead of a pump,
that available
delta-P is further
reduced the moment
you demand any
fluid from the
system (i.e. HP
bottle pressure
will drop), so
your manipulator
becomes weaker
over time.</div>
<div dir="ltr">Just
a few things to
think about.</div>
<div dir="ltr">Sean</div>
<br clear="none">
<br clear="none">
<div class="yiv8499684973gmail_quote">On
November 25, 2016
5:25:47 AM MST,
hank pronk via
Personal_Submersibles
<a rel="nofollow" shape="rect" class="yiv8499684973moz-txt-link-rfc2396E" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></a>
wrote:
<blockquote class="yiv8499684973gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;padding-left:1ex;border-left-color:rgb(204, 204, 204);border-left-width:1px;border-left-style:solid;">
<div class="yiv8499684973yqt2885590970" id="yiv8499684973yqt95748">
<div style="color:rgb(0, 0, 0);font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;background-color:rgb(255, 255, 255);">
<div id="yiv8499684973yui_3_16_0_1_1480075807070_2825">Hi
All,</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480075807070_2825">I have an idea to
replace the
hydraulic pump
for my new
manipulator
with a air
over hydraulic
system. It is
quite simple,
the hydraulic
oil reservoir
is a hp tank
that can be
pressurized
from a
designated HP
supply. The
oil return
goes to
another HP
tank to
receive the
oil. This
eliminates the
pump
completely and
that is a
dream. The
manipulator
can go through
54 complete
extensions and
retractions,
that is 54
complete
movements of
all functions.
</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480075807070_2825">After the oil is used
up, the oil
can be
returned to
the pressure
tank by
reversing the
air flow.</div>
<div dir="ltr" id="yiv8499684973yui_3_16_0_1_1480075807070_2825">Hank</div>
</div>
</div>
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