[PSUBS-MAILIST] Personal_Submersibles Digest, Vol 120, Issue 40

Wed Aug 16 22:25:12 EDT 2023

Hi Cliff,
I am interested in your comments re the pump slippage etc and operation of
the VBTs when you were using them.
My approach, untried and purely theoretical, was that most of the VBT
adjustment would be done just below the surface and only minor adjustment
for compression of vessels etc would be done at depth.  
I do appreciate that weight balance appears more foolproof.  Regards, Hugh 

-----Original Message-----
From: Personal_Submersibles <personal_submersibles-bounces at psubs.org> On
Behalf Of via Personal_Submersibles
Sent: Thursday, August 17, 2023 1:02 PM
To: personal_submersibles at psubs.org
Subject: Personal_Submersibles Digest, Vol 120, Issue 40

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Today's Topics:

   1. Re: Re VBT Pump (Cliff Redus via Personal_Submersibles)

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Message: 1
Date: Thu, 17 Aug 2023 01:01:56 +0000 (UTC)
From: Cliff Redus via Personal_Submersibles
	<personal_submersibles at psubs.org>
To: via Personal_Submersibles <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Re VBT Pump
Message-ID: <2137621386.758356.1692234116222 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

 Hugh, thanks for update on QSub.? I am looking forward to her dunk test in
your new test pool. I quite enjoyed sitting in her pressure hull in your
shop in New Zealand a few years back.? She will be quite something when
complete.
Best
    On Wednesday, August 16, 2023 at 06:43:41 PM CDT, via
Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Thanks, Cliff, Alec, Vance, Jon.

The model I was looking at, correction, was the Oberdorfer 994 which is same
as a 2000 series but 3/8" - 1/2"? and direct mounted not foot mounted as per
the 2000 series.

The other pump I liked was the Wanner D10 which is diaphragm and can do no
slippage and 250 -300 psi etc but it is not bidirectional.? However that can
be fixed with valves.

I am making some progress with my Q-Sub but made the mistake of going too
complex and trying to do everything.? I? have had issues with --- 1. BMS
systems for the LiFePO4 batteries and had to replace these.
2. Precharge systems for the 72 v and 144 volt electrics and voltage spikes.
3. Gear cable kinking for the mercruiser sternlegs.
4. Inaccessible fuses and not motor rated.
5. Mechanical seal leakage on the hydraulics.
6. Joystick pot issues.
7. Canbus systems at different voltages.
8. Rotary sensors too coarse required op amp addition to amplify signals for
small rotary movements with steering.
9. Port Engine starting issues.
10. Oil compensation line fittings leaks.
11. Software issues.

Still plugging along.? IN the meantime I have built a test pool same-same
Hank 8 ft deep 12 wide x 27 long, and another gantry crane for PVHO removal,
as well as a shed just for the sub.? This year it has to be finished.? Has
not even been in the pool yet!!
Regards,? Hugh

-----Original Message-----
From: Personal_Submersibles <personal_submersibles-bounces at psubs.org> On
Behalf Of via Personal_Submersibles
Sent: Thursday, August 17, 2023 3:21 AM
To: personal_submersibles at psubs.org
Subject: Personal_Submersibles Digest, Vol 120, Issue 36

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When replying, please edit your Subject line so it is more specific than
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Today's Topics:

? 1. Re: FW: VBT pump (Cliff Redus via Personal_Submersibles) ? 2. Re: FW:
VBT pump (Alec Smyth via Personal_Submersibles) ? 3. Re: FW: VBT pump (Jon
Wallace via Personal_Submersibles)

----------------------------------------------------------------------

Message: 1
Date: Wed, 16 Aug 2023 13:29:07 +0000 (UTC)
From: Cliff Redus via Personal_Submersibles ???
<personal_submersibles at psubs.org>
To: via Personal_Submersibles <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] FW: VBT pump
Message-ID: <536726240.403633.1692192547749 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

 Hugh, on my original design for the R300 I had a hard VBT just aft of the
pilot. At the time I had a small HPU in the boat.? My plan was to use a
Oberdorfer Bronze gear pump driven by a small hydraulic motor to move water
in and out of the VBT.? I don't remember the specs on the pump.? I had
motorized ball valves on the vent and flood side of the VBT.? Prior to using
this set up, I did some testing of this gear pump which I still have.? What
I found was an unacceptable amount of flow slippage at my max design depth.?
There was so much slippage that the pump could not blow the VBT at max
depth.? At that point I abandoned using a pump and vent to blowing the VBT
with air.? I eventually abandoned the VBT altogether for operability
reasons.? When I used this hard VBT to get neutral on the surface, the
pressure in the tank was low.? When at depth if I ever tried to use the VBT,
water would rush in until the pressure equalized with ambient water
pressure.? This made the boat nega!
 tively buoyant until air was added.? The other thing that bugged me was I
had a float style level sensor in the VBT.? The water level in the VBT was
always moving around so you never trust the reading.? I eventually abandoned
the VBT and now just add ballast at the boat CG where the VBT was located.?
I find this works great.? The other issue is the VBT restricted access to
equipment aft of the VBT so to work on any of this equipment, I had to
remove the VBT.? ?All in all, I found the VBT to be a pain in butt.
Cliff
Oberdorfer 944 Bronze

? ? On Sunday, August 13, 2023 at 04:57:24 PM CDT, via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:? 

Hi Guys

 ?

What make of pump is best for VBT water transfer in/out for 250 psi 1.5 kw.

I am looking at a gear pump 1.5kw Oberdorfer 944 Bronze.? These are only
rated for 10 bar.? I tried an hydraulic gear pump 30cc where I had a
stainless and bronze gear set made up but the aluminium body corroded form
the trials and I just found that they had used steel backed sleeve bearings.

 ?

Regards,

Hugh
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Message: 2
Date: Wed, 16 Aug 2023 09:41:53 -0400
From: Alec Smyth via Personal_Submersibles ???
<personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion ???
<personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] FW: VBT pump
Message-ID:
??? <CABECYQ7JnW3k0Jz+wtvG64tx4pApp=vj5vkF9yWW2NN0fQMU3Q at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

I second that (getting rid of VBT). I got rid of the VBT in my K250 years
ago to make space and turn it into a 2-person and to try and to simplify,
and it worked so well I never thought of using any other method on the
current sub. The only difference with Cliff's method is that I add or remove
floats, while he uses ballast. But either way, once you have a reference
point for how much ballast/buoyancy you need for a given crew weight, you
just make incremental changes and it never fails. You may be off neutral by
just a few pounds, but if you have vertical thrusters they're usually just
ticking over at slow RPMs to compensate.

Best,
Alec

On Wed, Aug 16, 2023 at 9:30?AM Cliff Redus via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hugh, on my original design for the R300 I had a hard VBT just aft of 
> the pilot. At the time I had a small HPU in the boat.? My plan was to 
> use a Oberdorfer Bronze gear pump driven by a small hydraulic motor to 
> move water in and out of the VBT.? I don't remember the specs on the 
> pump.? I had motorized ball valves on the vent and flood side of the 
> VBT.? Prior to using this set up, I did some testing of this gear pump 
> which I still have.? What I found was an unacceptable amount of flow 
> slippage at my max design depth.? There was so much slippage that the 
> pump could not blow the VBT at max depth.? At that point I abandoned 
> using a pump and vent to blowing the VBT with air.? I eventually 
> abandoned the VBT altogether for operability reasons.? When I used 
> this hard VBT to get neutral on the surface, the pressure in the tank 
> was low.? When at depth if I ever tried to use the VBT, water would 
> rush in until the pressure equalized with ambient water pressure.?
> This made the boat negatively buoyant until air was added.? The other 
> thing that bugged me was I had a float style level sensor in the VBT.?
> The water level in the VBT was always moving around so you never trust 
> the reading.? I eventually abandoned the VBT and now just add ballast 
> at the boat CG where the VBT was located.? I find this works great.? 
> The
other issue is the VBT restricted access to equipment aft of
> the VBT so to work on any of this equipment, I had to remove the VBT.
All
> in all, I found the VBT to be a pain in butt.
>
> Cliff
>
> Oberdorfer 944 Bronze
>
> On Sunday, August 13, 2023 at 04:57:24 PM CDT, via 
> Personal_Submersibles < personal_submersibles at psubs.org> wrote:
>
>
> Hi Guys
>
>
>
> What make of pump is best for VBT water transfer in/out for 250 psi 
> 1.5
kw.
>
> I am looking at a gear pump 1.5kw Oberdorfer 944 Bronze.? These are 
> only rated for 10 bar.? I tried an hydraulic gear pump 30cc where I 
> had a stainless and bronze gear set made up but the aluminium body 
> corroded form the trials and I just found that they had used steel 
> backed
sleeve bearings.
>
>
>
> Regards,
>
> Hugh
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
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Message: 3
Date: Wed, 16 Aug 2023 15:20:44 +0000 (UTC)
From: Jon Wallace via Personal_Submersibles ???
<personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion ???
<personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] FW: VBT pump
Message-ID: <1959084270.469930.1692199244774 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

 I'll chime in here...I removed the VBT from the K600 because it was fairly
well rusted inside and needed to be replaced, however I am planning on using
the ballast/float method instead and forgoing the VBT altogether for many of
the reasons Alec and Cliff cited.? I will say that it can be challenging to
change ballast on-station since the weight/floatation has to be transferred
somewhere and by somebody, however I see the K600 being trimmed for specific
missions prior to launch and not being trimmed dynamically on-station to
embark/disembark passengers or equipment.
Jon

? ? On Wednesday, August 16, 2023 at 09:43:35 AM EDT, Alec Smyth via
Personal_Submersibles <personal_submersibles at psubs.org> wrote:? 

 I second that (getting rid of VBT). I got rid of the VBT in my K250 years
ago to make space and turn it into a 2-person and to try and to
simplify,?and it worked so well I never thought of using?any other method on
the current sub. The only difference with Cliff's method is that I add or
remove floats, while he uses ballast. But either way, once you have a
reference point for how much ballast/buoyancy you need for a given crew
weight, you just make incremental changes and it never fails. You may be off
neutral by just a few pounds, but if you have vertical thrusters they're
usually just ticking over at slow RPMs to compensate.

Best,Alec
On Wed, Aug 16, 2023 at 9:30?AM Cliff Redus via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

 Hugh, on my original design for the R300 I had a hard VBT just aft of the
pilot. At the time I had a small HPU in the boat.? My plan was to use a
Oberdorfer Bronze gear pump driven by a small hydraulic motor to move water
in and out of the VBT.? I don't remember the specs on the pump.? I had
motorized ball valves on the vent and flood side of the VBT.? Prior to using
this set up, I did some testing of this gear pump which I still have.? What
I found was an unacceptable amount of flow slippage at my max design depth.?
There was so much slippage that the pump could not blow the VBT at max
depth.? At that point I abandoned using a pump and vent to blowing the VBT
with air.? I eventually abandoned the VBT altogether for operability
reasons.? When I used this hard VBT to get neutral on the surface, the
pressure in the tank was low.? When at depth if I ever tried to use the VBT,
water would rush in until the pressure equalized with ambient water
pressure.? This made the boat nega!
 tively buoyant until air was added.? The other thing that bugged me was I
had a float style level sensor in the VBT.? The water level in the VBT was
always moving around so you never trust the reading.? I eventually abandoned
the VBT and now just add ballast at the boat CG where the VBT was located.?
I find this works great.? The other issue is the VBT restricted access to
equipment aft of the VBT so to work on any of this equipment, I had to
remove the VBT.? ?All in all, I found the VBT to be a pain in butt.
Cliff
Oberdorfer 944 Bronze

? ? On Sunday, August 13, 2023 at 04:57:24 PM CDT, via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:? 

Hi Guys

 ?

What make of pump is best for VBT water transfer in/out for 250 psi 1.5 kw.

I am looking at a gear pump 1.5kw Oberdorfer 944 Bronze.? These are only
rated for 10 bar.? I tried an hydraulic gear pump 30cc where I had a
stainless and bronze gear set made up but the aluminium body corroded form
the trials and I just found that they had used steel backed sleeve bearings.

 ?

Regards,

Hugh
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Personal_Submersibles at psubs.org
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Personal_Submersibles at psubs.org
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