-----
Original Message -----
Sent:
Wednesday, February 15, 2012 5:21 PM
Subject:
RE: [PSUBS-MAILIST] Air compensation experiments
Alan,
Get
a Norgren plastic regulator and fit it to the downstream side of a scuba
reg. That gives you a normal 150 psi supply to a standard reg. you can
dial up 5 psi easily. I put in a SS spring.
Hugh
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan
James
Sent: Wednesday, 15 February 2012 4:59 p.m.
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Air
compensation experiments
Just tried some
light springs in the first stage & running it off low
pressure.
Even though the
springs were very light it was developing more pressure than I
wanted.
So very hard to
get a fine adjustment with springs.
Am realizing that
the fact this first stage just came back from servicing has a lot to do with
things.
New O-rings
throughout, & the operation was a bit stiff
initially.
Tried again
without the spring & off the low pressure. I got a flow without any
pressure differential.
I was getting
1psi pressure in air then 2psi when the regulator was about a foot down in
the water
I measured the
pressure when running the springless first stage off high pressure & it
was 11 psi.
From what I've
gleaned from other posts this would be too much
pressure.
I
may continue with the springless first stage running off the low
pressure but monitor it to make sure it
doesn't drop
below ambient.
----- Original
Message -----
Sent: Wednesday,
February 15, 2012 1:38 PM
Subject: Re:
[PSUBS-MAILIST] Air compensation experiments
I connected the
first stage without spring to another first stage fitted to the tank
because if I ran my
springless
first stage straight from the tank then that tank would be solely
dedicated to the equalization of
the motors, or
hull if I went that way. I only have two tanks & it's a bit of a
safety feature that I've incorporated
to have them
both running my life support either together or
separately.
Also I can play
around with the level of the regulator in the water column in relation to
the height of the motors
by having
it separate from the tank.
When testing I
didn't put the hose running from the reg in the water. I just lowered the
1st stage a couple of
feet in the
water to create a pressure differential. But as said very poor flow off
the low pressure.
Yes I remember
Karl saying he let the over pressure bubble out the seals on the way
up.
Also remember
someone commenting recently that having a balanced pressure across the
seals was a lot kinder
on them,
however I would rather ere on the side of having air bubble out the seals
than water coming in.
Am hunting down
some light springs for the first stage to try & get a slight over
pressure off the low pressure feed.
I also want to
try oil compensating the motors with the ambient pressure coming from a
regulator.
So further
experimentation required.
-----
Original Message -----
Sent: Wednesday,
February 15, 2012 11:41 AM
Subject: Re:
[PSUBS-MAILIST] Air compensation experiments
Alan,
Why did you have the first stage without
spring connected to the low pressure side of a separate normal first
stage? I think you can accomplish air compensation with only the
single first stage with no spring. I also think you need to have
the compensation hose connected to something that will contain the
pressure as opposed to just putting the hose in water as it sounds like
you did. Without a sealed end you end up with the same amount of
pressure on both sides of the first stage piston (assuming a piston
arrangement) which I think would lead to the high pressure valve inside
the first stage opening indiscriminately. Back pressure is
required.
Somewhere along the way, I don't recall if it was when
I talked to Karl at UI, or maybe what I read on this list, Karl has no
pressure release valve on his motors but just lets the air bleed out
through the motor housing seals when it is strong enough to do so.
That insinuates the motors are always under some amount of positive
pressure above ambient providing the back pressure needed to seal the
high pressure valve and keep air from bleeding
out.
Jon
On 2/14/2012 2:41 AM, Alan James wrote:
I posted a
little while back about Karl's system of air compensating his motors
using a
first stage
regulator with the spring removed.
I had a
system made up whereby I could run my first stage without spring from a
low pressure hose
connected to
the low pressure port of a 1st stage on the tank. I was thinking of
using this system to
equalize an
ambient sub hence the desire to run it off the low pressure
port.
All right in
theory but when I stuck the regulator under the water there was very
little air coming out.
To make
matters worse the air still came out when the 1st stage was taken from
the water.
I then ran
the system off high pressure, & the air came out before the
reg had descended in to the water
column.
I could stop
the flow easy enough with a finger; so a bit of back pressure would
control it.
The
conclusion to date is that it isn't as sensitive as a 2nd stage
regulator.
Am going to
source some light springs & hopefully develop a slight pressure
above ambient off the low pressure port.
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