Hi John,
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.
Regards Alan
----- 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:
Hi all
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.
Hope this makes sense.
Regards Alan