On Jan 19, 9:30 am, " wrote:
... I'll dive into my spare parts cabinet and look at it
again if I get some time. ...


Right, I just took it apart and put it back together. It is a Hammar
H20 E "for EPIRB use only". The insides are pretty much as I
remembered them. The major working parts are a knife and spring held
in place by a pin that is attached to a diaphragm that is held in
place by another spring. When it operates water pushes against the
diaphragm through two hollow pins on the knife side of the device
forcing the diaphragm into the low pressure chamber thus pulling the
retaining pin out and releasing the knife. The one I have sat in my
EPIRB in my cockpit for years and looks and operates like new.

There is one mysterious feature. On the top of the pressure casing
there is a small resin colored plug. It is visible from the outside
of the case through a hole in the label. I presume this keeps the
device from exploding if you take it up into space or something. On
the other hand it could be the little bit that dissolves every two
years so you have to replace it... Or, perhaps, they use the hole to
fill the chamber with inert gas... In any case, if the bung were out
the device would not operate. I suppose it is worth looking to make
sure it is there periodically, particularly if the release has been in
an airplane.

-- Tom.

On Sat, 19 Jan 2008 17:25:39 -0800 (PST), "
wrote:

... The major working parts are a knife and spring held
in place by a pin that is attached to a diaphragm that is held in
place by another spring. When it operates water pushes against the
diaphragm through two hollow pins on the knife side of the device
forcing the diaphragm into the low pressure chamber thus pulling the
retaining pin out and releasing the knife.
There is one mysterious feature. On the top of the pressure casing
there is a small resin colored plug. It is visible from the outside
of the case through a hole in the label. I presume this keeps the
device from exploding if you take it up into space or something. ...
I suppose it is worth looking to make
sure it is there periodically, particularly if the release has been in
an airplane.

-- Tom.


...er.... It takes about 6 psi EXCESS pressure like 13 ft depth of
water to actuate the sprung knife?

Clear on up to outer space, there is no excess pressure I know of.
Or am I misssing something?

Brian W

...er.... It takes about 6 psi EXCESS pressure like 13 ft depth of
water to actuate the sprung knife?

Clear on up to outer space, there is no excess pressure I know of.
Or am I misssing something?

Brian W

I take it he meant that it may be there to release pressure *inside* the
case to keep the case from "exploding" in a low pressure environment,
not imploding as would be the case of external pressure when sinking.
Red

On Jan 19, 7:15 pm, Red wrote:
....
I take it he meant that it may be there to release pressure *inside* the
case to keep the case from "exploding" in a low pressure environment,
not imploding as would be the case of external pressure when sinking.
Red

Yes, that's exactly what I was trying to say. It is a curious feature
and I'm just speculating about its purpose. Maybe it's for something
else.

-- Tom.

On Sun, 20 Jan 2008 00:15:08 -0500, Red wrote:

..er.... It takes about 6 psi EXCESS pressure like 13 ft depth of
water to actuate the sprung knife?

Clear on up to outer space, there is no excess pressure I know of.
Or am I missing something?

Brian W

I take it he meant that it may be there to release pressure *inside* the
case to keep the case from "exploding" in a low pressure environment,
not imploding as would be the case of external pressure when sinking.
Red


Yes, I see that possibility now.
In practice, containers can usually take several times more
internal over-pressure than internal under-pressure.
Take a look at your clear plastic soda bottle. It may go higher than
60 psi before going bang, but 2 or 3 psi from outside will do a number
on collapsing it.

Brian Whatcott Altus OK

On Sat, 19 Jan 2008 17:25:39 -0800 (PST), "
wrote:


There is one mysterious feature. On the top of the pressure casing
there is a small resin colored plug.

Obviously :-) a porous plug which equalizes pressure when dry and does
not do so when wet.

It is visible from the outside
of the case through a hole in the label. I presume this keeps the
device from exploding if you take it up into space or something. On
the other hand it could be the little bit that dissolves every two
years so you have to replace it... Or, perhaps, they use the hole to
fill the chamber with inert gas... In any case, if the bung were out
the device would not operate. I suppose it is worth looking to make
sure it is there periodically, particularly if the release has been in
an airplane.

-- Tom.

On Sun, 20 Jan 2008 11:02:16 +0000, Goofball_star_dot_etal
wrote:

On Sat, 19 Jan 2008 17:25:39 -0800 (PST), "
wrote:


There is one mysterious feature. On the top of the pressure casing
there is a small resin colored plug.

Obviously :-) a porous plug which equalizes pressure when dry and does
not do so when wet.


Thinking about that....if the leakage rate is slow, wet or dry,
then that would work for a hydrostatic release container which might
sink 13 feet in less than say 30 minutes....

Brian Whatcott Altus OK

On Jan 20, 1:02 am, Goofball_star_dot_etal
wrote:

Obviously :-) a porous plug which equalizes pressure when dry and does
not do so when wet.

That sounds reasonable and I suppose it would make the release depths
more consistent. For me the big question is, is this the bit that
goes bad in two years? As I've mentioned, mine was manufactured in
march of 2000 and it sat in my EPIRB case for years and I just
disassembled and inspected it yesterday and it looked absolutely
perfect...

-- Tom.