[PSUBS-MAILIST] conical hatch seat troubles

Fri Dec 2 10:02:21 EST 2016

If the sealing is handled entirely by the elastomer, then I wouldn't be too concerned about a 0.005" gap on the conical face.  0.002" would be better, but realistically you are correct in that both parts will exhibit deflection under pressure. As long as the hatch is locked in place by the contact friction, it should be able to carry the shell stress. Extreme stress concentration at the highest points of contact will self relieve by local yielding, and the deformation will likely take care of equalizing the rest.

The sandpaper / polish idea has merit to restore roundness.

Sean

On December 1, 2016 6:34:39 PM MST, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Sean,I figured out what your asking about the o-ring.  Yes it is
>possible to reduce the extrusion gap to zero, with the exception of the
>small area that has a .01 gap between the hatch and seat.  I have to
>assume there is an extrusion gap in that short area of .01 or less.  I
>would estimate that 25 lbs of water pressure would compress the o-ring
>so the hatch  is tight with metal to metal.Hank 
>
>On Thursday, December 1, 2016 2:27 PM, hank pronk via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
>
>Hi Sean,No the seal comes from the o-ring, the metal to metal is to
>carry the hull stress.  It is my feeling it will be okay because I have
>a significant reinforcement with the land ring.  Just a gut feeling
>lol.  I am not sure what you mean by compressing thee o-ring to zero.
> The hatch will close to within .02 in with vacuum from the compressor,
>the   o-ring is completely encapsulated at that point. Hank 
>
>On Thursday, December 1, 2016 12:53 PM, Sean T. Stevenson via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
>
>Hank - are you expecting the conical interface to perform as a metal to
>metal seal at depth? Or merely to carry the hull shell stresses? Do you
>know how much pressure is required to compress your o-ring sufficiently
>to reduce the extrusion gap to zero? Is this even possible? Or does the
>cone engage and prevent it?Sean
>
>
>On December 1, 2016 10:38:23 AM MST, hank pronk via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Brian,I test for fit with the o-ring out.  Don't worry about yours,
>flat hatches will bend like butter.  My K350 hatch had a .04 in dip in
>it and it flattened out right away.  You just need a bit more weight
>pulling on your hatch.  Gamma used to drip on every dive from the hatch
>seal.  I made an adjustment to tighten the one dog and that cured it.
> How hard is your o-ring?Hank 
>
>On Thursday, December 1, 2016 9:38 AM, Brian Cox via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
>
>Hank,   Is that with out the o ring installed?     Now you've got me
>worried,  I had to give my hatch a little help by sitting on it when I
>pulled a vacuum on it.  I'm not sure why exactly I'll have to check
>again. Brian
>
>--- personal_submersibles at psubs.org wrote:
>
>From: hank pronk via Personal_Submersibles
><personal_submersibles at psubs.org>
>To: Personal Submersibles General Discussi!
>on<personal_submersibles at psubs.org>
>Subject: Re: [PSUBS-MAILIST] conical hatch seat troubles
>Date: Thu, 1 Dec 2016 15:22:15 +0000 (UTC)
>
>Carsten,I can turn it but it is very heavy and wants to wobble in the
>seat or climb out because it is conical.  It is a solution though!   Is
>it necessary though?Hank 
>
>On Thursday, December 1, 2016 4:56 AM, "MerlinSub at t-online.de via
>Personal_Submersibles" <personal_submersibles at psubs.org> wrote:
> 
>
>  Hank can you turn the hatch in the seat ? 
> 3 Peace of sandpater all 120 degree and turning and water dripping
>from a hose or later Piston Paste between hatch and seat ? Making a
>leaver on the hatch and running the hole day around the submarine?30
>Turns clockwise and 30 turns anticclock. Than again. Do you have
>friends liking hard walking? Its a good evening with two friends and
>some sixpacks of beer It was exact that way Emile and I making the
>final seat of a dome seat.  vbr Carsten
>    -----Original-Nachricht-----Betreff: [PSUBS-MAILIST] conical hatch
>seat troublesDatum: 2016-12-01T12:00:56+0100Von: "hank pronk via
>Personal_Submersibles" <personal_submersibles at psubs.org>An: "Personal
>Submersibles General Discussion" <personal_submersibles at psubs.org>   Hi
>All,I have a problem with my conical  hatch seat.  I have discovered
>that I have a .005 in gap between the hatch and seat in two spots.  It
>seems the seat is oval with a gap at each end.  I have no way of
>measuring this other than placing video cassette tape ribbon strips
>between the hatch and seat.  What I do is, I cut the ribbon into 3 inch
>strips, then tape them in place so they are hanging over the seat.  I
>put one every two inches, then close the hatch.  The ribbons are then
>trapped tight in the gap.  if the ribbons can pull out then there is a
>gap.  Sure enough, I can remove one at the front, so I put two ribbons
>on top of each other in that spot and it still pulls out.  I add
>another making 3 ribbons thick and it is tight.  Then I tried doubling
>one ribbon in the front and one opposite in the back and they were
>tight.  The conclusion is that the seat is oval by .005 in at each end.
> I put the ! hatchback in the lathe and re-faced it, to be sure it is
>not the hatch.  It is the seat, it seems my flange facing machine is
>not perfect-not a big surprise.  This is still very good for a portable
>home made tool.I don't know if this a problem or not, how accurate does
>this have to be?  Will the assembly simply bend?  My feeling is the
>hatch and seat will deform to match under pressure.  To put it into
>perspective, I just measured a hair and that is .01 in. the same as the
>total gap combined.Hank
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