[PSUBS-MAILIST] Gamma bow dome

Pete Niedermayr via Personal_Submersibles personal_submersibles at psubs.org
Mon Mar 2 17:21:42 EST 2015


Would there be an advantage making viewport frames oversized to reduce warping?

Pete
--------------------------------------------
On Sat, 2/28/15, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] Gamma bow dome
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Date: Saturday, February 28, 2015, 12:31 PM
 
 ThanksAlan
         From: James Frankland
 via Personal_Submersibles
 <personal_submersibles at psubs.org>
 
 To: Personal
 Submersibles General Discussion
 <personal_submersibles at psubs.org> 
 
 Sent: Sunday,
 March 1, 2015 1:17 AM
  Subject: Re:
 [PSUBS-MAILIST] Gamma bow dome
  
  
 Alan,The four
 protrusions are the holes that the four mounting bolts
 attach to.  They are inside the hull and attach to dogs on
 the inside of the reinforcing ring. almost identical to a k
 boat hatch dog setup.RegardsJames
 
 On Friday, 27 February 2015,
 Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 
 
 James,in your
 retaining ring photo, what are the four protrusions
 with holes in,
 on the inside of the ring for?Alan
     
    From: James Frankland
 via Personal_Submersibles <personal_submersibles at psubs.org>
  To: Personal
 Submersibles General Discussion <personal_submersibles at psubs.org> 
  Sent: Saturday,
 February 28, 2015 4:49 AM
  Subject: Re:
 [PSUBS-MAILIST] Gamma bow dome
  
  
 It took me about 5 mins to do the drawing on
 MS paint! I think you mean something
 like Stachiw's book, page 524 fig 11.76.  Bottom
 drawing.  Probably will work just as well.  No machining
 required!
 
 
 On 27 February
 2015 at 15:35, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 Thanks, you went to some trouble making that
 drawing, but it certainly added clarity. In my case the
 outside wall of the acrylic is completely square and
 there's virtually no gap at all between seat and window,
 its literally a few thousandths. I could machine the seat to
 take an O-ring groove, as you did with the retaining ring.
 However, PVHO 2-2.11.1 says "As primary seals for
 standard window geometries shown in Figs. 2-2.1 through
 2-2.4, a soft elastomer compressed between the high pressure
 face of the window and retainer ring will be acceptable. The
 soft elastomeric seal may take the form of a flat gasket, or
 a seal ring with O, U, or X cross section." 
 Given its so easy to cut out a
 circular flat gasket, I think I'll try that first and
 see how it goes. If there are nuisance leaks, I could
 upgrade to an O ring by machining the appropriate groove,
 but I'll try the lazy approach first. These bolt-on
 window seats are nice in that they allow for later
 modification. 
 
 Best,
 Alec
 
 
 On Fri, Feb 27, 2015 at 9:56 AM, James
 Frankland via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 Hi Alec, The epdm
 gasket was really just to relieve stress on the seat of the
 dome.  This was with advice from the guy who built the
 Canary island subs who came to visit me.  Although of
 course it should provide sealing at higher pressure. 
  Emile made the dome and mounting
 ring and suggested I would need another seal for low
 pressure.  So, I made the low pressure seal an O ring
 sitting in a machined groove in the retaining ring.  
  See hastily drawn picture. 
  The gap where the O ring sits is
 nowhere near as severe as it looks in the picture, which is
 of course not to scale or anything.   I would love to say
 it was carefully engineered, but im afraid I just winged it
 a bit.  To start with the O ring groove was just a
 chamfer.  This didn't work as I couldn't get the O
 ring to stay in.  Then I machined it for a very small O
 ring.  Couldn't get it in.  Eventually, I got a groove
 and O ring combination that seemed to work.  There is lots
 of silicone grease on all surfaces as well.  It doesn't
 leak.  RegardsJames 
 ​  
 
 ​
 On 27 February 2015 at 14:05, Alec Smyth
 via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 Hi James,
 That's some good looking
 hardware! Just a question if I may. Do you have just the
 gasket for making a seal, or is there an O-ring as
 well? 
 My project sub
 has a bow dome seated in an aluminum ring. Currently the
 window is just sitting on a gasket with no O-ring, but
 I'm wondering whether to switch to an O ring. The window
 seat is 90 degrees square, so one possibility would be to
 chamfer the edge of the acrylic and put an O ring in the
 angle. That is what I did on Snoopy's hatch dome, it
 worked well and is a solution that doesn't require any
 changes to the seat. The other option is to put an O ring at
 the top of the acrylic and squeeze it with the retaining
 ring, but that would mean machining a chamfer into the seat,
 and would require machinery larger than what I have here. Or
 of course I could do nothing and see if it seals well with
 just an EPDM gasket.
 
 Thanks,
 Alec
 On Fri, Feb 27, 2015 at 8:40 AM, James
 Frankland via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 ​Hi Hank.   Yes,
 agreed, my dome does sit on a gasket.  The actual edge of
 the acrylic itself sits on a 1mm epdm gasket that sits onto
 the aluminium ring.  That ring bolts to the main
 reinforcing ring and has an o ring like you say.  Maybe
 this does give it a little bit of
 leeway. My dome is off at the moment,
 so I will have a look at the weekend and see if I can see
 any distortion on the reinforcing ring.  Im pretty sure
 there is none, or none that is detectable by the naked
 eye\straight ruler.  The alu ring seems to fis to it
 perfectly.   I suppose the best
 option is like you say, get it machined after welding.  You
 wont have to worry at all then. 
 ​   
 On 27 February 2015 at 13:23, hank pronk
 via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 
 
 James,
 
 I am just assuming it needs to be perfect ? and I can not
 imagine that it will not warp at least a small amount.  I
 am not experienced with how such heavy material will react.
 Your dome sits on a gasket witch may give you some
 forgiveness. Maybe Emile can comment having done this
 also.
 
 Hank--------------------------------------------
 
 On Fri, 2/27/15, James Frankland via
 Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 
 
 
  Subject: Re: [PSUBS-MAILIST] Gamma bow dome
 
  To: "Personal Submersibles General Discussion"
 <personal_submersibles at psubs.org>
 
  Received: Friday, February 27, 2015, 7:28 AM
 
 
 
  Do
 
  you need to go to all that trouble?  When I did mine,
 the
 
  reinforcing ring was milled flat on the seating surface
 and
 
  I just pre-heated it and welded it in.  It was so big
 I
 
  don't think there was any distortion and it
 doesn't
 
  leak. Just thinking of saving you
 
  what sounds like an expensive job.
 
  On 27 February 2015 at
 
  11:45, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 
  wrote:
 
  James,
 
 
 
  I am amazed at the equipment some of the big shops have.
 A
 
  vertical mill is probably the way to go.  I am checking
 out
 
  another option also.  There are machines made to
 machine
 
  pipe flanges that clamp on and are portable.  There is
 a
 
  company in Calgary that specializes in this. I am just
 not
 
  sure yet what the accuracy is yet.  It is nice that I
 live
 
  only 3 hr from a big oil town that caters to the oil
 
  industry.  You can tell that oil is low, and the shops
 are
 
  slower.  I ordered the ring on a Friday and it was
 ready
 
  Monday.
 
 
 
  Hank    --------------------------------------------
 
 
 
  On Fri, 2/27/15, James Frankland via
 Personal_Submersibles
 
  <personal_submersibles at psubs.org>
 
  wrote:
 
 
 
 
 
 
 
   Subject: Re: [PSUBS-MAILIST] Gamma bow dome
 
 
 
   To: "Personal Submersibles General
 Discussion"
 
  <personal_submersibles at psubs.org>
 
 
 
   Received: Friday, February 27, 2015, 4:08 AM
 
 
 
 
 
 
 
   Hi hank,Sounds like
 
 
 
   it will be a good
 
  modification.  How are they going to
 
 
 
   machine the ring?  Some sort of vertical
 
 
 
   mill?RegardsJames
 
 
 
 
 
 
 
   On Friday, 27 February 2015, hank pronk via
 
 
 
   Personal_Submersibles <personal_submersibles at psubs.org>
 
 
 
   wrote:
 
 
 
   Today I
 
 
 
   officially took the plunge and removed the forward
 
  ballast
 
 
 
   tank to install my new bow dome.  After much agony I
 
 
 
   decided to make the change.  I am not enjoying the
 sub
 
 
 
   because the forward window arrangement is not ideal
 for
 
 
 
   lakes with marginal visibility.  I went to the big
 
  city
 
 
 
   yesterday and picked up the reinforcing ring and
 should
 
  have
 
 
 
   it fitted in a couple of days.  I am bringing in a
 
  pressure
 
 
 
   welder to weld the ring and then the sub is off to
 the
 
  big
 
 
 
   city to machine the ring.
 
 
 
 
 
 
 
   Hank
 
 
 
 
 
 
 
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