[PSUBS-MAILIST] Gamma bow dome

James Frankland via Personal_Submersibles personal_submersibles at psubs.org
Fri Feb 27 10:49:07 EST 2015 

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.
>>
>> Regards
>> James
>>
>>
>> ​
>>
>>
>>
>>
>> ​
>>
>> 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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>>>>>
>>>>>
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>>>>>
>>>>>
>>>>>
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>>>
>>>>>
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>>>>
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>
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