[PSUBS-MAILIST] Gamma bow dome

Fri Feb 27 09:56:36 EST 2015

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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