[PSUBS-MAILIST] Gamma bow dome
Adam Lawrence via Personal_Submersibles
personal_submersibles at psubs.org
Mon Mar 2 18:41:09 EST 2015
Hi Pete,
I haven't commented on here for 10 years I bet!
Anyways, here is one approach, you can move the weld away from the port by making the port larger, basically integrating part of the hull into the port. I will attach a screen shot.
Best Regards,
Adam
-----Original Message-----
From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Pete Niedermayr via Personal_Submersibles
Sent: Monday, March 2, 2015 4:22 PM
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Gamma bow dome
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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