[Member-Forum] Moment of Inertia

Thu Mar 27 08:08:35 EDT 2014

Thanks Paul, that is very interesting. ~ Douglas S.

On Thu, Mar 27, 2014 at 6:05 AM, Paul Moorhouse <paul at steel-fish.com> wrote:

> Hi Douglas
>
> The traditional method was to cast using a slush of polymerised powder and
> liquid resin to keep the exotherm heat under control. The moulds were often
> quite rudimentary and the shrinkage large so massive over thickness is
> required to get what you want out of the casting. The thicker it is the
> more difficult it is to keep to a cooling rate that will not cause cracks.
> Once it has cracked, it is scrap. This is quite a contrast to how the
> material behaves at normal diving temperatures where it is extremely
> forgiving and in some configurations will extrude in preference to
> cracking. During the Alicia development we did a series of destructive
> model tests and the acrylic is definitely the toughest part of the
> submarine. We had an instrumentation cable port in the top of the test
> chamber that lead the wires out from the strain gauges on the inside
> surface of the test sphere. When they went bang at around 2,500 metres bits
> of acrylic came out of this ¾ hole and went clean through the roof of the
> building. We had to make a plastic plug to keep the debris inside the
> chamber.
>
>
>
> The German company making spheres for Triton are holding their cards close
> to their chest right now. I am hoping to be able to write about it when
> they they feel the time is right but for now the details remain under
> wraps. What I can tell you is they start with cell cast blocks over 200mm
> thick that have been slow polymerised under closely controlled conditions
> from 100% liquid. This increases the length of the polymer chains with
> superior mechanical properties as a result. These blocks are then heated
> and slowly squeezed between two metal formers to create the basic
> hemispheres. After machining and polishing the two hemispheres are bonded
> together using another new technique that produces a bond that is almost
> invisible and defect free.
>
>
>
> The new spheres are quite definitely the best that have ever been made.
>
>
>
> Paul
>
>
>
> *Paul Moorhouse*
>
> Design Engineer
>
> paul at steel-fish.com
>
> www.steel-fish.com
>
> #44 7837 542878
>
>
>
> *From:* Member-Forum [mailto:member-forum-bounces at psubs.org] *On Behalf
> Of *Douglas Suhr
> *Sent:* 26 March 2014 23:48
> *To:* Dan Still; PSUBS Member Discussion Group
>
> *Subject:* Re: [Member-Forum] Moment of Inertia
>
>
>
> "Hi Paul,
>
> can you tell us a bit more about the thermo forming of the 165mm sphere"
>
>
>
> I too am interested in hearing more about how such a thick personnel
> sphere is manufactured. Sounds like a daunting and frustrating task (with
> the multiple failures mentioned). ~ Douglas S.
>
>
>
> On Wed, Mar 26, 2014 at 9:17 AM, Dan Still <stillphototheater at yahoo.com>
> wrote:
>
> Anything with chips in them hate humans.
>
>
>
> On Wednesday, March 26, 2014 7:29 AM, Joe Perkel <josephperkel at yahoo.com>
> wrote:
>
> Wow, 24+ hours for email delivery and doubled to boot.
>
> Can iPads go insane?
>
> Joe
>
> Sent from Yahoo Mail for iPad <http://overview.mail.yahoo.com/?.src=iOS>
>
>
> ------------------------------
>
> *From: *Joe Perkel <josephperkel at yahoo.com>;
> *To: *member-forum at psubs.org <member-forum at psubs.org>;
> *Subject: *Re: [Member-Forum] Moment of Inertia
> *Sent: *Tue, Mar 25, 2014 4:00:01 PM
>
>
>
> Hi Paul,
>
> The question is anecdotal based on an off the cuff thought of upsizing the
> shell O.D. to 42" from 36". I am very hesitant to do this do to weight and
> handling issues however, several members have made a compelling rationale
> r/t simple comfort. At 53 I'm 6' 190 lbs and should expect that L to W
> ratio to change by build time!
>
> I have to think a bit about the shell thickness r/t welding and corrosion
> issues, but Depth no more than 350'. I seem to remember a cross section
> drawing of a T section somewhere with a simple L/W/H relationship to shell
> T, but can't find it again.
>
> I'll take that pdf if you don't mind. I'm not at home and won't be until
> later this week to do some number crunching.
>
> Thanks Paul!
>
>
> Joe
>
> Sent from Yahoo Mail for iPad
>
> Sent from Yahoo Mail for iPad <http://overview.mail.yahoo.com/?.src=iOS>
>
>
> ------------------------------
>
> *From: *Paul Moorhouse <paul at steel-fish.com>;
> *To: *'PSUBS Member Discussion Group' <member-forum at psubs.org>;
> *Subject: *Re: [Member-Forum] Moment of Inertia
> *Sent: *Tue, Mar 25, 2014 9:10:06 AM
>
>
>
> Joe
>
> As it happens, this is my day job. I have been designing submarine
> pressure vessels for the last 28 years. I am sure there are others on the
> forum who do this but I am happy to help if you would like, and others at
> PSUBS should the need arise.
>
> Frame size and spacing is inter-related and there is no one answer. I have
> developed some models based on the European pressure vessel code PD5500 so
> running a new configuration is easy and surprisingly quick. PD5500 produces
> much lighter vessels than ASME VIII which is really aimed at chemical
> plant. In this way it is more similar to military codes but it does rely on
> quality assurance levels that do not generally come with home construction.
> So to cater for this, you put a factor in. I apologise in advance for all
> of the calculations being in metric but give me info in either.
>
> I would need to know
>
> ·        Outside diameter
>
> ·        Shell thickness
>
> ·        Shell material
>
> ·        Frame material
>
> ·        Diving depth
>
> ·        Length of parallel body
>
> ·        Ends, hemi or 2:1 dished.
>
> ·        Preferred frame spacing
>
> ·        Inside or outside frames
>
> I can send you the PDF of the work sheet as the PD5500 sums do look very
> pretty.
>
> The next step is to design the hatch penetration and I can help you here
> also.
>
>
>
> This guy can thermo form your acrylic
>
> http://www.airesearch.nl/
>
>
>
>
>
> Regards
>
> Paul
>
>
>
> Paul Moorhouse
>
> www.steel-fish.com
>
>
>
>
>
>
>
> *From:* Member-Forum [mailto:member-forum-bounces at psubs.org] *On Behalf
> Of *Joe Perkel
> *Sent:* 25 March 2014 03:55
> *To:* PSUBS Member Discussion Group
> *Subject:* [Member-Forum] Moment of Inertia
>
>
>
> Where did I see the rule of thumb for T-section rib sizing relative to
> shell thickness? I can't seem to find it now.
>
> Joe
>
> Sent from Yahoo Mail for iPad <http://overview.mail.yahoo.com/?.src=iOS>
>
>
>
>
>
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