[PSUBS-MAILIST] calculation

Tue Jul 7 08:03:49 EDT 2015

Thanks Phil,that puts that theory to bed then.So what failed on the dome? Was it a laminated flange orsome thing like that?Alan
      From: Phil Nuytten via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Tuesday, July 7, 2015 5:21 PM
 Subject: Re: [PSUBS-MAILIST] calculation

AlanThe DeepWorker stainless dome retainer straps can’t be ‘wound tight’ – they go to a central UHMW hub just to put an even load on the acrylic hemi. The retaining straps are there to prevent the dome from burping or blowing off if the sub were to develop a high internal pressure that was unrelieved because of failure or damage to the over pressure vent. An unlikely event, but I did have a dome blow partly off in the early prototype ‘Sea Urchin’ many years ago. This was just upon hitting the surface with a relatively small overpressure. That was the last time I dove a sub without dome retainers. The water, she come in very fast!  It was during a  shoot for a show called ‘Frontier Man’ – I think it’s still on Youtube somewhere. Phil   

From: Alan James via Personal_Submersibles Sent: Monday, July 06, 2015 6:00 PMTo: Personal Submersibles General Discussion Subject: Re: [PSUBS-MAILIST] calculation Hank,I was looking at some Deep Worker photos. The dome retaining bandslook like they can be wound tight from a central point at the top.I am wondering if they pre stress these significantly so that there is less movementwhen they are compressed at depth. 
Also I commented on your retaining system when I first saw it, that I thought thevertical floatational force might move it upward, or the dome pivot out from the bottom.Perhaps you could exert more pressure on the dome with your clamping system?
Alan From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Tuesday, July 7, 2015 12:31 PM
Subject: Re: [PSUBS-MAILIST] calculation
 Does the window seat have some sort of inside diameter edge? I would think if it does not, then its pretty much guaranteed to slip with or without grease - with grease being the quieter less-terrifying option.  Best, Alec

 On Mon, Jul 6, 2015 at 6:50 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Sean,
Thank you for the input, I think I will just use weights like Alan says.
I am making a fixture to simulate the EPDM gasket compressed under my dome.  I want to test it with grease and without.  I will squeeze the gasket in the fixture then push the top plate sideways with a pusher bolt to see if the gasket allows movement.  I want to make sure my dome can expand and contract at depth.
Hank
--------------------------------------------
On Mon, 7/6/15, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Subject: Re: [PSUBS-MAILIST] calculation
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Monday, July 6, 2015, 9:08 AM

Hank - the force developed is dependent on the
stiffness of both the bolt material and of the specimen
you're pushing on.  You can't necessarily equate
this directly to torque because of friction in the bolt
threads and at the bolt end contact, and of course the
elasticity of the bolt itself. You can only estimate it. 
There are many online tools for calculating the developed
tensile force in a bolted connection, for example, but these
consider only the bolt as the deformable element, and
require an accurate estimate of coefficients of friction,
and this will change with lubrication. As you complicate the
system, it becomes more geometry dependent.
A 1" - 8 UNC 2A thread is 8 threads per
inch, so a set number of turns will give you the approximate
axial displacement (0.125" per revolution - approximate
because the bolt will change length under load). If you
assume a rigid fixture, then your strain is equal to the
overall change in length (calculated from # of bolt turns),
divided by the gauge length (distance over which the length
change occurs, which would be the length of your specimen
measured between the rigid fixture and the end of your jack
bolt). Compressive or tensile load is then calculated based
on the modulus of elasticity of the specimen. 
Alternatively, you can measure the load (make the bolt or
fixture into a load cell or strain gauge the specimen) and
calculate the material properties.
Load, axial displacement, modulus. You need any
two to calculate the third.
What are you making / testing?
Sean

On July 6, 2015 6:26:49 AM
MDT, hank pronk via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
Hi all,
I
need help, can anyone tell me how to calculate how much
force a bolt can push or pull using a torque wrench to turn
the bolt. So how many foot pounds of torque does it take to
rotate a bolt to  create 250 lbs push with a 1 in coarse
thread bolt.  I need to make a test fixture.
Hank

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