<div dir="ltr">Unfortunately I don't know the hardness, but it would be super high because the material is polycarbonate sheet. In my case the ring does not serve as a gasket. The dome is sealed by an O ring. The square edge of the acrylic is chamfered to take the O ring, and the flat plastic ring is just a spacer to get the O ring to touch both the chamfered acrylic and the window seat to form the initial seal. I had to experiment with a few thicknesses until I found one that made everything fit together just right. It was something like 1/16". <div><br></div><div>Best,</div><div><br>Alec</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jul 6, 2015 at 9:58 PM, hank pronk via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Alec, do you know the hardness of the plastic ring. The Acrylics hand book recommends min duro 80.<br>
<span class="">Hank--------------------------------------------<br>
On Mon, 7/6/15, Alec Smyth via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br>
<br>
Subject: Re: [PSUBS-MAILIST] calculation<br>
To: "Personal Submersibles General Discussion" <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
</span> Received: Monday, July 6, 2015, 9:52 PM<br>
<div class="HOEnZb"><div class="h5"><br>
A flat<br>
ring cut from thin plastic and lubricated with vacuum grease<br>
on both sides. I'm glad to say it doesn't make any<br>
sound at all.<br>
Alec<br>
On Mon, Jul 6, 2015 at 9:32<br>
PM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
wrote:<br>
<br>
<br>
Alec,<br>
<br>
What is under your dome.<br>
<br>
Hank--------------------------------------------<br>
<br>
On Mon, 7/6/15, Alec Smyth via<br>
Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
wrote:<br>
<br>
<br>
<br>
Subject: Re: [PSUBS-MAILIST] calculation<br>
<br>
To: "Personal Submersibles General Discussion"<br>
<<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
Received: Monday, July 6, 2015, 8:31 PM<br>
<br>
<br>
<br>
Does the<br>
<br>
window seat have some sort of inside diameter edge? I<br>
would<br>
<br>
think if it does not, then its pretty much guaranteed<br>
to<br>
<br>
slip with or without grease - with grease being the<br>
quieter<br>
<br>
less-terrifying option.<br>
<br>
Best,<br>
<br>
Alec<br>
<br>
On Mon, Jul 6, 2015 at 6:50<br>
<br>
PM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
wrote:<br>
<br>
<br>
<br>
<br>
<br>
Sean,<br>
<br>
<br>
<br>
Thank you for the input, I think I will just use<br>
weights<br>
<br>
like Alan says.<br>
<br>
<br>
<br>
I am making a fixture to simulate the EPDM gasket<br>
compressed<br>
<br>
under my dome. I want to test it with grease and<br>
<br>
without. I will squeeze the gasket in the fixture<br>
then<br>
<br>
push the top plate sideways with a pusher bolt to see if<br>
the<br>
<br>
gasket allows movement. I want to make sure my dome<br>
can<br>
<br>
expand and contract at depth.<br>
<br>
<br>
<br>
Hank<br>
<br>
<br>
<br>
--------------------------------------------<br>
<br>
<br>
<br>
On Mon, 7/6/15, Sean T. Stevenson via<br>
Personal_Submersibles<br>
<br>
<<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
wrote:<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
Subject: Re: [PSUBS-MAILIST] calculation<br>
<br>
<br>
<br>
To: "Personal Submersibles General<br>
Discussion"<br>
<br>
<<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
<br>
<br>
Received: Monday, July 6, 2015, 9:08 AM<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
Hank - the force developed is dependent on the<br>
<br>
<br>
<br>
stiffness of both the bolt material and of the<br>
specimen<br>
<br>
<br>
<br>
you're pushing on. You can't necessarily<br>
<br>
equate<br>
<br>
<br>
<br>
this directly to torque because of friction in the<br>
bolt<br>
<br>
<br>
<br>
threads and at the bolt end contact, and of course<br>
the<br>
<br>
<br>
<br>
elasticity of the bolt itself. You can only estimate<br>
<br>
it. <br>
<br>
<br>
<br>
There are many online tools for calculating the<br>
<br>
developed<br>
<br>
<br>
<br>
tensile force in a bolted connection, for example,<br>
but<br>
<br>
these<br>
<br>
<br>
<br>
consider only the bolt as the deformable element, and<br>
<br>
<br>
<br>
require an accurate estimate of coefficients of<br>
<br>
friction,<br>
<br>
<br>
<br>
and this will change with lubrication. As you<br>
complicate<br>
<br>
the<br>
<br>
<br>
<br>
system, it becomes more geometry dependent.<br>
<br>
<br>
<br>
A 1" - 8 UNC 2A thread is 8 threads per<br>
<br>
<br>
<br>
inch, so a set number of turns will give you the<br>
<br>
approximate<br>
<br>
<br>
<br>
axial displacement (0.125" per revolution -<br>
<br>
approximate<br>
<br>
<br>
<br>
because the bolt will change length under load). If<br>
you<br>
<br>
<br>
<br>
assume a rigid fixture, then your strain is equal to<br>
<br>
the<br>
<br>
<br>
<br>
overall change in length (calculated from # of bolt<br>
<br>
turns),<br>
<br>
<br>
<br>
divided by the gauge length (distance over which the<br>
<br>
length<br>
<br>
<br>
<br>
change occurs, which would be the length of your<br>
<br>
specimen<br>
<br>
<br>
<br>
measured between the rigid fixture and the end of<br>
your<br>
<br>
jack<br>
<br>
<br>
<br>
bolt). Compressive or tensile load is then calculated<br>
<br>
based<br>
<br>
<br>
<br>
on the modulus of elasticity of the specimen. <br>
<br>
<br>
<br>
Alternatively, you can measure the load (make the<br>
bolt<br>
<br>
or<br>
<br>
<br>
<br>
fixture into a load cell or strain gauge the<br>
specimen)<br>
<br>
and<br>
<br>
<br>
<br>
calculate the material properties.<br>
<br>
<br>
<br>
Load, axial displacement, modulus. You need any<br>
<br>
<br>
<br>
two to calculate the third.<br>
<br>
<br>
<br>
What are you making / testing?<br>
<br>
<br>
<br>
Sean<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On July 6, 2015 6:26:49 AM<br>
<br>
<br>
<br>
MDT, hank pronk via Personal_Submersibles<br>
<br>
<br>
<br>
<<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>
<br>
wrote:<br>
<br>
<br>
<br>
Hi all,<br>
<br>
<br>
<br>
I<br>
<br>
<br>
<br>
need help, can anyone tell me how to calculate how<br>
much<br>
<br>
<br>
<br>
force a bolt can push or pull using a torque wrench<br>
to<br>
<br>
turn<br>
<br>
<br>
<br>
the bolt. So how many foot pounds of torque does it<br>
take<br>
<br>
to<br>
<br>
<br>
<br>
rotate a bolt to create 250 lbs push with a 1 in<br>
<br>
coarse<br>
<br>
<br>
<br>
thread bolt. I need to make a test fixture.<br>
<br>
<br>
<br>
Hank<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
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</div></div></blockquote></div><br></div>