[PSUBS-MAILIST] Cylinder tolerance

[Rick Patton via Personal_Submersibles]

I thought that I remembered hearing from the group before I had my hull
rolled that you were allowed to be half the thickness of the hull so the
K-350 being 1/4" plate, I could be an 1/8" out of round.

Rick

On Mon, Aug 22, 2022 at 2:15 AM hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Neat sub James, the question has been answered by Alec, but I recall that
> window opening were allowed a greater out of roundness.
> Hank
>
>
> On Monday, August 22, 2022, 02:36:59 AM MDT, James Frankland via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> Smaller picture.....
> [image: image.png]
>
> On Mon, 22 Aug 2022 at 08:57, James Frankland <
> jamesf at guernseysubmarine.com> wrote:
>
> Picture didn’t seem to come through
>
>
> On Monday, 22 August 2022, James Frankland <jamesf at guernseysubmarine.com>
> wrote:
>
> Hi
> The idea is to make a small simple sub that I can operate and launch
> alone.  I think I could make something like this pretty quick.
> I’m just getting prices to see if it’s feasible.  Kind of based the idea
> on c-bug, R300 and deep flight dragon.
> Cylinder is 650mm x 2000 unstiffened.   Hence the thickness.  Tower 6mm.
> The fins are not intended to be diving planes or control surfaces.  The 4
> motors would rotate and the sub simply drive about on the motors.  The fins
> are really just for looks....
>
> Just an idea at this stage.
>
> Alec.  Yes the pics came through thanks.  Could you send me the whole page
> with the diagram it refers to.?  Thanks.
>
> Vance.  I will have it written into the contract the tolerance, so if it’s
> out, I can refuse it.
>
> 1% of 650 is 6.5mm allowed.  Seems a lot to me....
>
> Just ideas at this stage.  Criticism and thoughts welcome.
> Regards
> James
>
>
> On Sunday, 21 August 2022, Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Hi James,
>
> The ABS rules specify two conditions. First, that the out of roundness
> does not exceed 1% of the diameter. The second is more complicated. There's
> a table with a coefficient on each axis, showing curves of allowable
> eccentricities. That table takes into account more variables than the first
> rule (for instance, the length of the cylinder.) I'll attach two images in
> low res, in the hope they are under the mailing list attachment limit that
> way. Probably the simplest way to spec a cylinder is just to use the 1%
> rule.
>
> In practice, I found this a very tricky fabrication issue. The cylinder
> was supplied rolled but not welded, and although I don't recall its
> eccentricity I'm sure it was nowhere near 1% initially. I stretched the
> cylinder into roundness with the stiffeners, rolling them in along the
> greater diameter and then rotating them. Their fit was so tight, and the
> forces needed to stretch the cylinder so great, that it took several months
> of work to get them in.
>
> Hopefully this comes through with two attachments, but if it doesn't let
> me know and I'll email them directly.
>
> Best,
> Alec
>
>
>
> On Sun, Aug 21, 2022 at 11:58 AM James Frankland via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Hi All
>
> Im getting some quotes in for some rolled cylinders.
>
> What do people think i should ask for as the tolerance on roundness?
>
> I believe (from memory) that the K350 plans specified "cylinder to be
> within 1/8th (3.175mm) on diameter for a 3ft (914mm) shell .
>
> im quoting for a 650mm inside diameter 10mm cylinder.
>
> Im feeling i want to ask for 1mm on diameter.
>
> What do you guys think?
>
> Thanks
> James
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