[PSUBS-MAILIST] Cylinder tolerance

[James Frankland via Personal_Submersibles]

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
>>>> _______________________________________________
>>>> Personal_Submersibles mailing list
>>>> Personal_Submersibles at psubs.org
>>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>>
>>>
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