New Bug Reports/Feature Requests

[Linus Torvalds]

On Wed, Feb 24, 2016 at 6:25 PM, Linus Torvalds
<torvalds at linux-foundation.org> wrote:
>
> And this time, if you actually put in 15.3 liter, with subsurface you
> get a nominal size of 127 cuft, and a "actual" size of 119.6. So this
> time the "120" in the "HP120" is the actual size.
>
> But it's almost impossible to tell ahead of time. Is it the nominal or
> the actual size? Who can tell.

Ok, I went back and tried to look at a number of cylinders. Not all
that many, because quite frankly, it's painful to try to look things
up, but I tried to find a pattern.

The most common cylinder size in recreational scuba is AL80, and
everybody seems to do that by nominal size (so 77.4 actual).

The other sizes are really all across the map. The Luxfer AL72 and
AL50 is also nominal (real: 69.9 and 48.4).

But then the Luxfer and Catalina AL53 and AL63 look to be by actual size.

And then there's a Luxfer AL19/27 that says that the real size is
actually 19.9/27.9 cuft. Everybody else rounds to nearest, or rounds
up.

There's a Luxfer AL92 that claims a 3200 psi working pressure (crazy),
and has a real size of 90.3. That doesn't make sense in *any* model.
At 3200 psi, if the real size is 90.3, the nominal size should be
around 95. In no case does "92" make sense.

Most of the *steel* cylinders seem to be "actual size", although I
found one LP80 by Faber that seemed to take the Aluminum approach and
was just 78 (which is odd - since it's an LP cylinder, that's neither
actual _nor_ nominal, because at 2400+10% the air compressibility
hasn't become an issue yet.

But for the steel cylinders, there's the issue of some of them using
the plus-size (pretty much all LP, but also a lot of the HP ones). I
didn't do the math.

And the X8-119 that we looked at is claimed to be "real" 119, but as
mentioned earlier, when I take the claimed metric size, I don't
actually get that. But there might be rounding issues going on, so who
knows.

And I don't actually know how trustworthy the list I found is. It's
here, in case somebody cares:

  http://www.indianvalleyscuba.com/services%20page/Tank%20Inspection/information/CYLINDER%20SPECIFICATIONS.pdf

but on the whole I don't really find anything in there that changes my
opinion that "Imperial sizes are not reliable". Even when you find
spec sheets like this, they leave you wondering how accurate they
really are. Where did the numbers come from? Some manufacturers are
better than others in actually giving those things, it may be that
parts of those numbers in that table are just "we don't know, so we'll
just assume the name is according to real volume".

                       Linus