advice on pony bottles

[shoredivr]

You ignore that if you are a normal person and fill to the rated pressure, using the Imperial system you need no math.

Sadly this does not always happen with a fill.....

 

[DandyDon]

In this day and age, everyone should be able to operate in either system. Its like driving on the left (wrong side) of the road vs the right side of the road. Pay attention and it is not that big of a deal.

They tried that on a Mars lander once. Very expensive crash.

Agree with the conclusion! 1.5-3L is either O2 or suit gas, ponies start at ~4L

Gerbs

Do you dive with a pony, or just talking....?

Yes, and saying a cylinder is 20cuft can be deceptive IMO, it is assuming it is filled to max working pressure which, from my experience, shops rarely fill them to.

Do you dive with a pony? I don't have that problem.

I'm sticking with my previous suggestion: Get the biggest one you want to mess with as they're about the same price, use the same reg & sling - and planning details with something you never plan to use is just hypothetical anyway. We are talking about a pony, a smaller tank carried for bailout - not a stage deco bottle actually planned to use. You pack it in luggage for plane trips as mine sits right now for tomorrow's flight, hump it around airports & buses to the destination, get it to the fill shed the night before so it will be filled and ready to use the first day, carry it onto the boat, sling it for every appropriate dive, climb it up the ladder along with all of your other gear after each, never planning to use it. It's a hassle! But when the unexpected, unplanned time comes - more is better. Been there; was damned glad I had as much as I did for the slow ascent with excess.

I carry a 19 cf.

 

[GrumpyOldGuy]

Sadly this does not always happen with a fill.....

I agree, short fills are a bummer. If you are grossly short, you need to do a little math.

Most short fills are closer to 5% though, which is the same magnitude as SPG accuracy, temperature fluctuations and tank size labels (Eg AL80=77 cu ft). So it you really need to be spot on for your calculations, you need to consider all these issues also, which is a lot more math.

 

[Sas]

Do you dive with a pony? I don't have that problem.

Yes he does. Fills here average at about 215bar.

 

[elan]

10% underfill is normal here, not due to ignorant stations but just due to temperatures drop. Even if you fill it perfectly to 3000psi at the room temp you get 2700 -2800 psi when you get in the water as the water is way colder.

 

[DandyDon]

Yes he does. Fills here average at about 215bar.

from BAR to PSI Conversion Calculator with Altitude Correction
215 BAR = 3118.311 PSI at 0 FT Above Sea Level
I would not call that a short...?

3000 PSI = 206.843 BAR at 0 FT Above Sea Level

 

[elan]

BAR does not depend upon the sea level as far as I know. It is just as psi measure of force per square unit.

 

[k ellis]

Hey americans have started the transition to metric. When you go the store you purchase a 2 liter of coke or a one liter at the convenience store. May not be much but its a start :boxing:

 

[Druid]

*And even the British have switched!

Not quite. As far as diving goes we're metric, but later this evening I shall walk the half a mile to my local pub and drink several pints of beer

I strongly suspect it was a Brit who decided on the units for tyre sizes, nobody else is that comfortable mixing and matching metric and Imperial units.

215 BAR = 3118.311 PSI at 0 FT Above Sea Level
I would not call that a short...?

I would. My cylinders are all rated to 232 bar (3364.876 PSI). Anything below 220 is a short fill

 

[DandyDon]

We generally don't complain below 3,000 psi

Hey americans have started the transition to metric. When you go the store you purchase a 2 liter of coke or a one liter at the convenience store. May not be much but its a start :boxing:

Wine and spirits come in 750 mil bottles, altho we generally call them Fifths...

During WWII, the standard quart bottle of spirits was cut 20% to try to free up 20% more grain for the war effort, hoping that people who often bought a quart now and then would make do the same period of time on 4/5 quart or Fifth(1/5 gallon), and the marketplace adapted.

After the war, the packaging of Fifths continued, even tho one could also by those in quarts, and was applied to wine as well, and the marketplace adapted.

When wine started going Metric in Europe, most went with 700 mil, but the US regulatory body insisted that if metric, it had to be similar to the then traditional Fifth so as to not attempt to confuse, hence the 750 for the American market only, and the marketplace adapted.​

Amazing what will do to you when you don't pay attention. I've been buying liquid laundry detergent for decades, recently in the 100 oz jug that replaced the gallon as "more than 3 quarts," and that was handy in reusing jugs and mixing lawn herbicides: 2 oz of 2-4-d per 100 oz water = 2%. But more recently all producers went with "double strenght," repacking in all sorts of sizes to confuse us, knowing that we'll probly keep using the same measuring cup in the washer and boost net sales. The old gallon of laundry bleach is now 3 quarts, and gawd look what they did to a 3 pound can of coffee...!!