advice on pony bottles
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I think your tanks are generally rated higher than most of ours. Someone started "standard 80" and 3,000# as the norms here, and the marketplace adapted.it's not short. Just lower than the rated pressure. I do get fills up to 260 at some places though
burna
Contributor
Yep (see my earlier post), (2.65L @21.4Mpa (214 Bar) = 567.1L = 20cuft) But as I said in that earlier post, there are some reasons why I don't think it is that good after all.
1. If you test it at depth, then you need to get it re-filled every time.
2. If the reg gets purged for a second = re-fill + you can empty a little pony really quickly so may not have enough gas to get you up.
3. Costs the same as a 12 litre (~100cuft) to get filled which really sucks.
How do you work out how gas you have in a cylinder that is only half full?
Wouldn't you have to divide the total expanded gas (size of cyl. e.g 80cuft) by the max rated pressure (3000 psi) to work out the water capacity, then multiply by actual pressure to get actual volume of gas??
Is there an easier way??
We just multiply the cyl. water cap. by whatever pressure is in the cyl.
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.
I agree. Bloody Poms!!!
Agree, ours are rated to 232 Bar also.
We generally don't complain below 3,000 psi
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.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...!!
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.
My God! That's what we're talking about !!! :shocked2:
Yeah, 232 Bar normally which equals 3,364.8 psi.
kanonfodr
Contributor
How do you work out how gas you have in a cylinder that is only half full?
Wouldn't you have to divide the total expanded gas (size of cyl. e.g 80cuft) by the max rated pressure (3000 psi) to work out the water capacity, then multiply by actual pressure to get actual volume of gas??
Is there an easier way??
Yup, common sense. If I've only got 1500 PSI in my AL80 cylinder, which is rated for 80 cu ft at 3000 PSI, I cut my volume in half.
Now if you are wondering how we get our remaining volume on the fly underwater, that's what tank factor is for. Going back to our AL80 example, the tank factor is 2.5. So if I have 1000 PSI left, I can multiply 10 x 2.5 = 25 Cu ft of breathing gas left in the cylinder.
Another thing to remember, as I was taught, is that scuba math doesn't have to be too accurate as there are many variables in everything and rather than try to eliminate all of them or account for them, we simply say good enough. I know that if I have 600 PSI left in my LP95 tank (TF of 3.5) then the operation is 6 x 3.5 = 21 cu ft or for mental math (for myself) I turn it into 3(2 x 3.5) = 21 cu ft.
Peace,
Greg
burna
Contributor
Ok, yes perhaps "half full" was a bad example!! 
kanonfodr
Contributor
It may have been a bad example, but I will most certainly take advantage of it .
Peace,
Greg
. Peace,
Greg
burna
Contributor
And why not too??
How do you calculate this "tank factor" that tho doth speaketh?
How do you calculate this "tank factor" that tho doth speaketh?
elan
Contributor
kanonfodr
Contributor
Just to elaborate, Tank Factor is a rough guide for how many cubic feet of breathing gas remain per 100 PSI. That's why we can do the math in tens instead of hundreds or thousands because we once again only require a close enough number. That, and it keeps the math way easier.
Also, many tanks share a common tank factor (LP95 and HP130 both use a tank factor of 3.5) and I believe I have a list somewhere of common tank factors. I will have to look for it, though...
Peace,
Greg
elan
Contributor
also, many tanks share a common tank factor (lp95 and hp130 both use a tank factor of 3.5) and i believe i have a list somewhere of common tank factors. I will have to look for it, though...
peace,
greg
hp100 = lp72 , al80 ~= lp66 The tanks that have similar internal volume would have the same tank factor.
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