My final word. And this in no way applies to you Ulsterkiwi, because you don't seem to dive this way. I think some divers might strap on a 3L pony and think "I've got redundancy" and find themselves at 35 metres inside a wreck. In this case I would suggest that the pony is not so much redundancy as a false sense of security.
Ali Perkins wrote:ChuckyBob wrote:In a wreck/cave a 3L may only give you the opportunity to run out of gas twice.
Haha you're cracking me up Greg!
Ulsterkiwi wrote:.........go figure. At the back of this guys mind is "if it all goes to sh** I have another air supply" whereas in actuality what he has is something very different.
Taravana cave for example. Its doable on a single tank. But what happens if that single tank bled dry due to a bust LP hose when you got to the back of the cave?
On the other hand, it does require him to use and as a result test it on every dive.
divepirate wrote:so perhaps a comment from experienced divers in respect to a 'backup' air source would be good.
Something that can be used in the event that you are sitting at 30-40mtr's and your primary air source packs a 'snot' and your buddy is half way to the other side of the wreck or reef, finning in the opposite direction.
I have dived with a chap who carries a pony because he dives on his own a lot. Fair enough. His rig is set up so that he runs his BCD from a direct feed from the pony...
ChuckyBob wrote:What are people thinking when they buy something like that?
What are the sellers thinking when they sell it??????
Ali Perkins wrote:Ulsterkiwi wrote:I enjoy the added security of a redundant system with a meaningful amount of air for the depths I go to. I am also a more useful buddy with the ability to hand off the pony rig to others so thank you for pointing out that benefit!
I hope I'm not being too provocative by posting here (not my intention) but I was pondering the utility of a 3 litre pony bottle... instinctively it doesn't seem like much gas to me.
So I thought I'd do the maths:
Assuming a 3L bottle filled to 210 bar, you have 630L of gas.
Assuming a surface air consumption (SAC) rate of 20L/minute (a fairly normal diving breathing rate).
At 20 metres you will consume 60L/min which means your pony bottle will last 10.5 minutes.
At 30 metres you will consume 80L/min which means your pony bottle will last ~8 minutes.
Now assuming that if you're switching onto your pony bottle something is probably going wrong, so it is highly likely your SAC will be elevated, let's say 30L/min.
At 20 metres you will consume 90L/min which means your pony bottle will last 7 minutes.
At 30 metres you will consume 120L/min which means your pony bottle will last ~5 minutes.
It is my understanding that many people under stress will have a SAC in excess of 30L/min.
I guess I would conclude from all of the above that a 3L pony bottle has fairly limited utility. And if you were in a situation that someone required you to hand that over to them, well I'd hope they were making their way to the surface pretty promptly!
Anyone else care to weigh in with their thoughts - maybe I'm being too conservative?
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