random wonderment

[FightingDrag]

is there a small tank that complements snorkling/freediving that can be re-filled with a bicycle pump and used in 2-3 bursts before its empty? for snorkling to dive and stay and examin that odd fish, or freedivers as a safety?

i think it would be something to have nice as recreational or simply as a nice tool for anything.

THX

 

[vladimir]

Hmmm...this may have been discussed before. Let me see...oh, here it is:

http://www.scubaboard.com/forums/basic-scuba-discussions/320812-spare-air-some-thoughts.html

Although it can't be filled with a bicycle pump, I think Spare Air might meet some of your specs: it's small, and you use it in a few bursts before it's empty.

Would you want to breathe air that's been through a bicycle pump?

 

[ajduplessis]

Using a bottle for snorkelling with 2 or 3 burst sounds like a overkill. Rather work on your breathing. If you have cash to burn I can give you my banking details.

 

[diversteve]

Given that a bicycle pump - at least mine - only goes to 100PSI and scuba gear is 3000PSI - I'm going to say no...

 

[FightingDrag]

I have seen spair air, but, how do i refill it?

I want to be able to dive, surface, refill, and go back down.

not dive, surface, to shore, to shop, refill, and go back.

 

[diversteve]

You'd have to rent a tank to refill it from. It comes with a fill adapter. Submersible Systems - Filling the Spare Air

 

[noreastDIVER84]

There is the spare air, or the spare air, or a scuba setup.

I don't have the greatest lung capacity, but I can snorkel / freedive down to about 30' and be down for maybe 30 seconds and bubble the air out as I come up. Not that 30 seconds is that long, but at 30' to be holding your breath, it is long enough.

I tried the spare air in the pool at the dive shop and got maybe 5 good relaxed breaths out of it laying on the bottom at 10'. If you are snorkeling or doing anything more than nothing, it doesn't last long.

By the way, bike pump air tastes really bad, don't ask how I know this either.

 

[ptyx]

I have seen spair air, but, how do i refill it?

I want to be able to dive, surface, refill, and go back down.

not dive, surface, to shore, to shop, refill, and go back.

Time for some math/physics.

The best pressure I could find for a foot pump is 140 psi. Let's take the case of a really good foot pump delivering 150psi.
Now let's take a really good diver, with 0.5 cuft/min SAC.
And a really shallow depth, 10 ft.
And a decently sized scuba tank, the AL80 - which despite its name holds about 77ft at 3000 PSI. Now, it weights 30 pounds, and I don't think a freediver would want to drag that, but it will do for the explanation.

At 150 psi, this tank will hold an amazing 3.85 cuft of air.
At 10ft, ambient pressure is about 19 PSI, so the tank can deliver less than 3.4 surface equivalent cuft of this air, assuming a perfect regulator (won't happen).
At this depth, the RMV of our diver is .65 cuft/min.

So the whole setup would last an amazing 5 minutes and 20 seconds. I'd expect real gear (i.e. non thermodynamically perfect regulator, diver closer to .7 SAC and a bit deeper) to deliver less than half of that. That's just not worth the pumping.

There is just no way to have a small low pressure tank deliver any reasonable amount of air, even at shallow depths. Since increasing the tank size won't help as it will impact your RMV negatively, your only option would be to find a foot pump delivering really high pressure - and be ready to spend a lot of time pumping.

 

[diver 85]

Hmmm...this may have been discussed before. Let me see...oh, here it is:

http://www.scubaboard.com/forums/basic-scuba-discussions/320812-spare-air-some-thoughts.html

Although it can't be filled with a bicycle pump, I think Spare Air might meet some of your specs: it's small, and you use it in a few bursts before it's empty.

Would you want to breathe air that's been through a bicycle pump?

The bicycle pumps got me confused..........

 

[diver 85]

I have seen spair air, but, how do i refill it?

I want to be able to dive, surface, refill, and go back down.

not dive, surface, to shore, to shop, refill, and go back.

Your second line's gunna have you stumped----without a 'regular' tank hanging around.....