What's your pony setup?

[Subcooled]

I'm taking the SDI Solo class soon and am looking into a pony rig. Something between a 19 and a 40 I imagine. What do you use, how are you carrying it?

An emergency ascent from 60 feet is very simple.

First of all it is 1/2 of the distance you can do horizontally on one breath without beeing an athlete. I am not talking about what can be done comfortably. I am talking about what can be done without passing out (my limit is about 60m or 180ft horizontal, swimming suit, no fins). Freediving is a wonderfull pursuit. Try it for a while! And, oh, if you breathe overpressure oxygen (=scuba) then you will have some extra time. Carbon dioxide will feel bad anyway, but **** happens.

Second, as you ascend (from 60ft), the relative overpressure in you scuba cylinder will grow and will give you a number of extra breaths. I know this both from theory and from actual practice (was not a drill). I was wearing a rather small 7 litre cylinder monkey style. Breathed it empty at 60ft, got more breaths on ascent.

I am absolutely sure, that ANY air cylinder, be it 10 or 19 or 40, will be a wonderfull and usefull thing if you only can keep your head calm when **** hits the fan.

Two moderately sized sidemounted cylinders is a stress-free and balanced solution. Equally used, they can be trusted.

 

[markmud]

Guess I missed the question... I've only "practiced" with it a handful of times. Once I've got the reg in my mouth, there isn't any difference from using the regular backmount cylinder. My "normal" is to orally inflate my bcd at the surface so there's no change there if my main tank is unusable. If I was really on the pony (not practicing) I would not consider a safety stop, I'm going straight up unless I'm in deco (which I have never had an "accidental" deco obligation). I normally orally inflate my SMB, so the procedure there does not change if I'm on the pony. Generally if I actually have to use the pony, dive's over immediately.

I might have to be re-educated. I didn't do any real dives (outside my pool) in 2020. There's a plague going around or something... not sure of the details .

Hey kelemvor,

Thanks for responding. I enjoy corresponding with you.

You said it. Once you are on your pony bottle the diving is no different. It is really easy. Inhale, exhale, and ascend slowly until you hit the big SCUBA tank in the sky. I just don't get the pony bottle wars. Dive and let dive.

thanks again,
m

 

[Wibble]

My 'pony' setup...

A manifolded twinset, sidemount or CCR with bailouts.

Those all have more than enough gas for the entire dive and all have redundancy to turn a 'disaster' into a minor inconvenience using your normal switching.

If renting, then would make up a sidemount set from ali80s or 7 litre (dunno what you call those).

I simply don't like the principle of a pony; a small amount of gas just for emergency. I like to be able to breathe from my 'backup' at any time; it's usage should be normal on every dive.

YMMV

 

[Gareth J]

My 'pony' setup...

A manifolded twinset, sidemount or CCR with bailouts.

Those all have more than enough gas for the entire dive and all have redundancy to turn a 'disaster' into a minor inconvenience using your normal switching.

If renting, then would make up a sidemount set from ali80s or 7 litre (dunno what you call those).

I simply don't like the principle of a pony; a small amount of gas just for emergency. I like to be able to breathe from my 'backup' at any time; it's usage should be normal on every dive.

YMMV

7's

 

[Gareth J]

@Wibble

In the UK cylinders are generally referred to by the cylinder water capacity.

Hence a 7 litre cylinder cylinder is a 7. A 12 litre cylinder, a 12, etc.

Metric units make things very easy.
A 12 litre cylinder with 200 bar [1] fill pressure has 2400 litres of gas.
A surface breathing rate of 20 litres a minute (which is a bit high)[2], at 20m give 3x20 = 60 litres a minute at 20m [3].
2400/60 gives 40 minutes of gas 2(40/3) = 26 minutes of dive time, 13 minute turn pressure with a third in reserve (66 bar).

Gareth

[1] 1 bar = 14.7 psi

[2] We use 25 l/min for teaching purposes, a large number of divers are at 15l/min or less.
[3] 10m = 33ft, 20m = 66ft. For every 10m depth of water, pressure increase 1 bar, so at 20m absolute pressure is 3 bar.
[4] A normal (lower pressure ?) cylinder fill pressure is 232 bar, most divers assume a 220 bar fill (to allow for cooling). Below 210, you assume you have been short changed .

 

[Wibble]

So easy using SI units. Staggeringly difficult using traditional non-integrated units.

I get really konfuzed with this nominal working volume but not knowing the pressure.

E.g. how much gas is in this tank with this pressure.
SI units: wet volume (litres) x pressure (bar/ata) = litres of gas at the surface

 

[Manatee Diver]

So easy using SI units. Staggeringly difficult using traditional non-integrated units.

I get really konfuzed with this nominal working volume but not knowing the pressure.

E.g. how much gas is in this tank with this pressure.
SI units: wet volume (litres) x pressure (bar/ata) = litres of gas at the surface

We just use tank factors. For an AL80 it is 2.5cuft per 100psi. An AL40 is 1.3. I know the factor factors of all the tanks I commonly dive off the top of my head, and have a chart in one of my notebooks for those that I don't commonly dive. Though more likely I would just pull out my phone can calculate the tank factor.