What size Pony?

[Ulfhedinn]

What size pony would or did you purchase and why?

I know this is similar to beating a dead horse but I thought instead of asking what do you recommend for me its better for all to see what people choose for themselves to get a better idea. "Can you say runon sentance"

 

[DevonDiver]

It's really going to be determined by your SAC and the dives you intend to do. There's a lot of factors to consider. Scuba Diving with a Pony Cylinder

If the pony is for emergency ascent use, you need to calculate your minimum gas requirement from the max depth you'll be at. If you're planning on diving in an overhead environment (i.e. wreck penetration), then you need to calculate gas requirements to allow exit and ascent. In those circumstances, you should be using the 'rule of thirds' for your gas... so the pony should match, at least, 1/3rd of your gas as a contingency.

To calculate your gas requirements, take a look at my blog: Gas Management Workshop

I use doubles for most of my diving now. My day-to-day set-up allows me to slot in AL80s on cambands, so it's convenient for travel and general diving where rental cylinders are used. I used to have a 3L pony, that was ok for ascents from recreational depths.

 

[Hatul]

For recreational diving the 19 is a good compromise and is good to 130 ft. For shallow dives <60 ft I also have an older 13 that I take. These tanks with a reg and sling clips have a negative buoyancy of about 3 lbs, so I take 2lbs off the side of the pony.

With the small tanks you have to remember to top them off before diving.

Adam

 

[Crush]

Re-posted from http://www.scubaboard.com/forums/tanks-valves-bands/372271-pony-redundant-set-up-2.html .

At least PADI and NAUI teach that there is a place for a redundant air supply (i.e., a pony) in diving, especially with deep dives. The choice is really up to you.

Personally, I like the idea of a redundant air supply but at this stage in my diving I am not into doubles. I therefore opt for a pony on some dives. Dives on which I believe that a pony is reasonable are: deep, cold, solo, or any combination thereof. I may well have missed something.

There was an excellent link at Rock Bottom and Gas Management for Recreational Divers (Rock Bottom and Gas Management for Recreational Divers | Spherical Chicken) which shows that, if you want to go deeper but within recreational limits, a 19 is a good size, and 13 is a tad too small.

The best advice that I can offer is that, if you choose to dive with a pony, practice deploying it and stowing it regularly. Since a pony has a small capacity it will run down quickly. I top mine off from my main tanks with a device such as this: Tank to Tank Equalizer With Gauge reviews and discounts, IST (Tank to Tank Equalizer With Gauge discounts on sale IST)

I find that surface-swimming face-down with one mounted on your back is a pain. You might consider a stage/deco straps such as those indicated in Stage/Deco Straps and Hose Retainers by Dive Rite - Dive Gear Express (Stage/Deco Straps and Hose Retainers by Dive Rite - Dive Gear Express) rather than a mounting bracket.

I sling mine like this: DIR-diver.com - Stagebottle rigging (DIR-diver.com - Stagebottle rigging). The only objection that I have heard to slinging a bottle is that it might get in the way if you are lobster hunting. I would stress that, if you dive with a pony, deploy it regularly so that it is second nature.

I prefer to sling my pony for the following reasons:

1. I can put the pony on or take it off in seconds - no tools, no hassle. I suppose that I could "hand it off" to someone underwater, but I don't think that this will realistically be necessary;
2. I can always see my pony tank and the reg. I can see if my reg is free-flowing, or if there appears to be a leak from the O-ring. If it snags on something, I can see what it snagged and fix the situation;
3. My basic gear configuration is unchanged - I use a primary and a bungee'd octo/secondary necklace. The pony reg is bungee'd to the pony bottle, far from my other two regs, and therefore will not be confused with them; and
4. I can consult the pressure gauge on my pony - this gauge is obviously connected to the pony and therefore will not be confused with my main tank pressure.

As a final note, many tech divers will pressurize their stage bottle then turn the valve off to prevent inadvertent gas loss during a dive. Perhaps one day I will do this, but so far, my pony is pressurized and the valve stays open during the dive. This might not be great if I had to rely on that gas for a deco obligation, but I believe that I am likely to see a leak in the pony.

Safe diving.

 

[Hatul]

It's really going to be determined by your SAC and the dives you intend to do. There's a lot of factors to consider. Scuba Diving with a Pony Cylinder

If the pony is for emergency ascent use, you need to calculate your minimum gas requirement from the max depth you'll be at. If you're planning on diving in an overhead environment (i.e. wreck penetration), then you need to calculate gas requirements to allow exit and ascent. In those circumstances, you should be using the 'rule of thirds' for your gas... so the pony should match, at least, 1/3rd of your gas as a contingency.

To calculate your gas requirements, take a look at my blog: Gas Management Workshop

I use doubles for most of my diving now. My day-to-day set-up allows me to slot in AL80s on cambands, so it's convenient for travel and general diving where rental cylinders are used. I used to have a 3L pony, that was ok for ascents from recreational depths.

I'm surprised by your last statement. A 3 L is a Spare Air and it's not enough to make a safe ascent from 130 ft. If you calculate this out you'd run out with high risk of injury.

Adam

 

[DevonDiver]

I did calculate it. I did also use it... for an emergency ascent from 36m/118ft due to freeflow in an ice-cold quarry. Go figure...

Not sure where you get the impression that a 3L cylinder is a spare-air. Perhaps the 'Metric Fairy' didn't visit your household yet?

From John Liddiard's website, exploring the use of 3L cylinder as bailout for CCR..

The chart shows the time available for decompression stops at 6 metres or 3 metres for a given depth of dive. The bailout supply is a 3 litre pony cylinder, either full (232 bar) or half full (100 bar), and an average RMV (Respiratory Minute Volume) of 25 litres per minute.

A diver carrying a 3 litre pony cylinder for bailout could ascend from 50 metres and complete either 6 minutes of stops at 6 metres or 8 minutes at 3 metres. However, if the pony was only half full at the time of the emergency, they wouldn't even get close to the surface (the time available is negative), and that is all provided their RMV does not shoot up above 25 litres per minute with the stress of the situation.

It also shows that a 3 litre pony cylinder can be a viable bailout option for dives involving short amounts of decompression. The corollary is that for dives involving more than a few minutes decompression a better bailout strategy is necessary, which is pretty much back where I started, using a twin set and rule of thirds.

 

[Hatul]

I did calculate it. I did also use it... for an emergency ascent from 36m/118ft due to freeflow in an ice-cold quarry. Go figure...

Not sure where you get the impression that a 3L cylinder is a spare-air. Perhaps the 'Metric Fairy' didn't visit your household yet?

From John Liddiard's website, exploring the use of 3L cylinder as bailout for CCR..

Sorry my mistake. I mistook 3L for 3 cu ft. The 3L is the metric style of measuring by volume of compressed air and the imperial style is expanded air. The 3L tank is in fact nominally our 19 cu ft.

Adam

 

[Hatul]

deleted

 

[koozemani]

I was considering a 19cf, but found a ridiculous deal on a 30cf, so that's what I use. I wear it slung.

 

[cbrich]

30 or 40 cu. ft. I would take a 40 cu. ft. cylinder because then I can use it for a deco cylinder.