How big of a tank as a Pony????

[brian_dixon]

I have managed to get a hold of a nice extra reg and want use it for a Pony tank set up. I have noticed pony tanks range between 6 cubic feet and 40 cubic feet. At what point does the pain in the *** of carrying an extra tank along equal the benifit of carrying one along? I usually dive in warm water, between 70-100 fsw. I am not planning on using it to dive solo at those depths, but rather as a reduntant back up. Would the volume differ any? Thanks for the input.

For your viewing pleasure here are some pics i took on my AOW dive at the Speigel Grove.
Keep in mind I am no National Geographic Photogropher :59:

 

[pt40fathoms]

Six (6) cf. is just too small for most practical bailout applications. Forty (40) cf. is fine if you are looking for bailout from a dive where deco is expected, but in most cases we carry AL80's as staged deco bottles which double as bailout if needed. After a while it seems that most people migrate to the thirteen (13) cf. bottle. It’s enough for bailout from 120 feet safely ascending at thirty (30) feet per minute, do a three (3) min stop, and surface with plenty of reserve left over. It is also small enough no not be a detriment to buoyancy and trim. So I would have to say if you are considering purchasing a pony bottle, buy the thirteen (13) cf., simply because after a few years that’s what everyone else seems to end up with.

Of course you must remember that a pony bottle is never a substitute for proper gas management. It should only be treated as, and used for, emergency bailout and nothing more.

 

[matt t.]

All of the 6 and 13 cu. ft. bottles I have seen were used as Argon bottles. IMO it doesn't make much sense to go with anything less than 30 or 40 cu. ft. Both of these larger sizes can eventually be used as deco bottles in the future should your diving go that way. The larger sizes are also better for re-sale. How do you plan to mount the bottle? Rigged as a stage, or mated to your main tank?


Matt

 

[LUBOLD8431]

Oh, do we have to go here again??? The big pony debate.

The smallest pony I would use (and expect it to be useful in an emergency to get me back from 100ft or so) is a 19. Currently, I am using a 30. However, I hate it carrying a pony, so whenever I do a dive that I would want to use a pony on, instead I dive doubles. Unless when I am teaching some classes, and I will use the pony. My pony is my buddy on training dives with students (that might start another debate)...

 

[IndigoBlue]

...At what point does the pain in the *** of carrying an extra tank along equal the benifit of carrying one along? ...

13 cu ft is where the pain equals the benefit, in my opinion.

6 cu ft is too small, agreed.

Some people will suggest you need a 20 or 30 cu ft, so that you can take forever solving whatever issue is the matter at 99 ft depth.

But 13 cu ft is more than enough, because:

Ascent air consumption:

99/30 seconds x 4/2 ATAs x 0.75 cu ft per min = 5 cu ft

1.46 ATAs x 3 min x 0.75 cu ft per min = 3.3 cu ft

5 + 3.3 = 8.3 which leaves 1/3 of your pony unused if it is a 13 cu ft bottle.

 

[IndigoBlue]

Six (6) cf. is just too small for most practical bailout applications. Forty (40) cf. is fine if you are looking for bailout from a dive where deco is expected, but in most cases we carry AL80's as staged deco bottles which double as bailout if needed. After a while it seems that most people migrate to the thirteen (13) cf. bottle. It’s enough for bailout from 120 feet safely ascending at thirty (30) feet per minute, do a three (3) min stop, and surface with plenty of reserve left over. It is also small enough no not be a detriment to buoyancy and trim. So I would have to say if you are considering purchasing a pony bottle, buy the thirteen (13) cf., simply because after a few years that’s what everyone else seems to end up with.

Of course you must remember that a pony bottle is never a substitute for proper gas management. It should only be treated as, and used for, emergency bailout and nothing more.

This is apparently the only other person here who knows how to do the math properly.

 

[Boogie711]

My pony is usually an AL80, unless my dive buddy is diving doubles. In which case, I have two pony bottles. My dive buddy is usually kind enough to carry my pony for me on his back.

 

[perpet1]

13 cu ft is where the pain equals the benefit, in my opinion.

6 cu ft is too small, agreed.

Some people will suggest you need a 20 or 30 cu ft, so that you can take forever solving whatever issue is the matter at 99 ft depth.

But 13 cu ft is more than enough, because:

Ascent air consumption:

99/30 seconds x 4/2 ATAs x 0.75 cu ft per min = 5 cu ft

1.46 ATAs x 3 min x 0.75 cu ft per min = 3.3 cu ft

5 + 3.3 = 8.3 which leaves 1/3 of your pony unused if it is a 13 cu ft bottle.

I 100% agree with you that a 13cf tank is more then enough for a safe backup at 99feet.
That said, since you state,

This is apparently the only other person here who knows how to do the math properly.

could you please explain......
"99/30 seconds x 4/2 ATAs x 0.75 cu ft per min = 5 cu ft"
for those who may not understand where your numbers come from.

 

[brian_dixon]

How do you plan to mount the bottle? Rigged as a stage, or mated to your main tank?


Matt

I intend to mount it to my primary tank useing some kind of bracket. Which brings me to the question of what is the best way to mount a pony?

 

[LUBOLD8431]

Tiger Gear Pony Bracket. Best one out there. Its not cheap though. Its a machined Aluminum two piece bracket, one on the CAMBAND OF YOUR BC (edited from main cylinder), one on the pony, and they slide together and then lock with a pin.