Balanced or Unbalanced for Pony

[mac_diver]

In case you missed it in DA Aquamaster's (and others) post, an unbalanced reg does not breath harder at depth as suggested by Web Monkey but breaths harder as the tank pressure drops below 500. This is a very desirable trait in a pony reg. Rather than shooting to the surface from depth, do the safety stops. If the reg becomes hard to breath, then surface. Even if you didn't complete the entire stop, some stop is better than no stop. Also for 130 ft dives a 20 cu ft pony might not be enough for ascent with stops. From 130, you really do want to complete your safety stops. As mentioned before, use a 30 or a 40 cu ft pony.

 

[LJinFLA]

Thanks DA. Sounds Like I was in the ballpark on saying typically 30 to 32 max on deep dives and higher on Mid level dives. I was planning on using a 19CF pony rather than a 30 because i was just looking for redundancy and a quick bailout to the surface.

But you are the second vote for air only in your personal bottle. Does anybody use Nitrox in a pony?

 

[Michael Freeman]

I just set up an al40 with a DIN mk25/s600 and brass SPG. ( I sling it w/ a Dive Rite sling kit and a 40' and 6' hose)

I was a little nervious as I realized how big the bottle was and thought I may have gone too big, but I really hardly notice it on land, and it is no issue underwater except you have to remember to clear objects a few inches higher then without a pony bottle.

I mainly went to the AL40 so I could use it as a deco bottle in the future. A smaller bottle may 'Look' better on the surface, but underwater the extra length of the 40 doesn't really add any handling problems. About the only thing I have noticed is that I touch it when I want to use my bc dump on the bottom left side.

Practiced a few times last weekend. No big deal to deploy, but did find out the reg was upside down the first time I pulled it, so a little practice to realize this type of stuff isn't a bad idea.

I think I will put in some EAN32 next time I get it filled, I don't see a down side to Nitrox in this case.

 

[DA Aquamaster]

I think I will put in some EAN32 next time I get it filled, I don't see a down side to Nitrox in this case.

A 40 offers a lot of capacity so topping it off is not that large an issue as even only half full you still have 20 cu ft and more than you would with a full 19 cu ft pony.

Topping off the pony is however the one area where using nitrox can be problematic. If you test your pony reg pre-dive and practice with it on occasion, eventually you use a substantial amount of the gas in the pony and a 6, 13. 19, 30 or 40 cu ft pony, no longer has anywhere near 6, 13, 19, 30 or 40 cu ft in it. At some point you no longer have sufficient gas in the pony to provide the redundancy you need and you need to either top it off or re-fill it.

When you top off a pony with air in it, you still have air in it. However unless your LDS banks 32%, 36%, or whatever you have in the pony, it's a lot harder to just top off a pony full of nitrox. If your LDS transfills O2, it is almost impossible, so you have to accept using a less than full pony of 32%, or accept using a full pony with a percentage of O2 that declines every time you top it off with air.