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Hi, Don. The fact is that people use a pony as a redundant source of air because they are either deco diving or are using it to extend their bottom time. In either case the pony does become an independent double, actually worse than an ID. If true redundancy is your goal this is best accomplished with doubles and a iso manifold, your rescue diver friend is right on target and a very intelligent person. If a hose or reg fails, he closes the valve of the offending reg and has access to 100% of his back gas. Should he have a failure of the valve assembly he closes his iso and has access to 50% of his gas without the task loading of switching regs every X minutes. You have to look at your rig and figure out where the failure points are. The number one failure points are 1st stage and hose failures, so *that's* what you need to plan for. Manifolds never fail (I have never seen or even heard of a manifold failure of other than an OMS, which is a flawed design). So you need to plan for the most likely event. If you have a reg or hose failure with a single and "no stop" and are doing rule of thirds, you will have plenty of time to reach the surface, a pony is not needed. If you are worried about your buddy running out of air, then you need to follow rule #1 and don't dive with idiots. Even if this means calling the dive. Look, doubles are great. The secret to enjoying diving is eliminating the things which make a dive no fun. You get doubles, air is no longer an issue. You get a drysuit, cold is no longer and issue. You get a reel and liftbag, getting lost is no longer an issue. You get a scooter and currents are no longer an issue. You make your own hangline and the hangbar fistfights are no longer an issue. You get my drift? Mounting a pony on your tank upside down is horrifying strokery, and you will realize this the first time you do a dive with a set of doubles. The idiots at the dive shop don't know what they are talking about and this statement they made to you should make you suspicious of anything else they ever offer to you in way of "advise". I have to tell you I have been down the road you are currently on and regret every single dive I wasted fucking around with stupid, misguided gear configs. I learned the hard way. But, Don, you know what they say, a lesson learned the hard way is a lesson learned, right? Jim ------------------------------------------------------------------- Learn About Trimix at http://www.cisatlantic.com/trimix/trimix.html > From: "Don W." <donw_s11@sw*.ne*> > Organization: Southwestern Bell Internet Services > Date: Fri, 29 Oct 1999 23:33:11 -0500 > To: Jim Cobb <cobber@ma*.ci*.co*> > Subject: Re: Newbie question > > Hi Jim, > > I'm sending this private and please bear with me because my > questions are sincere and not from some agenda. > > Jim Cobb wrote: > >> -If you are diving with a single and think you need a pony, what you really >> need are doubles. >> -And if you don't think you need doubles, then you don't need a pony. > > Are you saying this because the pony is just like independent doubles? > That is... you can't get to the gas in the failed system--which in this > case would be the bulk of your gas? > >> IOW if you are doing diving where safety cannot be assured by rule of thirds >> and a buddy then you need doubles. > > I guess that you are saying that 30 cubic ft of gas may be an adequate > bailout, but will not give you any reserve, while an isolation manifold > on doubles will still leave you with your reserve. Is this what you mean? > >> And in recognition of this inane hard-headedness which is typical of scuba >> divers in that some are going to use a stupid pony with their single come >> hell or high water I will recommend to those that you set up your pony as a >> stage bottle (DIR style) and clip it on like a stage. > > I've been looking at doing this, but haven't tried it yet. Probably will > soon. > >> Many moan and groan that this will cause the bottle to get in their way. But >> when attached to your tank you really can't get at your pony and it is a >> horrible snag/drag/balance hazard. > > This is not true if the pony is mounted thoughtfully. My pony is mounted in > tight against my BC upside down with the valve positioned about where my right > hand hits naturally. The total weight and drag is much less than doubles. > BTW, the 1st stage reg of the pony is above the bottom of the single 80, so > it isn't easy to back it into anything, and if I sit down the 80 catches > the weight. If I need to, I can detach the whole pony and hand it to someone. > > I know you guys have probably debated and debunked this into the ground, but > it still seems like a good option for deep no-deco or light-deco dives. > > BTW, a local fire dept rescue diver I know uses two 40's set up with an > iso-manifold which makes a light redundent rig for shallow diving. I > mentioned > this today while getting some bottles filled, and the dive store people > thought > it was a horrid idea because of the added failure point--the manifold. WTF?? > Have you ever personally known of a manifold failure? Do they happen? > > You can copy this to the techdiver list if you want. I just wanted to hear > your reasoning behind what you wrote. > > Cheers, > > Don W. > >> Jim >> >>> From: Karen Nakamura <karen@gp*.co*> >>> Date: Fri, 29 Oct 1999 11:30:03 -0400 >>> To: Jim Cobb <cobber@ma*.ci*.co*> >>> Subject: Newbie question >>> >>> >>> Hi everyone : >>> >>> I'm very much a beginning diver; but finding the whole tech realm very >>> fascinating. I wish I had been more cave diver aware when I first bought my >>> equipment, now I'mrealizing that I have about a $1000 worth of trash rec >>> scuba gear and am making the slow transition to saving up money and >>> purchasing what I should have bought in the first place. > > <snip> > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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