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Bill Wolk wrote: > > All -- > > Many thanks to everyone who responded to my message on why PST 104s are > the preferred tank for cave and tech diving. I got some terrific > responses and appreciate the time they took. For the list and anyone > who's interested, they're summarized below. Basically, the consensus is > that the PSTs have a reputation for being more durable *and* for caving > they start more negative and stay more negative so you stay off the roof. > Here's the summary. A few of the authors would like me to point out > that their responses are based on personal opinion so your mileage may > vary. > > Best - > > Bill > > ------ > > Original Message: > > > I'm in the market for a set of doubles and checked the archives for > > recommendations. It looks clear that almost everyone is using PST 104s > > but I can't figure out why. What about OMS 98s or 112s? > > > > Here are the specs I have -- am I missing something or are these > > notoriously innaccurate buoyancy and weight specs just plain wrong: > > > > cu. ft Fill Wt. Bouyancy Full/E liters > > OMS J-098G S 98 2640 38 -7.73 / 0 15.45 > > OMS J-112G S 112 2640 41 -8.00 / -1 17.66 > > > > As far as I understand it, the PST 104s (can't find reliable specs) have > > about the same weight and buoyancy characteristics as the OMS112s for > > less capacity and are larger and heavier than the 98s for not much gain > > in air. Before I regret buying a pair of 98s, I'd appreciate any help > > you can offer. > > Responses -- > > Jon Breazile, breazile@ne*.co* wrote: > > >The 104s are great because they are heavy. The OMS 112s are almost > >the same. The more you can take off your weight belt, the better. > >The 104s also have a history of being very tough. Some people have > >had sets for 20 years with a lot of overfilling (3500 PSI) and they > >still pass hydro. > > J. Scott Landon, landonjs@a1*.sw*.um*.du*.co* wrote: > > >the pressed steel tanks are several pounds more negative and have thicker, > >better steel. if you empty your oms tanks, you will be too buoyant. i > >have an original set of 104s from 1971/1972 that are still perfect. buy > >pressed steel tanks unless you are using them for sidemount cave diving or > >deco bottles. trust me, you want the 104s. the galvanized finish is much > >better than painting as well. > > and one more thing: > >ever notice how oms magically had there 95s become 98s when the physical > >dimension of the tank did not chnage. they are 95s, not 98s. don't let a > >little savvy marketing fool you. buy the pressed steel 104s. > > Jeff Bentley, jbentley@cr*.co* wrote: (This gets the zen message award) > > >Are you sure there is only 104 in the tank when at working pressure? > > Bill Bowden, BBOWDEN@co*.vo*.fl*.us* wrote: > > >IMHO- I've got a set of 104's and a set of 112's. I use the 112's the most. > >Lighter out of the water, better bouancy characteristics, slightly more air, > >paint over galvanized for the ocean, internal coating for the ocean. 104's > >are more traditional and almost indestructable. > > Laurence J. Roth, roth@me*.ne* wrote: > > >I've been diving OMS 98's off shore and I don't notice any difference form > >PST 95's. (I wouldn't be surprised if the actual capacity was the same) > >The tanks are manufactured in Italy and are the same tanks Scubapro and > >some other dealers sell. I have a couple of steel 80's made by the same > >company, that I use for stage bottles and they are excellent. (short, > >neutrally buoyant, and higher capacity than the usual 72's) > > > >I wouldn't recommend the OMS manifolds since they have brass to brass > >connections. The Scubapro / Diver's Supply, etc. manifolds (they are > >made by the same Swiss company) are much better and have long, dual o-ring > >connections. They will survive being "bumped" much better > > Ron Price, RPRICE@wp*.it*.lu*.ed* wrote: > > >I've noticed the preference for PST-104s among the > >cavers. I dive mostly deep wrecks (140'-250') in the > >Great Lakes and here I see A LOT of OMS tanks. I > >dive OMS-120's and wouldn't recommend them > >unless you are large/tall person. At 6'3" I can get a > >way with it. 120s with two slings are alot to handle. > > > >I think the OMS tanks have great characteristics (e.g., > >weight, buoyancy, etc) and I see them routinely get > >pumped to 3,300-3,500PSI -- even though its not > >recommended and I avoid it. The 120's provide > >enough gas for ANY dive that I'll ever do, and probably > >too much gas for most of the diving (<300') that I do. If > >had to do it again, I would go with 112s (they become > >127s at 3,000PSI). I think that 98s might be a little > >close (diving something like 3rds) for some deeper > >dives. It all comes down to what type of diving you're > >doing. > > > >It may come down to price. I haven't bought any 104s, > >so I don't know how they compare... but, OMS tanks > >aren't cheap. Be prepare to drop $380-450 per > >tank---- > > Michael Picou, picou.michael@MA*.DC*.ST*.FL*.US* came through with specs > (go Michael!) > though my gut reaction is that this is the innacurate U.S. Divers info > since the bouyancy change full to empty isn't enough to account for the > gas volume. > > >I have some info on the PST 104's that I found in Vol 15 No. 4 of > >Discover Diving Mag, I will assume its accurate: > > > >capacity 104 @2400 psi > >O.D. 8 in > >length 26.19 > >weight 46lb > >buoyancy -5.3full/ -2.5 empty > > > > The buoyancy is interesting in that for a set of 104 doubles the > >gain is > > 5.6 lbs. (full to empty), while the OMS would be around 15 lbs. > >You may also want to check the length of the OMS as this can be a > >problem for (me included) short folks. Good luck!! > > And....last but not least, Peter Gottlieb, TMBG@ix*.ne*.co* provided > the gossip and a guarantee <g> -- > > >I don't have any scientific data, just gossip, speculation and a lilttle > >logic. Take it for what it's worth. > > > >1) A few months ago, I read a letter from the president of OMS stating > >something to the effect of, "OMS tanks are just as good as other tanks, > >and they are actually quality tanks. Really. There's nothing wrong with > >OMS tanks. In fact, let me tell you how we make them, and how they are > >really good tanks. Really." Sounded almost too good to be true. The only > >time I have ever read spin control like that was when it was needed. > > > >2) A friend of mine dove a set of double 121's and found them > >excessively buoyant once they were about 1/2 capacity, with full cave > >gear (this would include a neoprene driest, though). > > > >3) Another friend was interested in purchasing a set of OMS tanks, and > >asked a dealer rep if they would guarantee that new tanks would, under > >normal diving conditions, pass the first hydro in 5 years. He wouldn't. > >Even Genesis has replaced failed high pressure tanks that are older than > >that. There are 104's made 40 years ago that are still being restamped. > > > >4) How is it that tanks that are the same physical size (displacement > >and internal volume), and material are different weights? Wall > >thickness. I have heard that the way the OMS tanks, in general, are made > >lighter than comparable steel tanks by decreasing the wall thickness, > >and using an internal coating. Due to this coating, the tanks cannot be > >whipped, or tumbled. If you never drain your tanks, that might not be so > >bad, but the slightest bit of debris that gets in could damage the > >coating. Not to mention if some yahoo shop worker isn't paying attention > >and whips/tumbles them anyway - bye bye coating, bye bye tanks, hello > >corrosion. > > > >Again, while these are just gossip and speculation, I am sticking with > >the tried and true pst's, which have a history, and great reputation. I > >did try an OMS46 for a deco bottle, that was just about perfect, until I > >got to the price. For that money, I can get 3 AL80's. I will put up with > >the size difference. ...[snip].... If you're not happy with > >the pst's, I will buy them off you. > > > >Let me know if they work out for you. Maybe they are the singing fat > >lady for whom we are all looking. > > Best Regards -- > > Bill > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. Originally, I did not respond as I do not have specs, manufacturing notes, etc.; but I did hear a rumor that the recently made Pressed Steel 104's are not the exact same tank as the age-old tried and true PS 104'sof 20 years ago. Since rumor and speculation is OK I figured I would pass some more along. Cheers Tom -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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