Did I get double 50's?

[kramynot2000]

I responded to a craigslist ad and picked up a set of what are supposed to be double steel 50's. The tanks are marked Voit with a Voit manifold, two bands and mounted on a black plastic backpack. They are steel (3AA) but have a max pressure of 2250. I thought steel 50's were 1800. Looks like the first hydro was in 1970 with a "+". Last hydro'd in the late 80's.

Anyway, these are the smallest tanks I think I've ever seen doubled up. Next to my 72's they are only about 2/3 as tall and look a little skinnier. So does this sound like steel 50's? If so, anyone know the bouyancy characteristics of these tanks?

EDIT:

Pix are below. The tank to the right is an LP72. Now that I look at the little dubs closer they look to be the same diameter as the LP72.

Thanks

 

[james croft]

Nice score. It is even possible they could be 38 CF tanks as well. Either way they will be nice to dive and have a nice trim. I wish I could find a set of those on Craigslist....

 

[Eric Sedletzky]

Very nice find indeed!

 

[Akimbo]

The Voit 50s were 2250 PSI. The small 1800 PSI tanks were converted CO2 (I think) bottles. I had both. Attached is a clip from their 1963 catalog and a photo with some black twin 38s in the background. The 38s had hemispherical bottoms and large taper threads at the top, 1" I think. Note the bushing reducers between the tank and valve.

Edit: I still have some of the doubles bands. I believe the diameter was the same as the old 72s. Mine measure 6.85" OD… probably 6-7/8" nomonal

 

[DA Aquamaster]

I had a set of 1800 psi tanks (a bit taller) and a set of 2015 psi healthways tanks similar in height to yours. Both made great doubles.

 

[captain]

I had a set of the Voit 2250 doubles, I found them too negative and traded them for double 72's which are less negative than the 50's

 

[elmer fudd]

Those look almost identical in size to the "double 50's" I bought on craigslist about 3 months ago. Mine are US Divers though and are rated to 2015 psi. I've had my own doubts about their true capacity, since they appear so much shorter than my 72's. Still, I charge them up a little high and I'm able to hang out at 50-60 feet for about an hour, so they seem to be big enough.

As Captain mentioned, they are much more negative than 72's, but since temperatures never get much above 55 degrees here, that's not really a problem for me. I still need lead to overcome my suits buoyancy.

 

[oldmossback]

These are twin 45's at 2250 psi..at 10% over they are 49.5psi or 50cuft each.....sportsways brand....sold them to kingairpilot.....too heavy for this old man......

These are twin 38's at 1800 psi....US Divers...not CO2 bottles.......they are twin 40's at 10%......they are fitted with a USDRam and Mossback hookaport adapter I developed in late 07.

These are twin 40's at 1880 psi...Voits.......at 10% over they are twin 43.26 at 2150 they are 45's........this one is fitted with my prototyped USDRam/Mk3 when I first tested it in june 09. Didn't have the benefit of a pool.....used a lake.......

The USD and Voit tanks are the same size, however the voits have the tapered pipe thread neck. the USD's and the Sportsways have the standard .75 straight thread...In case anyone asks how I got these figures: since both tanks are the same size, I used the 0.021 factor from the USD.s for determining the cuft. on the Voits and USD.......I used 0.020 for the sportsways.

The voits are older but have a higher pressure rating........really odd.........I routinely run them at 2150.....pump to 2250 and they cool down to 2150

 

[duckbill]

I've had my own doubts about their true capacity, since they appear so much shorter than my 72's.

Ah, heck. Empty your doubles and fill your steel 72. Let them all settle to room temperature and get a pressure reading on your 72. Then connect the 72 to the twins and equalize them all. Let them settle back to room temperature and get a pressure reading.

If you give me the preliminary "full" steel 72 pressure reading and the equalized pressure reading I'll do the math for you and you won't have to wonder any more.

 

[kramynot2000]

Ah, heck. Empty your doubles and fill your steel 72. Let them all settle to room temperature and get a pressure reading on your 72. Then connect the 72 to the twins and equalize them all. Let them settle back to room temperature and get a pressure reading.

If you give me the preliminary "full" steel 72 pressure reading and the equalized pressure reading I'll do the math for you and you won't have to wonder any more.

Shoot, why didn't I think of that! I'm going out of town for the weekend but when I get back I'll hook up a whip and figure this out.