Manifold stress caused by tank bands?

[Tim_pacnwdiver]

I got a free pair of Alum 50s and tried to replace a “vintage” yoke manifold with a Thermo manifold. The cross bar doesn’t adjust short enough to work with the bands I have.

The bands are probably for 7.25 and these tanks are 6.89

The center to center measurement was about 8 ½” when I laid everything out loose. But when I go to tighten the bands it pulls the tanks together so the top band has a gap between the band and the tank the bottom band tightens on the tank but makes the pair taper together.

The taper is maybe a quarter inch over the 19” length.

I’m worried about the stress 3000 psi would be put on the manifold or the threads of the tanks.
Can I shim the tanks inside the bands with rubber or something?

What are my options?

 

[Greg Barlow]

Contact Joel Silverstein at www.techdivinglimited.com He will likely steer you in the direction of proper fitting bands. Bands that work correctly will avoid stress to the manifold. The bands need to support the tank weight, not the manifold.

Greg Barlow

 

[cool_hardware52]

I got a free pair of Alum 50s and tried to replace a “vintage” yoke manifold with a Thermo manifold. The cross bar doesn’t adjust short enough to work with the bands I have.

The bands are probably for 7.25 and these tanks are 6.89

The center to center measurement was about 8 ½” when I laid everything out loose. But when I go to tighten the bands it pulls the tanks together so the top band has a gap between the band and the tank the bottom band tightens on the tank but makes the pair taper together.

The taper is maybe a quarter inch over the 19” length.

I’m worried about the stress 3000 psi would be put on the manifold or the threads of the tanks.
Can I shim the tanks inside the bands with rubber or something?

What are my options?

The right bands an manifold are the best answer.

OTOH..... You can shim the bands, but becareful you don't create a water trap that holds saltwater against the tank.

Have you tried mounting just the bands? Are the tanks non parallel with just the bands? Is the effect reversed if you swap the bands top and bottom?

Are the tanks a consistant diameter over their entire lenght? Are the tanks bowed banana like?

Roll the tanks on a known flat surface. That should show you if the tanks are straight.

When you do have just the bands installed check the C to C distance on the tank outlets.

If your tanks are a little weird buying new bands won't solve the problem.


Tobin

 

[Tim_pacnwdiver]

Thanks for the replies,

The bands match and the tanks roll fine. I guess I have 3 options:

1) Manifolds with a shorter isolator (any suggestions?)
2) Bands built for 6.89 tanks (do these exist?)
3) Shimming (would rubber be the material to use?)

I've seen some mention of custom bands I'll go search for that link. Funny how free stuff can cost you.....

Thanks again!

 

[Gilldiver]

6.9" is the standard dia for the old steel 72's. You should be able to go with standard gear.

If you want to go with custom bands, contack Vic at:

victor341968@hotmail.com

He made up some fine looking bands for my set of 72's with an older manifold that had 8.25" on center spacing. Cost for the bands was about $110 delivered. Quality was right on with what you would get from Highland Mills.

 

[cool_hardware52]

Thanks for the replies,

The bands match and the tanks roll fine. I guess I have 3 options:

1) Manifolds with a shorter isolator (any suggestions?)
2) Bands built for 6.89 tanks (do these exist?)
3) Shimming (would rubber be the material to use?)

I've seen some mention of custom bands I'll go search for that link. Funny how free stuff can cost you.....

Thanks again!

If your tanks check out talk to Joel at Techdivinglimited. I think he has some shorter center section for manifolds


Tobin

 

[Scared Silly]

As Tobin as says a short manifold isolator or as Pete/Tobin says different bands. I think shimming is asking for problems. My suggestion would be different bands. Highland is selling off their remaining stock of bands that XS Scuba is not buying. I picked up a pair of 7" bands for $100 from Joe. Quick and easy and great service. I think I saw some 6.9s on the list as well.

Why new bands? If the currents bands are 7.25 they will be easy to sell. Whereas a stubby manifold is will be harder to sell.