Matching tanks-- lengths aren't the same

[rjack321]

Listen to the senior members here (Luis and DA). 1/4" is no big deal. Even if you aren't using boots just make sure the manifold is even and unstressed (turns easily). And that the tanks are parallel. Done.

If you had variance of 1/2", 5/8", or more then I would look at getting another tank and making a single out of the unmatched one.

 

[SparticleBrane]

I seem to remember Leadking saying awhile back that if a dealer calls in an order for tanks and specifies that they're for doubles, they break out the calipers to measure tank length for a good match.

 

[Thadmn]

Thanks, I probably will in the future, however $$. One thing at a time! I also want to see how I like the weight of the higher pressure tanks.

 

[Thadmn]

Yes, I work from the necks down, of course.

 

[The Kraken]

Although it may be an annoyance, the difference in length between the two tanks is not and engineering or critical issue.

When attached to the manifold, the tanks, by nature of the method of attachment to the manifold, are at a common "height" if you would.

The only issue is if one desires to stand the tanks upright, then there would be a tilt to either the left or right.

In the order of operation, tanks are attached to the manifold first and then the bands are secured. Once the tank bands are secure, any undue strain on the manifold is negated.

In the grand scheme of things, the 1/4" difference in tank length will have no effect upon either the performance of the manifold or the tanks, and certainly won't affect the diver's performance under water.

the K

 

[DA Aquamaster]

When you are talking about face seal manifolds are you referring about the US Divers or Sherwood styles that used industrial CGA type of fittings between the center manifold and the tank posts?

They are both standard metal to metal CGA fittings (different sizes) and my experience is that if they were not damaged or dirty they are very reliable. If they have any scratches or they are not perfectly clean they may never seal, but once sealed I have never heard of one failing. Have you?

I've never had one leak - until reassembled, when as you indicate a scratch or dirt can make them a real pleasure to get to reseal. Because of potential resealing issues, the couple sets I had, I preferred to leave the manifold assembled and screw the tanks off each post for visual inspection.

I think one of the potential issues with the design may have been some minor bending and prior abuse of the comparatively thin center manifold with subsequent alignment issues if used on different tanks and bands.

I just can't see that as being a problem with a manifold of current design where things are both more heavily constructed and not able to get seriously out of alignment if properly assembled.

I have a semi-vintage (1980’s) Sherwood manifold with double yoke outlets (one in the center) in one of my sets of doubles and I would not trade it for any other manifold. I am actually looking for a second one to put together a set of twin 50’s.

They work great for double hose regs with the double hose reg on the center post and the backup on the right post. I used to have a couple but sold them to a vintage diving friend several years ago and I am consequently also looking for another one.

The connection between the center manifold piece on my Poseidon tanks to the two individual tank valves is with a 5 thread DIN connection. The manifold basically has two males and one female fitting (and a reserve mechanism in the center). The connection is rigid enough that you can pick up the tanks by the center manifold without any fear. Actually the system has no top band. Instead it has a rubber block for the shoulder straps. This rubber block is tightened between the tanks putting a lot of tension on the manifold.

I have a set of twin 30 cu ft USD doubles that have a solid manifold and no bands. Instead there is a rubber block that slips between them and the tanks are then held in place on a BC with a regular cam band. That particular set up visibly flexes even with the solid manifold design, and I think it is one design where a three piece manifold would probably not work well at all.