Manifold and Band Spacing

[b1gcountry]

I have a pair of Worthington HP100s that I've had for a while.

I ordered a Sea Elite 300-Bar Manifold from Divers-Supply,

along with some Dive Rite 7.25" Bands

When they first came in the mail, I received 3/8" hardware. After a long ordeal and three returned packages, I now finally have some 5/16" threaded rod, which actually fit through the bands I have. The problem is when I measure the center-center distance between the tanks with the bands on, it comes out about 8 1/4". When I measure the center-center on the manifold, it is about 8 3/8". I have the manifold adjusted as small as it will go, and it is still wider than the center-center of my bands by 1/8". Is this normal?

I figured I was ordering the bands and manifold from the same place at the same time, so I thought they would be compatible. The manifold is also an adjustable double O-Ring design, so I figured it would fit most modern bands. Am I wrong?

Due to the exchange process, they also sent me this real cheap set of tack-welded bands. When I put these bands on the tanks, the center spacing is still the same.

I don't want to mess up my new manifold. If I try to install bands with a center spacing 1/8" less than the manifold, will I have problems? If so, what is the problem, the bands, or the manifold?

Thanks,
Tom

 

[Jimmer]

That manifold should be 8.46" centre to centre. When you tighten the bolts on the bands does it visibly bring the bottom of the tanks in closer, so that the gap between the tanks is noticeably off?

 

[b1gcountry]

The manifold can easily be adjusted to have 8.5" center spacing. The min spacing is 8.375". I would guess it would be able to adjust as large as 8.875".

I have not put the manifold on the tanks yet. I don't want to try to force the bands on and mess up the manifold.

 

[Jimmer]

If I were you I would put the bands and manifold on, and start tightening the two very slowly, rotating the cross bar to match as you tighten the bands. Just watch the tanks and see if they maintain parallelism as you tighten the bands. If they stay visually parallel, you have nothing to worry about, if you can see an obvious mis-alignment then you should slow down and don't tighten further.

 

[rjack321]

Have you tightened down the bands and measured the spacing then (no manifold)?

The "flats" between the band loops should push the tanks apart a little. Dive-rite only makes 8.5" spaced bands. SCUBA Diving Equipment and gear for Technical, Wreck and Cave Diving: Dive Rite, Inc - Product Catalog - 7.25" Tank Bands
click tech specs on the far left. So I'm skeptical of your 8.25 inch measurement. I suppose they could be defective, but seems unlikely.

 

[DA Aquamaster]

Go slow in tightening both the upper and lower bands and alternate to keep them parrallel. During the process keep checking the cross bar between each band adjustment - it should still turn failry easily, if not, the center to center spacing is getting off and if so shorten or lenghten it as required until it turns easily again.

 

[Colliam7]

The problem is when I measure the center-center distance between the tanks with the bands on, it comes out about 8 1/4". When I measure the center-center on the manifold, it is about 8 3/8". I have the manifold adjusted as small as it will go, and it is still wider than the center-center of my bands by 1/8". Is this normal?

One thing I have found in assembling my doubles is that it can be challenging to get the threading started on BOTH valves in essentially the same place. If you are not particularly careful, it is easy to get one started and get a full turn on the threads, before the other starts threading. IF this happens, it is possible that you could end up with center spacing on the manifold that, even when tightened to the most narrow spacing, is larger than the tank spacing.

I figured I was ordering the bands and manifold from the same place at the same time, so I thought they would be compatible.

They should be compatible, but not because of ordering from the same place, same time. They should be compatible because the spacing is essentially standard, across brands. If you use 7.25” bands on 7.25” tanks, or 8” bands on 8” tanks, you should end up with equivalent center-center spacing that any adjustable manifold should handle easily. Note, that the manifold is ‘sized’ only according to the tank threads, not the tank size.

Go slow in tightening both the upper and lower bands and alternate to keep them parallel. During the process keep checking the cross bar between each band adjustment - it should still turn fairly easily, if not, the center to center spacing is getting off and if so shorten or lengthen it as required until it turns easily again.

If I were you I would put the bands and manifold on, and start tightening the two very slowly, rotating the cross bar to match as you tighten the bands. Just watch the tanks and see if they maintain parallelism as you tighten the bands. If they stay visually parallel, you have nothing to worry about, if you can see an obvious mis-alignment then you should slow down and don't tighten further.

Tightening the bands and the cross bar slowly and essentially in parallel is the best advice. As DA notes, you should find something of a ‘sweet spot’ as you tighten (rotate) the manifold. In other words, as you tighten the bands, you should also feel that the manifold needs to be rotated to a point where it again moves easily (before the end nuts are tightened, of course). The goal is to get to the point that the bands are fully tightened, and the sweet spot allows the manifold to be positioned with the isolator valve up and facing slightly inward (30 to 40 degree angle toward the diver), after which the end nuts can be tightened. And note that, as Rjack321 mentioned, as you start tightening the bands the tanks will initially come together, but as you finalize the tightening, the spacing bars will actually push them very slightly apart. So, the final test of the optimal manifold position is made with the bands FULLY tightened.

I don't want to mess up my new manifold. If I try to install bands with a center spacing 1/8" less than the manifold, will I have problems?

You may (and probably will) NOT have problems. The ultimate test is, ‘Does the manifold leak?’ If you assemble the rig, pressurize the tanks, and there is no leak, you are OK.

 

[b1gcountry]

Have you tightened down the bands and measured the spacing then (no manifold)?

The "flats" between the band loops should push the tanks apart a little. Dive-rite only makes 8.5" spaced bands. SCUBA Diving Equipment and gear for Technical, Wreck and Cave Diving: Dive Rite, Inc - Product Catalog - 7.25" Tank Bands
click tech specs on the far left. So I'm skeptical of your 8.25 inch measurement. I suppose they could be defective, but seems unlikely.

Yes, the measurement was with the bands on and tightened. The bands look like the pic in the link, and have a product code on the UPC label that reads GM1033HD (Dive Rite's site says the bands are product code GM1033-Set.) There is a price tag on them that says $82.95, which brings up a question in my mind how old they are since they are almost double that price on the website (maybe the spacing changed over the years?) The store also sent me a crappy pair of lightweight tack welded bands that they also claim are Dive Rites, but I know they are not.

I've just had so many returns with Divers Supply that I'm paranoid now. I will try the bands on the manifold, and just be really careful snugging the bands up. I'm off to a race now, I'll let you know what happens when I get back.

Tom

 

[amascuba]

Yes, the measurement was with the bands on and tightened. The bands look like the pic in the link, and have a product code on the UPC label that reads GM1033HD (Dive Rite's site says the bands are product code GM1033-Set.) There is a price tag on them that says $82.95, which brings up a question in my mind how old they are since they are almost double that price on the website (maybe the spacing changed over the years?) The store also sent me a crappy pair of lightweight tack welded bands that they also claim are Dive Rites, but I know they are not.

I've just had so many returns with Divers Supply that I'm paranoid now. I will try the bands on the manifold, and just be really careful snugging the bands up. I'm off to a race now, I'll let you know what happens when I get back.

Tom

Are you measuring from the center of the DIN valve on the left post to the center of the DIN valve on the right post?

 

[cool_hardware52]

I don't want to mess up my new manifold. If I try to install bands with a center spacing 1/8" less than the manifold, will I have problems? If so, what is the problem, the bands, or the manifold?

Thanks,
Tom

Sorry if I'm repeating what others have suggested.

Put only the bands on the tanks and snug them up. Check to make sure the tanks stay parallel. Some times crappy bands are well, crappy and not closely matched. If the tanks aren't parallel, swap the bands top and bottom and try again. Tanks are not perfectly round, and perfectly straight, or exactly on size either.

Take your manifold and adjust it to match the C to C of the tanks as they are assembled with the bands. If the manifold is adjusted all the way in and the tanks are closer together, it's never going to work. Carefully measure the C to C distance. One trick is to measure from the same point on each tank, instead of trying to estimate when you are at the center of the threaded opening. For example measure from the top edge of the neck on one tank to the same top edge of the other.

Most "modern" manifolds are nominally 215 mm (8.46") Earlier manifolds were often narrower, some as close as 185mm (7.28") 207mm (8.15") was pretty common size.

If you have bands of "unknown" origin it's conceivable that they are for a different manifold.

Good luck,

Tobin