This is of an XS Scuba rotating crossbar manifold (based on the Thermo manifold I believe):
Rotating Crossbar vs Captured O-Ring?
- Thread starter mahjong
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This is of an XS Scuba rotating crossbar manifold (based on the Thermo manifold I believe):
:
cool_hardware52
Contributor
My information is straight from the technical staff at Thermo, before they sold their scuba valve product line to XS.
The *ACTUAL* measurements I made in my shop before producing ISO bar extensions confirmed exactly what the Thermo engineers stated, i.e. the manifolds are
*NOT* intended to be adjusted for differing Center to Center distances
The max one rotation is to allow for positioning the valve orifices only.
The fact that wide sprread failures are not seen speaks only to the efficacy of a single (inner) oring.
Believe what ever you prefer to, I know arguing with you is a pointless waste of time.
I'll stick to what the Thermo Engineers told me and was confirmed with my own depth mics.
Tobin
lol ok. Pardon me for daring to present information that appears to conflict with your own findings - which BTW I don't doubt are accurate. I just wonder if they're as universally applicable as your statement "Current barrel oring style manifolds are *NOT* adjustable for varying center to center distances on doubles" makes out
I don't know the details of your bands but if they are anything like the Millworks bands they will probably work. For instance when you put 7.25" Millworks bands on 6.9" or 7.0" diameter tanks the flats of the bands will wrap around the tanks and ever so slightly spread them further apart. This doesn't impact the manifold much as the tanks are basically the same center to center distance as 7.25" tanks would be.
Is it perfect? No. Will it work, yes if the manifold threads are all the way engaged -plus or minus 1 thread. Be sure to check the tanks for parallel-ness before use.
OP
mahjong
Contributor
Thanks. The bands in fact could pass as Millwork bands--but I guess bands are bands. They are designed for nominal 8.5" spacing when locking down 6.9" tanks. If the c-to-c spacing on bands designed for 7.25" tanks does not change significantly when locking down 6.9" tanks (I would have thought the spacing would change quite a bit), then my setup should work, the tank diameter difference being only .06"). My technician didn't think there would be a problem, but we'll see. I'm heading out of town (Hawaii, actually, dive gear in toe) for a week and my tech too will be out of town, so we'll attend to the task in about 1.5 weeks.
cool_hardware52
Contributor
When I assemble a set of bands, tanks and manifold for the first time I do the following:
1) Assemble *ONLY* the tanks and bands. Snug up the bands.
2) Compare the resulting center to center distance of the cylinders to the manifold when it is assembled as recommended. It's pretty easy to hold the dip tubes along side the tank necks.
If the C to C is the same for the tanks and the manifold proceed. If they aren't find out why and get the right parts.
Tobin
OP
mahjong
Contributor
Will do, Tobin. That sounds like the wisest approach.
By the way, a follow up note on the manifold adjustability issue. If you click on the OMS link I offered in my initial post, you will see in the specs chart that the centerline distance OMS states for their rotating crossbar manifold is a range: 209mm - 222mm, or 8.228" - 8.74". That strikes me as a pretty good range.
By the way, a follow up note on the manifold adjustability issue. If you click on the OMS link I offered in my initial post, you will see in the specs chart that the centerline distance OMS states for their rotating crossbar manifold is a range: 209mm - 222mm, or 8.228" - 8.74". That strikes me as a pretty good range.
cool_hardware52
Contributor
Two thoughts:
Why would one ever need a manifold at 222mm, 8.74 Inches. The largest tanks in common service are 8" dia. 8/2 + 8/2 + ~.4" (band bolt) yields 8.4" or pretty close to 215 mm. Are there scuba tanks that are ~8.5 in in dia?
I wonder if the orings are all engaged at max c to c adjustment.
Tobin
OP
mahjong
Contributor
At the very least I think you can see how trying to figure all this out is not easy. I'm of the mind at this point that there is a lack of standardization among the major companies, even if there is a tendency towards it--ie, 8.5" spacing. And then add the history--the old manifolds with a wide variety of c-to-c spacing are still out there.
I for one would much prefer a nonisolation manifold for my mainly recreational application (though "recreational" is a stretch for any diving in northern CA, I would say). I'd happily take a J valve/reserve manifold, or better two plain elbows with no valves but the one in the center, that had 8.5" c-to-c spacing. Does such a manifold exist? If not, at some point I will seek out someone to custom make some bands according to my tanks and prefered nonisolation manifold. For now I will begrudgingly go with isolation and two valves/reg sets and long winding hoses, a horror show of unnecessary complication.
I for one would much prefer a nonisolation manifold for my mainly recreational application (though "recreational" is a stretch for any diving in northern CA, I would say). I'd happily take a J valve/reserve manifold, or better two plain elbows with no valves but the one in the center, that had 8.5" c-to-c spacing. Does such a manifold exist? If not, at some point I will seek out someone to custom make some bands according to my tanks and prefered nonisolation manifold. For now I will begrudgingly go with isolation and two valves/reg sets and long winding hoses, a horror show of unnecessary complication.
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