Doubles bands not fitting perfectly

[davel518]

I think this is the right forum for this, let me know if you disagree.

I recently put together a pair of double AL 80s. The band is totally snug on both cylinders. The upper is good on one tank, but i can 'jiggle' it a bit on the other. Not much, just a mm or so, it's not loose just not perfect. It's already quite tight so I hate to crank on the bolt more. I'm inclined to think this is fine since one band is totally firm, and this one is certainly fine side to side. These are highland bands so I doubt it's an issue with them being misshapen.

- Should I be concerned? It seems ok but obviously need to be quite comfortable if I'm using these on deco dives. Less worried about recreational. Maybe I'm just paranoid.
- Any idea how to improve this without just tightening? Thinking maybe a couple pieces of foam tape as a shim.

Thanks in advance.

 

[divad]

- Any idea how to improve this without just tightening? Thinking maybe a couple pieces of foam tape as a shim.

Maybe a length of same-width bicycle innertube? (it will never die........unless you burn it.)

You can use it as is, or cut it for single ply as necessary.

 

[kelemvor]

Another option is to use a simmilar width piece of webbing. Usually webbing is really a hollow tube, you just need to cut the right length and work the tube open with your fingers and slide it right on. That's what I use. Mainly because I had webbing and was too cheap to spend $2 on an innertube.

Innertube or webbing will also have the benefit of covering any sharp edges or burrs so they can't damage soft gear that might contact the bands. Maybe highland has properly chamfered all the edges, but that seems like a LOT of work to do to a band so I doubt it.


Edit: oops I was thinking of sidemount bands. I suspect you're talking about the bigger backmount. I don't have a solution for backmount. Those could reasonably be chamfered in manufacturing.

Another unlikely possibility is that the tight tank has expanded some. If you have 12" or larger calipers, try measuring both tanks under the band. I have no idea if tolerance on tank exteriors is bad or if that would be acceptable. I'm sure someone else would know.

 

[Heka]

Did you tighten the bolts little bit at a time taking turns between the bands or did you tighten one band all the way and then another?
I've had similar situation and the band setteled perfectly when tighten little by little.

 

[_Ralph]

I think this is the right forum for this, let me know if you disagree.

I recently put together a pair of double AL 80s. The band is totally snug on both cylinders. The upper is good on one tank, but i can 'jiggle' it a bit on the other. Not much, just a mm or so, it's not loose just not perfect. It's already quite tight so I hate to crank on the bolt more. I'm inclined to think this is fine since one band is totally firm, and this one is certainly fine side to side. These are highland bands so I doubt it's an issue with them being misshapen.

- Should I be concerned? It seems ok but obviously need to be quite comfortable if I'm using these on deco dives. Less worried about recreational. Maybe I'm just paranoid.
- Any idea how to improve this without just tightening? Thinking maybe a couple pieces of foam tape as a shim.

Thanks in advance.

How is the manifold spacing?

If that is off, it can throw off the bands as well


_R

 

[Rose Robinson]

I think this is the right forum for this, let me know if you disagree.

I recently put together a pair of double AL 80s. The band is totally snug on both cylinders. The upper is good on one tank, but i can 'jiggle' it a bit on the other. Not much, just a mm or so, it's not loose just not perfect. It's already quite tight so I hate to crank on the bolt more. I'm inclined to think this is fine since one band is totally firm, and this one is certainly fine side to side. These are highland bands so I doubt it's an issue with them being misshapen.

- Should I be concerned? It seems ok but obviously need to be quite comfortable if I'm using these on deco dives. Less worried about recreational. Maybe I'm just paranoid.
- Any idea how to improve this without just tightening? Thinking maybe a couple pieces of foam tape as a shim.

Thanks in advance.

Hi Dave,

I have the inside of my doubles bands lined with black Gorilla Duct tape. Helps snug up the bands without over-tightening the bolts, prevents dis-similar metal reaction, and keeps the salt away from the area between the inside of the bands, and the outside of the tanks.

Tape is replaced each year when the tanks are serviced.

I was shown this by my tech instructor a long time ago, using standard duct tape. I find the Gorilla tape is much more durable, does not deteriorate, and does not leave any residue when it's time to change it. If you use the ''wide'' Gorilla tape, it's easier to install, and using a utility knife, you can trim off the excess. The whole process takes only a couple of minutes.

Rose.

 

[PfcAJ]

Somethin ain’t right. I’d bet your manifold spacing isn’t dialed in.

 

[rddvet]

Only time I’ve ever had an issue is when I didn’t assemble them right. Anytime that happens I pull them apart and start again and it’s always right. Tbh I’ve become a lazy bastard. Whenever my tanks are due for hydro I let the shop install and uninstall the manifold and bands. I can do it but my time is worth more than the little bit extra they charge.

 

[rjack321]

I would not dive improperly assembled doubles...

1. lay the tanks on as flat of a surface as you can
2. loosen both band bolts
3. loosen the nuts of the manifold cross bar
4. snug down band nuts barely finger tight
5. examine the spacing and adjust the cross bar in or out until both bands are laying identically on the cylinders
6. tighten band nuts a turn or two
7. check crossbar, should not be binding, should still move freely
8. alternate tightening the band nuts couple turns to each
9. tighten manifold nuts

 

[davel518]

Thanks everyone - this is incredibly helpful. I'll give these a shot. Hopefully loosening up the whole rig solves the problem. I like the Gorilla glue tape idea Rose, even if I can sort out the fit without it.

Scubaboard really is the best.

Dave