Bands-manifold mismatch?

[AbyssalPlains]

You need 8" bands for the LP95s. If you have those and a standard adjustable manifold, you'll be fine. There are decent videos on how to do it, I think scubatoys had one for a while. The trick is to get the crossbar started evenly on both sides, then tighten the bands and shorten the crossbar back and forth, making sure the crossbar is always free to move. I have taken apart doubles for inspection, put them back together with the same bands and manifold, and had to futz with them annoyingly to get the iso valve to freely point up when everything was tightened. It's just a bit of a pain, but you'll get it. I'd take the duct tape off, BTW. Just remember to do get the crossbar started evenly in both valves, then a turn on the bands, one on the crossbar, etc....

Don't listen to this "life support" crap. You're not going to kill yourself or anyone else. If you screw up, your tanks will leak and you might bend or damage the manifold. Hardly life or death.

Thanks for the encouragement. I took another stab at assembling the doubles just now (before I read this) and gave up. Well, actually I did manage to put them together but I didn't like the end result very much. The crossbar was turning freely, until I tightened the upper bands down. Then it became very hard to turn. It did turn, but only with force. So I loosened the bands again, nudged the tanks around a bit, repeated the process. With each turn of the screw on the bands, the crossbar becomes harder and harder to turn, in either direction. It just doesn't seem right. I don't understand why that happens.

Another thing I don't understand is how I'm supposed to alternate between turning the crossbar and the bands. After all, the crossbar has to be screwed in pretty much all the way BEFORE I can even put the bands on. If I put the bands on first, even loosely, there is not enough distance at the top to insert the crossbar. And accordingly, as long as the crossbar is not screwed in all the way, the tanks are too far apart to accommodate the bands.

I wanted to give the whole setup a shot in the pool tomorrow, but at the very end of tonight's process, I discovered that the bolts are too short to accommodate my backplate and the wing.

Doh.

I'm going to take the whole setup to Joel at Tech Diving Limited next weekend. I hope I can get a hold of him. I tried calling several times, but nobody answers the phone.

 

[Goferrin99]

Thanks for the encouragement. I took another stab at assembling the doubles just now (before I read this) and gave up. Well, actually I did manage to put them together but I didn't like the end result very much.

Does everyone assembles their doubles lying down....??

I tried to assemble my first set standing up and it allowed the tanks to walk apart and rotate a little around the axis of the manifold. This sent everything out of true in all planes. Lying down keeps the centre line of the tanks on one plane and all you have to worry about is toe in or out. This is easily measured with a tape around the tanks just below each band. Tighten each band until there is +/- 1mm or 1/16" difference.

An easy check if everything is true is is the tanks won't rock easily on a flat surface while standing. If they wobble easily then either the centre lines are not parallel or the tanks are different lengths.

If anyone has any comments or corrections please add them. I'm no seasoned expert when it comes to doubles.

 

[AbyssalPlains]

Does everyone assembles their doubles lying down....??

I tried to assemble my first set standing up and it allowed the tanks to walk apart and rotate a little around the axis of the manifold. This sent everything out of true in all planes. Lying down keeps the centre line of the tanks on one plane and all you have to worry about is toe in or out. This is easily measured with a tape around the tanks just below each band. Tighten each band until there is +/- 1mm or 1/16" difference.

An easy check if everything is true is is the tanks won't rock easily on a flat surface while standing. If they wobble easily then either the centre lines are not parallel or the tanks are different lengths.

If anyone has any comments or corrections please add them. I'm no seasoned expert when it comes to doubles.

I'm afraid I don't understand what "toe in or out" means. Can you clarify, please? Perhaps it's an expression, but I have never heard it. (English is my second language.)

 

[Goferrin99]

I'm afraid I don't understand what "toe in or out" means. Can you clarify, please? Perhaps it's an expression, but I have never heard it. (English is my second language.)

Toe in is when the bottom of the tanks are closer together than the tops. Toe out is the opposite. It's easy to check as the tanks will not sit flat either standing up or lying down but will rock like a table with one short leg

 

[AbyssalPlains]

Took everything apart and reassembled - only this time without the locking nuts on the crossbar. And voila - the crossbar turns freely even when bands are tightened down.

From what it looks like, the locking nuts are too thick - about 7 threads when there is only room for 5 threads once the tanks are at the distance dictated by the tightened bands.

I am planning to take the tanks to the pool tomorrow - is it dangerous to use them without the locking nuts? I read on the board that some people leave them loose so I can't imagine it being a problem. Of course I realize that it's not a permanent fix. It looks like the manifold and/or the nuts are simply not the right ones for this setup.

Apparently, Joel won't be here this coming weekend, but I hope that someone can sort me out at TDL when I stop there this coming weekend.

 

[Goferrin99]

I am planning to take the tanks to the pool tomorrow - is it dangerous to use them without the locking nuts? I read on the board that some people leave them loose so I can't imagine it being a problem.

Plenty of people leave the nuts loose or remove them all together. The logic being that if the isolation valve hits something during a dive the crossbar will rotate rather than the valve or manifold being damaged.

Enjoy

 

[AbyssalPlains]

Plenty of people leave the nuts loose or remove them all together. The logic being that if the isolation valve hits something during a dive the crossbar will rotate rather than the valve or manifold being damaged.

Enjoy

Cool. Thanks, buddy!

 

[AbyssalPlains]

On the past weekend, I took the twinset to TDL and had Scott look at them. He did an amazing job. Took everything apart, inspected all the parts and replaced what needed to be replaced. Everything is O2-clean now. Turns out the trouble I had with the set indeed came from a band-manifold mismatch. Whoever put the tanks together in the beginning didn't know what they were doing. Scott sold me a pair of Highland bands that fit perfectly. I dove my rig in Lake Mohave the next day and already love it. After only four dives on my steel doubles, I can't see myself going back to single Aluminum 80s ever again unless I'm forced to.

Thanks to all of you for your helpful comments and recommending TDL. Those guys are just amazing.