Spoon:
guys just installed my manifolds and tank bands on my tanks. perfect fit my only concern is that the spacing at the lower part of the tanks is narrower than the top part. its not noticeable or anything but i saw it. their seems to be no stress on the manifolds and the tanks seem to be carrying the weight fine? this ok?
also when lifting them tanks is it ok if i carry the tanks from the base and tank bands leaving the manifolds hands free?
my first twins rig so excited to test!
A few points here.
The tanks should be absolutely parallel.
The bands should be tight, but not so tight that the flat parts where the bolts are get deformed, but still pretty darn tight.
The crossbar or isolator on your manifold should be able to turn without too much effort before you tighten the nuts locking it into position. The isolator or crossbar should be as close to perfectly centered between the two valves as possible.
Assembling the entire system is much easier if you have a sturdy flat table where you can lay the tanks and slide them around. The process of tightening everything is a lot of... Tighten the upper bolt a little. Then tighten the lower bolt a little. Then check the mainfold and adjust a little. Then go back to the bolts. Then back to the manifold. To really get it right takes some time, and you need to be very willing to take it all apart and start over if things don't look just right.
When you are finished the tanks should be parallel, the isolator needs to be free to move before you tighten it into position with the nuts, the isolator valve should be tilted a bit toward the back of your head to make the valve a little easier to reach.
At least in the United States the standard center distance for the bolts is 11 inches, and precisely 11 inches. Many backplates now have a short slot for the bottom bolt, some plates do not. Even if you have a slot you should try to get the standard spacing because you might in the future use a different plate for one or two dives, and it would suck to need to re-adjust the spacing.
Speaking of adjusting the doubles, be extremely cautious if you try to adjust the tanks when pressurized. Never loosen both bands on pressurized tanks, doing so invites damage or failure of the manifold. If you get it right the first time you should not need to adjust them, but heck we live in the real world, so be really careful.
For carrying the tanks try pointing the bolts away from you with the cylinders standing upright. Now put your left hand on the outside of the left hand valve (not between the cylinders at all) and put your right hand between the cylinders at the base and with your palm toward the base of the right hand cylinder lift them up so the valves are more or less pointed toward your left bicep and the bottoms of the cylinders are pointed toward your right hip. The end result is that the cylinders are somewhat diagonal accross your abdomen. You can also carry them by putting your hands on the valves atop each cylinder, just be careful to never lift them by the center of the isolator. This is a very tempting place to carry the cylinders from but it may damage your manifold if it gets bent. Always be careful not to hurt your back when carrying doubles. If you need to carry them very far either get some wheels or attach them to your back plate and wear them.
Enjoy the doubles, but now you really need to keep an eye on your bottom time since air will not be a limiting factor.
Mark Vlahos
