Triple 72's
- Thread starter Gilldiver
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OP
Gilldiver
Contributor
I had to break down the rig to replace an O-ring so had a chance to take some comparison photos.
The top is the long bar made from a 3.5 extension and a 3.25 CGA 540 Nipple and nut. This is the bar used with the triple 72s and gives an 8.25 on center spacing. The bottom bar made from a trimmed and re-tapped 3.5 extension and a 2.25 CGA 540 nipple and nut to be used with 5 diameter 30 or 40 cubic foot tanks.
This photo shows how the bands were made in 2 parts:
There are two pieces to each band which run from the from the right front overlap to the back left overlap both circled. Each part was made from 48 long by 1.5 inch wide stainless steel strips. If I were to keep this rig for normal diving I would do some trim of these overlaps and then have them welded together. The half rounds are made from ¾ half round stainless bar stock available from McMaster Carr. The Eye bolts used are stainless steel 5/16 by 5" long from the home store. For a 30/40 triple set I should be able to do an entire band with one strip just as Captain has done.
Pete
The top is the long bar made from a 3.5 extension and a 3.25 CGA 540 Nipple and nut. This is the bar used with the triple 72s and gives an 8.25 on center spacing. The bottom bar made from a trimmed and re-tapped 3.5 extension and a 2.25 CGA 540 nipple and nut to be used with 5 diameter 30 or 40 cubic foot tanks.
This photo shows how the bands were made in 2 parts:
There are two pieces to each band which run from the from the right front overlap to the back left overlap both circled. Each part was made from 48 long by 1.5 inch wide stainless steel strips. If I were to keep this rig for normal diving I would do some trim of these overlaps and then have them welded together. The half rounds are made from ¾ half round stainless bar stock available from McMaster Carr. The Eye bolts used are stainless steel 5/16 by 5" long from the home store. For a 30/40 triple set I should be able to do an entire band with one strip just as Captain has done.
Pete
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Any commercial shear should happily gnaw 1/4" stainless 12 feet wide. Look for them in big A/C shops, specialty welding shops, machine shops, or shipyards.
OP
Gilldiver
Contributor
Standard shear size for most thinner gauge sheet is 4'x12' or 48" x 144". You can get longer but it is a specal cut. I work for Sikorsky Aircraft and it is a very rare aircraft skin that is larger then a 4x12 sheet. At Boeing, your milage may differ.
I got my strips from the scrap bin of a chemical processing line design/build firm. They didn't have any 12' scrap but did have a lot of 48" long pieces, free is always better and paid for.
Another place to look for strips of stainless would be a truck body shop that does custom and repair work. They may have some stainless around from the last time they did a refer.
I got my strips from the scrap bin of a chemical processing line design/build firm. They didn't have any 12' scrap but did have a lot of 48" long pieces, free is always better and paid for.
Another place to look for strips of stainless would be a truck body shop that does custom and repair work. They may have some stainless around from the last time they did a refer.
This thread is proof that if there is ANYTHING you want to know about diving... the answer can be found (or made) on Scubaboard!
OP
Gilldiver
Contributor
After a few years of keeping you eyes open you may find that there is just not much that hasnt been done one way or another in the past electronic being the exception. Twins and triples have been used since the start of SCUBA, BCs in a primitive form almost as long, back plates go back to at least the early 60s etc.
We just find new ways to make things or rediscover what someone had done on their own before. My technique, and Captains, for the triple bands is just a modification of how the 1 steel doubles bands worked from the start with an overlap and bolt holding it all together. Im just surprised that someone never came up with using a USD J-60 valve as the base for a triple manifold before. As for triple 72s, Captain pointed out that they are in the USD 1968 catalog as a special order using a cheater bar to connect two tanks in a doubles formation and the 3rd tank behind them connected by a pipe to the cheater bar.
We just find new ways to make things or rediscover what someone had done on their own before. My technique, and Captains, for the triple bands is just a modification of how the 1 steel doubles bands worked from the start with an overlap and bolt holding it all together. Im just surprised that someone never came up with using a USD J-60 valve as the base for a triple manifold before. As for triple 72s, Captain pointed out that they are in the USD 1968 catalog as a special order using a cheater bar to connect two tanks in a doubles formation and the 3rd tank behind them connected by a pipe to the cheater bar.
OP
Gilldiver
Contributor
Diving the triple 72s
Well, they are heavy on land, but they are just about the same as my twin 130s with a stainless back plate. The biggest difference is that they are wide and you have to keep that in mind to keep from bumping just about everything.
I wasnt able to get them to a dive shop that would fill this type of rig for me, most of the other dive shops would get crossed eyed if I brought them in, so I sacrificed the fills in a set of time 72s, mu 100s, and a single 120 and ended up with 1700 psi in the triples. The manifold held this rock steady for 2 days with no drop in pressure, so they seem to be solid.
For todays trial I took them to a pool and dove with a dive class. I had on the top to my ¼ farmer John and ended up needing 5# of lead to hold steady at 10 feet.
I knew that I had them on most of the time as there just is a lot more mass to control. Some more work in getting the harness adjusted might help, but it will not eliminate the fact that there is just a lot of weight back there. In all positions except vertical, I was able to easily. When in the vertical, head up or down, the tanks want to pull you over onto your back and it takes a good bit of effort to control this. But after some practice I was able to do barrel rolls and loops with ease.
Do to the size and the way the mass is spread out to your sides I wouldnt want to do a beach dive with these and any boat dive would need to have a boat with a very sturdy ladder and some way to brace yourself at the sides as you came up it. No way would I ever want to dive this rig in a chop.
Here is the proof, the pool was a bit dark and my camera will only go to ASA 400 so they are a bit grainy.
Pete Johnson
Well, they are heavy on land, but they are just about the same as my twin 130s with a stainless back plate. The biggest difference is that they are wide and you have to keep that in mind to keep from bumping just about everything.
I wasnt able to get them to a dive shop that would fill this type of rig for me, most of the other dive shops would get crossed eyed if I brought them in, so I sacrificed the fills in a set of time 72s, mu 100s, and a single 120 and ended up with 1700 psi in the triples. The manifold held this rock steady for 2 days with no drop in pressure, so they seem to be solid.
For todays trial I took them to a pool and dove with a dive class. I had on the top to my ¼ farmer John and ended up needing 5# of lead to hold steady at 10 feet.
I knew that I had them on most of the time as there just is a lot more mass to control. Some more work in getting the harness adjusted might help, but it will not eliminate the fact that there is just a lot of weight back there. In all positions except vertical, I was able to easily. When in the vertical, head up or down, the tanks want to pull you over onto your back and it takes a good bit of effort to control this. But after some practice I was able to do barrel rolls and loops with ease.
Do to the size and the way the mass is spread out to your sides I wouldnt want to do a beach dive with these and any boat dive would need to have a boat with a very sturdy ladder and some way to brace yourself at the sides as you came up it. No way would I ever want to dive this rig in a chop.
Here is the proof, the pool was a bit dark and my camera will only go to ASA 400 so they are a bit grainy.
Pete Johnson
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