bungees and tank positioning

[seedy]

I have an xdeep style home made rig and am using bungees around the tank valve handle. (as per Xdeep and Rob Neto) I have mounted my regs the same as in a Brian Kakuk video
and have the valves handles facing down and the 1st stages facing inside. When I stretch the bungees over the valves
the bungee pulls and rotate the tanks about 45 degrees so the tank valves now face out to the side ....defeats the purpose a bit as everything is now not where I wanted it.
Do I have the bungees too tight...( I would say they are reasonably tight, they take a bit of pulling over the tank valve)or perhaps the btm clip position is wrong.
Looking behind the diver at the right hand tank, the tank valve is at 3 o'clock and the btm clip is at 8 o'clock....
the trim of the tanks isn't too bad, the rear could go lower a bit. Thanks for any help

 

[Subcooled]

An idea:

There is pull upwards on the outer side (due to the bungee). This causes rotation: the inner side wants to go down. If the lower attachment (carabiner, clip, whatever) sits on top of the (center line of) tank, then the tank can roll (as the attachment moves closer to your body).

The lower attachment point should not be on top of the tanks center line, but 45 degrees off center (~between you and the tank). Then the tank cannot roll. Any rotation of the tank would then pull the clip downwards, and as metal isnt elastic, nothing happens.

The clip is at 8. Handle at 3 ==> change 45 deg more ==> clip is at 8, handle at 6?
Try and tell us what happened.

_____________________
I have only used negative steel tanks, so don't know how aluminum tanks behave. I cant comment on the bungees either, without pictures.

 

[a878bob]

I guess I'm a little confused on your valves and setup, what type of valves are you using ?

Brian Kakuk and the xdeep guys look like they both dive modular valves with regs inside, valve handles out or up into the armpit and bungees around the modular post, not the cylinder valve handle. This is the way I do it as well.

The position of the valve and handle is dictated by the bottom clip position. To keep my handles up into my armpit at a 45, my bottom clips on my al80's are at 2:00 on the left and 10:00 on the right, when looking down on your cylinders. My hp100's are different of course because the bungies don't pull as much.

So start by adjusting the position of the bottom clips until they sit just right for you. Everybody is a little different.

 

[seedy]

I saw a Brian kakuk video where he had his valve handles facing down with mk25 regs facing in to the diver. Looks really neat setup. So that is what I was aiming for. I have modular valves and have been bungeeing around the tank handles. I think rotating 45 degree extra may do the trick. I will try that and report. Thanks for your time and help

Sent from my Nexus 7 using Tapatalk

 

[Subcooled]

Brian Kakuk and the xdeep guys look like they both dive modular valves with regs inside, valve handles out or up into the armpit"

(what is a modular valve?)

The tank valve knob should point down/out. In that position is is easy to rest your arm against your breast and feather the valve. This is especially important if free flows are usual. In other environments other setups may be beneficial.

If the valve knob is pointing out or up, feathering becomes more complicated. The tank is also less securely held. Although the knobs are better protected, two usability factors are against.

 

[Jim Lapenta]

A modular valve is one normally found on a set of doubles. The stem if you will that the crossbar screws into is longer than a valve designed for not using a manifold.

 

[a878bob]

So if the valve handle is pointing down at the cave floor, you put the bungie around the cylinder valve handle? And do you use the opposite hand and reach across your body to feather the valve ?

I haven't seen this before, if somebody would post a link to a video, I'd like to see it.

 

[Subcooled]

Yes. The bungee goes round the cylinder knob (and runs on the outside of the cylinder, from the shoulder/D ring to the handle, around it, back). It does not go around the neck of the cylinder.

Unfortunately I have no video of that It is very easy and natural to rest the opposite arm, bent 90 degrees, against ones chest, and with a slight movement of the wrist, turn the cylinder valve open and closed. If the knob points out of the chest, it quite naturally meets your hand.

Procedure:
1) suck on the reg. No air is delivered.
2) a careful turn of the wrist until air starts to flow
3) quickly open more for a decent breath, then close the valve, near the end of the inhalation
4) once it is closed, suck the hose empty

Almost no gas goes to waste. I did this quite comfortably for twenty minutes on a training dive. One hand is of course busy all the time and there is a fair amount of task loading.

 

[Dive-aholic]

Looping a bungee around most steel tanks works well because the heaviness of the steel tanks keeps them from rotating around as you describe. Some steel tanks will begin to rotate once they get down to a certain pressure - Faber LP85s start to rotate around 2200 psi and Faber LP95s start to rotate around 1600 psi. This usually isn't a problem because most cave divers are going to finish their dives with 1800-2000 psi in their tanks. Aluminum cylinders start get light enough to make the bottom end floaty around 2500 psi. If you loop a bungee around the valve even at 3000 psi they will rotate. At 2500 psi the bottoms will be angled up quite a bit. So rather than loop around the knob the bungee works better coming around the entire neck of the tank. This keeps the valve end where it needs to be while keeping it from rotating. Then at around 2500 psi you can relocate where the bottom clips are attached so the tanks remain trimmed out.

 

[seedy]

I tried today with Faber 10.5l tanks and later with Faber 7l tanks. I rotated the bottom clips further around but still had the rotation issues,maybe not quite as much. I think I'll do some pool testing to get to the bottom of this. If I can get it sorted i will be very pleased with it. I live a way from the coast with no dive shops and no other side mount divers I know to help, so this advice is much appreciated

Sent from my Nexus 7 using Tapatalk

---------- Post added February 2nd, 2014 at 06:03 PM ----------

How do you get a loop bungee around the cylinder neck?I was thinking of using a clip on the end of the loop,and pull that around the neck and clip back on the loop. This would maintain the backwards pull of the bungee...

Sent from my Nexus 7 using Tapatalk