Hollis Prism 2 rigid tank mount

[telemonster]

Hello all,

One thing that is a bit of a weak point to me on the Prism 2 is the tanks. They strap to the unit using velcro, which seems great as far as speed to replace. But without a stand, the weight of the unit on the tank valves (which have rubber shock absorbing bumpers) tends to push the tanks back out of the straps for me.

After diving this weekend and seeing a unit (xccr) with the sexy Metalsub tank mounts I started to think about the prospect of adding those. But those are made to for different shaped units and wouldn't be practical to add to the Prism 2 without making adapters.

After thinking about the adapters, I think it might just be easier to make a custom set of milled aluminum mounts that would allow the tanks to rigidly mount to the frame. Something similar to the Metalsubs but not meant for tank shapes -- custom to the prism 2.

Positives I can see would be:
- Easy to swap the tanks (unscrewing din slowest part)
- Can sit unit on tank valves without the tanks sliding around, without a stand
- Can remove the velcro straps

Negatives I can see:
- Tanks now need to have the mating brackets to swap on
- Need to investigate aluminum, dissimilar metal corrosion potential issues
- Tanks might sit out a bit further left/right to allow for brackets.
- Probably a tethered stainless steel release pin, button operated.
- Tapped holes in aluminum for mounting parts to Prism frame might be a weak point due to aluminum softness

I imagine two blocks for each tank + C clamp w/ protector, then two blocks for each tank that mount to the Prism frame where the velcro straps currently sit. Pin would go into the top.

I have some friends with CNC mills and stuff. I might try to whip up a design or two in Sketchup 3d. Not sure what the aluminum cost is.

Stand isn't a bad idea also, I'm not discounting that.

Thoughts?

 

[RVBldr]

I'm finding that I need to loosen up the top straps to get the tanks out of the way a bit to latch the bucket. As long as you can do that, a better mount would be great.

 

[telemonster]

I'm finding that I need to loosen up the top straps to get the tanks out of the way a bit to latch the bucket. As long as you can do that, a better mount would be great.

Yea, same. The mounts could be "thick" enough to push the tanks out far enough that the can latches clear the tanks.

 

[markcic]

If you bolted on a plate with the right slots milled in it between the upper and lower parts of the H plate, you could use something like the Revo tank mount.

 

[rongoodman]

Why not just get a stand?

 

[stuartv]

If you bolted on a plate with the right slots milled in it between the upper and lower parts of the H plate, you could use something like the Revo tank mount.

View attachment 544111

That's a good point. Those slots are very basic, if you will. Should be pretty darn easy to fabricate something that a rEvo tank fixation would attach to.

And, @telemonster, I have an idea where you might be able to get access to a rEvo to use as a template... And borrow some actual rEvo tank fixations to use for testing purposes...

Also, just an FYI, rEvo also has "travel" tank fixations.

https://www.oceanedgeoutfitters.com/Travel-Tank-Fixation-Oxygen-Side-rEvo-R586-p/revo-r586.htm

and

https://www.oceanedgeoutfitters.com/Travel-Tank-Fixation-Diluent-Side-rEvo-R587-p/revo-r587.htm

Having the right mounting base on your Prism would make the travel fixations very handy for, well, traveling and renting tanks. I'm going to buy a set for myself at some point.

 

[rddvet]

Don't know anything about Prisms, but Kent Tooling makes some amazing pony/ccr bottle brackets. Very well built and sturdy, and can hold up to lp50s.

Straight Back Pony Brackets (NON OPEN CIRCUIT) from Kent Tooling Diving Products

 

[telemonster]

I was thinking something like this, where one side bolts to the two existing frame mounts. The top having the pin to secure it, the bottom being angled in such a way that the bottom goes in first and is captured.

The tank side would be rounded off.

Rough idea (not to scale, I didn't take measurements before throwing it together. Need to redo it.

 

[telemonster]

Why not just get a stand?

I actually just got a stand from Don Six. Haven't installed it yet and checked to see if it eliminates my desire to make solid tank mounting system.

 

[OceanEyes]

Hey telemonster. Glad that you opted to have Don Six make a stand for you. I’m more than satisfied by the one he designed and made for my Pathfinder. (I happened to click on the “like’ tab for the suggestion that you get a stand as posted by @rongoodman. I should have recommended that you contact Mr. Six, but was not sure if he made stands for the Prism.)

You may still want to pursue a new tank mounting system, but you probably no longer need to do so. One minor benefit that you may not have considered is that by eliminating the tank mounting hardware, you will make your life just a little bit simpler when you travel with your RB, and have to rely on rental cylinders. You will have a few less items to pack as you will not have to bring along whatever hardware that you’d have to attach to the rental tanks. Having fewer things to pack and carry is a small blessing.