Buying the Octopus - does it need to be same model/similar?

[MaxTorque]

i DELIBERATELY mis-match my primary and secondary regulators!

Not mis-matched in terms of quality or cost, but mis-matched in terms of brand! This is avoid a "regulators react the same" issue. Any failure is going to stem from both a root cause, but also that particular designed susceptibility to that cause.

So by using a regulators of different designs, we remove a potential, one problem affects all equally type scenario.

The downside is i don't have parts commonality, but tbh, beyond a couple of O-rings and a diaphram, there isn't a lot of user servicable stuff inside a regulator these days, so carrying spares for each really isn't costly or bulky/heavy.

(if i'm not flying somewhere, tbh, i'll probably have my spares case with me that has a whole spare 1st and 2nd in anyway........ ;-)

 

[Centrals]

"Regulators react the same issue"?
All the regulators have the same issue if divers not looking after them properly.

Probably the only reasons why AP has both diaphragm and piston 1st stage and so many different 2nd stages.
Apeks is just the opposite.
I carry service kits but no spare parts. Diaphragm? Check them at home first leaving for diving.

 

[MaxTorque]

I'm talking about the reaction of regulators due to the fundamental effects of their design.

For example, more or less heatsinking, the diameter and stiffness of the diaphram, the leverage ratio of the actuation lever, the diameter and pneumatic balancing of the control orrifice, the amount of venturi effect in the mouth tube, and even things like the effect of UV or temperature on the material it's made from.

This could have a significant effect on the way a regulator acts, consider a few situations:

Rust debris from an internally rusty tank partially blocks the 1st stage sieve. IP drops dramatically as a result. The reg with the highest orrifice area will supply the most air, whilst a reg with a small orrifice will choke.

The 1st stage suffers creep as the HP seat breaks up. A reg that has a low amount of pressure balancing will freeflow first, a reg with a higher balance proportion will stay operating.


Basically, with different regs from different manufacturers, there is a greater chance that both you regs will NOT do the same thing, purely due to those baked-in design choices that differ between the brands.

Broadly this, might, mean that when one of regs freeflows, the other doesn't. That could make a difference.....

In high reliability system that are part of a redundant backup design, it's very common to ensure your individual redundant systems are not designed, and these days, not coded, by the same team, for the very reason of avoiding systematic faults

 

[Jafo19D]

My primary is a C370 and my secondary is an R095. I only Rec dive and I have no desire or interest in diving anything requiring a wetsuit over 5mm so I think that for my purposes that R095 is good enough. I also trust SP and I don’t think they’d sell something dangerous

 

[Centrals]

Rust debris from an internally rusty tank partially blocks the 1st stage sieve. IP drops dramatically as a result. The reg with the highest orrifice area will supply the most air, whilst a reg with a small orrifice will choke.

The 1st stage suffers creep as the HP seat breaks up. A reg that has a low amount of pressure balancing will freeflow first, a reg with a higher balance proportion will stay operating.


Basically, with different regs from different manufacturers, there is a greater chance that both you regs will NOT do the same thing, purely due to those baked-in design choices that differ between the brands.

Broadly this, might, mean that when one of regs freeflows, the other doesn't. That could make a difference.....

In high reliability system that are part of a redundant backup design, it's very common to ensure your individual redundant systems are not designed, and these days, not coded, by the same team, for the very reason of avoiding systematic faults

Have you got anything to substantiate that larger orifice would not be choked in your mentioned example?
The orifice in nearly all Apeks 1st stages are the same regardless of cost fro FSR to US4!
Do you think SP G260 and most Apeks 2nd stages are entirely different in design?
Apeks XTX 200 and AT20 2nd stage is nearly identical in the mechanism of the moving part.

What are you talking about?

 

[MaxTorque]

I have nothing to substantiate anything, but differences are differences, and being different may (not will) prevent a multiple failure from occuring due to the same root cause, whereas we can be certain that with identical regs, both are equally suceptable to the failure mode...... ;-)

BTW: The flow control orrifice in a regulator is "choked" during operation, ie the air flows through it at mach 1 (supersonic) this is how/why the opening area of that orrifice controls flow rate. As IP drops, that choking occurs at a lower flow rate, so at maximum opening, the larger the orrifice, the greater the flow potential

People are often sniffy about old regs like the classic SP R095, but the fact is, i suspect more hours have been spent safely underwater on a basic SP reg than pretty much any other reg, as they were, and often still are, the staple reg for most dive schools and hire gear for at least the last 15 years!

For sure, if you need cold water or ultimate low breathing effort performance, look else where, but i suggest that a well maintained ultra simple R095 is probably one of the most robust regs ever......

 

[MaxTorque]

BTW, one small advantage of using a basic non-pneumatically balanced second stage is that it will most likely freeflow well before a balanced design. This means if you get 1st stage IP creep due to seat damage, mechanical blockage or freezing, your basic second will freeflow before the reg you are breathing from, and whilst it does that, you can keep breathing happily from your primary as the secondard effectively vents the freeflow.

And of course, if you just doing no-deco Rec diving, then you know using your secondary will be at most limited to some tens of minutes of use, so having it adjusted up a bit tighter (ie at a higher cracking pressure) means it's less likely to freeflow as you enter or leave the water.

 

[Centrals]

Well maintain equipment regardless of brand and design!

 

[rsingler]

@MaxTorque has an intriguing philosophy. I can't fault it, though it's success would depend upon a very subtle accident cascade.
But the notion of using a downstream reg as the canary in the mine for rising IP, not to mention being more forgiving of grit in the water due to its simple design is a good plan for an octo. Since you can tune it to be as light a breather as your primary, it's a good alternative philosophy to "two identical seconds".

 

[USdiver1]

My preferred rig is to have identical second stages [primary and octo]. This makes service more efficient in that each second stage is using the same parts and can be tuned to provide the same performance. I believe in the "donate your primary" second stage to the OOA diver and take the octo for your own use. Why? Because you know the primary second stage is working as you are currently using it. If a panicked diver needs air, that is an immediate need, you should be able to purge/clear the octo more efficiently than a diver under stress. Also, you will know how well your primary has been working and if the octo is at that same range of performance when you breathe from it.