Why do piston regs cost more than diaphragm regs?

[James79]

I will admit, the only time I ever said "wow, that reg breathes great" was a few years back when I rented a Sherwood balanced piston from a local quarry. Of course, it might just have been tuned perfectly, too.

In my (admittedly limited) experience the subjective experience of a reg is more dependent on the tuning than the particular reg... I rebuild an use 60's era Conshelfs, and tune them to breath better than any rental reg I've ever used. When you get a spectacular reg tech, then you can start seeing the limits of just how well a given reg can be tuned... but for most of us mere mortals a pretty well tuned reg will breathe "great."

 

[James79]

I'm working on something that has me modeling a balanced piston... and it gives me some insight into how complex the machine work to make one has to be. While it is a simple reg in terms of function, there is a lot of machining steps needed to make one. I dare say more than needed for a diaphragm. An unbalanced piston, on the other hand, is a super simple design in function and machine work.

Respectfully,

James

 

[Eric Sedletzky]

Are pistons more expensive, though? There are inexpensive unbalanced pistons out there (Edge\Sea Elite, Cressi, Oceanic, Tusa) and the Scubapro Mk2 is lower priced than any diaphragm regs in the Scubapro line, isn't it? Sherwood has balanced pistons designed for cold water that are considerably less expensive than the Mk25.

The Mk25-style designs do have the swivel turret and extra ports and I assume there are also some design differences in the second stage. From what I can tell, unbalanced pistons are usually the cheapest, followed by the diaphragm designs, followed by the balanced pistons. I usually rent gear for salt water diving, and the regs are almost always unbalanced pistons. I will admit, the only time I ever said "wow, that reg breathes great" was a few years back when I rented a Sherwood balanced piston from a local quarry. Of course, it might just have been tuned perfectly, too.

Yes, MK2’s are cheaper than mid priced diaphagms but there also very little to them. Actually new MK2 evo’s aren’t that cheap anymore.
I’m guessing, but I’ll bet part of the reason diaphragms tend to be better priced that pistons is because there’s more infrastructure to support production.

99% of your breathing performance will be in the second stage. You could take a top notch 1st stage and put a really crappy badly tuned second stage on it and it will breathe horrible. You could take a very poorly performing low IP 1st stage and put a very high end balanced second stage on it perfectly tuned and it will breathe great.
The second stage does not care or know what’s feeding it, as long as there is pressure, unless it’s a very poorly performing and out of tune second stage, then it cares. A high end top of the line balanced second stage is capable of making up for a lot of pressure differentials and poor flow.

If I had to start from square one and was in the market for a new reg it would be a MK2/R190 and I’d add a G260 as the primary on a long hose.
This combo would last me the rest of my life and serve my needs perfectly for any diving I do.
The MK2 is dirt simple and parts can be sourced easily.

 

[MrVegas]

The MK2 is dirt simple and parts can be sourced easily.

What about the cold water divers, though? I'm diving sealed diaphragms because everyone gets frowny-faced if you're diving unsealed, unbalanced pistons in 45F water. (Maybe with good reason - but actual statistics are hard to come by on free flows.)

 

[Divin'Papaw]

The MK2 is my desert island reg. If I was stranded on a desert island the MK2 would be my choice.

But where would you get fills?

 

[Belzelbub]

... and why exactly? Honest question. I've heard people say they are "better" for years, but I've never heard a solid argument as to why.

Neither have I. The only argument I’ve heard that might have some validity is that a piston can flow more gas than a diaphragm. But that falls apart in the real world as either are capable of providing way more gas than could be used.

I dive both fairly regularly. Personal regs are Zeagle diaphragms, but I also use Atomic pistons regularly. I see no reason to switch my personal regs to piston. Plus, my Zeagles are sealed which makes post dive cleanup much simpler.

But where would you get fills?

Surely the Professor will be able to whip up a watermill powered compressor. Probably have to connect a few coconuts unless he brought some cylinders. I wonder what the working pressure is on a coconut.

 

[Jcp2]

But where would you get fills?

It depends on which resort he is staying at on Bonaire.

 

[Eric Sedletzky]

But where would you get fills?

Good point.

 

[James79]

I wonder what the working pressure is on a coconut.

I'm getting echoes of Monty Python:
lol

James

 

[lexvil]

Upon reflection and since the main makers of piston Regs is Scuba pro and Atomic that in itself may be the answer.