The New Atomic TFX

[rsingler]

reading elsewhere that the factory spec for cracking pressure is supposed to be 0.5".

Can you share where you saw this?

 

[stuartv]

BTW, adjustment of the cracking effort is exactly like the D400: just unscrew the top cap with a small pin face spanner and use a standard screwdriver to unscrew the cap which adjusts poppet spring pressure.

Thank you! I might have to order a spanner from somewhere. Otherwise, I think I can handle it....

 

[stuartv]

Can you share where you saw this?

Well, it is mentioned in your very first post that started this thread.....

But, I thought I had also seen it in some official literature as being the actual factory spec, too, which I cannot find now (after a somewhat cursory search).

 

[Geo7]

BTW, adjustment of the cracking effort is exactly like the D400: just unscrew the top cap with a small pin face spanner and use a standard screwdriver to unscrew the cap which adjusts poppet spring pressure.

Does the Atomic (Scubatools) 1st stage tool fit the TFX top cap?

 

[lowwall]

Based on what I know about car engine exhaust valves, I *think* the Pi * r^2 thing is not the right comparison. I think the correct way to compare is by circumference. 29.5 / 27 yields a 9% increase. Still nothing to sneeze at.

Good point that the cross section of a tube may apply less than the circumference. I'd add to that that the flexibility of the diaphragm will dictate how far it folds open. The more flexible it is, the more the cross section may come into play as well (i.e. the flow increase may go beyond 9%).

Engine valves are an incomplete model. They are solid and the entire valve is pulled away from the port. The area that the exhaust gases can escape from is the circumference of the valve times the height of the lift. In other words it's the surface area of the walls of a cylinder or Pi*diameter*height. So yes, if keeping the lift the same when modifying your engine, the exhaust area only increases by the circumference. Which is the primary reason manufacturers shift to multiple valves per cylinder when trying to increase performance.

OTOH, second stage exhaust valves don't lift. The center is fixed in place and the rest of the valve deforms when internal pressure sufficiently exceeds external pressure. If the deformation is evenly distributed around the circumference and only moves a small amount, then it's roughly analogous to car engine valves, except the area available for gas to release is a truncated cone rather than a cylinder. However, if the deformation is large enough for the valve to completely fold then the available area does become the full area of the circle. The reality is likely between the two.

How do exhaust valves actually deform? Are there any slow motion videos of exhaust valve movement under different breathing rates?

 

[scrane]

View attachment 796845
But the diaphragm retainer is a very thin plastic piece, and incorporating threading might make it a deal breaker for 3D.

Do you think cutting slits in the collar might help the D’s.

Looking at your previous photo showing the tfx and d400 diaphragm assemblies it’s hard to believe they are from different manufacturers. Did I hear that the designer of the d series now works for Atomic. It will be interesting as different components are revealed

 

[lowwall]

How do exhaust valves actually deform?

As I'm continuing to think about this it occurs to me that we are neglecting the force needed to open the valve which might the real advantage of larger valves. If we think of a section of the valve from center to edge as a lever, you'll obviously need less force to start moving that edge as the length increases. Which means it should open at a smaller increase in pressure over ambient. Right?

 

[Geo7]

Looking at your previous photo showing the tfx and d400 diaphragm assemblies it’s hard to believe they are from different manufacturers. Did I hear that the designer of the d series now works for Atomic. It will be interesting as different components are revealed

Yup, I read the "D" in D400 stands for Doug Toth, and the "G" in G250 stands for Dean Garraffa (I think according to a John Bantin article). Many employees left Scubapro when Johnson Outdoor alienated the staff (according to an article by Bret Gillilam). Dean and Doug then founded Atomic and built what was basically an improved Mk10 with an improved G500 ... out of titanium... The Atomic T1 in the mid 1990s.

I agree that many parts look like a D400 clone. The TFX is an improved D400, and in my mind I call it the "D400T." What amuses me is that so many manufacturers, both new ones and established ones try to innovate here and there, but no one revived this most legendary reg. Even the D420 abandoned the co-axial exhaust that made the D300-D400 special. I did not see the point in getting a D420 because of that.

It seems that over three decades the reg gurus on Scubaboard have praised the D400 more than any other reg. So it amuses me that all other manufacturers left the opportunity wide open for Atomic to revive their baby, improve it and make it out of titanium. I was sold immediately when I read co-axial exhaust, bigger diaphragm, center-balanced valve, and titanium.

 

[stuartv]

Tangent, but since there are clearly some posters in this thread that are very knowledgeable about Atomic regs... (and we're all anxiously awaiting a post-dive report on the TFX...)

Q: Is the Ti2 octo identical to a yellow B2, save for a different face plate and no ComfortSwivel?

I just want confirmation that I can buy a face plate and knob for a B2 to change my new Ti2 to have no yellow - and also not have it bearing a label that would suggest it is substantially different than what it really is.

And while I'm on the subject, what's the difference between a T3 2nd stage and a B2 2nd stage, apart from the face plate and Ti vs brass ComfortSwivel? I'm thinking maybe they are identical inside? In which case, it would be just as legit to put a T2 or T3 face plate on a Ti2 as putting on a B2 face plate?

 

[Belzelbub]

Did I hear that the designer of the d series now works for Atomic.

Works for Atomic might be a bit of an understatement. More like started Atomic. Along with the designer of the G series.