G250 flow vane

[rsingler]

The way you have them now puts the vane cutout facing the diaphragm.
The reverse is known as the "rental configuration", and minimizes the VIVA venturi action, that was a selling point for Scubapro 20 years ago. I'm not surprised that you picked up on the subtle performance difference, Simon.
But most shops have no idea it's even an option to reverse position. In fact, at a Scubapro technician seminar, the trainer was even unaware of it, and initially instructed the class to assemble in rental config. It's only mentioned in a quarter page window in a few service manuals. It required some diplomacy on my part, with 30 people watching, to point out that he had it backwards, lol. Doh!

 

[rsingler]

Good idea to reduce diameter... plastic mouldings have a nasty habit of stress cracking if sustained point loads are too high over time.

I suspect that molding diameter and tolerance was calculated pretty closely by Scubapro. They're a pain in the a** to deal with, but pretty good designers. This part isn't designed to come out but once in a blue moon, and I'm concerned that making that initial insertion easier by reducing bump diameter might leave you with an empty hole in your case on some dive years from now.
I think @buddhasummer reassured us all about the second insertion, but you have a good point - we shouldn't be changing that o-ring every year.

 

[buddhasummer]

I'd wonder if you're going to use those in G250s if one should install take out and re install then leave them alone until that O ring goes. That way you've reduced any stress?

 

[rsingler]

I'd wonder if you're going to use those in G250s if one should install take out and re install then leave them alone until that O ring goes. That way you've reduced any stress?

Yep. I don't touch the vane unless the circlip has corroded out or there's damage to the vane. Maybe an o-ring replacement if someone sends me a cruddy eBay reg to restore, but that's about it.

 

[Fibonacci]

I've rebuilt four G250's so far this year, two had quite bad corrosion pitting on the underside of the c-clip which makes replacing it a very good idea as its in the airway.
All had coloured o-rings that had hardened, crumbled on removal... while installed they would probably still seal OK but a new o-ring made the vane feel much better in operation.

 

[buddhasummer]

I replace all O rings on every G250 I get as par for the course, ditto spring, orifice, adj knob and new S-wing poppets. I have more money than sense, and actually not much of either it seems.