Greg Barlow
Contributor
Mares offers some metal looking plastic cases, but it's a cheap looking metal color and is, after all, still only plastic.
The durability of a plastic case absolutely sucks compared to a chrome plated brass case. I see 30-40 year old chrome plated brass second stages come in for service all the time (virtually all of them made by Scubapro and US Divers/Aqualung, given the superb parts and service support offerred by those companies for older models).
DA,
What Mares second stages "look" like metal? They do offer brass bodied second stages in both the full sized version such as the Abyss, and the smaller bodied, Proton series. These offer all of the advantages that you mentioned in your excellent summary of plastic versus metal second stage housings. The front cover is not metal, but it doesn't need to be for thermal advantages.
ScubaPro advertises their "new" S600 Classic in this fashion on their Asian site:
" Based on the design of the renewed Scubapro classic metal second stage, this unique look includes a metal knob and cover
Excellent performance in cold water
Impact and shock resistant"
A metal cover does nothing to alleviate the problem of a plastic housing and valve assembly, as the heat transfer would be very minimal. IMHO, the worse thing that ScubaPro did was to drop the metal valve assembly. Apeks and Atomic both realize that metal simply works better in this regard. ScubaPro simply has allowed the bean counters to call the shots on this important feature.
The Mares metal bodied Protons are very nice in that they offer the thermal advantages, along with very few parts. I really like being able to adjust them through the port plug on the side. You can also easily remove the cover underwater. The MR12 III, Abyss, etc. style is tougher to finely adjust, and can't be disassembled underwater.
I think that ScubaPro could win back a lot of tech divers if they offered a small brass bodied second stage (similar to the metal Proton) paired with their excellent MK17 first stage that you are so fond off. They could still make it a balanced adjustable, if they choose to do so. I would also make a larger exhaust tee, to alleviate the problems of the smallish ones used.
Now I know why I like the discontinued Mares Akros so much. It had metal inserts to help with the thermal concerns, along with a large, efficient exhaust tee. I use two on my doubles, and they are sweet breathers when set to a cracking effort of 1.25". I'm not sure how effective the metal inserts are, but I've never had any ice chips passing through the mouthpiece despite temps in the low 30's.
Greg Barlow