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Discussion of diving methods and equipment available prior to the development of BCDs beyond the horse collar. This forum is dedicated to the pre-1970 diving.
Vancetp
Master Diver
Posts: 303
Joined: Tue Oct 04, 2016 7:26 pm
First Name: Phillip
Location: Belmont CA

NED HydroTwin II

Sun Jun 28, 2020 1:21 pm

I got another NED HTII which I have just finished rebuilding. I'm posting this because it is different than the other two HTIIs I've worked on. This created a temporary sense of disappointment when I realized it was different from my my spares. Having the spare parts was one of the main reasons I bought this reg!

This one's HP side has a raised volcano orifice, a flat, square brass poppet like USD, and a long HP pin. The other 6 Sportsways DH regs I've worked on have the Healthways type dished hard seat and plastic cone soft seat. Unfortunately, the seat on this different poppet was shot: deeply grooved and crumbling.

ImageIMG_5388 by Vancetp, on Flickr

ImageDSCF3386 by Vancetp, on Flickr

However, the first stage body is identical to the others, and I decided to try to install the NOS parts I had on hand. Aside from having to make a new HP pin, it worked perfectly.

Looking through my pictures of teardowns done on Sportsways regs, I saw that the balanced single hose first stages have a similar flat poppet.

ImageDSCF3462 by Vancetp, on Flickr

Note the one piece balance chamber with the exposed o-ring. It is held in place by the plastic washer on the poppet assembly. Much easier than the o-ring buried in a groove the old style had. This is much like the improved USD setup. I thought this would be of interest.

The NED is done and works perfectly!

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