Cold water: Does 2.stage matter?

[ams511]

Precisely. The SRB3600 first has a wide ISP and can be dropped down to 120-125 psi. The heat sink mod to the second stages involved a simple part swap. Otherwise, a great number of the part numbers seem to be common between the service manuals (again, only for the seconds). I’ve used he same 1st stages to drive my Jetstream seconds in a few configurations with great success, with he addition of an OPV on the hose.

I was a bit bored and looked at the old articles. The only modification mentioned was using the heat exchanger from the Blizzard and adding to the Maximus. Also it was mentioned that they wanted the ability to tune it down. So you are correct. I thought the Blizzard also had some Teflon coated parts, but I could be mistaken.

Sherwood used to sell the Ultima which was a Sherwood first and a Jetstream second. Not sure where the OPV was located.

I am not sure why Sherwood never capitalized on this and came out with a "McMurdo" edition of the Maximus with all the modes already made. They would have owned the cold water market.

 

[texspeleo]

I was a bit bored and looked at the old articles. The only modification mentioned was using the heat exchanger from the Blizzard and adding to the Maximus. Also it was mentioned that they wanted the ability to tune it down. So you are correct. I thought the Blizzard also had some Teflon coated parts, but I could be mistaken.

Sherwood used to sell the Ultima which was a Sherwood first and a Jetstream second. Not sure where the OPV was located.

I am not sure why Sherwood never capitalized on this and came out with a "McMurdo" edition of the Maximus with all the modes already made. They would have owned the cold water market.

The heat/moisture exchanger ( p/n 25-3902-22) was common to both the Blizzard and Oasis 2 second stages. Actually the only differences between these second stages are the color of the faceplate insert and the recommended IP. Both use the SRB3601 first stage, and the Teflon coated piston seat came in all versions of the SRB3601. The Blizzard IP was 120-135, while the Oasis specified 135-150, but same model first stage for both regs. The SRB3801 first stage came with the Ultimas, which was a nice design, that handled a little higher volume of air, and only used 3 different O-rings in the balanced piston vs the 6 of he SRB3601, but both are bone simple to work on. 3801 IP is 150 +/- 10 psi. I have a couple of the 3800 seconds (just rebadged Jetstreams) in my sidemount rig, but also use the 3601 first to drive them. The 3801s were just too long and always in the way on sidemount bottles.

 

[texspeleo]

The NEDU article lumps the Poseidon’s and Sherwood’s together, but (again, basing this on my recollection of a 15+ year old email conversation with the diving director down there), the Sherwood had only one failure in the the study, which was a second stage freeflow. The Poseidon’s had three, but all were first stage over pressurizations.

Which reminds me...the OPV was in the large hose flange in the 3800 Ultimas, but I converted mine with the XS Scuba adapters so I could use regular hoses, and added a screw in OPV the the port off the first, though I’m thinking about trying it down by the connection to the second to keep it fully out of ice buildup.

 

[MR12111]

The heat/moisture exchanger ( p/n 25-3902-22) was common to both the Blizzard and Oasis 2 second stages. Actually the only differences between these second stages are the color of the faceplate insert and the recommended IP. Both use the SRB3601 first stage, and the Teflon coated piston seat came in all versions of the SRB3601. The Blizzard IP was 120-135, while the Oasis specified 135-150, but same model first stage for both regs. The SRB3801 first stage came with the Ultimas, which was a nice design, that handled a little higher volume of air, and only used 3 different O-rings in the balanced piston vs the 6 of he SRB3601, but both are bone simple to work on. 3801 IP is 150 +/- 10 psi. I have a couple of the 3800 seconds (just rebadged Jetstreams) in my sidemount rig, but also use the 3601 first to drive them. The 3801s were just too long and always in the way on sidemount bottles.

Are the parts still available for these 3801's ...they have a unique piston ..it only needs replacing if the metered bleed/filter gets clogged .. I used this with a mares mr12 2nd stage for years .. "in the buisness" stone dependable and great performance ..