Sherwood scuba, SR 2
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OP
Geo7
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I realize I know more about the various iterations of levers in the G250 (which is not that much, by any stretch) than Sherwood SR models. Anyone cares to provide a summary with pointers beyond what one can google? Some History? The new ones seem to have Dean Garraffa's (Atomic co-founder) handwriting all over it...
The SR's are dry piston firsts/ standard end balanced barrel seconds.
Sherwood touts the gas flow, and indeed the piston bore ID is larger than the Mk25. In fact, their using a larger piston end diameter than shaft diameter for balancing (like many mfrs now incl SP and AA) is carried to such an extreme that the piston has to be assembled out of two parts (16 & 38) during reassembly: the piston shaft is passed down thru the bore and screwed into the piston head. Sounds weird, but it's easy. A hex key and a small pin face spanner hold the two pieces while you screw them together.
Their other claim to fame beyond flow is their dry seal mechanism. A diaphragm seal like the environmental seal on any diaphragm reg covers a metal disc. This disc presses on three plastic rods that pass thru thin bores in the outer reg body. Those rods are actually the legs of a little hollow stool (15) whose top lies behind the piston head. Thus, ambient pressure is applied to the back of the piston, not thru water holes in the side of the reg's ambient chamber, but by direct pressure from those rods sensing ambient at the end of the regulator. The ambient chamber remains dry.
To try to escape the old criticism of Sherwoods constantly "leaking air", the ambient chamber vents only on ascent, and only a few cc's total in a dive.
The second stage is fairly ordinary, with the exception of having an external link between a sleeve (2) where the hose connects and the orifice (5) inside. Thus, you can adjust the orifice on the fly about 1/16 of a turn at a time. It also has a microadjust (19) like the G260 or S620.
Altogether, nice engineering ideas from a very old scuba company.
Sherwood touts the gas flow, and indeed the piston bore ID is larger than the Mk25. In fact, their using a larger piston end diameter than shaft diameter for balancing (like many mfrs now incl SP and AA) is carried to such an extreme that the piston has to be assembled out of two parts (16 & 38) during reassembly: the piston shaft is passed down thru the bore and screwed into the piston head. Sounds weird, but it's easy. A hex key and a small pin face spanner hold the two pieces while you screw them together.
Their other claim to fame beyond flow is their dry seal mechanism. A diaphragm seal like the environmental seal on any diaphragm reg covers a metal disc. This disc presses on three plastic rods that pass thru thin bores in the outer reg body. Those rods are actually the legs of a little hollow stool (15) whose top lies behind the piston head. Thus, ambient pressure is applied to the back of the piston, not thru water holes in the side of the reg's ambient chamber, but by direct pressure from those rods sensing ambient at the end of the regulator. The ambient chamber remains dry.
To try to escape the old criticism of Sherwoods constantly "leaking air", the ambient chamber vents only on ascent, and only a few cc's total in a dive.
The second stage is fairly ordinary, with the exception of having an external link between a sleeve (2) where the hose connects and the orifice (5) inside. Thus, you can adjust the orifice on the fly about 1/16 of a turn at a time. It also has a microadjust (19) like the G260 or S620.
Altogether, nice engineering ideas from a very old scuba company.
Good point @rhwestfall ! Yes, a floating orifice.
Also worth mentioning that it has that dumbed down "single adjustment" knob like the Aqualung MBS. One action both increases cracking effort and decreases Venturi assist. Their only mistake, tho' perhaps understandable in a world of 3-day certification.
Also worth mentioning that it has that dumbed down "single adjustment" knob like the Aqualung MBS. One action both increases cracking effort and decreases Venturi assist. Their only mistake, tho' perhaps understandable in a world of 3-day certification.
Just to make sure I understand you both, you don't like the combined cracking/venturi adjustment feature in the MBS and SR2? Why?
Two different functions. I almost never change my cracking effort, except when scootering. I might use it to stop a dribble of freeflow in a reg that's tuned too light.
But I often decrease my Venturi assist, especially on my octo for giant stride. I also crack it back a little on my deep dives where increased air density makes Venturi assist a little more vigorous, unless I need the extra "oomph" in current.
If you need to hand off your octo when you've forgotten to turn the Venturi back to "Dive", it still breathes just fine. If you hand your octo with the knob cranked in to your OOA buddy, it may add to their panic because he/she may feel like they're not getting enough air, because it breathes so stiffly.
When we've dumbed down training so much that divers aren't taught the difference between the two functions, or worse - that the manufacturers successfully sell it as an "improvement", then we've gone too far.
But I often decrease my Venturi assist, especially on my octo for giant stride. I also crack it back a little on my deep dives where increased air density makes Venturi assist a little more vigorous, unless I need the extra "oomph" in current.
If you need to hand off your octo when you've forgotten to turn the Venturi back to "Dive", it still breathes just fine. If you hand your octo with the knob cranked in to your OOA buddy, it may add to their panic because he/she may feel like they're not getting enough air, because it breathes so stiffly.
When we've dumbed down training so much that divers aren't taught the difference between the two functions, or worse - that the manufacturers successfully sell it as an "improvement", then we've gone too far.
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