Lightweight small 1st stage alternatives

S. Marc

As above, any of you changed from the sherwood type factory supplied 1st stage to a light weight small first stage (clamp / yoke).

I have two Tavco steel spheres with yoke pillar valves now, courtesy of a very helpful local diver (thanks again Rob), but my DS4 regs are heavy, same goes for my Poseidon 1st stages, all of which are Din, and with the yoke adaptor these make the rig extremely butt heavy.

Looking for an alternative small light weight balanced first stage - preferably one that can be modified so it has a fixed IP so I can run my rig with a KISS valve.

Any suggestions are much appreciated.

Marc

jkaterenchuk

Marc

Scuba Pro MK2's are fairly compact and light compared to DS4's. I do not know if you can fix the IP. They are also extremely inexpensive and easy to maintain.

John

icediver

You will probably have to add weight somewhere else if you're diving cold.
I had added 4lbs weight to the top of the Kiss which made for horizontal in the water and no weight belt.

S. Marc

Hi Terry,

I have a 6 and 4 lb head weight for the 2 classic kiss rigs we have that work really well.

This is for a BMR 500 though, and with the steel spheres and heavy 1st stages, it is a bit ass heavy.

It is quite a bit more negative than a CK though, so trim weight consisted of 2 lbs in two small halcyon weight pockets on the shoulder part of the harness when I used aluminum 19 cu ft tanks mounted sideways.

Just looking for alternatives, and I need to buy a couple of yone 1st stages anyway as the spheres have yoke pillar valves.

"Marc

Scuba Pro MK2's are fairly compact and light compared to DS4's. I do not know if you can fix the IP. They are also extremely inexpensive and easy to maintain.

John"

John I will take a look at the scubapro regs.

Thanks,

Marc

Brad_Horn

Marc,

Have you thought of a yoke US1 for Dil and a Yoke DS1 for the O2, that should cull a little weight?

That way you can just swap the fixed IP guts of your DS4 over. If you need more 3/8 ports just add a manifold/Y down the line.

Regards
Brad

lizardland

Why not use a needle valve? That way you don't have any depth restriction and can use any 1st stage. The unit has a manual O2 bypass anyway so no need for the KISS MAV. You could even pull the solenoid out and splice a needle valve in its place.

I've got a Scubapro MkII 1st stage on my dil side. To be honest, I still prefer the original Sherwoods. Unfortunately I needed to replace the valve on my dil sphere and all I could get was an O2 valve so the Sherwood dil 1st stage wouldn't fit hence the move to the SP MkII. They are small but still heavier than the Sherwoods. I've also got steel spheres so a bit arse heavy, though I only really notice it on deco.

Cheers,

Stuart

Dave Sutton

Poseidon 300 first stages with the old-style DIN/Yoke adapters are ideal.

Small. Easy to service. Easy to adjust IP (hex-key). Yoke adapter is small and when installed it does not even look like an adapter. Easy to find used, and cheap. The yoke adapters are a LOT smaller than the current ones, as the regulators are 150 BAR DIN, not 200 BAR DIN and as a result the length of the DIN threads is shorter and the yoke adapter is also scaled down. The entire thing is almost as small as the old Sherwood setup.


BEST features are more subtle, and they have to do with the porting.

The HP port adapter from 1/8 BSP to 3/8-24 UNF allows the original HP hoses of the Mark-15 to be used. Makes a clean installation.

But better:

The 1/8 BSP low pressure port of a Poseidon 300 first stage accepts a McMaster-Carr stainless steel 1/8 BSP to 1/8 NPT adapter that allows the stainless steel hoses to the rig to be attached with ease. It's much harder to find a 3/8-24 UNF male to 1/8 NPT adapter.

There are a few ways to block these regs for fixed IP use as well, commonly involving brazing over the hole thru the hex-adjustment plug so the diaphragm does not see external pressure. A little Google will turn it up.


Dave

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S. Marc

Thanks for all the replies and suggestions.

I have managed to source a pair of Mk15 1st stages and will be drilling and tapping and plugging the holes in the cap of the O2 1st stage so it becomes non depth compensating.

I will see how this works out.

I know there have been a few threads on this forum regarding increasing the IP of the diluent 1st stage so a second stage reg can be fed on the diluent side, but

Anyone know what the mk15 02 1st stage normal IP is? I understand it uses shims to adjust.

To run the KISS valve I would need to set it at around 11 bar for the 0.7 L per minute.

Thanks,

Marc

Dave Sutton

Marc,

The Sherwood regs run at a normal IP of about 130-ish PSI. They do use shims to adjust the spring pressure, anyone who has ever worked on Sherwood regulators will have a stack of shims. These are common to any of a large number of older piston type first stages.

The IP increase you have read about is an IP increase on the diluent side so that the Mark-15 Schraeder-Type ADV is more effective (IE: "faster"). The Mark-16's use a diluent IP of about 240 PSI for this reason. Otherwise divers either descend slowly on the ADV or need to ride the manual add valve on faster descents. The IP increase scheme is all about that, not about feeding a second stage. Quite the oppisite in fact... 240 is way too high for a second stage while the original IP is ideal.



Dave

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S. Marc

Thanks Dave,

Marc