rEvo modifications, tweaks and customisations

[inquis]

So, am I correct that if you set the needle for when you are swimming, if you totally stop and you don't adjust the needle, it could take you hyperoxic?

If you set it to exactly match the swimming workload, then sure it would eventually, which is why we're supposed to look at the PO2 once in a while. You already know that forgetting to do stuff has consequences. Forget to bump the needle when you stop, and PO2 might go up, possibly hyperoxic. Forget to vent the loop when you descend and PO2 goes up, possibly hyperoxic. Forget to add O2 as you ascend and PO2 goes down, possibly hypoxic. These aren't any different in my mind -- they're merely characteristics of diving a CCR, and awareness is key to living.

 

[211ratsbud]

So, am I correct that if you set the needle for when you are swimming, if you totally stop and you don't adjust the needle, it could take you hyperoxic?

I mean, yes. Inquis answered above. But the short answer is yes.

In further summary I liked the needle valve over the CMF because I could adjust it for the task. Granted it does take a little more awareness.

 

[inquis]

if you set the needle for when you are swimming, if you totally stop and you don't adjust the needle, it could take you hyperoxic?

awareness is key to living.

Specifically to that hyperoxic possibility, it's yet another reason why min loop volume is so important. Let's say I was at minimum loop volume at a PO2 of 1.2 prior to stopping. Those extra O2 molecules obviously raise the PO2, but they also increase the loop volume. In my case, getting to a PO2 of 1.6 adds more than an entire liter of extra volume to the loop at 100 ft. (Even at 180 ft, it's more than half a liter, and at 300 ft it's about 0.3 liters, more than half the average person's tidal volume.)

Not feeling the slight resistance at the end of inhale as well as the substantial buoyancy increase should be a huge clue that something is "unusual" and prompt you to glance at your monitor.

Min loop volume is a wonderful thing for lots of reasons.

 

[stuartv]

Hey, you kids! Get off my lawn!!

LOL!!

I wouldn't shun a unit because it had a needle valve. While they *may* add just a little bit of extra task loading, they are obviously not a total hazard. Plenty of people dive them - and live.

I also can't see myself changing my rEvo to use one. The one and only benefit of "adjusting O2 flow to match workload" doesn't seem like juice that is worth the squeeze (on a rEvo).

But, while I wouldn't shun a unit for having a needle valve, I will shun any unit that is manual only. No solenoid and setpoint controller means Stuart doesn't want it. I will be the first one to say I am not perfect and I am not the World's Best Diver. I make mistakes sometimes. I haven't died or killed anyone else yet. Nevertheless, I'll stick with my electronic safety net.

I'm not sure if there are any factory units on the market with a solenoid AND a needle valve. So, that may mean I never experience a needle valve.

I just hope Mr_V will go easy on me and allow me to keep up when we dive and he's got his needle valve and I am lagging behind from all the extra work I'm having to do on my rEvo in order to maintain my pO2....

 

[DiverDiverRUOK]

Hey, you kids! Get off my lawn!!

LOL!!

I wouldn't shun a unit because it had a needle valve. While they *may* add just a little bit of extra task loading, they are obviously not a total hazard. Plenty of people dive them - and live.

I also can't see myself changing my rEvo to use one. The one and only benefit of "adjusting O2 flow to match workload" doesn't seem like juice that is worth the squeeze (on a rEvo).

But, while I wouldn't shun a unit for having a needle valve, I will shun any unit that is manual only. No solenoid and setpoint controller means Stuart doesn't want it. I will be the first one to say I am not perfect and I am not the World's Best Diver. I make mistakes sometimes. I haven't died or killed anyone else yet. Nevertheless, I'll stick with my electronic safety net.

I'm not sure if there are any factory units on the market with a solenoid AND a needle valve. So, that may mean I never experience a needle valve.

I just hope Mr_V will go easy on me and allow me to keep up when we dive and he's got his needle valve and I am lagging behind from all the extra work I'm having to do on my rEvo in order to maintain my pO2....

Other benefit of the needle valve is it doesn't require a fixed IP first stage since you can dial it back to compensate for increased IP with depth.

 

[stuartv]

Other benefit of the needle valve is it doesn't require a fixed IP first stage since you can dial it back to compensate for increased IP with depth.

My comments were based on the Fathom page that Mr_V linked, which does describe using it with a fixed IP O2 reg.

 

[DiverDiverRUOK]

My comments were based on the Fathom page that Mr_V linked, which does describe using it with a fixed IP O2 reg.

Interesting - I hadn't looked that closely at the fathom docs. It seems to me that the whole reason a needle valve is beneficial over a CMF orifice is that ability to reduce the flow so you can run a standard reg without depth limitations, though I suppose from a manufacturer standpoint the risk there is you're relying on the diver to reduce that flow to avoid hyperoxic events.

 

[mr_v]

Interesting - I hadn't looked that closely at the fathom docs. It seems to me that the whole reason a needle valve is beneficial over a CMF orifice is that ability to reduce the flow so you can run a standard reg without depth limitations, though I suppose from a manufacturer standpoint the risk there is you're relying on the diver to reduce that flow to avoid hyperoxic events.

Not the way Fathom runs it. Fathom has an IP adjustment kit for their O2 regs to increase potential depth.

The discussion about needle valve alternatives for rEvo has been interesting and educational, but, I am actually with Stuart on this one - rEvo dives fine as-is. If I could get a needle valve 3 button MAV for a reasonable price, I'd try it just to try it. The stock rEvo setup works just fine.

After diving rEvo and Meg back to back, I've learned to appreciate several rEvo features that rEvo divers may take for granted, e.g., the unit is just so easy to put together, dive, and post-dive; all in the original form.

 

[stuartv]

Not the way Fathom runs it. Fathom has an IP adjustment kit for their O2 regs to increase potential depth.

The discussion about needle valve alternatives for rEvo has been interesting and educational, but, I am actually with Stuart on this one - rEvo dives fine as-is. If I could get a needle valve 3 button MAV for a reasonable price, I'd try it just to try it. The stock rEvo setup works just fine.

After diving rEvo and Meg back to back, I've learned to appreciate several rEvo features that rEvo divers may take for granted, e.g., the unit is just so easy to put together, dive, and post-dive; all in the original form.