Seems like im not the only one who likes playing with RB's

A Place for Discussions On All The Various mCCRs, eCCRs, SCRs & Diving Profiles.

Re: Seems like im not the only one who likes playing with RB's

Postby ChuckyBob » Thu May 13, 2010 9:39 am

I agree with BB and Paul on this.
With a manual system regardless if it has a CMF or not you are always checking your PPO because you have too.
So if the CMF got blocked you would soon notice. At this stage you would simply have a full manual system so you haven't lost any thing over a full manual system in the first place.
There is very little that make the CMF valve flow more. A rise in IP would cause it but with a OPV on the 1st stage this is unlikely.

As it is I can't hear my CMF when wearing a hood. Perhaps this is due to where the injection point is.

As for the argument of CMF vs solenoid.... this really comes down to personal preference. As a noobie to CCR diving my choice would be manual, then perhaps graduate to hybrid.
User avatar
ChuckyBob
Member
 
Posts: 1288
Joined: Fri Apr 03, 2009 1:51 pm
Location: over here.

Re: Seems like im not the only one who likes playing with RB's

Postby binklebonk » Thu May 13, 2010 9:49 am

ChuckyBob wrote: As a noobie to CCR diving my choice would be manual, then perhaps graduate to hybrid.


Why is that? And I mean this from a stance of genuine curiosity. I'm not trying to set up a this is better than that argument...
User avatar
binklebonk
Member
 
Posts: 1776
Joined: Wed Apr 01, 2009 5:03 pm
Location: Peoples Republic of Wellingtron

Re: Seems like im not the only one who likes playing with RB's

Postby ChuckyBob » Thu May 13, 2010 10:09 am

I think its important to learn how to run the unit and always monitor PPO.
With a manual unit you are forced to do this. You need to watch your PPO and addO2 when needed ( less often with a CMF).
Once you throw a computer in charge of a solenoid you dont need to monitor your PPO any more. The computer does if for you. You dont need to add O2 as the computer does that too.
You could soon become very complacent and just rely on the computer doing what it always has for the last 2 years until one day it doesnt.

So my preference is a manual system that the diver must control. Throw in a solenoid as a back up (after the diver has had plenty of experience and manual running and monitoring are full engrained) and this takes care of those moments where the diver may not be able to manually add O2 for what ever reason. This could be as simple as in the middle of grabbing a great photo or working their way past a small obstruction or something more serious like attending to a fellow diver in trouble.

Edit: A hybrid system also gets past the depth limiting of a CMF based system.
User avatar
ChuckyBob
Member
 
Posts: 1288
Joined: Fri Apr 03, 2009 1:51 pm
Location: over here.

Re: Seems like im not the only one who likes playing with RB's

Postby Andy » Thu May 13, 2010 10:13 am

ChuckyBob wrote:So my preference is a manual system that the diver must control. Throw in a solenoid as a back up (after the diver has had plenty of experience and manual running and monitoring are full engrained) and this takes care of those moments where the diver may not be able to manually add O2 for what ever reason.


But you could still drive a eCCR manually, though?

I know plenty of people who dive eCCR that way - the set point on the solenoid is low (0.8) and they use manual add to keep it higher (1.2). So the solenoid shouldn't ever fire on a dive unless they screw up.

There are so few units that allow you to "upgrade" (ignoring the home build option), as far as I am aware the rEvo and the mytical Colkan Eagle.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: Seems like im not the only one who likes playing with RB's

Postby ChuckyBob » Thu May 13, 2010 10:20 am

For sure you can.
But you would still be having to add O2 very often.
Put in a CMF valve and the frequency you add O2 is a lot less.
A hybrid system like this also means if you do run it as a eCCR the solenoid fires a lot less often resulting in less power being drained from the batteries and less wear of the solenoid.

Fact is O2 always needs to be added. With a proper CMF set up O2 will always be added.
User avatar
ChuckyBob
Member
 
Posts: 1288
Joined: Fri Apr 03, 2009 1:51 pm
Location: over here.

Re: Seems like im not the only one who likes playing with RB's

Postby binklebonk » Thu May 13, 2010 11:49 am

ChuckyBob wrote:So my preference is a manual system that the diver must control. Throw in a solenoid as a back up (after the diver has had plenty of experience and manual running and monitoring are full engrained) and this takes care of those moments where the diver may not be able to manually add O2 for what ever reason. This could be as simple as in the middle of grabbing a great photo or working their way past a small obstruction or something more serious like attending to a fellow diver in trouble.

For one of my dives Alan had me running a reel (I ran out about 400ft of line all over the bloody place.. up down though round under over) doing tasks at predetermined times as well as throwing in a few drills and failures all the time running the reel. I didn't find the task loading to be too much, though it certainly peaked when ascending and trying to reel in and add O2 at the same time.. :D . I find the need to inject O2 in the loop (assuming a constant depth and light workload) for me was about once every 6-8 minutes. One of the skills I found to be the most important to learn was learning to anticipate and look ahead to what was going to happen and stay ahead of the changing PO2 "curve". Just because you monitor often (more often?) on a CMF system doesn't make for more task loading how hard is it too look at a HUD or glance at your comp?
Edit: A hybrid system also gets past the depth limiting of a CMF based system.

The CMF valve is limited but the unit it's attached to isn't. Depth compensating 1st stage on a second O2 supply works.

I certainly don't think that the CMF way is the only way or even necessarily the "best" way. It's a way, I'm comfortable with it and I like the way it molds my diving behaviour.
User avatar
binklebonk
Member
 
Posts: 1776
Joined: Wed Apr 01, 2009 5:03 pm
Location: Peoples Republic of Wellingtron

Re: Seems like im not the only one who likes playing with RB's

Postby ChuckyBob » Thu May 13, 2010 12:23 pm

A quick calculation shows me that with a 0.8 l cmf flow and a 1 l metabolism you will be addind o2 at 1/5 of a rate compared to a full manual system or eCCR driven manually. I would consider that a significant drop in task loading.

I take you point about depth and cmf. There are several solutions to this. But I guess I like the idea of a hybrid system more to do with the redundacy aspect. In saying that I have no plans to make my IDA a hybrid ;)
User avatar
ChuckyBob
Member
 
Posts: 1288
Joined: Fri Apr 03, 2009 1:51 pm
Location: over here.

Re: Seems like im not the only one who likes playing with RB's

Postby binklebonk » Thu May 13, 2010 12:27 pm

.........
User avatar
binklebonk
Member
 
Posts: 1776
Joined: Wed Apr 01, 2009 5:03 pm
Location: Peoples Republic of Wellingtron

Re: Seems like im not the only one who likes playing with RB's

Postby binklebonk » Thu May 13, 2010 12:42 pm

ChuckyBob wrote:A quick calculation shows me that with a 0.8 l cmf flow and a 1 l metabolism you will be addind o2 at 1/5 of a rate compared to a full manual system or eCCR driven manually. I would consider that a significant drop in task loading.
Yup I agree. Are you referring to the depth where the CMF no longer works or in general? I guess for me I having no experience at the depths where this becomes an issue, which would be slightly shallower (80m) for me than say Paul as I metabolise at around .6 and he's about .7 lpm. Such concerns are a few hundred hours away yet :wink:
User avatar
binklebonk
Member
 
Posts: 1776
Joined: Wed Apr 01, 2009 5:03 pm
Location: Peoples Republic of Wellingtron

Re: Seems like im not the only one who likes playing with RB's

Postby ChuckyBob » Thu May 13, 2010 1:01 pm

The cmf will fail to work at a depth= to half the IP. But after that it will work as a leaky valve reducing it's flow rate as you approch IP depth. It simply means you have to add o2 manualy more often. This is still better than a pure manual system IMHO. Of couse once to get close to IP depth manual add will no longer work so in this regard a full manual system with a compensating reg wins. Unless you modify the cmf reg fir a higher IP or better yet have a second and redundant o2 tank uth a manual add. Best of both worlds plus redundancy! From what I understand this is how Paul had his set up for the Taupo dives .
User avatar
ChuckyBob
Member
 
Posts: 1288
Joined: Fri Apr 03, 2009 1:51 pm
Location: over here.

Re: Seems like im not the only one who likes playing with RB's

Postby Paul » Thu May 13, 2010 1:08 pm

better yet have a second and redundant o2 tank uth a manual add. Best of both worlds plus redundancy! From what I understand this is how Paul had his set up for the Taupo dives .


Yes that's correct! And that setup removes the depth limitation associated with the CMF valve.
Who needs a hobby when you have an obsession?
User avatar
Paul
Member
 
Posts: 282
Joined: Thu Jan 29, 2009 9:16 am
Location: Wellington

Re: Seems like im not the only one who likes playing with RB's

Postby ianskip » Fri May 14, 2010 9:16 am

Andy wrote:I know plenty of people who dive eCCR that way - the set point on the solenoid is low (0.8) and they use manual add to keep it higher (1.2). So the solenoid shouldn't ever fire on a dive unless they screw up.


I have driven my inspo manually like this for many many hours. More often, I dive it conventionally and let the controller maintain the ppO2. Driving it manually does make you look at the ppO2 display more frequently which is what it's really all about: "know your ppO2!" Reducing the number of times the solenoid fires also prolongs battery life which appeals to the tight prick in me. When doing deco, it's common practice to manually boost the ppO2 above setpoint in which case the solenoid's doing no work at all.

Skip
User avatar
ianskip
U/W Photographic genius
 
Posts: 22
Joined: Thu Mar 12, 2009 2:42 pm
Location: Auckland

Re: Seems like im not the only one who likes playing with RB's

Postby ChuckyBob » Thu May 27, 2010 10:11 pm

Finally got my IDA up and running again.
Short video of it in the pool...

http://www.youtube.com/watch?v=nfKlv1C0494&feature=player_embedded
User avatar
ChuckyBob
Member
 
Posts: 1288
Joined: Fri Apr 03, 2009 1:51 pm
Location: over here.

Previous

Return to Rebreather Diving

Who is online

Users browsing this forum: No registered users and 1 guest

cron