why hate safety devices?

[peterbj7]

I used to use a mechanical dive watch for pool instruction. On two different occasions I noticed that it was running and keeping accurate time, but somehow during the pool session it had lost time. One time it was about 10 minutes, and the other time it was close to 20. The obvious explanation was that it had stopped for that length of time and then started again

I guess I must just have been lucky, and you very unlucky. I've had a couple of clocks do that in my life, because the mechanism is exposed to the elements, but never so far a water-resistant watch, cheap or expensive, mechanical or digital. And I don't know anyone who has admitted to that happening. If it did, it would probably do so at other times when the malfunction could be detected.

I may be foolish, but I'm prepared to trust a watch that I've used for eight years and which has never at any point given any cause for concern. But in any case I always carry a redundant computer/watch. Then we get into the realms of two devices both failing at the same time in the same way, or at any rate with the same effect. Reckless as I am, I'll chance that.

 

[mrbeast1414]

I used to use a mechanical dive watch for pool instruction. On two different occasions I noticed that it was running and keeping accurate time, but somehow during the pool session it had lost time. One time it was about 10 minutes, and the other time it was close to 20. The obvious explanation was that it had stopped for that length of time and then started again.

That is a pretty serious error.

If a timing device fails during a dive and you see that it has failed and have no good backup, you abort the dive. If it fails and then starts again without your noticing it, you are potentially screwed. If it just starts slowing down, you are potentially screwed.

I guess I prefer a catastrophic failure to one I don't really notice.

completely agree, its the ones that you cant see that scare me...

 

[bvanant]

As I understand it, the main problem with studying DCI is the huge variables. When Haldane first pressurised his goats to 6 ATA (about 165 fsw equivalent), kept them there for 30 minutes, and then brought them to surface pressure immediately, two died almost immediately, three died within a few hours and one was asymptomatic. When your variables are that wide, it is pretty hard to draw bright white lines.

Sure if you do only 6. That's why our clinical trials test 1500 subjects or so.
Bill

 

[MXGratefulDiver]

Sure if you do only 6. That's why our clinical trials test 1500 subjects or so.
Bill

... so whaddya do with all the dead goats?

... Bob (Grateful Diver)

 

[halocline]

That's about, oh I don't know, maybe 20,000 orders of cabrito.

 

[bvanant]

... so whaddya do with all the dead goats?

... Bob (Grateful Diver)

Barbecue
Seriously, the reason that I asked earlier about things like nerve conduction was to be able to do tests on rats or rabbits. Goats are too smelly for my taste.

Bill

 

[Rick Murchison]

Barbecue
Seriously, the reason that I asked earlier about things like nerve conduction was to be able to do tests on rats or rabbits. Goats are too smelly for my taste.

Bill

Rats & rabbits may be ok for narcosis studies, but for DCS you need a larger animal to get any kind of useful data. An entire rat is probably a "ten minute tissue" at most, at least for classic bends 1 or 2. They're probably lousy subjects for osteonecrosis, too.
Rick