Wow! Meg design - dont know if I like this

Drmike

exactly

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Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

wedivebc

Can't speak for the others but I for one thank you for pointing out weak points in the design of our beloved meg. Even if it just reinforces the need for proper training and following manufacturer protocols.

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Dave....

Man is the only animal burdened with the knowledge he will eventually die

Moray Brown

Agreed -

Drmike

Do you have data for this? I would have thought the inhale gas temp (along with O2 injections) would differ from post scrubber temp and would stay that way. Directionality of the loop gas flow would determine that...I would have thought. But if you have data then Id be interested in seeing it.

I have lots of Meg diving buddies (and ex-buddies ), Ive seen the amount of water that can form on the cells myself and how it screws up cell outputs, Ive heard them moaning about it. Theres posts here about it. Theres no doubt condensation gathers on the cells and that it effects the ppo2 readings. If I can reduce or illiminate that condensation why not? (I have no idea if I can but Ill try)

This isnt Meg specific. Almost all mass market rebreathers suffer from this. Ive said it for years but IMO any design that allows condensation to develop on the cells and corrupt the readings is just bad bad bad. The vast majority of users havent dived MK15 series units so having wet sensors just becomes accepted by the masses as the norm as perfectly ok - something that Ive always found to be very-very strange.

Sure we can put protocals in place to compensate for the condensation (such as drying the head between dives) just like doing a sensor pressure test would help gaurd against bypass - but these are fixes to make up for IMO poor design.

Ok I really am going to shut the f_ck up now

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

UWSojourner

Besides you Dr. Mike I haven't heard of any other sensors spontaneously-destructing mid-dive. Do you have any other data points for that potential problem? From my look at the unit, I'd say bypass at that point, while possible, is very unlikely if the sensors are installed correctly. As has been pointed out, the predive checks should catch a problem.

On the other hand, in my more limited experience with the unit (less than Ron's anyway), I have found substantial condensation on the faces of the sensors. As the Meg is my first unit I had just assumed that condensation occurs on ALL surfaces inside the loop, not just on the O2 sensors. Are the sensors in other RBs not experiencing condensation also?

mverick

I own a Meg and like it.

A Meg does have things I don't like and, You've just found one.

I don't like a hole from the inhale to the exhale side. I like one path only.

I'd prefer the sensor carrige didn't come away from the lid. That it was one piece. And put 3 sensors in.

I'd prefer the O2 injected in that area instead of in the can.

I'd prefer the can came insulated.

I'd prefer there was a BMCL option.

I'd prefer a back housing ala Prisms. That pops on and off easy. To keep from banging the hoses.

I'd prefer safety shields on the inlet to the head for exhale and inhale. As in, have the hose fit down inside a tube before the connection. That way you hit that before the hose or the leed in nipple on the head.

I'd like a angle on the inlet and exhale on the head. Or even a 90 and have the head about 2 in thick to accomodate the o2 sensors. 90 goes into the BMCL's and a outlet either under the arms or over the shoulder. But if you can pull off a path under the arms without having the hoses over your shoulder you clean up the path hugely and guard the hoses....

Now, you know what I've been contemplating.. LOL...

fredrik

I had the feeling that ISC had a very limited numbers of instructors beacuse they only wanted "the best".

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Fredrik
Rekodeko, Sweden
http://www.rekodeko.se

RonMicjan

you know you cant...

I dont have exact data on temps throughout the various parts of the loop, but I know the pod temp, cause there is a sensor there, and the water temp, there is a sensor in the handset too, and the difference between them is usually 5-10degrees F, so I assume (could be a mistake, especially on this forum) that the internal temps couldnt vari much more than that, the plastic on the can is a bit of an insulator as is the gas in the loop, so theromdynamically, all the inside bits should be about the same temp. could be an interesting test though.

I really have never had a moisture problem on the cells even after 3 hour dives, but I do crack the head between dives, or at the end of the day and let the inside dry out, keeps the bug growth down too.

designing your own CCR there mikey?

Im thinking a metal plate type heatsink that is exposed to ambient water on one end and has loop gas running into it just prior to the cells on the other end, would collect moisture and keep it off the cells. troube is now what do you do with that moisture you have collected?

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decoweenie

Mike,

My internet is down until Monday so can't reply to your PM about my idea of modifying the lid earlier. Here is what I am planning to do:

- cross the Hammerhead sensor placement design into the Meg lid.
- reverse the flow (i.e. center tube = inlet to scrubber)

Once I have the Internet back up, we could discuss more.

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dive2dive2000

I had the same problem (PRISM) last year. SMI replaced them. Seems they had one shipment where the whole lot was defective.

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Safe Diving,
Martin