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georgeaustin
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AMF MR 12 II cracking inches of H2o

Tue May 31, 2016 11:46 pm

Guys, I'm looking at all the threads on the AMF MR12 II but can't find info on what you guys are setting the cracking inches to. As well -

I'm seeing that it likes 1 3/4 inches or nothing. By nothing I mean that If I adjust the lever height locknut inward to try to get a lower cracking inch below 1 3/4, it freeflows as I tighten down the case ring. WTH? Interesting thing seen is that just by looking at the bottom box, I can see that its not square to the centerline. I put the bottom box on my ground flat surface, outboard side down - it' aint flat!

Point 2 is that the other MR12 II I have, does have a nice flat bottom box OD but that one doesn't like a cracking inch below 1 3/4 either. It settled on 1 3/4 inch and is very happy there. Any attempt to make it more sensitive, - freeflow.

My question is - what do you guys set the cracking to in inches of water on these MR 12 II's - ?

**I have the OEM diaphragms in there - not the Abyss silicone . .






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Bryan
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Re: AMF MR 12 II cracking inches of H2o

Wed Jun 01, 2016 6:50 am

Are you asking about lever height that you might measure with a ruler or tape or cracking effort as measured with a manometer/magnehelic ?
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Re: AMF MR 12 II cracking inches of H2o

Wed Jun 01, 2016 9:54 am

I sometimes find that cracking effort just doesn't tell the whole story about how pleasant a regulator actually performs during a dive. You might try taking it diving to see how you feel about the reg in actual use.

Also, keep in mind that the "recommended" Intermediate pressure is just a suggestion (in my opinion anyway). There are variations in the second stage springs that can make one regulator breathe fine at 135, and you may have to bring another of the same type up to 145 or more to get the same feel that you are looking for. Since we can't adjust the second stage spring tension downward on these regs, we can get the same effect by just raising the IP. Going up 10 or 15 psi isn't going to hurt the regulator if that's what it takes to get the performance where you like it. Keep in mind that you might like it fine the way it currently is set if you test dive it.

Good luck, and keep us posted on your results.
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georgeaustin
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Re: AMF MR 12 II cracking inches of H2o

Wed Jun 01, 2016 12:28 pm

Bryan - No - I'm just using a bucket of water on the floor - the reg starts to hiss right at the end of the mouthpiece flange (1.75 inch)

AD - Interesting. I had the reg connected to a Conshelf with a gage connected to an LP inflator. The Connie IP was at 110 but I bumped it up to 140 during the test of the MR12 and yes, that made quite a bit of difference in breathing effort but who can tell in the living room? I'm going to take the MR 12 diving on Friday and see how it works.

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Re: AMF MR 12 II cracking inches of H2o

Wed Jun 01, 2016 4:42 pm

I would tell you two things if we were drinking buddies, which hopefully someday we will be:

1.) Get a magnahelic. Find a cheap on on Ebay for like 40 bucks.

2.) I , personally, have had multiple MR-12s (MR-12III's especially) that I have had to .6" on a magnahelic. Now, like Luis and Greg will tell you, due to case geometry fault, I wouldn't dive one with the cracking pressure that low as it will bubble when head down.

Check your second stage spring, and your second stage seat. The fact that you have so much spring tension on the second stage makes me guess that you have a nicked or double grooved second stage seat, or a weak second stage spring. This is all just my opinion.
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georgeaustin
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Re: AMF MR 12 II cracking inches of H2o

Wed Jun 01, 2016 8:35 pm

So, Ron - you've set up an MR with .6 inches of water for cracking?
Thanks, Ron and AD - I was thinking of the second stage spring too -
The question still stands though - what have other users of the MR 12 II been able to set their cracking pressure to? 3/4 inch? 1 inch? ( I will get a magneholic ) I've just always used a bucket of water to set up regs - seems to have worked ok.

The thing is with this reg - a 32nd of a turn on the locknut can make the difference between a reg that will free flow and a reg that works ok - pissing me off

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Re: AMF MR 12 II cracking inches of H2o

Thu Jun 02, 2016 2:09 am

I have physically set mine that low. IIRC I had IP set to 145PSI and the second stage set to .6" which was actually too low. I ended up setting it at 1", which for my style of diving is about as low as I'd like it.
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Re: AMF MR 12 II cracking inches of H2o

Thu Jun 02, 2016 12:16 pm

Thanks, guys - I will report its performance after tomorrows dive

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Re: AMF MR 12 II cracking inches of H2o

Thu Jun 02, 2016 8:47 pm

Build your own device to test inhalation and exhalation effort in inches of water. Probably costs about $3 or $4 for clear plastic tubing. You can attach a ruler as seen here, or just make your own measured markings on the tube or mount surface. You can tape the whole works to the wall, or use retaining loops like I did. Can be made even simpler than this, but this is more fun.
manom1.JPG
Obtain several feet of clear plastic tubing and attach to a wall or other mount. I used 1/4" ID X 3/8" OD tubing. If the ID is too small, surface tension tends to make the readings less accurate. The tubing to upper left is long enough to reach my regulator being tested. This is the suction hose, but you could use the right side for that if you prefer. The tube going up from right side can be cut off at top of ruler, but I chose to extend it into a container to catch the water if I exhale too hard. I colored the water to make the readings more obvious in the photos, and used a syringe to fill the tubing exactly to the Zero level.
tube-mp.JPG
testing.JPG
With a little practice you can easily seal your lips around the tube and mouthpiece.
Inhaling from the tube and mouthpiece showed that my trusty Calypso-J began to flow at -7/8" of water pressure.
When you exhale the water rises into the positive pressure tube on the right.

Or you can get really basic and skip all the loops and tubes and attachments to wall, using just a single tube with one end marked every quarter inch for two or three inches. Put that marked end into a glass of water with the other in your mouth. Inhale gently and note how far the water rises in the tube before the reg begins to deliver air. I carry a 3' tube like this in my simple tool kit that goes to dive locations with me. Very simple, but still accurate.
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georgeaustin
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Re: AMF MR 12 II cracking inches of H2o

Fri Jun 03, 2016 8:51 pm

Thanks, Bill - awesome -

I did a test dive today with the MR 12 II - Nice little breather as is although I do think I'll get a silicone Mares Abyss diaphragm and it will be very, very nice.

I bumped up the IP before the dive to 140 psi from 125, just for the heck of it. It doesn't breathe quite as nice by mere fractions as my Conshelf 14's but nevertheless, performed just fine. Its a keeper.

89 fsw X 45 minutes. Water temp at Redondo Veterans Park 57F on surface and, wait for it, 51F at 35fsw. That is chilly in a 3 mil. Hurry Summer.

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Re: AMF MR 12 II cracking inches of H2o

Sat Jun 04, 2016 9:13 am

Sorry that I got to the party a bit late.... From what I have found in my experience of having rebuilt Voit regs for several years, the case geometry fault limits the cracking effort to a minimum of 1.1-1.3" with most examples. Yes, on my own personal regs, I have set them to 0.9-1.0", but they are virtually on the edge of free flow while in the normal swimming position.

The Mares silicone diaphragms make a marked difference. With the Mares diaphragms being available, there simply is no reason not to use them.

As far as intermediate pressure goes, I use 130 psi as my "standard" setting on the diaphragm design single hose models. I check the IP on a reg fairly often, and a standardized setting is easy to use as an indicator. Considering that there is little to no advantage to increasing the IP, I just choose to use the 130 as my benchmark.

To my eyes, the MR12 II is the most attractive second stage design of all time.

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Ron
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Re: AMF MR 12 II cracking inches of H2o

Sun Jun 05, 2016 2:14 am

There you go man. Greg has forgotten more than most of us will ever learn about Voit/Mares, so you have heard it from the lung himself. 8)
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Re: AMF MR 12 II cracking inches of H2o

Sun Jun 05, 2016 10:05 am

Thanks, Greg - yeeeeeee!

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Re: AMF MR 12 II cracking inches of H2o

Mon Jun 06, 2016 6:29 am

Nice to see you Greg.

A note on the manometer, they are accurate and work well but it is important to note that if you use a standard ruler as your scale you must double the reading (or add both sides together). For example, if you inhale and the water column moves up by 1 inch, the actual value is 2 inches (1x2).
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Re: AMF MR 12 II cracking inches of H2o

Mon Jun 06, 2016 8:56 am

Herman wrote:Nice to see you Greg.

A note on the manometer, they are accurate and work well but it is important to note that if you use a standard ruler as your scale you must double the reading (or add both sides together). For example, if you inhale and the water column moves up by 1 inch, the actual value is 2 inches (1x2).
Wow, at first that hurt my brain. :? Thank you, Herman, for pointing that out!

In the past I had always used a straight tube dipped into a glass of water, which works properly, and reads comparable to my Magnehelic gauge. For the illustration I built it with a "U", thinking it would be nice to also easily read the exhalation pressure. I didn't give a thought to the effect of the weight of water on the other side of the U. Now I see that the U worked in the same manner as a Pulley attached at a load, reducing the lifting effort by one-half!

My apology to all for not thinking that out better, and disseminating faulty information. So, if using a U-shaped tube, do as Herman suggests, and mark your own graduations. However, if you just drop a tube straight into the water, it works fine with a ruler or true markings on the tube. Easier to carry around a little coil of 3' of tubing anyway!
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