Conshelf vs MR12/MR12II first stages

[jconley]

I know there is a wealth of regulator knowledge on the VDH forum.

There are those that are Aqua Lung and/or Voit/Swimaster and/or Scubapro fans. I happen to have a fondness for all three for different reasons.

I am curious about opinions about the Conshelf vs the MR12 / MR12 II first Stages. Both balanced diaphram regulators. VDH has service kits for both.

I know Luis is a big fan of the Conshelf first stage. But, what about the MR12 first stage. One thing, I have seen what appears to be several first stages that are all referred to as MR 12 first stages. I am interested in the version that has a yoke that is part of the casting of the first stage. It's IP pressure is adjusted by a big allen wrench on top. It also has two lp ports off one side and a lp and hp ports on the other side. I believe an older version only has 2lp ports instead of three.

I am interested in pros and cons of each. Opinions?

[Bryan]

viewtopic.php?f=17&t=8734&hilit=Voit+MR+12

viewtopic.php?f=17&t=7960&hilit=MR12

viewtopic.php?f=17&t=5321&hilit=MR12

viewtopic.php?f=17&t=7396&hilit=MR12

Greg Barlow is Mr MR 12

[Greg Barlow]

The difference in performance between the Conshelf and the MR12 first stage is minimal. The fact that the units both use the same high pressure system is a testament as to its dependability. With both, I highly suggest that you utilize a balance chamber that includes the back up ring.

One advantage for service is that it is far simpler to replace the size -006 o-ring in the balance chamber of the Conshelf. The Voit system was roll crimped after the washer, o-ring, and ring were installed. You can replace the o-ring in the Voit, but until you get the knack of it, four letter words may pass from your mouth. After having replaced nearly a hundred of them, I can do so pretty quickly.

I really like the hose routing of the MR12, particularly with the 3 LP ports version. The Conshelf, as well as the MR12 III, can create some odd angles for hoses.

A dive buddy has the Conshelf cold water system installed on ones of his MR12 II regs. The parts are a drop in fit.

One design over the other? In my opinion, all personal preference. I do have a special fondness for appearance of the Swimaster MR12 II second stage.

Greg

[luis]

I rebuild a few MR-12 (and several Voit Titan) using a modified Conshelf balancing chamber. The modification is not hard and once done any future service is much easier to replace the -006 O-ring.

A while back I posted pictures of that modification and how I did it. I will try to find the post later and copy the pictures.

IMO, it is actually much easier to replace the balancing chamber with a modified Conshelf type than trying to replace the O-ring in the original Voit balancing chamber. This opinion is based on my skill level, not Greg’s.
I know it is not original, but it is internal and it is functionally equivalent.


Once this modification is done, I consider either first stage to be equivalent to each other. In some ways I like the MR-12 valve module concept.

I don't like the hose routing on the Conshelf XIV, but I really like the hose routing on the Conshelf 21. I also had several Conshelf XIV modified with an extra LP port on the top left and that solved all the hose routing (Herman did a great job).


Here is a related thread with some pictures.
viewtopic.php?f=17&t=5806&p=50281&hilit ... ber#p50281

[luis]

From:
Re: Got a couple of single-hose regs. Options?
Sat Aug 27, 2011 12:02 am


Here are my results of finding a replacement balancing chamber for a Voit regulator like the MR-12. This would also work on the Trieste or the Titan.

Below are pictures of three balancing chamber. On the right is the original Voit balancing chamber. On the left is the Mares Balancing chamber. Notice that the diameter of the top is very large. There is no way to insert the snap ring with that diameter head.



On the center is the Aqua Lung balancing chamber with the four little spacers. The spacers are too tall as compared to the Voit flange. So I first thought of just filling them down to the same height as the thickness of the Voit flange, but cutting them off and using shim washer will be easier and make it a perfect fit.



Notice the small opening size of the Voit balancing chamber on the right. Replacing the O-ring in this chamber is a hassle.



After cutting the tabs on the Aqua Lung balancing chamber I just stacked several shims to match the needed thickness.



Here is a picture of the original Voit chamber in the first stage assembly.
Notice on the left the modified Aqua Lung balancing chamber and the shim washers.



Here is the Aqua Lung balancing chamber installed in the Voit first stage with the required shims for a perfect fit.



The outside diameter of the shims is 0.498 since they are design for a perfect fit on a 0.5” bore. I will place one shim below the balancing chamber to provide perfect structural support to the balancing chamber and the rest will be on the back side (the ones visible in this view) to match the thickness of the original balancing chamber. The fit can be adjusted to perfectly match the space better than the original balancing chamber.

I bought two thicknesses of shim washers from McMaster Carr:
93574A713: 18-8 Stainless Steel Bearing Shim, .020" Thick, .378" Id, .498" Od
93574A707: 18-8 Stainless Steel Bearing Shim, .005" Thick, .378" Id, .498" Od

I may not end up using the 0.005” thick shims, but it can give more precise fit.
For the one in the picture, 4 of the 0.020 shims provided a perfect fit.

[jconley]

Thanks to Luis, Greg and Bryan
Jeff

[jconley]

Luis
You had mentioned that you felt the conshelf IP could be raised enough to support the poseidon cyklon 300 second stage. Do you feel the MR12 II first stage could safely do that as well.