|
Post by nikeajax on Jan 23, 2020 12:26:25 GMT -8
Stooopid question time for me... Mark, the only stoopid question, is the unasked question it's better feel dumb than to be dead To echo Charlie, yep, the balance chamber makes it so JB
|
|
|
Post by scubalawyer on Jan 23, 2020 13:02:34 GMT -8
SL, It's all about part #4 in the schematic John posted. US Divers calls it a balance chamber. That chamber puts tank pressure on both sides of the HP seat, so that whatever pressure is in the tank, it's BALANCED. The springs are there in any diaphragm 1st stage. Pistons have springs too. I adjust the IP at full pressure, but always like to check it at around 300-500 psi as well. Good Dives, Charlie Ok, I see that now. My old man eyes couldn't tell what part#4 was and the description just says, "Retainer - 1st Stage." Guess I wasn't very artful in my description. Balanced it is! I was talking with David Doubilet (Nat Geo photo guy) at a party last night (yeah, I know, name-dropping ). Apparently he used the MR12 quite a bit back in the day.
|
|
|
Post by herman on Jan 23, 2020 14:13:14 GMT -8
It's balanced, you don't have to have springs on both sides of the balance chamber like the RAM. The problem you have here is the oring in the balance chamber (part 6 in assembly 3)is a pita to replace. Voit intended for you to replace the assembly rather than the oring like you do in a USD reg (same oring). You can set it at any tank pressure but if you intent to set the second stage the very edge, then do so at low tank pressure. Even though it's balanced, it's not perfect and will vary some. Unlike piston regs, diaphragm regs increase IP as tank pressure gets lower....until they meet.
|
|
|
Post by vance on Jan 23, 2020 17:23:14 GMT -8
CJ and I were having this conversation yesterday. Hopefully, I have it right.
On a RAM, a balance chamber block replaces the DA style crown block. Although they look very similar, the DA crown block has no o-ring and no balance chamber drilled up into it. It's drilled through for the HP soft seat stem to fit into . The RAM balance chamber has drillings up into it and has a groove machined into the end for the o-ring, but the top is solid.
The RAM HP soft seat has a hole drilled all the way through the stem, but the DA's HP soft seat stem is solid. The DA's HP pin simply presses into the divot on the end of the soft seat and lifts it off the orifice. The HP pin on the RAM penetrates up into the soft seat and lifts it via an internal step. Different step depth drillings on different soft seats creates the long/short pin length issue.
As I understand it, HP air pressure finds its way around the pin, up through the soft seat stem drilling and into the balance chamber, pressurizing the tiny space to tank pressure. Booyah! You have equal air pressure on both sides. Kinda.
|
|
|
Post by spirou on Jan 1, 2022 4:39:37 GMT -8
|
|
|
Post by spirou on Jan 1, 2022 4:43:35 GMT -8
This Mr 12 arrive to me this week, he is very clean, i'm Gone do the servicing. For the second stage, i must buy a tool the lever screw
|
|
|
Post by vance on Jan 2, 2022 9:38:56 GMT -8
It looks like you have the old style balance chamber block. It is a pain to get the o'ring in and out of, but it is doable with patience. Use a brass pick to dig around in there! Steel picks will gouge/bend/scratch the brass block. A new style will fit if you want to replace it. They are much simpler to service. If you replace the HP seat, you might need to replace the pin as well. The step inside the HP seat is deeper on the replacement seats. Get a hex nut driver to remove/replace the lever nut. They look like a screwdriver, but have a hex socket. Push the lever down, grab the nut and unscrew it. Works fine for replacing/adjusting, as well. Just assemble the lever parts and thread the nut on a bit. With the lever down, screw it back on. Adjust until the slack is taken up. Pressurize it and continue to adjust as needed. There a a couple of threads that discuss rebuilding these. vintagescuba.proboards.com/thread/3439/voit-mr12
|
|
|
Post by spirou on Jan 2, 2022 18:26:03 GMT -8
Thanks for all information, i will check, about thé compansation chamber, i well ses that it was not so easy as a block from USD, is it possible to use a USD block chamber? Anotber question, about the lenght of the pin, is the pin for a new Seat availlable on vdh ? Screenshot_2021-12-09-21-19-53-749 by Frédéric Callebaut, sur Flickr
|
|
|
Post by spirou on Jan 2, 2022 18:30:25 GMT -8
I find this screwdriver not easy to find 1/4 always not in stock, here it IS Europe and metric system
|
|
|
Post by SeaRat on Jan 2, 2022 18:36:41 GMT -8
This Mr 12 arrive to me this week, he is very clean, i'm Gone do the servicing. For the second stage, i must buy a tool the lever screw I don't think so. I think you need a wrench which will go between the lever and the nut, grab the nut, and you can turn it. The MR-12 has a square second stage poppet, and so won't turn like the USD poppet. Depressing the lever will also let a closed wrench in so you can remove it in the second stage. Below are some photos that should help. AMF Voit MR-12 Sheet001 by John Ratliff, on Flickr MR-12 Spec Sheet002 by John Ratliff, on Flickr IMG_1266 by John Ratliff, on Flickr IMG_1267 by John Ratliff, on Flickr John
|
|
|
Post by vance on Jan 2, 2022 19:23:58 GMT -8
Fred,
That's a very expensive nut driver! I'll send you one next time I ship something to you. A 7mm hex socket would probably do in a pinch. Do you have a small ratchet wrench or driver handle?
|
|
|
Post by vance on Jan 2, 2022 19:29:05 GMT -8
Thanks for all information, i will check, about thé compansation chamber, i well ses that it was not so easy as a block from USD, is it possible to use a USD block chamber? Anotber question, about the lenght of the pin, is the pin for a new Seat availlable on vdh ? You can use the new type USD balance chamber, but it isn't THAT hard to replace the o'ring. I'm not sure they sell a pin that will work. I always cut a longer Conshelf pin to fit.
|
|
|
Post by spirou on Jan 2, 2022 21:28:22 GMT -8
Fred, That's a very expensive nut driver! I'll send you one next time I ship something to you. A 7mm hex socket would probably do in a pinch. Do you have a small ratchet wrench or driver handle? Yes, i have even a socket of 1/4 but i have already try but thé socket is a bit wide, scew like on the photo is narrow don't worry, thanks for info about the pin.
|
|
|
Post by spirou on Jan 2, 2022 21:31:12 GMT -8
This Mr 12 arrive to me this week, he is very clean, i'm Gone do the servicing. For the second stage, i must buy a tool the lever screw I don't think so. I think you need a wrench which will go between the lever and the nut, grab the nut, and you can turn it. The MR-12 has a square second stage poppet, and so won't turn like the USD poppet. Depressing the lever will also let a closed wrench in so you can remove it in the second stage. Below are some photos that should help. AMF Voit MR-12 Sheet001 by John Ratliff, on Flickr MR-12 Spec Sheet002 by John Ratliff, on Flickr IMG_1266 by John Ratliff, on Flickr IMG_1267 by John Ratliff, on Flickr John Thanks a lot, i will Come back soon
|
|
|
Post by nikeajax on Jan 3, 2022 9:15:49 GMT -8
I would highly recommend replacing the valve-seat/1st stage poppet if it is the original one: the material used becomes brittle and shatters/disintegrates due to the high pressure exerted upon its surface. Also, get some model airplane paint to touch up your label too JB
|
|