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Post by SeaRat on Jul 21, 2023 20:42:12 GMT -8
You can make your own, by going to a fabric shop and buying a square meter of neoprene-impregnated nylon fabric. This is what the original MR-12 diaphragms were made of. Coat the sealing surface on the regulator with silicone grease, then spread a bead of Shoe-Goo in the sealing surface. Place the fabric onto this beat, there spread another bead of Shoe-Goo on the top of the fabric. Lower the bottom box, after of course putting silicone grease on it, onto the surface, and let the whole thing set for 48 hours. You’ll end up with a diaphragm that is custom-made for that regulator.
You’ll need to put a stainless plate onto the diaphragm, either by glueing it or by screwing it down (rivets work too). That’s what the lever will sit against.
Good luck,
John
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Post by vance on Jul 22, 2023 7:48:42 GMT -8
I believe the HP diaphragm is the part in question, not the main.
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Post by Fibonacci on Jul 27, 2023 17:34:17 GMT -8
Yes, currently concentrating on finding suitable HP diaphragm material... got the name of a chap via the HDS UK who may carry Heinke/SG Merlin NOS spares, emailed so fingers crossed! Have tracked down via hydraulic suppliers that BSPP to SAE ORB adaptors exist, now to find one in 316 stainless or nickel plated brass...  BSPP to ORB adaptor by fibonacci101, on Flickr |
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Post by vance on Jul 28, 2023 6:53:53 GMT -8
Just for the sake of discussion of the HP diaphragm, I recently help test new made Dacor R-1,2,3 HP diaphragms, and the reinforced neoprene material turned out to be too soft or too thin. Without shims (these don't have an adjuster), the IP was only around 80 psig.
It appears that the MkV uses shims (part #17 on the diagram, page 1 of this thread) to regulate IP. The MkVI has an adjusting screw. I wonder if they're interchangeable? The diaphragm has a complicated through bolt assembly kind of like the Sportsways diaphragms have.
I don't quite understand part #8, "valve seating".
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Post by Fibonacci on Jul 28, 2023 15:27:55 GMT -8
Yes, my thoughts too as I pulled it down and noticed that the original HP diaphragm had become quite compressed from age or overtightening... would have to affect IP. The MKV and MKVI both run quite low IPs vs RAMs etc Page 7 of the Merlin MKVI Service Manual states the IP should be initially set at 90-100psi on a new diaphragm, then settle back to between 80-90psi on a full tank with the OPV set to blow at 120psi. To check this accurately needs an IP bleed off the surface supply port, hence my sleuthing for 3/8"BSPP to SAE-3 port adaptors. It would seem that the MKVI adjustable Top Cap #1 would fit the MKV which would be a very handy upgrade, I just don't yet have a MKVI on hand. It has a square adjuster hole vs the usual hex... I suppose to stop unauthorised fiddling?  Merlin MKVI HP side IP adjust by fibonacci101, on Flickr Part #8 is the HP seat, listed as Nylon but more likely Ultra High Density Polyethylene. See sectioned view, its a very robust self-cleaning cone style seat.  Merlin Diaphragm and HP Seat by fibonacci101, on Flickr  Merlin Diaphragm and HP Seat sectioned by fibonacci101, on Flickr The reserve is present on most MKV's I've seen but not common on the MKVI's usually being blanked off.  Merlin MKVI HP reserve blank off by fibonacci101, on Flickr It's quite an elegantly simple design:  Merlin Reserve Body ASSY by fibonacci101, on Flickr When the tank is full the plunger is compressed allowing full air volume to the diver  Merlin Reserve Body ASSY full tank sectioned by fibonacci101, on Flickr When tank pressure drops to 300psi, a small groove in the seat still allows some air to pass giving the diver an indication air is low.  Merlin Reserve Body ASSY sectioned by fibonacci101, on Flickr When the reserve lanyard is pulled, the plunger moves to the stop pin allowing the remaining air to be used at full volume.  Merlin Reserve Body ASSY actuated sectioned by fibonacci101, on Flickr |
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Post by vance on Jul 28, 2023 16:22:39 GMT -8
..... It would seem that the MKVI adjustable Top Cap #1 would fit the MKV which would be a very handy upgrade, I just don't yet have a MKVI on hand. It has a square adjuster hole vs the usual hex... I suppose to stop unauthorised fiddling?..... I was wondering about the key interface. It should have been hex, but I think you got it: discourage fiddling by the public. A plug with a 3/8 x 24 tpi o'ring adapter shouldn't be too hard to make. The difficult part is getting the screw pattern right. If you could find a blank, that'd be an easy mod. |
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Post by nikeajax on Jul 28, 2023 17:42:16 GMT -8
You'll have to forgive me if I didn't read things correctly, but why is the IP so low? This is like tilt-valve low! Or, might it be like the US Divers 1030 Calypso where the second stage valve-seat was incapable of sustaining higher pressures due to its poor design? Just curious  JB |
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Post by Fibonacci on Jul 28, 2023 18:01:36 GMT -8
Yep I think I have found a UK hydraulic supplier with stocks of solid brass 3/8" BSPP plugs that could be drilled and tapped for a SAE-3 ORB Port. Strange Heinke designed in quite a sea water trap in the HP spring housing, the MKV could have had an end opening as well as side ports... and the MKVI could have also had the MKV's side ports!  Merlin MKV HP Spring Housing by fibonacci101, on Flickr  Merlin Cap Diaphragm and HP Seat sectioned by fibonacci101 on Flickr The previous diaphragm diameters were just a sketch model, since updated to correct 37mm diameter! |
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Post by Fibonacci on Jul 28, 2023 18:10:08 GMT -8
You'll have to forgive me if I didn't read things correctly, but why is the IP so low? This is like tilt-valve low! Or, might it be like the US Divers 1030 Calypso where the second stage valve-seat was incapable of sustaining higher pressures due to its poor design? Just curious JB Not sure, seems odd indeed... I had to recheck that myself but it's there in the official service manual. The second stage tilt valve seems to be non-adjustable, and the spherical end simply swivels in a similar recess in the body, the flat face is the seal area. The Venturi Tube also acts as the seat and is cut at an angle so the tilt valve lever meets the LP Diaphragm correctly... theoretically you could could rotate the Tilt Valve a few degrees either side to adjust how high it sits in the body under pressure. However this is not mentioned in the service manual! I will test this when I finish 3D modelling the body... bugging me now   Merlin LP Tilt Valve by fibonacci101, on Flickr |
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Post by nikeajax on Jul 28, 2023 18:23:19 GMT -8
Oh, OK, so it is a tilt-valve: that's my answer I remember before I really got it about TV's, I tried to use one as an octo for a downstream valve, and I just couldn't understand why it was so doggy and had this horribly agonizing delay on inhalations, something like half a second!!!! Very disconcerting  JB |
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Post by Fibonacci on Jul 28, 2023 19:57:52 GMT -8
LP Venturi seat appears to be angled at 7 deg to allow the LP Tilt Valve correct interface to the LP Diaphragm. While most of the air will go straight up the venturi tube, a significant amount will vent past the Tilt Valve stem into the can... swirl around and then go up the inhale hose. Wonder how they worked that percentage out?!  Merlin LP Tilt Valve and Venturi Tube ASSY by fibonacci101, on Flickr |
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Post by nikeajax on Jul 29, 2023 7:20:44 GMT -8
Er-ah... Huh? If I didn't know any better, I would swear you designed that just to mess with our heads--well I'll be dogged!
JB
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Post by nikeajax on Jul 29, 2023 7:29:33 GMT -8
I'm so charmed by that design, that I can almost imagine these ladies installing something like that on a Hawker Hurricane!  And of course they used this book to derive that 7-degrees! www.gutenberg.org/ebooks/71292Jaybird |
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Post by vance on Jul 29, 2023 7:46:56 GMT -8
LP Venturi seat appears to be angled at 7 deg to allow the LP Tilt Valve correct interface to the LP Diaphragm. While most of the air will go straight up the venturi tube, a significant amount will vent past the Tilt Valve stem into the can... swirl around and then go up the inhale hose. Wonder how they worked that percentage out?! Merlin LP Tilt Valve and Venturi Tube ASSY by Graeme Cameron, on Flickr Very interesting design. Many tilt valve stems reach the diaphragm via a bend in the rod. It seems it would have worked in this case. The venturi tube slot would work as a guide to keep the valve from rotating. Is there some airflow advantage in their method? You might get away with slightly rotating the venturi tube to adjust lever height, but turning it off-center might cause the stem to bind in the slot. |
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Post by vance on Jul 29, 2023 8:00:08 GMT -8
Graeme, could you add a photo of the inside of the regulator that shows the tube and valve, please?
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