RFC: second stage seats substitutes

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couv:
Couv says,

The difference in i.d. between the largest and smallest seal in the above is not going to be an issue as the size of the groove the o-ring fits in will determine the installed inside diameter (As long as it's stretched a bit.)

The difference in cross section (0.02 mm < 0.00079 inches) is insignificant. Therefore, buy a quality seal from your favorite vendor.

In the past, the Usual Suspects got very good service from Precision Associates, Inc. Their site has a handy tool where you can enter the dimensions of the o-ring needed and they'll have a product code for it. McMaster-Carr is the diver's online hardware store:

http://catalog.precisionassoc.com/advanced/precision-associates-inc-o-rings/special-size-o-rings-1083?

http://www.mcmaster.com/#9263k546/=b5zwwm

But Couv ain't always right and welcomes any corrections.
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COUV is married I see. :)

Reading the Parker Oring manual, an interesting read for those of us who like this stuff, the exact diameter of an Oring or its mating surfaces are not critical. The way they describe the sealing action of an oring is to compare it to a very viscous liquid that flows when pressure is applied. The viscous liquid (oring) flows into the space between the mating surfaces but stops when the space and pressure are not enough to allow it to continue, plugging the hole. As long as the pressure is not great enough to make it "flow" through the spaces between the mating surfaces the seal is complete. The smaller the space between the mating surfaces or the more viscous (higher durometer) the more differential pressure it can hold. So slight differences in the oring diameters should not cause an issue as long as the manufacturing tolerances of the mating parts (reg) is kept within reason. If you read the specs on orings, there are often 2 columns of sizes, the "advertised" size and the actual size plus a column for allowed size variances, they are not exactly high tolerance items....at least not the ones we use.
 
Interesting observation:

I re-did a 109 and a G250 I recently scored. Both have the metal orifice, no nick, and I fitted a S-wing poppet with a Trident A148 seat for the 109, and an original SP seat for the G250. I tuned them both to a hair less than 1 hour pass sealing point, maybe 20°, and about 22mm/.9" of water. I let them sit in a closet to break-in.

After a week, the 109 (now 156) with the Trident seat is exactly were it was before, while the G250 with the SP seat hisses a bit and requires another 10° or so to seal. Both still crack at 22mm/.9" of water.

So it appears the Trident seat might be a bit harder than the original SP seat.
 
My daughter was given a Conshelf XIV setup that I may have to do some work on. It looks like it was last serviced in 1991 and not dove since (service tag still attached). IP checks out solid at 140. 2nds seem OK but leaks from the HP spool and the schradder valve. I was looking at the LP seata and they seem to be a bit thicker than My homemade seat for my Subapro's. It looks to me like they are 2mm and the 1/16 inch seat raises the lever height too much. Plus the USD seats seem to be much softer than the duro 80 I use. It feels more like duro 50 or 60. I noticed the fixed orifices in the inlet fittings do not have a smooth or sharp an edge as the scubapro orifice which may explain the need for a softer seat. I think I will try a sheet of 2mm nitrile from M-C and see if that does the job. Probably not going to happen real soon as all you guys talking about trips made me lay one on for Bonnair in August.

Anybody have any input on duro 50 vs duro 60? M-C also has silicon, duro 50 in 2mm so that is another material option. I may also try the 17/64ths punch while I am at it but the 9/32nds looks just right for the Conshelf.
 
Bother Zung,

I'm honored to have my name alongside the Master on your charts; however as far as I know, it was Awap who did 100% of the research for the tools and materials to make these. Additionally, he's done all of the work involved in producing any that I've ever used.

Couv
 
couv:
On a couple of AIR 2 units I rebuilt, I was considering that a thicker seat would be of some benefit as the lever adjust nut was on the very last poppet thread. This of course is more of an issue with the Second Generation AIR 2 as it does not have an adjustable orifice like the later generation models. However, I found the seats to be a perfect fit as far as diameter goes.

c
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couv:
LTSD,

I'm convinced that Awap has the correct diameter punch. But I would be interested to see how a slightly thicker seat behaves. What is the next thickness sheet? .....I guess I could go look that up........:dork2: myself.


Edit: Ok, it seems that the next thickness is 50% thicker at 3/32" ....I bet that would do nicely in cases where one is running out of poppet threads.
McMaster-Carr

Here is a 12" X 12" X 3/32" sheet of EPDM duro 80A
McMaster-Carr
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Zung:
That's a good one, Bro, thanks. It's in between the Trident AA88 and the A149, and it should be a close match for the Aqualung stuff that have a cavity of 2 mm deep.

So the relevant specs are:

McMASTER #: 8985K135
Material: EPDM Rubber
Durometer Rating: 80A
Thickness: 3/32" / .094" / 2.38 mm
Width: 2"
Length: 36"
Price: $5.57
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couv:
Bother Zung,

I'm honored to have my name alongside the Master on your charts; however as far as I know, it was Awap who did 100% of the research for the tools and materials to make these. Additionally, he's done all of the work involved in producing any that I've ever used.

Couv
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Bro, if I hurt anybody's feeling, it was not my intend, BUT the above were your contributions as far as I know.
 
It's hell when you grow old. I forgot those post. They say the first thing to go is the memory and the next is the uhm...well, anyway the first thing to go is the memory.
 
couv:
It's hell when you grow old. I forgot those post. They say the first thing to go is the memory and the next is the uhm...well, anyway the first thing to go is the memory.
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The 2nd thing that goes is the only reason you were not going to buy another wing.:mooner:
 
Great minds forget alike. Pirranha and Hog both have a 30+ lb wing for about $200 right now. I may have to push the button. Any suggestions on which one?
 
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