Question O-Rings Vs Quad Rings for Piston Seal on MK10 Clone

[JP_SCUBA]

Yes. A softer o-ring will cause more friction in the piston movement at higher tank pressures.

MK10s generally have more rise in IP at high tank pressures than do other SP balanced piston 1st stages. I'm sure this is due to the smaller piston head. Basically, there is less total force on the piston head, with the same friction issues of the MK5 at the HP piston o-ring spot, so friction increase is a higher percentage of total force. The more that o-ring extrudes or gets moved around, the more friction there is and that increases the force required to push the piston against the seat. Higher duro o-rings are supposed to extrude less. You may already know this stuff, if so please excuse my verbosity.

The best performing HP o-rings I've used are 90 duro polyurethane o-rings. But they have a different set of problems, primarily shorter shelf life. I got a batch of bad ones once and I just stopped using them, now I use EPDM or viton.

No worries, once I read your comment, that was my thought as well and since, in this case, I've replaced the 010 o-ring with a 010 Quad/X-ring the surface friction/drag would be essentially double due to the 4 sealing surfaces instead of just 2.

 

[Kupu]

No worries, once I read your comment, that was my thought as well and since, in this case, I've replaced the 010 o-ring with a 010 Quad/X-ring the surface friction/drag would be essentially double due to the 4 sealing surfaces instead of just 2.

Perhaps I am misunderstanding your comment, but I was hoping friction will be reduced by switching to quad ring? Assuming same durometer.
A stated benefit of quad rings is that the grooves on the inside and outside diameter of the ring retain lubricant, thereby lowering friction and extending packing/seal life.

 

[JP_SCUBA]

Perhaps I am misunderstanding your comment, but I was hoping friction will be reduced by switching to quad ring? Assuming same durometer.
A stated benefit of quad rings is that the grooves on the inside and outside diameter of the ring retain lubricant, thereby lowering friction and extending packing/seal life.

No, just trying to think/work through all of the pluses and minuses of the seal change/upgrade and Kupu brought up a good point. The quad/X-ring I'm using at present is a 70 duro. buna and I'm trying to source 90 duro Viton locally. I still have to set the reg up again and do the incremental IP checks at the various tank pressures as Halocline suggests. It seems to function well as it is now but I need to do a little more testing. The 90/Viton should have less extrusion.

 

[rsingler]

After $180 and two months waiting, Precision Associates just finished their run and shipped me their minimum order quantity of 150 quad o-rings in size 2-010, duro 90 Buna-N.
If folks are still interested in trying this out as a high pressure piston shaft o-ring on a Mk5, Mk10, M25 or Atomic, DM me and I'll send you ten for $2 (my cost for the custom order plus a stamp).

 

[lexvil]

Unless math has changed should it be more like $1 each?

 

[Jcp2]

$180/150 = $1.20 each, plus postage.

 

[lexvil]

$180/150 = $1.20 each, plus postage.

Actual math, yes $1.20 at least

 

[rsingler]

Oops!
That Minimum Order Quantity and them having to make a special custom run really added up, didn't it?
Glad I didn't pay attention when I placed the order.
Okay. Make it $10 for ten o-rings and the stamp is free. I don't need to make money on this.

 

[JP_SCUBA]

After $180 and two months waiting, Precision Associates just finished their run and shipped me their minimum order quantity of 150 quad o-rings in size 2-010, duro 90 Buna-N.
If folks are still interested in trying this out as a high pressure piston shaft o-ring on a Mk5, Mk10, M25 or Atomic, DM me and I'll send you ten for $2 (my cost for the custom order plus a stamp).

Oops!
That Minimum Order Quantity and them having to make a special custom run really added up, didn't it?
Glad I didn't pay attention when I placed the order.
Okay. Make it $10 for ten o-rings and the stamp is free. I don't need to make money on this.

Hey rsingler... I DM'ed you but I'm not sure if I did it correctly but I'll take 2 quantities of 10 unless you're limiting them so there's enough to go around in which case I'll just take 10. I didn't see your post that you had received the "X"rings on Tuesday. Hopefully you have some left. Please let me know... Thanks ... JP

 

[rsingler]

Interested in what y'all find.
I've got two Mk5's holding up nicely so far.
But man! It's a PITA getting a sharp knife edge past that first blade in the X.
I wonder if rounded-knife-edge pistons like the Mk25 will be easier...