on line source: mk-2 hp piston seat

[johndiver999]

I suspect you know this but just in case you don't, the seat is pushed out by inserting a thin rod (blunt end of a small drill works well) up into the head of the piston then into the small hole behind the seat. You don't "dig" it out from the seat end.

Well that is obviously the way to do it, however it's not something I thought of. Thanks for the help. Really.

So are we convinced that seat from northeast scuba will work?.

Incidentally, I asked about O-ring sizes recently and people were very helpful and I ended up buying the o-rings for the piston of a sherwood reg. I compared those new ones to the old one in the MK-2 and it looked the same,so I replaced and also seems to work.

 

[Couv]

Well that is obviously the way to do it, however it's not something I thought of. Thanks for the help. Really.

So are we convinced that seat from northeast scuba will work?.

Now, I'm waiting for you to purchase one and tell us. ;-)

Incidentally, I asked about O-ring sizes recently and people were very helpful and I ended up buying the o-rings for the piston of a sherwood reg. I compared those new ones to the old one in the MK-2 and it looked the same,so I replaced and also seems to work.

Piston head is a -022
Piston stem is a -008

See attachment.

 

[rsingler]

I'm half tempted to use the Trident A246 and just use a punch to create thin plastic 1/8" discs that I could tack to the back of the seat with a drop of glue to shim it up to ~3.5mm height.

 

[Couv]

How much higher is the IP with a Trident A246 vs a SP seat?

 

[rsingler]

How much higher is the IP with a Trident A246 vs a SP seat?

Dunno. I suspect a lot. I wasn't sure the volcano would reach up into the pocket left by the short seat and not bang into the metal of the piston before it reached the HP seat. I didn't try.
But if Scubapro 0.010" shims give you 4-5 psi IP change, I imagine a missing millimeter would be a really big increase.

 

[herman]

Well, I guess I'd better get my calipers out and check my spares. :-(

@herman Didn't you come up with a homemade/machined seat for the MK2?

It's been a long time since I experimented with this but yea, I made some seats for piston regs in the past. I had some success doing it. As I recall, I was using nylon rods that I cut to length. Next time I get some shop time I'll see what I can come up with, I know I still have a lot of nylon rod stock

 

[Couv]

Dunno. I suspect a lot. I wasn't sure the volcano would reach up into the pocket left by the short seat and not bang into the metal of the piston before it reached the HP seat. I didn't try.
But if Scubapro 0.010" shims give you 4-5 psi IP change, I imagine a missing millimeter would be a really big increase.

Yeah, I guess my non-metric mind did not consider how big of a difference that is. If the seat does not protrude beyond the piston stem then that spells bad news.

While you were typing the above, I took a bit of time to measure my spare seats and damn if I don't have the wrong sizes (fat boys.) I do have a couple of MK2 kits should I need them (and sure enough the seats are the dimensions you stated.)

@rsingler -always with the bad news.

 

[rsingler]

Nah! It's fine! Use the short seat! Your new IP of 161 is perfect for your Poseidon Cyklon!

 

[rhwestfall]

I know I still have a lot of nylon rod stock

And we have a need....

 

[johndiver999]

Since I've already admitted my ignorance.... why can't you just shove a 1 mm washer under the spring as a shim? won't that be equivalent to lengthening the piston?