Scubapro MK15 serivce

[Couv]

An old wives tale is that a satin finish will retain traces of lube longer than a mirror polish.

Call me an old wife then. Every hydraulic/pneumatic actuator, accumulator, or landing gear strut I've ever opened or serviced had a cross hatch pattern purposely put into the cylinder wall so that the fluid or lubricant is better retained. This pattern retains the fluid or lubricant so that the seal effectively "floats" on the fluid and reduces wear. Windshield wipers are much more effective on a new windshield than an old one because after years of sandblasting the windshield hold a bit of water in the tiny pot marks. Now, I don't mean for you guys and gals to go out there and use a cylinder hone inside your regulator, but I'm against a mirror finish on the cylinder wall and piston stem. Smooth is good for windshields-bad for pistons and cylinders. ...so there Old Man.

 

[rsingler]

But don't your struts have a hydraulic reservoir to slowly replenish lube bit by bit?

I guess that's just one more reason to have a sealed piston! You have your own reservoir of lube for your satin piston.

And I have to admit, I have a striking memory of taking a corner at far too high a speed in my car as a younger man. I attribute my survival to the cobblestone street. A flat road would have gripped and flipped me.

 

[Couv]

But don't your struts have a hydraulic reservoir to slowly replenish lube bit by bit?

No.

I guess that's just one more reason to have a sealed piston! You have your own reservoir of lube for your satin piston.

Yes, and with a decent boot it works very well.

And I have to admit, I have a striking memory of taking a corner at far too high a speed in my car as a younger man. I attribute my survival to the cobblestone street. A flat road would have gripped and flipped me.

That is why you see slicks on race cars-more surface area=more traction resulting in sticking rather than sliding.

Traction & friction good for race cars tires-not good for race car pistons & cylinders.

 

[rsingler]

Well, I've gotta defer to an expert.
I'm always learning from you, @couv !
I guess no more polishing my shaft.

 

[Couv]

But don't your struts have a hydraulic reservoir to slowly replenish lube bit by bit?

Pilot, "Hey Couv, that looks like a pretty bad hydraulic leak to me."

Couv, "Don't worry about it Captain. You have enough hydraulic fluid to outlast the fuel load."

 

[rnln]

Thanks everyone.

 

[halocline]

I finally took my MK15 apart, cleaned all parts well, and found that there are pitting/scratching on the cap/ambient-chamber (#20) and piston base (#15). I run my finger nail through it slowly and I do feel it. Do you think these can be reuse or trash?

Thanks

The ambient chamber looks fine, maybe a bit of micromesh to polish it. You need to take the plastic bushing off the piston and look under it; that's where most of the corrosion usually is. The small pits on the piston head o-ring groove might be problematic, but the only way to know is to reassemble, pressurize, submerge, and look for very slow bubbling (less than one/sec) out of the ambient chamber, along with a very slow decrease in IP over a few minutes, then a 'burp' back to normal IP. I think with a little micromesh cleanup, a nice soft o-ring on the piston head, don't forget the plastic spacer which goes on the ambient side of that o-ring, you'll be ok.

BTW, I have a 13 cft pony that I have used for diving exactly one time probably 10 years ago. But I find it very useful for checking this sort of thing because it's much easier to move around than a full size tank.

 

[Jacobyz]

MK15 experts, I have what may be a dumb question. My MK15 has been carefully, and successfully, disassembled, with moderate residue and corrosion in the body cavity. I have been following along with the advice to not remove the plastic bushing on the ambient chamber side of the HP o-ring, and now wonder whether I can submerge the affected chromed body piece into the usual 50/50 mix of white vinegar and water I use to clean the chromed pieces, with the ambient-side bushing in place. Or, do I need to “spot-clean?” Thank you for all of the information!!

 

[Angelo Farina]

I usually submerge everything (including rubber and plastic pasts) of my reg in a solution made using WC-cleaning detergent, which contains a lot of acid. Apparently it does no harm to rubber and plastics...

 

[halocline]

and now wonder whether I can submerge the affected chromed body piece into the usual 50/50 mix of white vinegar and water I use to clean the chromed pieces, with the ambient-side bushing in place.

Yes, no problem.