Reference Cell Test Results, Help to Determin Resolution

[zstine]

Originally Posted by boatbod

Connecting anything to a PSS seems like a recipe for a bad outcome. Those stainless rotors crud up and pit easily. The carbon seal less so, but certainly not an ideal conductor.

Please enlighten everyone why you wanted to eliminate a simple zinc?

I'm not trying to eliminate a zinc on my boat. Just trying to get conductivity between the shaft and the engine. I have a dripless, so apparently I can bond between the carbon and the engine and not need to install a brush. that's super easy fix.. or I can go the brush route, but I have basically no exposed shaft. So the brush would have to ride on the OD of the stainless collar for the dripless. And I'd have to engineer some mounting brackets which I assume need to be spring loaded to deal with brush wear. that's a bit of a pain but not a huge issue. Isn't using the carbon creating an issue if electrolysis starts pitting the sealing surface? I'm not sure having current running through that seal surface is ok?

Is the SS collar going to pit if there's 1/4V running through it to the carbon?

sorry for slow reply on my own thread, but I'm not getting emails when people post on this... weird. I get them for all other threads. and this thread never made the email push of 'today's new threads'. related?

[boatbod]

You can't run a brush on the exterior surface of the ss collar because it has two holes for set screws and is therefore not a smooth surface.

[tkeithlu]

The shaft brush IS a spring - it's about a foot long, straight, with holes for mounting so that it bears against the shaft. But, you do need about 3/4 inch of clear shaft to run it against. The "brush" is more a "block" at the end and sticks down about 3/4" as well. You don't have to worry about it pitting, because it's in continuous contact with the shaft. There are no sparks or the like - it's just a continous contact. As I may have said before, you are welcome to the one I'm looking at right now for the cost of my mailing it to you. I don't need a second one.

[groundtackle]

Boatbod, You could notch the brush so it doesn't skip on the holes or even just let it make its own notch over time. It wont hurt the collar, might fill the holes with dust.
One thing that has always bugged me about those collars is the (2) 90 deg opposing set screw design that doesnt center the whole unit. When tight it jams that collar to one side squashing o-ring, other side is relaxed. Why wouldnt they put (3)? because they want the i.d. to parallel the shaft so face stays true. This brings me back to brush on the collar....its not centered so it wont run true. Maybe good enough for a brush but I can't look at that thing bouncing around. In fact, i cant look at that collar move after spending all that time with alignment. I stick mine on a dummy shaft and machine it true first (dont tell them that)
Senor, I think your system is good, solves your problem and you monitor it. I think PYI will say something about, they really want to discourage folk from playing with their seal.
They got a bad rap and still people bring up the whole boat will sink blah blah. I have never had a problem with one that was installed properly. They want to protect that image.
ce

[senormechanico]

That is exactly why I haven't mentioned anything about it to PYI.

I'm taking responsibility for my experiment and if pitting happens, I'll go another way.
The boat's a multihull and unsinkable. It's also at my dock so I can easily monitor any leakage, should it happen.

I had a shaft brush on my previous boat, and it was a PITA. Besides, it made RFI in my HAM rig and AM radio when motoring.

[groundtackle]

Senor, you should see the stuff I experiment with on my own boats. Its a test lab. God help the guy that steals it one day. If he gets anything actually up and running he will never be able to turn it off...
I would love to go for a spin in that machine of yours one day, Nick has a little a dock in Sidney, come on by.
ce

[boatbod]

There are so many things I dislike about the PSS I could probably write a small book. Customers apparently love 'em though, so that keeps my techs busy fixing and adjusting to stop the leaks.

[RaymondR]

Originally Posted by boatbod

Connecting anything to a PSS seems like a recipe for a bad outcome. Those stainless rotors crud up and pit easily. The carbon seal less so, but certainly not an ideal conductor.

Please enlighten everyone why you wanted to eliminate a simple zinc?

I feel I should disagree with the above.

Since the carbon is in intimated contact with the SS rings face it should make excellent electrical contact and since the carbon is continuously rubbing against the SS (at least when the shaft is turning) it should polish off any crud which might tend to form.

If brushes cause interference to a HF radio they must be causing sparks and not an excellent electrical connection. Intuitively the PSS solution has greater appeal to me.

[boatbod]

Originally Posted by RaymondR

I feel I should disagree with the above.

Since the carbon is in intimated contact with the SS rings face it should make excellent electrical contact and since the carbon is continuously rubbing against the SS (at least when the shaft is turning) it should polish off any crud which might tend to form.

If brushes cause interference to a HF radio they must be causing sparks and not an excellent electrical connection. Intuitively the PSS solution has greater appeal to me.

Everyone is entitled to their own opinion. Mine is formed through 3 years of personal PSS ownership followed by 13 years of boatyard operation.

Food for thought: if the carbon face were in perfect contact with the stainless rotor, would the seal leak?

[RaymondR]

Mines been in operation for about three years and has yet to leak a drop consequently I'm assuming there is intimate contact between carbon and SS. Quod Erat Demonstrandum.

[boatbod]

Originally Posted by RaymondR

Mines been in operation for about three years and has yet to leak a drop consequently I'm assuming there is intimate contact between carbon and SS. Quod Erat Demonstrandum.

Hope it stays that way. Mine did not.

[senormechanico]

The only time mine allows any water past is when I push on it.

[groundtackle]

I have had failures but always something else if properly installed. Obviously alignment, busted engine mounts, super soft mounts with engines that won't sit still especially when idling, fire, a guy jammed his deck brush into it. Worst one was a fella that whacked a log and threw his 26" max prop blade into the hull and bent the shaft. The most common is people dont realise there are two set screws. I'm not sure exactly what kind of seal handles all of these issues. I always mark the shaft and hull with a sharpie so i know if anything has moved. Also have made sticks or a fork of wood that fits down there against something to use a measure. Kinda like an undersize crab ruler. Leave it on a string close by for a handy reference
What exactly is your issue with them Boatbod, something we should know about?
ce

[RaymondR]

The carbon face seal is one of the commonest and most reliable sealing systems, millions of car engines have them and the great majority last for the life of the engine.


The PSS seal looks well designed and durable and like it should give reliable service for many years provided one changes the bellows every few years.


It would be interesting to mount two of them on a shaft and get a resistance reading across the running seals. I say two of them because I can't think of another way to get as reliable a reading.

[senormechanico]

It's not a resistance reading, but after electrically coupling mine as above, I got exactly the same voltage reading on my bonding system to the reference cell.
I measured the prop shaft, the bonding system in the middle of the boat, and at the forwardmost thruhull.

AFAIK, it's working fine.