|T O P I C R E V I E W
||Posted - May 06 2012 : 20:56:36
six years ago we added PSS shaft seals during the refit. We went from 1.25" shafts to 1.75"
I noticed one dripping and went to tighten the clamp and the worm screw head simply twisted off with nearly no torque.
There are four clamps on the "bellows" and I had a tough time extracting the broken one and it's mate (photos attached). I do not believe I did any damage to the bellows, just my knuckles.
It appears that there are two clamps on each side (pix attached)
1) For an application like this, why didn't PSS supply the absolute highest quality stainless clamps instead of these hardware store type? seems penny wise and pound foolish.
2) Any ideas as to how I can get to the clamps on the aft side?
3) Anyone had similar failures? This kind of hidden problem reminds me about the total loss of Captain Art's 55' vessel.
Any comments, advice or encouragement would be appreciated as I won't be comfortable until I have replaced all 8 of these.
photos follow - and yes it's really tight in there.
|11 L A T E S T R E P L I E S (Newest First)
||Posted - May 13 2012 : 10:11:56
Take a hose clamp and put it on the shaft resting next to the collar that slipped. Cheap insurance to keep it from slipping.
||Posted - May 13 2012 : 07:22:05
Just use 2 AWAB clamps.
I should add, I mean 2 on each end.
||Posted - May 13 2012 : 07:09:48
Where were the T-clamps made?
||Posted - May 13 2012 : 06:50:16
a couple of relevations.
WHile working on replacing the clamps, I found that the port stainless steel "rotor" had clearly slipped forward, towards the transmission, thus reducing the pressure necessary to maintain a seal.
I confirmed this by comparing the measurements from the collar to the transmission coupler port to starboard.
Removing the locking and main set screws confirmed that they were in fact loose and neither set screw showed the "crush" on the tip that I would have expected to see.
I put a tape marker on the shaft, and after a few blows from a deadblow hammer to a 2x4, the rotor was moved aft about 1/2", thereby restoring the "fit" to the seal via the bellows.
With no "crush" on the set screws, I squirted some locktite on the threads and tightened both setscrews down nicely.
I noticed a bit of surface rust on the port coupler, and some stains on the shaft while there is none on the starboard side.
I now recall having to do this same thing a few years ago on the stbd side for the same reason.
So it looks like I am the one guilty of overtightening the clamps in an effort to stop the drip.
Nevertheless the clamps were rusty, so I have taken the suggestion to replace them with TEE clamps.
The only question remaining is this:
Since the TEE clamps are far wider than the hose clamps, I do not believe I can get two on each end of the bellows.
Do you think I am good with one on each end, or should I add (I think I should) one AWAB next to the TEE clamp?
I plan on wrapping this up today and putting her in the water to chjeck for leaks.
THANKS FOR YOUR RESPONSES !
||Posted - May 10 2012 : 21:55:19
there are better metals to use BELOW the water line in stead of SS that can handle the corrosion. I've had other SS clamps fail at the solder joints as well.
||Posted - May 08 2012 : 19:03:26
I'd see if PSS has a recommended torque rating when using T-clamps. You can over tighten them, too, easier than a standard worm drive like an AWAB. And, they are not infallible and need inspection; I have had one fail on a dry installation on an engine; and in a wet location need to be of the best quality stainless regardless.
||Posted - May 08 2012 : 18:24:41
PSS manual says bellows should be replaced every 6 years. I replaced mine this winter. Clamps looked fine, but there was some crevice corrosion on the rotor face.
||Posted - May 07 2012 : 07:11:25
Use T clamps.
||Posted - May 07 2012 : 05:14:26
I knew those clamps and the T clamps existed, but did not know them by name.
The overstressing makes sense the way the thing just came off, however corrosion is an obvious concern here too.
Good thing they were double clamped!
Perhaps a T clamp would be a better choice here ?
||Posted - May 06 2012 : 23:00:45
They used the same clamps that most everyone uses. I don't like them either, but they likely failed because they were over stressed when installed.
Few people use something decent like an awab, but that's what you should get.
||Posted - May 06 2012 : 21:41:56
I just figured out how to get to the aft pair of clamps.....
through the lazarette there are two access openings to the rear part of the shaft log.....
photo follows below
So the question si WHY would PSS provide this type of clamp in such a critical area vs. the high quality SS clamps??