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Old 25-10-2013, 12:29   #1
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PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

I've searched the forum and called the manufacturer but have not been able to get any advice or tips about how center the shaft in the stern tube (with the boat IN the water) before aligning the motor's shaft to the prop shaft.

Because the PSS shaft seal's bellows are flexible, when I removed my diesel engine and the prop shaft couplings, the PSS bellows let the shaft sag down a bit and I know the shaft is no longer in the center of the stern tube but off center towards the bottom. Does anyone know of any 'tricks' like measuring, or calculating some way to get the shaft back up and centered in the tube so I can then align the new motor's shaft to the prop shaft? (Yes, it's a motor, not an engine---10Kw electric drive).

Also, the shaft coupling I have is not like the typical couplings with the large flange. Here's a photo of the type I have (double split collar type, only mine is in stainless). This type will force the prop shaft to be aligned with the motor shaft, but...not necessarily in alignment with the center of the stern tube or cutlass bearing... Thanks for any advice or tips.
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Old 25-10-2013, 15:47   #2
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

Skipper,

It is possible that not only is the shaft out of vertical alignment, but due to the spring nature of the PSS, the prop may have also been forced up against the cutlass bearing. With the PSS attached the stern tube is not available as a shaft alignment reference. Unless you can use a bulkhead or something else as a reference you will only be able to guess at the shaft alignment. Considering the rigid nature of your proposed shaft coupling that would not be a very good long term setup.

A better plan might be to haul the boat. Start by removing the PSS. Then if necessary pull the shaft and replace the cutlass bearing. Position and align the shaft with the stern tube. Temporarily lock the shaft position in place. Install the motor, aligning it with the shaft. Remove the temporary shaft position lock. Reinstall the PSS. Then install a flexible coupling between the shaft and the motor.

Best of luck,

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Old 25-10-2013, 15:50   #3
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?


I do not understand?

"Because the PSS shaft seal's bellows are flexible, when I removed my diesel engine and the prop shaft couplings, the PSS bellows let the shaft sag down a bit and I know the shaft is no longer in the center of the stern tube but off center towards the bottom."

It sounds like the engine alignment is forcing the shaft to move. Its the engine that is being aligned to the shaft, not the shaft to the engine.


I do not know how to center the shaft in the tube with the bellows on and the boat in the water. The centering of the shaft in the tube should have been done when the boat was out of the water with the bellows loose. However the center of the tube may not be critical as long as the shaft is not touching/rubbing against the tube





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Old 25-10-2013, 15:57   #4
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

Just use a bush or a specially turned piece of material to fit the shaft and the inside of the stern tube and cut it into three pieces so that it can be easily inserted to centre the shaft.
If you are doing it in the water you will have to seal the shaft from the outside, which may be difficult.

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Old 26-10-2013, 17:59   #5
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

You have a single shaft bearing so shaft height alignment is not so critical. Simply measuring the lowest position of the shaft then lifting and measuring the highest point then divide x2 will be good enough. Also do the same for side to side. Afterwards do the normal check for radial and axial alignment. Because you only have one shaft bearing you should not fit a flexible coupling as you need the gearbox thrustbearing to hold the shaft in alignment. A flexible coupling will allow runout of the shaft.
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Old 27-10-2013, 11:07   #6
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

NoTies has the answer.
It's always worked for me.
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Old 27-10-2013, 11:10   #7
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

i found that my prop shaft was in perfect position when the engine was properly aligned.
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Old 27-10-2013, 12:30   #8
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

Quote:
Originally Posted by Viking Sailor View Post
Skipper,

It is possible that not only is the shaft out of vertical alignment, but due to the spring nature of the PSS, the prop may have also been forced up against the cutlass bearing. With the PSS attached the stern tube is not available as a shaft alignment reference. Unless you can use a bulkhead or something else as a reference you will only be able to guess at the shaft alignment. Considering the rigid nature of your proposed shaft coupling that would not be a very good long term setup.

A better plan might be to haul the boat. Start by removing the PSS. Then if necessary pull the shaft and replace the cutlass bearing. Position and align the shaft with the stern tube. Temporarily lock the shaft position in place. Install the motor, aligning it with the shaft. Remove the temporary shaft position lock. Reinstall the PSS. Then install a flexible coupling between the shaft and the motor.

Best of luck,

Thanks for your suggestions. I have confirmed with underwater photos that my prop and shaft are in the proper fore/aft position and the PSS bellows are holding a measured and proper length of 6.225 inches (1" shaft) from the aft end of the bellows to the forward stainless collar surface---so that is not a problem. Yes, hauling the boat would have resulted in me not posting here at all, but I was curious if there were any tricks I was unaware of that would let me align the shaft since there is no front bearing supporting the inboard end of the shaft. With my installation (no front bearing) a flex coupling would not be a good idea at all as the flexibility could possibly let the shaft run out wear the cutlass bearing more rapidly.

I have since come up with a somewhat off the wall idea that will get me pretty close. I won't be able to try this until latter this week. Of all things it involves the use of my iPhone. See my last post... Thanks...
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Old 27-10-2013, 13:44   #9
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

Quote:
Originally Posted by NoTies View Post
You have a single shaft bearing so shaft height alignment is not so critical. Simply measuring the lowest position of the shaft then lifting and measuring the highest point then divide x2 will be good enough. Also do the same for side to side. Afterwards do the normal check for radial and axial alignment. Because you only have one shaft bearing you should not fit a flexible coupling as you need the gearbox thrustbearing to hold the shaft in alignment. A flexible coupling will allow runout of the shaft.
Yes! Thanks No Ties. This is exactly what I ended up doing for now. I totally agree with you on the "no flex coupling" for my installation. The electric motor drive does have two thrust bearings locked onto the drive shaft on both sides of the belt-drive pulley so the motor shaft is locked for and aft for sure.

I have since come up with a whacky idea that will tell me if my shaft is aligned vertically in the stern tube---or not, with the boat in the water...and of all things it involves the use of my iPhone! Let me explain; There are about six inches of stern tube protruding inside the hull in the bilge and accessible before it meets the PSS bellows hose clamped to it. The surface of this stern tube is rather smooth and I began to wonder; if I could measure the exact angle of the stern tube in the hull, then in order for the prop shaft to be exactly in the middle of the vertical plane of the stern tube, the prop shaft must read the exact same angle. (This of course "assumes" that the factory put the strut/cutlass bearing in exactly the right place and angle). Simple geometry states two parallel lines are equidistant and thus must share the same angle---no other case would fit.

As the old joke goes; "If you can think of something you need to do, well... there must be a APP for that!" Ha! That thought sent me scurrying to the iPhone app store to see if there was any kind of worthy app for highly accurate measurement of angles using my iPhone. Behold! There is! It's called The Tiltmeter App... For a lousy $1.99 I got the most amazing and highly accurate inclinometer, that according to one reviewer matches his companies highly accurate mil-standards instruments. (there is also a free version to try it out, it just doesn't do data logging and some other cool stuff.)

This is pretty exciting. So tomorrow I am going to measure the angle of the stern tube and then compare that to the angle of the shaft exiting the PSS Shaft Seal and I'll have an indication how far off center I am. Here's the best part. When I measure the relative angle of the stern tube, I can lock in that angle as a reference (within 1/10 of a degree or 6 minutes of arc) by hitting the lock icon. If my shaft does need adjustment, then I am going to use masking tape to hold my iPhone on top of the prop shaft in the vertical plane) and by adjusting my motor mounts, as the prop shaft angle gets close to the stern tube reference angle the iPhone begins to beep. The beeping changes to a steady pattern when you get to the exact reference angle and you are done! I will re-post here later in the week and let you all know if this worked out as planned.

Now that I think about it, this Tiltmeter is really incredible for numerous leveling projects on boats. In the water a regular bubble level is useless because of the slight listing of the boat, but using Tiltmeter's reference lock you can transfer "relative level" to any other place in the boat. Say you want to install a level shelf making sure it's level to all your counter tops. All you have to do is lay the iPhone on a level counter top as a reference, (works for either fore/aft or athwart-ship), then hit the lock icon and then take your iPhone to the bulkhead and align it using the "beep" method, then mark it. Pretty cool if you ask me. And no, I am not affiliated with ANY software or sales company that sells or has anything to do with this Tiltmeter app. Were it not for my problem of shaft alignment I would have never thought to look for this app in the first place. I hope this works as I plan, and I will re-post here to let everyone know. In the mean time if anyone would like to see what the app looks like here is a link to the website with some screenshots >> The Tiltmeter App

Thanks for everyone's ideas and suggestions.
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Old 27-10-2013, 14:55   #10
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How does it allow for the rocking motion of the boat?
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Old 27-10-2013, 15:29   #11
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

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How does it allow for the rocking motion of the boat?
I don't know yet, but I'm not on a mooring. I'm in a slip in a back harbor. The app seems to also have some internal damping built in so it's not jumping around a lot. Aboard my boat there is very little motion on a calm day in the slip...but one thing I didn't mention is that this app will log data as often as I want, (literally at intervals every tenth of a second or up to minutes or more...) I could get off the boat, wait for it to settle and then I could average the logged data, or run a linear regression app on the data if I really wanted to get picky. But more importantly I was concerned about the trim fore and aft when I measure the stern tube and then move my body weight forward to measure the prop shaft. (it's only a 32' boat with 26' LWL) This is an experiment in process, so I will know more later. Also, I just realized do have a way of reaching the prop shaft by reaching through a galley door opening so I won't have to move my body weight forward. Besides, at this point all I am looking for is to be close. I think this app will let me get much closer than just close. It's darn accurate and all I am doing is "relative" angles anyway. Sure hope this works. One thing I am sure of; it's a keeper app for other shelf or bulkhead installations of anything you need to check vertical or horizontal alignments aboard. Thanks... more later...
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Old 27-10-2013, 15:59   #12
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

My experience with measuring angles longitudinally on cylindrical objects is that it is very important that the measuring tool runs precisely along top dead centre (TDC). If the tool is even slightly skewed, it will give an erroneous reading. I'd be inclined to place your phone atop a small level (or custom made guide) that has the "V" groove in it which will allow it to run along the TDC more reliably.

I think I would also consider the No-ties idea in measuring the centre by moving the shaft up and down (and to the sides if required). It should be relatively easy to make a wooden block that wedges between, say the bilge, and the shaft to hold it at the correct position. Then you adjust the motor too high initially and then progressively lower/change angles until everything lines up.
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Old 27-10-2013, 17:40   #13
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

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Originally Posted by Reefmagnet View Post
My experience with measuring angles longitudinally on cylindrical objects is that it is very important that the measuring tool runs precisely along top dead centre (TDC). If the tool is even slightly skewed, it will give an erroneous reading. I'd be inclined to place your phone atop a small level (or custom made guide) that has the "V" groove in it which will allow it to run along the TDC more reliably.

I think I would also consider the No-ties idea in measuring the centre by moving the shaft up and down (and to the sides if required). It should be relatively easy to make a wooden block that wedges between, say the bilge, and the shaft to hold it at the correct position. Then you adjust the motor too high initially and then progressively lower/change angles until everything lines up.

Good points! And yes, as I mentioned I have already done "No Ties" suggestion of manually finding the center and it is installed this way now. I am just going to measure tomorrow with the Tiltmeter to see where I am.

Per your suggestion I just now tried an experiment with my iPhone/Tiltmeter here in my kitchen using a cylindrical object (marble rolling pin). I propped the rolling pin up on the edge of the sink so it was at a 5 degree angle measured by the Tiltmeter and setting it vertically and lining it up to be visually parallel and the indicated angle read exactly 5 degrees. I then very slowly moved the iPhone out of being visually parallel with the cylinder. Once it looked WAY out of parallel I got an angular change to 5.2 degrees and I could sense the iPhone slightly rocking if I pressed the iPhone down in a fore and aft motion parallel to the cylinder. Since the prop shaft is only 1" in diameter I anticipate that this type of error will be more critical, but also easy to test for. I'll just do the same test and see if the first noticeable change in degrees is still looking perfectly in parallel or it it's easy to see I am not lined up. I suspect I will be able to still get very close using this method---we'll see. Certainly closer than where it is now, unless I was very lucky with my "feel" method. Thanks for a great tip and I'll post my findings later.
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Old 29-10-2013, 11:04   #14
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

I made it down to the boat yesterday (Freedom 32 Hoyt design), to measure the angle of the stern tube and compare that to the angle of the prop shaft. Here's what I got using the iPhone's Tiltmeter app;

Stern tube angle 7.9 deg.
Prop Shaft (rough aligned engine) 8.8 degrees.

I then lowered the motor mount adjustment nearly all the way down and was able to get 8.2 degrees. To get it any lower will require me to remove the locking nuts on the bottom of the motor mount jack screws, or better, relocate the L-brackets higher on the motor housing (lowers the motor). However, at this point it time I'm going to go ahead with the electric drive installation and deal with this alignment issue when I can power up the system and do some actual running of the motor. If all goes well enough with the present setup then when I haul out before next summer I will pull the shaft (I need a cutlass bearing anyway) and at that time I can do a proper alignment with the PSS bellows removed from the stern tube. In the meantime, I feel this is close enough, and the iPhone Tiltmeter app not only told me where I was, but it was very easy to use. This app is a keeper for any other alignment projects that may come up. Thanks to everyone for their help and suggestions!
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Old 29-10-2013, 13:45   #15
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Re: PSS Shaft Seal; any tricks to finding the center of the shaft in the stern tube?

How about measuring the shaft angle at bottom contact with the tube, then angle when it contacts the top?
Split the number difference and you're in the middle, vertically.
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