Vibrating shaft at slightly high revs.

[Three Sisters]

One of Nigel Calder's books, going on twenty years ago, was the reference used for my first time. You tube ? Never looked for it there.

[ramblinrod]

Originally Posted by Hoohaa

Sounds like a catch 22. If i install the bolts then it will pull it into alignment. I can definitely make a horizontal adjustment but vertically will be out. I'll be getting some measuring instruments on Sunday. Then i should be able to get some accurate measurements between the flange faces. Obviously I haven't done this before so any advice is appreciated.
Maybe a YouTube video on the subject?



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The shaft has to be supported so that it is concentric with the hull exit and strut centres.

Then the motor (transmission output flange) is aligned parallel and concentric to the coupler flange.

Be careful how you go at the service provider. It is common after a major alignment (e.g. pull the motor and change the shaft or mounts), to have to fine tune it after a run-in period (20-50 hours).

[Three Sisters]

Originally Posted by Hoohaa

Pics

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Was there any obvious gap differences while separating the flanges ?

Or changes in the gaps while rotating the prop shaft ?

Looking for basic stuff you could do while waiting for your tools.

[Hoohaa]

No obvious gap differences butits clearly out of alignment.
I am off the boat atm.
I will do my best to get the shaft aligned with straight edge and spaces. Will be back on board Tuesday.

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[a64pilot]

I believe it is common for one of the flanges to have a smaller flange that inserts into the other half, if just barely separated, this supports the shaft allowing you to measure.
I take a feeler gauge and lightly clamp a leaf between the two flanges, say a .010 for instance, then of course you measure the rest of the gap and move the motor around so that you have .010 gap all the way around the flange.
It's not hard, doesn't take much mechanical ability, just patience and the desire to get it right is all.

If for some reason one of your flanges doesn't have a lip on it that inserts into the other flange, you should be able to install one bolt with th

[Hoohaa]

My flange has a plastic spacer or flexible joint.
And I think an anode is preventing the metal flanges coming together. I can put a spacer in with the feeler gauge or should reinstall the flexible joint?

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[GILow]

Originally Posted by Hoohaa

My flange has a plastic spacer or flexible joint.
And I think an anode is preventing the metal flanges coming together. I can put a spacer in with the feeler gauge or should reinstall the flexible joint?

The "plastic spacer" is almost certainly a flexible coupling, most likely something like one of these:

Poly Flex Group - Advanced Polymer Technology for Vibration Control - 4 Bolt

As I said way back on post #14, check the flexible coupling has not gone hard and distorted. I can practically guarantee that is the problem. I have seen it before. You will not be able to check the faces are in alignment with the coupling in place, as it will NOT be true. Even if it was replaced when the work was done I would not trust it for checking alignment.

[ramblinrod]

Originally Posted by GILow

The "plastic spacer" is almost certainly a flexible coupling, most likely something like one of these:

Poly Flex Group - Advanced Polymer Technology for Vibration Control - 4 Bolt

As I said way back on post #14, check the flexible coupling has not gone hard and distorted. I can practically guarantee that is the problem. I have seen it before. You will not be able to check the faces are in alignment with the coupling in place, as it will NOT be true. Even if it was replaced when the work was done I would not trust it for checking alignment.

??? The purpose of a flexible coupling is to make up for minor mis-alignment and take the shock out of start-up / direction change. ????

Regardless, it doesn't look like a flexible coupling.

[Cheechako]

How thick is the plastic spacer? Maybe take it out and not have to shorten your shaft! My feeling is 2.5 " of shaft overhang is not causing this, However I doubt most sail props are well balanced at all. So the more overhang you have, the smaller the shaft, the bigger the prop, the more wobble you may have for sure.

[a64pilot]

Originally Posted by ramblinrod

??? The purpose of a flexible coupling is to make up for minor mis-alignment and take the shock out of start-up / direction change. ????

Regardless, it doesn't look like a flexible coupling.

Sometimes they are called drive savers too, idea of course is to be a fuse that breaks before your driveline / engine mounts / boat does.

[Hoohaa]

The last photo has the flexible coupling removed. I am sure it was new when they installed the new shaft.
I am trying to think of the best way to check the gap with the feeler gouge whilst having this inch wide gap between the metal flanges.
Correct me if I am wrong but i should install a couple of bolts and using a spacer and feeler gouge i can check the gap.
With this gap, i think the biggest hurdle will be getting the shaft properly aligned before I start taking the measurements.

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[Three Sisters]

If you have an inch-wide gap to align

[Three Sisters]

If you are aligning the two flanges with an inch-wide gap, just an idea, the backside of the slide caliper has two tangs to measure an opening to .00 mm/in accuracy.

The shoulder of the bolts should penetrate the flanges to create a smooth path for the two flanges to travel while tightening. However if the center of the one flange is machined to fit inside the second flange for tightening, then you may have bolts with a full thread along the shank. Or both techniques are used.

The plastic spacer or drive saver or whatever it is and the presence of the anode, where ever that may be mounted, and the fact that the two flanges cannot be pulled tight together without the plastic flange in place is making it a more complicated task.

Possibly you need 3 or so temporary bolts with identical spec and longer shoulders to bridge this inch gap between flanges, document the measurements, adjust accordingly. Bolt together and smooth motoring.

I'll be looking for the "smooth motoring" post.

[Hoohaa]

Good idea. I will get a set of digital feeler gauges and can measure the gap directly. I should be able to get some bolts in. Stay tuned.
Off to Bunnings to buy an assortment of measuring devices.
Thanks TS and thanks for the call Bob.

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[Cheechako]

Originally Posted by Hoohaa

No obvious gap differences butits clearly out of alignment.
I am off the boat atm.
I will do my best to get the shaft aligned with straight edge and spaces. Will be back on board Tuesday.

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How far out is the shaft unsupported from the stuffing box? If a foot or less I would not even worry about it.... sag is almost non existent.
For face alignment, I prefer to use a number of small ~ 1/8" drill bits in lieu of feeler gauges. Ones that are a few thousanths apart in size. I use the butt end of the drill bit and find the gap differences searching around the coupling at 90 degree places. Slide the shaft and coupling up tight against a drill bit, then search around the other side to see the difference.
You can then adjust alignment to where the same drill bit goes in all around, and the next one up does not go in.