Vibration and visible shaft wobble

[raymond]

We are still having serious problem after much work and expense.
Our 1998 Albin 28TE is equipped with a 270 HP Cummins, ZF-V-Drive Trans 1.5 reduction.
The shaft is 1.5 dia x 8 ft long, supported only at both ends.
The shaft is straight and run out with CPLG is good. Cutlass is new. Shaft seal is new, motor mounts are new and shaft alignment is within .002.
With the shaft out of the boat we checked it's static deflection or sag from it's own weight with a straight edge. It sags .038 inches. Sag would be somewhat less in boat due to shaft being supported at one end by cutlass and other end by rigid CPLG. However rigid CPLG can only be aligned to slope of sagging shaft.
An 1.5 inch shaft this length running at 1600RPM would never be considered in designing machinery.
I'm getting desperate and considering some drastic moves I.e.
1. Mis aligning CPLG to compensate.for deflection in shaft.
2. Adding a bearing - very difficult since shaft runs under engine.
Are there a lot of Albins out there with this design. Having or not having this problem?
I would really appreciate any information or where I might find some professional help. It looks like Albin is out of business again.

[Russell]

I had a similar problem of shaft wobble a few years ago on my 97 model. My mechanic found that the internal flange of the stern tube had decomposed and broken off. It centers and stabilizes the stern tube. The two bolts holding it in were not capable of preventing it from moving without the flange. The problem is the stern tube is not bonded to a zinc so it undergoes electrolysis. You will find pictures and sources on this link:
viewtopic.php?f=5&t=6176&p=36418&hilit= ... ube#p36418

[jleonard]

8 feet is pushing the design lit of a 1.5 inch shaft. It needs a support bearing. Aquamet has a spec sheet that will confirm this.
Find an Fafnir/Torrington RCJC 1.5 bearing and install it on a bulkhead. Or a similar bearing if a bulkhead is not available. Make sure the bearing has a lock collar.
Hope this helps

[DougSea]

8 feet is pushing the design lit of a 1.5 inch shaft.

While I have no doubt as to the accuracy of this statement, (Jay knows his stuff!), it IS the way the vast majority of 28TE's are set up. So I'd start looking at what's different in your case. Have you had a chance to look at any other V-drive 28's to compare it to? Something's up.

I'm assuming you have had the prop serviced and it's been eliminated as either the source or a contributor to the issue.

[Tree]

Not quite the same problem but when we first launched FP2 we noticed a noticable amount of vibration from 3400 rpm upwards.

Shaft alignment and engine alignment were spot on as was the balance on the propeller. When we pulled the engine for another issue, we found that 3 of the 6 bolts in the crank pulley were sheared off where the previous mechanic had made a bodged job of it.

Ok we did also replace the cutlass bearing like yourself while doing everything, but now there is no sign of any vibration - just an idea that may be worth investigating? I suspect that missing those three bolts played major factor in the vibration that we had.

[jleonard]

Doug, that doesn't mean it's a sound design or that it cannot be made bulletproof.
To locate the exact source of the vibes, use a "rocks glass" (real glass not plastic) filled half with water. While underway place the glass at various places. The amount of vibration of the water will locate the source, the glass may even bounce if it's really bad
Could it be oil canning of the hull due to prop clearance?