Shaft U J ,s on boats?

[dsw]

Any thoughts of this setup which charges the 12v bank.

Shaft bolted to the crank shaft pulley (350hp sabre) which

Has 2 U Joints into 2 Plummer bearings which i have noticed

Are fixed to the shaft so it can’t move forward or back even after

I removed the grub screws.

Reason i ask is vibration at certain speeds and i hate vibrations.

Plus not really enough room to fit an alternator to the engine.

 

[Malish]

To my untrained eye the pulley looks out of alignment and the lower of the two bearing blocks need to move to the right a smidge, But that large washer is preventing the movement, any reason for its presence.
Any grease applied to the nipples recently?

 

[Alex_Blackwood]

To my untrained eye the pulley looks out of alignment and the lower of the two bearing blocks need to move to the right a smidge, But that large washer is preventing the movement, any reason for its presence.
Any grease applied to the nipples recently?

Miles out of line, surprised the bearing would last any length of time. Actually the shaft looks bent! Probably not , but certainly out of line.

 

[rogerthebodger]

Those Plummer blocks are in a self-aligning mount so the alignment of the Pummer block is of no significant.

If the shaft is bent that would cause vibration

 

[penberth3]

Those Plummer blocks are in a self-aligning mount so the alignment of the Pummer block is of no significant.

If the shaft is bent that would cause vibration

Self-aligning bearings do have their limits! With the arrangement shown there's plenty of space, no excuse for having it so far out.

 

[rogerthebodger]

Self-aligning bearings do have their limits! With the arrangement shown there's plenty of space, no excuse for having it so far out.

Self-aligning bearings do have their limits as do all mechanical designs.

Having spent many years in the design of mechanical and electrical systems I know too well some of the limitations.

My setup has a self-aligning thrust bearing on my prop shaft being a flanged Plummer block mounted on a fabricated frame so need an allowance for self-alignment as I do not have machined faces to bolt a fixed bearing to

I also have a PSS seal that has a self-aligning bellows as many other stern seals have.

My boat originally hs a rigid stern gland that I replace with the PSS for better self-alignment.

Yes, the Plummer blocks could be aligned better but currently vibration would IMHO and experience would not be caused by the current malalignment. A bent shaft or incorrect fitting of the Vee belt drive pully would cause vibration described by the OP

 

[dsw]

ok in that photo it does look out of line and i have moved it while the engine
was running and after a lot of tapping left and right,back and forth it was running
smooth at all revs but when i took the boat for a run the vibration was there at certain
speeds under load. So should the shaft be able to slide back and forth as the engine
is soft mounted?

 

[PaulRainbow]

Those Plummer blocks are in a self-aligning mount so the alignment of the Pummer block is of no significant.

If the shaft is bent that would cause vibration

The alignment of the Plummer bearing is of significance, because the pulley is out of alignment with the alternator pulley. The two shafts have to be parallel.

 

[Paul1962]

Self-aligning bearings do have their limits as do all mechanical designs.

Having spent many years in the design of mechanical and electrical systems I know too well some of the limitations.

My setup has a self-aligning thrust bearing on my prop shaft being a flanged Plummer block mounted on a fabricated frame so need an allowance for self-alignment as I do not have machined faces to bolt a fixed bearing to

I also have a PSS seal that has a self-aligning bellows as many other stern seals have.

My boat originally hs a rigid stern gland that I replace with the PSS for better self-alignment.

Yes, the Plummer blocks could be aligned better but currently vibration would IMHO and experience would not be caused by the current malalignment. A bent shaft or incorrect fitting of the Vee belt drive pully would cause vibration described by the OP

Concur all the above - I would be tempted to align the Vee Bellt pulleys and maybe disconnect the UJ's to see if they are moving freely - they "may" have a grease nipple point in their centres. The free running of the self sligning plummer blocks could also be checked too

 

[Alex_Blackwood]

ok in that photo it does look out of line and i have moved it while the engine
was running and after a lot of tapping left and right,back and forth it was running
smooth at all revs but when i took the boat for a run the vibration was there at certain
speeds under load. So should the shaft be able to slide back and forth as the engine
is soft mounted?

You may, even if you get everything aligned, have what is known as "Critical Revs" due to the set up of all the equipment, engine, engine mounts, shaft etc. at certain revs you will get vibration. This is all a bit complex and can sometimes only be overcome by avoiding that Rev. band. I have been in ships, with slow speed (120 RPM) engines where at 90 Revs the ship would rattle like a can of rusty nails. We didn't run at 90 RPM!
I would suggest that you get the alignment of the shaft and pulleys sorted. Check the bearings for wear, check your engine mounts ( How old are they?) Check that the engine is correctly mounted on the mounts. I know of a case where the injector pump springs kept breaking, due to incorrect mounting of the engine. As has been suggested check the UJ as well.
Good luck!

 

[Boater Sam]

The belt drive to the alternator is miles out of line. I suggest getting everything in line properly and see how you go.

 

[dsw]

should the shaft be able to move freely so no thrust load on the bearings,

 

[Alex_Blackwood]

should the shaft be able to move freely so no thrust load on the bearings,

What exactly do you mean by "Move freely" Vertically, horizontally or lengthways? Or all three
If they are, as I suspect, ball bearings they will take thrust. You should not have thrust on that set up, what is there to provide thrust unless the engine is jumping around a bit! BTW. Don't try and sort alignment with the engine running as you mentioned previously.

 

[rogerthebodger]

Those type a Plummer blocs will take thrust as they are what are called deep groove ball gearings.

We used to use lots of these on the mechanical handling equipment I was involved in designing many years ago

I have on my boat the one at the lower left as a thrust bearing taking the prop thrust in both forward and reverse

 

[Plum]

Any thoughts of this setup which charges the 12v bank.

Shaft bolted to the crank shaft pulley (350hp sabre) which

Has 2 U Joints into 2 Plummer bearings which i have noticed

Are fixed to the shaft so it can’t move forward or back even after

I removed the grub screws.

Reason i ask is vibration at certain speeds and i hate vibrations.

Plus not really enough room to fit an alternator to the engine.View attachment 197228

Can you pls post a picture showing both UJs in the same shot and how they are attached to the crankshaft pulley.

 

[billskip]

"Critical Revs"

Yes, if it's a problem with resonant frequency.

 

[oldharry]

The vee belt pullies are way out of line, and will eat belts. Unlikely to be the cause of the vibration, but will cause no end of grief on a trip as they cut through belts in fast order. Pulleys need to be fairly precisely aligned to each other to avoid rapid wear of the drive belt.

Is there any play in the UJ's? That will soon cause vibration which can be speed sensitive. Also consider drive shaft balance.

 

[Alex_Blackwood]

Yes, if it's a problem with resonant frequency.

Agreed, but I just didn't want to get too technical and end up with a discussion about harmonics and resonant frequencies etc.