Gland Packing/Alignment

[rusty69]

If I disconnect the prop shaft coupling from the R&D coupling, and assuming that there is no discernable wear in the SKF bearing/plumber block, can I then align the shaft to be concentric with the stern tube by simply (assuming it is adjustable) moving the SKF bearing horizontally and vertically, and measuring the gap between shaft and tube with a drill bit until they are equal?

 

Assuming it was once in alignment, and now the gland follower is worn, what is the likely hood that the SKF bearing is also worn as a result that the engine mounts have degraded, or will the R&D coupling offer enough 'give' to accommodate it? 

 

How do I adjust the height of the SKF bearing? Do I need to put metal shims beneath the plate that holds the bearing, to the bearer?

 

Once I have achieved this. Is it then a case of moving the engine to align the gearbox output shaft with the disconnected shaft, and then reconnect the two?

 

I probably won't risk it, but am I on the right kind of track

[Tony Brooks]

1 hour ago, rusty69 said:

How do I adjust the height of the SKF bearing? Do I need to put metal shims beneath the plate that holds the bearing, to the bearer?

 

That is the usual way of doing it.

1 hour ago, rusty69 said:

Once I have achieved this. Is it then a case of moving the engine to align the gearbox output shaft with the disconnected shaft, and then reconnect the two?

 

That's it, and I think that your semi-flexible coupling has a bolt head that forms a gap you can measure as you rotate one half coupling. So first get the height and transverse position of the engine right by siding the coupling together and ensuring the lands on the coupling slide into the mating recess. Then use that bolt head and feeler gauges to get the two parts angularly aligned to within 0.05mm (I think that is what PRM say).

[Rincewind]

7 hours ago, rusty69 said:

I probably won't risk it, but am I on the right kind of track

7 hours ago, rusty69 said:

If I disconnect the prop shaft coupling from the R&D coupling, and assuming that there is no discernable wear in the SKF bearing/plumber block, can I then align the shaft to be concentric with the stern tube by simply (assuming it is adjustable) moving the SKF bearing horizontally and vertically, and measuring the gap between shaft and tube with a drill bit until they are equal?

 

You are on the right track!

SKF bearing housings usually have elongated mounting holes to allow some adjustment.

Shims - It is unlikely that you will need any shims IF – (and that’s a big IF 😀) the shaft was originally aligned correctly and that the shims, if any, have not turned to rust!  If the shims (if fitted) are ok and the above is true, then theoretically, the shaft cannot move in a vertical plane unless the SKF bearing has collapsed.

 

Before you do anything else, clean the components and surrounding areas with a wire brush. 

(1)  With a sharp scriber or nail, scribe a line around the bearing housing base onto the bearer.

(2)  When the shaft is cleaned use a permanent marker pen to mark a wide band around the shaft at the mouth of the stuffing box. Place a steel ruler against the face of the stuffing box and where it touches the shaft; scribe a line on and around the shaft.

You now have reference points to return to should anything move unexpectedly.  The line on the shaft will record the position (distance) of the propeller relative to the hull as it is now. 

While the boat is out of the water you could measure the distance between propeller hub and the hull and make a note of that for secondary reference as well.

Prior to re-aligning the prop shaft, remove all the old packing.

7 hours ago, rusty69 said:

Assuming it was once in alignment, and now the gland follower is worn, what is the likely hood that the SKF bearing is also worn as a result that the engine mounts have degraded, or will the R&D coupling offer enough 'give' to accommodate it? 

That, I have to say, can only be ascertained by close examination of the bearing and engine mounts. 

 

When you come to repack the gland:-

Assuming that you have bought a length of packing and not "ready cut rings" wrap the packing around the shaft and with a sharp knife, cut the loose packing end at 45 degrees (looking down from above onto the shaft) and then cut a turn of packing at 45 degrees so that the ends overlap and mate with each other forming a ring with no bulge or gap.  - A fair amount of precision is required here.  This will ensure that no "short cut gap" will be introduced to the gland which otherwise could be the case if the ends were cut straight. (I.e. cut short at one end 😁)  

Install the first ring with the ends at the 12 o'clock position, the second ring with the ends at the 4 o'clock position and the third ring with the ends at the 8 o'clock position.  Push each turn into the gland with the gland follower to keep them square and finally tighten the gland follower retaining nuts finger tight with an extra half turn with a spanner.  Use two nuts on each stud locking them together.  The final adjustment will be when the boat is in the water.

[rusty69]

Thanks Tony and Rincewind for your detailed replies.

 

I will go clean the area up, and go from there.

[rusty69]

OK  I have cleaned and marked. Undone the bolts on each side of the R&D coupling, but they refuse to separate. 

 

The shaft won't move backwards. It sounds like metal on metal in the tube. 

 

Any ideas before I re assemble it? 

 

 

Eta 

Can't upload sound. Forum won't allow it

Edited June 27, 2023 by rusty69

[Rincewind]

Could we have a few pictures of the coupling arrangement please.

 

When you say "metal to metal sound", where exactly is the sound coming from - the stern tube bearing area or the SKF bearing?

 

I would not expect the shaft to move backwards as it would be held in position by the SKF bearing.  These are usually Spherical roller or ball race bearings mounted on a tapered sleeve on the shaft with the outer race sandwiched between two spacer rings within the bearing housing. If this is the case then removing one of the rings (the rings have a section cut out in them to allow them to be placed over the shaft after assembly), will allow the shaft to be moved back by about 6mm (or whatever the width of the ring is).

 

Temporary replace the coupling bolts and then remove the two long bolts holding the bearing housing cap in position and remove the bearing housing cap for inspection of the arrangement and condition.  The cap may need tapping with a mallet if it is stubborn. Note that the cap casting is normally "keyed" so that it mates with the base one way only.  Post a picture of what you see inside.

 

[rusty69]

22 minutes ago, Rincewind said:

Could we have a few pictures of the coupling arrangement please.

 

 

 

 

22 minutes ago, Rincewind said:

I would not expect the shaft to move backwards as it would be held in position by the SKF bearing.  These are usually Spherical roller or ball race bearings mounted on a tapered sleeve on the shaft with the outer race sandwiched between two spacer rings within the bearing housing. If this is the case then removing one of the rings (the rings have a section cut out in them to allow them to be placed over the shaft after assembly), will allow the shaft to be moved back by about 6mm (or whatever the width of the ring is).

 

Ok, I think I found that out by removing the top half of the bearing housing, I had  assumed (wrongly)that the shaft would move within the bearing. This does not seem to be the case.

 

 

Is the ring the thing I have posted in the pic above shown on the gland follower?

 

 

The other problem I now have, is that having scored the plate beneath the bearing, this has now moved position on the support beneath.

22 minutes ago, Rincewind said:

When you say "metal to metal sound", where exactly is the sound coming from - the stern tube bearing area or the SKF bearing?

 

Not sure, it sounds like the tube, but its probably the bearing.

 

 

ETA. At this stage, I have not removed any of the old gland packing.

 

 

Edited June 27, 2023 by rusty69

[Rincewind]

It appears to be a double row ball race with only one spacer ring, is that correct?

 

What is the general appearance of the ball race? Shiny / rusty / discoloured? well greased? Dirty grease? does the grease feel gritty when you rub a little of it between your fingers?

 

Not sure what is going on there but the housing felt seals do not make contact with the shaft allowing grit, water and other debris to enter the bearing.  A different type of shaft seal should have been used (they are available) but installing them now would mean removing the bearing from the shaft.

 

If that ring came from the coupling side of the bearing then there is no scope for moving the shaft backwards while it is bolted down.

 

The only way that I can see to disengage the coupling is to slacken the four clamping bolts on the (brass?) coupling and slide it along the shaft.  That would be normal anyway if the flexible coupling were to fail in normal use.

[rusty69]

2 minutes ago, Rincewind said:

It appears to be a double row ball race with only one spacer ring, is that correct

It only has one spacer, yes. 

3 minutes ago, Rincewind said:

It appears to be a double row ball race with only one spacer ring, is that correct?

 

What is the general appearance of the ball race? Shiny / rusty / discoloured? well greased? Dirty grease? does the grease feel gritty when you rub a little of it between your fingers?

 

Not sure what is going on there but the housing felt seals do not make contact with the shaft allowing grit, water and other debris to enter the bearing.  A different type of shaft seal should have been used (they are available) but installing them now would mean removing the bearing from the shaft.

 

If that ring came from the coupling side of the bearing then there is no scope for moving the shaft backwards while it is bolted down.

 

The only way that I can see to disengage the coupling is to slacken the four clamping bolts on the (brass?) coupling and slide it along the shaft.  That would be normal anyway if the flexible coupling were to fail in normal use.

Or unbolt the bearing altogether. 

 

Either way, I'm getting a bit out of my depth here, so am just going to try and re assemble it. 

 

 

Thank you for your help. 

11 minutes ago, Rincewind said:

It appears to be a double row ball race with only one spacer ring, is that correct?

 

What is the general appearance of the ball race? Shiny / rusty / discoloured? well greased? Dirty grease? does the grease feel gritty when you rub a little of it between your fingers?

 

Not sure what is going on there but the housing felt seals do not make contact with the shaft allowing grit, water and other debris to enter the bearing.  A different type of shaft seal should have been used (they are available) but installing them now would mean removing the bearing from the shaft.

 

If that ring came from the coupling side of the bearing then there is no scope for moving the shaft backwards while it is bolted down.

 

The only way that I can see to disengage the coupling is to slacken the four clamping bolts on the (brass?) coupling and slide it along the shaft.  That would be normal anyway if the flexible coupling were to fail in normal use.

Well greased, slightly dirty. Clean bearings, no grit 

[Rincewind]

Rusty,

PM'd you