Engine to prop shaft aligment

[nicknorman]

New(ish) boat with Beta 43 (rubbery mounts) and Centaflex coupling, now 1 year and 500 hrs old. I think I should check the engine alignment since it seems quite easy to adjust (threaded rod for height and slots in mounts for lateral) and whilst it is very smooth at canal speeds, it was perhaps a bit rumbly at river severn speeds. However, I have never done this before so any tips would be useful please...

 

I believe I need to temporarily remove the centaflex coupling and replace it with something solid - Somebody mentioned a "half coupling" - what is that, where would I get it and how do I do it?

 

Do I check the alignment at the the flange that is right at the exit from the gearbox (by unbolting and separating slightly said flange)?

 

Is any allowance made to optimise alignment for when engine is driving (presumably having moved slightly on its rubber mounts) or is it always done to optimise alignment with no drive torque applied? (not sure how one would align it under torque, just wondered...)

 

TIA

 

nick

[rjasmith]

New(ish) boat with Beta 43 (rubbery mounts) and Centaflex coupling, now 1 year and 500 hrs old. I think I should check the engine alignment since it seems quite easy to adjust (threaded rod for height and slots in mounts for lateral) and whilst it is very smooth at canal speeds, it was perhaps a bit rumbly at river severn speeds. However, I have never done this before so any tips would be useful please...

 

I believe I need to temporarily remove the centaflex coupling and replace it with something solid - Somebody mentioned a "half coupling" - what is that, where would I get it and how do I do it?

 

Do I check the alignment at the the flange that is right at the exit from the gearbox (by unbolting and separating slightly said flange)?

 

Is any allowance made to optimise alignment for when engine is driving (presumably having moved slightly on its rubber mounts) or is it always done to optimise alignment with no drive torque applied? (not sure how one would align it under torque, just wondered...)

 

TIA

 

nick

 

Nick,

 

I would have a look at Tony Brooks training website here (unless you have already done this). It gives a good basic description of the alignment process and is probably more relevant than me giving a description of how I went about aligning a ten foot long solid shaft through three pillow blocks and two sets of half couplings with a 1.5 ton Kelvin engine at the far end!

 

I was a beginner then - I probably still am but seemingly millions of shims later (no adjustable mountings in my case!) it all seems to be about right.

 

Richard

[BEngo]

New(ish) boat with Beta 43 (rubbery mounts) and Centaflex coupling, now 1 year and 500 hrs old. I think I should check the engine alignment since it seems quite easy to adjust (threaded rod for height and slots in mounts for lateral) and whilst it is very smooth at canal speeds, it was perhaps a bit rumbly at river severn speeds. However, I have never done this before so any tips would be useful please...

 

I believe I need to temporarily remove the centaflex coupling and replace it with something solid - Somebody mentioned a "half coupling" - what is that, where would I get it and how do I do it?

 

Do I check the alignment at the the flange that is right at the exit from the gearbox (by unbolting and separating slightly said flange)?

 

Is any allowance made to optimise alignment for when engine is driving (presumably having moved slightly on its rubber mounts) or is it always done to optimise alignment with no drive torque applied? (not sure how one would align it under torque, just wondered...)

 

TIA

 

nick

 

Regardless of the apparent ease of adjustment, aligning an engine is harder than it looks, unless you think well in 3D. The centaflex is there to absorb any misalignment so unless its miles out you probably don't need to do anything with the alignment.

 

That said, if you REALLY want to...

 

You should adjust so that the centreline of the engine output is an extension of the centreline of the shaft. There are three things that are important:

 

The centre of the engine output flange must be in line with the centre of the shaft

The centre line of the engine (or gearbox if its not the same C/L as the engine) must be parallel to the centre line of the shaft in both the vertical plane and the horizontal plane.

 

Remove the centaflex and get to a bare shaft from the prop. Check that the shaft is still a good fit in the stern bearing - not loose. Otherwise you are wasting your time.

 

Check that the flange on the engine/ g'box is at right angles to the shaft both vertically and horizontally- Use an engineers square on the output flange with the blade along the shaft. Move the engine around to suit.

 

Next check that the centre of the shaft coincides with the centre of the engine/ g'box output. The easiest way to do that is by clamping a dial indicator to the engine/g'box output flange and rotating it around the shaft, adjusting the engine position so that the needle on the dial does not move as the engine output coupling is rotated. If you don't have a dial indicator then you need to put a half coupling on the shaft. A half coupling is a bit like the flange on the engine output, but with a hole and clamp bolts to fit onto a shaft. Put this on the shaft and bring it up close to the engine. Measure the distance from the edge of the half coupling to the edge of the output flange top, bottom, left and right. Adjust the engine position to make it the same all round. You want to get it less than 0.010 inches ideally, so you need an accurate measuring device. A vernier depth gauge or micrometer depth gauge is ideal. When you have sorted out the centreline alignement repeat the squareness test.

 

Keep trying until the engine passes both tests without adjustments. Think hard about what effect any adjustments to one alignment will have on the other alignment, or you will end up chasing your tail. Try to keep the mountings all in roughly the same state as far as adjustments go- you don't want one side fully up and the other side fully down, for example.

 

If you have a long (Over 3ft) solid prop shaft from the stern tube to the centaflex then you need to account for any droop, which can be calculated.

 

Once you have done refit the centaflex and bolt it all up tight without disturbing the adjustments. Put some paint or tippex on the engine mounting nuts/ bolts so you can see if they move in future.

 

You can't just separate the gearbox connection flanges and check they are aligned because the centaflex will move to accommodate any misalignment.

 

 

You also can't do anything about the engine moving when under load- that's what the centaflex is for, and one reason why you want the mountings all about the same degree adjusted.

 

N

 

Edit for spilling

Edited April 14, 2012 by BEngo

[nicknorman]

Thanks guys. I have looked at the excellent TB website and have the general idea, it is the specifics I am not so sure of.

 

I like the idea of the dial gauge on the gearbox flange rotating around the shaft to check for parallel offset!

 

On the half coupling, I don't quite understand what to do: Currently there is a Centaflex which is inserted in the prop shaft - ie I presume the prop shaft is in 2 pieces with a short bit between the centaflex and the gearbox flange? So if I remove the Centaflex which I clearly have to do, the remaining bit of prop shaft, although having some fore/aft movement, would surely not be able to be pulled sufficiently far towards the engine to get near the gearbox flange (without removing the prop). I rather presumed that a half coupling would be something that would replace the centaflex but be rigid, allowing the two sections of prop shaft to be rigidly connected so that the existing two halves of the gearbox flange can be separated just enough to measure all round with feeler gauges, parallel offset detected etc. Perhaps the thing I am thinking of has another name? Or am I totally off the mark?

 

I am quite keen to check the alignment because people are telling me that the rubber mounts can "settle" early in their life, with the whole engine sinking a bit. I would rather check it now than wear out the shaft etc later.

 

ETA could the thing I am thinking of be something that is attached to the shaft and one remaining half of the centaflex so as to make the whole coupling rigid?

Edited April 14, 2012 by nicknorman

[koukouvagia]

Regardless of the apparent ease of adjustment, aligning an engine is harder than it looks.

You can say that again. When I had the Kelvin fitted, the so-called engineer who did it managed to misalign the engine in two planes. To cut a very long story short, it took a real engineer, who knew what he was doing, the best part of a week to do the job properly. I'd never dream of tackling that myself – admittedly, the K2 is a bit of a lump to manoeuvre into the correct position.

[nicknorman]

You can say that again. When I had the Kelvin fitted, the so-called engineer who did it managed to misalign the engine in two planes. To cut a very long story short, it took a real engineer, who knew what he was doing, the best part of a week to do the job properly. I'd never dream of tackling that myself – admittedly, the K2 is a bit of a lump to manoeuvre into the correct position.

I can totally see that with something like your engine, presumably shimmed etc, mounted on wood, it would be a work of art. However the Beta mounts do look easy to adjust - slacked the locknuts and wind the engine mounts up and down, slacken the bolts holding feet to the bearers and move in an arc in the slots. So moving it I think will be fairly easy, moving it into the correct position will only be easy if I have a good way to measure what is the correct position!

 

Obviously your "real" Kelvin engineer took a lot of time and trouble, but for me I tend to think along the lines that the "not so real" engineer of the type I seem to find, will be thinking more about the time than me (to whom time is free) and so might settle for a less precise final position. Or to put it another way, these days I struggle to trust an engineer that I don't know very well, and I don't know any in the vicinity of our boat. In any case, it is all part of the learning curve that is boat ownership!

[Bobbybass]

I will say this...(only once..in the words of 'Ello 'Ello)

 

Just get it about right...

and then enjoy life...

 

If you spend your life worrying 'like others on here do'

' Dial guaging'......thickness guaging...etc...forever...

get it rough...it WILL do !!

 

Then....go...and get on with it...!!!

[nicknorman]

I will say this...(only once..in the words of 'Ello 'Ello)

 

Just get it about right...

and then enjoy life...

 

If you spend your life worrying 'like others on here do'

' Dial guaging'......thickness guaging...etc...forever...

get it rough...it WILL do !!

 

Then....go...and get on with it...!!!

What about worrying about painting whilst wearing one's Jimmy Savile fancy dress getup?

[RLWP]

Lots of potential for getting that job wrong. Go boating instead

 

Richard

[nicknorman]

Lots of potential for getting that job wrong. Go boating instead

 

Richard

Sorry Richard, I am just not that kind of guy! At the very least I want to see if/how far out it is, even if I don't adjust it.

[system 4-50]

I don't understand why there is so little support for such a complex task.

When the engine was first installed it was presumably set up right.

So there should be some way of telling whether the engine has moved since that time.

The obvious way it seems to me would be to have a reference mounting on the engine block for a laser pointer in all 3 planes and mark the engine bay walls or equivalent with circles to show where it is.

Then it would be easy to check for drift.

Also it would be easier to check the degree of wobble whilst running.

OK it wouldn't solve everything eg gearbox changes but surely(!) it would be

1) useful

2) easy to implement

How say you?

Edited April 14, 2012 by system 4-50

[cereal tiller]

New(ish) boat with Beta 43 (rubbery mounts) and Centaflex coupling, now 1 year and 500 hrs old. I think I should check the engine alignment since it seems quite easy to adjust (threaded rod for height and slots in mounts for lateral) and whilst it is very smooth at canal speeds, it was perhaps a bit rumbly at river severn speeds. However, I have never done this before so any tips would be useful please...

 

I believe I need to temporarily remove the centaflex coupling and replace it with something solid - Somebody mentioned a "half coupling" - what is that, where would I get it and how do I do it?

 

Do I check the alignment at the the flange that is right at the exit from the gearbox (by unbolting and separating slightly said flange)?

 

Is any allowance made to optimise alignment for when engine is driving (presumably having moved slightly on its rubber mounts) or is it always done to optimise alignment with no drive torque applied? (not sure how one would align it under torque, just wondered...)

 

TIA

 

nick

Hi nick

if your engine is ok at canal speeds,it may that your propeller is AERATING when the boat is running at river speeds.

 

my boat runs smoothly up to 2200 rpm,beyond those revs the prop. will rumble as is draws in air.

 

you should only be concerned if the 'rivets'on the hull start loosening.

[RLWP]

So, how much have the flexible mountings relaxed then? Nobody knows. Have the mounts all relaxed by the same amount? Nobody knows. What height was anything set to? Nobody knows.

 

Richard

 

Can you measure a laser beam to a mark on a hull to less than 0.010"?*

 

 

 

*No

[system 4-50]

So, how much have the flexible mountings relaxed then? Nobody knows. Have the mounts all relaxed by the same amount? Nobody knows. What height was anything set to? Nobody knows.

 

Richard

 

Can you measure a laser beam to a mark on a hull to less than 0.010"?*

 

 

 

*No

I'm ignorant so please be patient. Are you saying that a drop of 10 thou at the forward mountings is enough to cause a problem? If so, how much of a nut turn is that? 1 flat? A tenth of a flat?

[nicknorman]

Hi nick

if your engine is ok at canal speeds,it may that your propeller is AERATING when the boat is running at river speeds.

 

my boat runs smoothly up to 2200 rpm,beyond those revs the prop. will rumble as is draws in air.

 

you should only be concerned if the 'rivets'on the hull start loosening.

Yes it could be aerating, although the stern sinks pretty low in the water with that much power on. The other thing I haven't mentioned is the need to adjust the stern gland packing twice now in 500 hrs (though only by a flat or so) and that occasionally the prop shaft makes a bit of a screeching noise - which is barely audible on the counter, but can be heard inside. Winding the greaser on some more seems to fix it, although I always grease at the end of the day.

 

Wow, if the rivets start loosening the boat might sink.....Oh well, maybe not!

 

I'm ignorant so please be patient. Are you saying that a drop of 10 thou at the forward mountings is enough to cause a problem? If so, how much of a nut turn is that? 1 flat? A tenth of a flat?

If you think of the clearance between the prop shaft and the stern tube / bearing, 10 thou is quite a bit. Although the Centaflex takes up a bit of misalignment, it is not like a pythondrive etc with double UJ and anyway the compression of the rubber in the centaflex will put unnecessary side load on the prop shaft / tube / stern bearing.

 

I think Beta have designed the engine mounts to be quite easy to adjust but it would be difficult to mark up the engine position to the required accuracy for future reference.

 

So, how much have the flexible mountings relaxed then? Nobody knows. Have the mounts all relaxed by the same amount? Nobody knows.

That is what I want to find out!

[Keeping Up]

<snip> The other thing I haven't mentioned is the need to adjust the stern gland packing twice now in 500 hrs (though only by a flat or so) <snip>

 

That doesn't sound at all unusual to me. I reckon to have to do twice as much adjustment as that, at least twice in 500 hours - although admittedly the shaft and bearing have been together now for about 10,000 hours

[nicknorman]

That doesn't sound at all unusual to me. I reckon to have to do twice as much adjustment as that, at least twice in 500 hours - although admittedly the shaft and bearing have been together now for about 10,000 hours

Well that is good to know thanks, but did you have to adjust it that much when it was new (or newer)?

[Keeping Up]

I'd say it was about the same as you are doing now when it was fairly new, so it's now four times as frequent as it was. Another feature is it depends what has been used for the packing material, mine needed less packing when I started using neoprene instead of the original

[nicknorman]

I'd say it was about the same as you are doing now when it was fairly new, so it's now four times as frequent as it was. Another feature is it depends what has been used for the packing material, mine needed less packing when I started using neoprene instead of the original

Thanks

[Chris Pink]

I don't know what all the teeth sucking is about. I've recently aligned an engine on a 10 foot shaft and it was easy. The interesting thing is that what we thought by eye matched what we measured.

 

However...

 

The measurements were made 8 foot from the engine so any change was enormously amplified by the length.

 

How long is your shaft?

 

And is there anywhere near the stern gland you can measure. The further from the engine the easier it to measure.

 

...I'm writing this and I've just remembered i'm on the Op's ignore list so I'll stop trying to be helpful. Idiot.

[RLWP]

I don't know what all the teeth sucking is about. I've recently aligned an engine on a 10 foot shaft and it was easy. The interesting thing is that what we thought by eye matched what we measured.

 

However...

 

The measurements were made 8 foot from the engine so any change was enormously amplified by the length.

 

How long is your shaft?

 

And is there anywhere near the stern gland you can measure. The further from the engine the easier it to measure.

 

...I'm writing this and I've just remembered i'm on the Op's ignore list so I'll stop trying to be helpful. Idiot.

 

That's a shame Chris

 

Richard

[Eeyore]

New(ish) boat with Beta 43 (rubbery mounts) and Centaflex coupling, now 1 year and 500 hrs old. I think I should check the engine alignment since it seems quite easy to adjust (threaded rod for height and slots in mounts for lateral) and whilst it is very smooth at canal speeds, it was perhaps a bit rumbly at river severn speeds. However, I have never done this before so any tips would be useful please...

 

I believe I need to temporarily remove the centaflex coupling and replace it with something solid - Somebody mentioned a "half coupling" - what is that, where would I get it and how do I do it?

 

Do I check the alignment at the the flange that is right at the exit from the gearbox (by unbolting and separating slightly said flange)?

 

Is any allowance made to optimise alignment for when engine is driving (presumably having moved slightly on its rubber mounts) or is it always done to optimise alignment with no drive torque applied? (not sure how one would align it under torque, just wondered...)

 

TIA

 

nick

Enters lions den with some trepidation

You could just check that the shaft is passing centraly though the follower on the stern gland.

Use a small flat bladed screwdriver as a primitive taper gauge, it will go in betwwen the shaft and follower to the same depth all the way round the shaft if it is the centre. If its central its probably ok; touching is bad and definetly needs attention.

The noise you mention suggests to me that the gland follower may have been tightened down too much? Are you using the method in Tonys (TB Training) notes.

Steve

[bizzard]

About a month ago i went out to a boat that had lost its drive. The owner had sometime before stuffed ''forced''3/4''packing into his 5/16''stern tubes gland,it was obviously far to tight so couldn't get much if any grease,seized the shaft up suddenly solid causing the engine to gearbox drive-plate to sheer all its drive splines. It took me 3hours just to get the shaft free.

[nicknorman]

Enters lions den with some trepidation

You could just check that the shaft is passing centraly though the follower on the stern gland.

Use a small flat bladed screwdriver as a primitive taper gauge, it will go in betwwen the shaft and follower to the same depth all the way round the shaft if it is the centre. If its central its probably ok; touching is bad and definetly needs attention.

The noise you mention suggests to me that the gland follower may have been tightened down too much? Are you using the method in Tonys (TB Training) notes.

Steve

Hi Steve

 

The trick you mention with a screwdriver might show something, however it assumes that the follower (I presume you mean the bit that is pulled down by the nuts) is correctly aligned, that would require the studs to be perfectly straight and the holes the studs go into to be perfectly aligned. That might or might not be the case so I think I would prefer to decouple and check the clearances in the normal way.

 

The prop is totally free to turn - the first time I adjusted it, it was still seemingly as free to turn as ever but the stern tube became quite warm to the touch so I backed it off a fraction - still seemed just as free to turn but now runs cool.

[bizzard]

Hi Steve

 

The trick you mention with a screwdriver might show something, however it assumes that the follower (I presume you mean the bit that is pulled down by the nuts) is correctly aligned, that would require the studs to be perfectly straight and the holes the studs go into to be perfectly aligned. That might or might not be the case so I think I would prefer to decouple and check the clearances in the normal way.

 

The prop is totally free to turn - the first time I adjusted it, it was still seemingly as free to turn as ever but the stern tube became quite warm to the touch so I backed it off a fraction - still seemed just as free to turn but now runs cool.

To adjust the grease pusher precisely you can use the internal width gauge part of a 'Vernier' between either side, between tube flange and pusher flange,just by the sides where the studs pass through.

Or internal calipers of course.

Edited April 14, 2012 by bizzard