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fudd

Noisy drive shaft

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Good morning. 

When I go above a slow walking pace I get a loud ringing-rumble from the prop shaft. It sounds a bit like a carwheel bearing has failed. The sound goes away completely at lower revs. It’s a trad with a hollow lorry type drive shaft with a universal joint at each end. The prop shaft is coupled to this and then goes through a split bearing housing, I believe it’s called a plummer block, and then through the stern gland. I can’t tell where the noise is coming from exactly. The sound carries on through the hollow shaft and makes it hard to tell where it’s coming from. I can’t feel any vibration anywhere. An engineer thought it could be the bearing spinning in the housing so he drilled and tapped it to take a grub screw. It hasn’t made any difference. It did look like there were scorch marks on the outer bearing. I tightened the grub screw reasonably tightly but I don’t want to distort the outer bearing ring. Could it be the stern gland?  

Thanks in advance Steve P

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New noise or old? Has it always done it? Anything been changed recently to cause this? Any groundings or impacts in reverse?

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2 minutes ago, fudd said:

Good morning. 

When I go above a slow walking pace I get a loud ringing-rumble from the prop shaft. It sounds a bit like a carwheel bearing has failed. The sound goes away completely at lower revs. It’s a trad with a hollow lorry type drive shaft with a universal joint at each end. The prop shaft is coupled to this and then goes through a split bearing housing, I believe it’s called a plummer block, and then through the stern gland. I can’t tell where the noise is coming from exactly. The sound carries on through the hollow shaft and makes it hard to tell where it’s coming from. I can’t feel any vibration anywhere. An engineer thought it could be the bearing spinning in the housing so he drilled and tapped it to take a grub screw. It hasn’t made any difference. It did look like there were scorch marks on the outer bearing. I tightened the grub screw reasonably tightly but I don’t want to distort the outer bearing ring. Could it be the stern gland?  

Thanks in advance Steve P

Oh dear, if a bearing is spinning in the housing you fit new parts, not try to bodge the old ones.

 

So three possibilities. The bearing in the thrust/plumber block and it sounds as if this may be the case, or one/both of the UJs has worn bearings, probably the spiders. It will probably be easiest to take the hollow propshaft off to test/renew the UJs, if they have four circlips in the ends they are fairly easily overhauled. If the bearing cups are retained by staking (denting the metal) then not so easy.

 

If its not that then it will be half coupling off the shaft and renew/rebearing the thrust block

 

 

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4 minutes ago, Boater Sam said:

New noise or old? Has it always done it? Anything been changed recently to cause this? Any groundings or impacts in reverse?

It did it when I got the boat 7 years ago but only at very high revs

5 minutes ago, Tony Brooks said:

Oh dear, if a bearing is spinning in the housing you fit new parts, not try to bodge the old ones.

 

So three possibilities. The bearing in the thrust/plumber block and it sounds as if this may be the case, or one/both of the UJs has worn bearings, probably the spiders. It will probably be easiest to take the hollow propshaft off to test/renew the UJs, if they have four circlips in the ends they are fairly easily overhauled. If the bearing cups are retained by staking (denting the metal) then not so easy.

 

If its not that then it will be half coupling off the shaft and renew/rebearing the thrust block

 

 

The UJs are greased a couple of times a year. There doesn’t appear to be any play or heat generated anywhere. The grub screw was a get me home mod. 

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Start at the prop and work forward. Is the prop clear? Tight? Any up and down play in the rear of the stern tube? Work forward checking for play in bearings.

 I would assume that the bearing blocks have no grease nipples. Can you get the noise with the boat tied up? if so a stethoscope ( or just a piece of pipe held to the ear ) on the bearings whilst running may narrow it down.

If all else fails take the shafts out and examine them. The plummer blocks bearings can be replaced with repair kits, you may have to change them all as finding a pitted race would involve dismantling them anyway.

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Just now, Boater Sam said:

Start at the prop and work forward. Is the prop clear? Tight? Any up and down play in the rear of the stern tube? Work forward checking for play in bearings.

 I would assume that the bearing blocks have no grease nipples. Can you get the noise with the boat tied up? if so a stethoscope ( or just a piece of pipe held to the ear ) on the bearings whilst running may narrow it down.

If all else fails take the shafts out and examine them. The plummer blocks bearings can be replaced with repair kits, you may have to change them all as finding a pitted race would involve dismantling them anyway.

I’ve checked as best I could for any play and there isn’t any. When I took the bearing housing off it was packed full of grease. Yes the noise is the same when it’s tied up. I’ll try the stethoscope and see if I can narrow it down. I’m beginning to think it’s the bearing. 

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The lorry propshaft may be out of balance a bit being as the noise is only there at a certain speed. You could try clipping a Jubilee clip or two around the shaft body, the scroll part will act as balance weights, and experimenting by moving them around to see if they either alter the noise or quieten it. A worn bearing noise would normally be present at any revs, unless engine noise masks it.

Edited by bizzard

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4 minutes ago, fudd said:

I’ve checked as best I could for any play and there isn’t any. When I took the bearing housing off it was packed full of grease. Yes the noise is the same when it’s tied up. I’ll try the stethoscope and see if I can narrow it down. I’m beginning to think it’s the bearing. 

Use a very long screwdriver, or mooring pin.

Keep your face, clothes, hair etc well away from rotating shafts.

 

Push the mooring pin 'hard' into your ear, then 'dab' and hold the other end onto the various (non-spinning) drive train components, you will not only hear the noise, but will feel the 'vibrations' transmitted up into your ear-bones. Move it around until you get to the 'peak' of the vibration / noise levels and that's the problem area.

  • Greenie 2

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I have had a thrust bearing, actually a Plummer block type being used to take axial loads as yours, show the same symptoms. Quiet at low speed but noisy above a certain load. On dismantling I found that due to slight misalignment the bearing had been locking up under load and the prop shaft then spun in the inner race, causing the noise.

Check soon or you may be looking at prop shaft replacement.

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Ok thanks everyone. I’ll do what I need to do and let you know what the problem turns out to be for future reference. 

Steve P

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I had exactly these symptoms develop when I had the Beta BD3 engine in this boat, particularly the 'ringing' noise in the cardan shaft. I did most of what has been suggested to no avail. 

 

It turned out to be the drive plate between the engine and gearbox falling to bits. Failing drive plates can cause some really weird noises and symptoms in my experience. 

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10 minutes ago, Mike the Boilerman said:

I had exactly these symptoms develop when I had the Beta BD3 engine in this boat, particularly the 'ringing' noise in the cardan shaft. I did most of what has been suggested to no avail. 

 

It turned out to be the drive plate between the engine and gearbox falling to bits. Failing drive plates can cause some really weird noises and symptoms in my experience. 

I’ve just checked for play at the gearbox end of the drive shaft. There is some play there where the shaft comes out of the box. It’s a PRM 150. When I rattled the shaft up and down there was a similar ringing sound so it could be the output shaft bearing. 

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Is the engine mounted centrally, or offset to one side? I have a similar set up with an offset engine and a long truck prop shaft arrangement running under the back cabin. I get the same rumbling noise at certain low speeds, but can usually find a sweet spot where the vibrations cancel out. I think it's a product of the engine torque reversals, backlash in the gearbox and the long unsupported prop shaft. One day I'll look at fitting CV joints, but it's been like that for years now. Two things I did that helped reduce the vibrations were to reinforce the Plummer block bearing mounting with additional plating between the base plate and the bearing support making it really solid. Also I fitted a heavy coil spring and washers inside the splined end of the shaft to put some preload on the bearings. This made most improvement. I used an old valve spring and an assortment of washers to give some end load. This is assuming your shaft is splined at one end and your Plummer block is taking the thrust. Firstly though I'd strip and clean the bearing make sure it's ok. If the outer race is thick enough, you can always fit an anti rotation peg by grinding a square notch on the corner with a thin slitting wheel and drill and tap the housing to suit for a grubscew, say M4 or M5. 

Hope this helps. 

 

 

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And if one end of the shaft UJ coupling is on sliding splines, the UJ spider joints at either end need to be aligned precisely and correctly  or the transmission will be horribly knobbly.

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I’ve checked the oil, it was a little low, I put about a quarter of a pint in. Started it up and put it in gear and I noticed the gearbox was moving about slightly. Is this normal or have I got the dreaded it’s all going wrong syndrome?

Edited by fudd

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1 hour ago, fudd said:

Started it up and put it in gear and I noticed the gearbox was moving about slightly.

 

WHAT???????!!!!!!!!!!!!

 

Moving about in what way? The whole engine/gearbox assembly can move a bit on the flexible engine mounts but the gearbox should be rock solidly attached to the engine and move with it, if anything moves at all. 

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Shouldn't there be a THRUST block in there somewhere?

A Plummer bloc is not a thrust bloc (per se)

 

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On 05/08/2018 at 13:37, Mike the Boilerman said:

 

WHAT???????!!!!!!!!!!!!

 

Moving about in what way? The whole engine/gearbox assembly can move a bit on the flexible engine mounts but the gearbox should be rock solidly attached to the engine and move with it, if anything moves at all. 

Just a little twitch, barely noticeable at all really. Maybe I’m panicking. 

On 05/08/2018 at 17:32, OldGoat said:

Shouldn't there be a THRUST block in there somewhere?

A Plummer bloc is not a thrust bloc (per se)

 

The Plummer block has got a castellated nut and tab washer. I assume there is some sort of sleeve that clamps the shaft in place. It’s been like it for 20 odd years so hopefully it’s been installed correctly. 

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On 05 August 2018 at 12:08, bizzard said:

And if one end of the shaft UJ coupling is on sliding splines, the UJ spider joints at either end need to be aligned precisely and correctly  or the transmission will be horribly knobbly.

I was going to raise this. The yokes at each end of the prop shaft must be at 90 degrees to one another or noise, vibration and bearing wear will result.

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Sounds like a taper mounted bearing. Is it a thin round ring nut with 4 slots in it and a tab washer around the shaft?  If it is, then What you are seeing is the end of the adaptor sleeve. tightening the skf ring nut draws the tapered adaptor collet through the tapered bearing bore clamping the bearing onto the parallel shaft. Once the nut is backed off the bearing can be driven off the taper with a brass drift and a big hammer. They can be really tight. 

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Hmm. As I understand it aren't the yokes supposed to be in the same plane? So up to a point one cancels out the other? I.e in phase? Got me thinking now. 

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1 minute ago, crossley said:

Hmm. As I understand it aren't the yokes supposed to be in the same plane? So up to a point one cancels out the other? I.e in phase? Got me thinking now. 

 

As I understand it the yokes each end need to appear be at the same angle of rotation as each other but when you look carefully, they are 90 degrees out of phase. So that each cancels out the change in angular velocity of the other throughout one half a rotation. 

 

Not that there any significant degree of change in angular velocity with the tiny offsets a boat propshaft is usually dealing with. But it is something people seem to like to worry about. A bit like the pattern of their battery interconnects. 

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44 minutes ago, Sir Nibble said:

I was going to raise this. The yokes at each end of the prop shaft must be at 90 degrees to one another or noise, vibration and bearing wear will result.

Should be like this.

DA6352JGS__39823.1478788732 propshaft.jpg

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Tomorrow morning I’m going to an engineer in Braunston. I’ve told him what I think the problem could be and he thinks it might be that the output shaft needs shimming. Hopefully that’s all it is. I’ll report back. Oh, I found out it’s a PRM160D not a 150. Don’t know what difference that makes though. 

Thanks everyone. 

1 minute ago, bizzard said:

Should be like this.

DA6352JGS__39823.1478788732 propshaft.jpg

Mine is just a plain 7 foot long 4” tubular shaft with Uj at either end

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