Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2021 19:35:56 GMT
DIY job, or best left to those versed in the intricacies and finer details of thinking in three dimensions whilst wielding a set of enchanted feeler gauges?
Answers on a postcard please.
|
|
|
Post by Telemachus on Oct 9, 2021 19:56:38 GMT
DIY job, or best left to those versed in the intricacies and finer details of thinking in three dimensions whilst wielding a set of enchanted feeler gauges? Answers on a postcard please. Well when I was just a baby (about 8 years ago) the advice on CWDF was that it was far too difficult and should be left to the “professionals”. So needless to say I did it myself and it was no big deal. Even though it was a new boat and the alignment was barely out, getting it spot on made a noticeable difference to vibration - which went from “not a lot” to “barely detectable”.
|
|
|
Post by TonyDunkley on Oct 9, 2021 20:34:42 GMT
DIY job, or best left to those versed in the intricacies and finer details of thinking in three dimensions whilst wielding a set of enchanted feeler gauges? That depends entirely on the level your mechanical skills, and the type of shafting, couplings and engine mountings you've got -- solid or flexible -- and the type of misalignment that you're checking for or wanting to correct -- angular, axial, or both.
|
|
|
Post by Telemachus on Oct 9, 2021 20:58:56 GMT
On ours there was a centraflex coupling, the flange of which conveniently had a kind of protrusion on one end and recess on the other. If the axial alignment is correct they just come together without any effort. So it was easy to adjust. For the angular alignment I needed feeler gauges, although eyeballing the size of the gap was probably just as effective. Like all these things, it is a trivial job made harder by (in our case) having to sprawl uncomfortably on top of the engine, head down to get to the coupling.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 10, 2021 8:05:35 GMT
I have read the notes on Tony Brooks excellent web site, and a detailed answer he gave in response to a question in canal boat magazine. Whilst it sounds complicated in theory, I was hoping that the practice might be a bit easier.
Apart from measuring the gap at the R&D type flexible coupling and inspecting the rubber engine mounts, I have done little more at this stage.
My current thinking is that if I were to mark the engine mount adjustment bolts with either a dab of paint, or a centre punch indentation, and then note any adjustment I make, at the very worst, I can align it back as it is now if I don't improve the alignment. I would then have he option to call out someone who has done it before.
|
|
|
Post by tonyb on Oct 10, 2021 8:11:45 GMT
Please note that in an ideal world, many types of flexible couplings should be removed and a dummy put in place. Not that it is done very often. This is because you can't be sure the two faces of a flexible coupling are true, and I know at least two types that can take a set. If there is a set, then it makes angular realignment difficult.
It is also important to ensure that the weight on the mount pairs (front pair, back pair) are equal or you can get the engine rocking on the diagonal.
Then there is the complication with flexible stern glands and a Cutless shaft bearing where the coupling will happily wave about radially. The shaft needs supporting in the centre of the free movement while the alignment is carried out, especially with flexible engine mounts that tend to drop over time. I have had a boat with a flexible coupling taking water where the shaft had worn through the bottom of the stern tube at one point.
None of this is meant to make it seem difficult, but it may be best to have it done for you once and watch the process like a hawk so you know what to do next time. Also allow plenty of time to do it yourself, it can be very frustratin.
|
|
|
Post by tonyb on Oct 10, 2021 8:15:16 GMT
I have read the notes on Tony Brooks excellent web site, and a detailed answer he gave in response to a question in canal boat magazine. Whilst it sounds complicated in theory, I was hoping that the practice might be a bit easier. Apart from measuring the gap at the R&D type flexible coupling and inspecting the rubber engine mounts, I have done little more at this stage. My current thinking is that if I were to mark the engine mount adjustment bolts with either a dab of paint, or a centre punch indentation, and then note any adjustment I make, at the very worst, I can align it back as it is now if I don't improve the alignment. I would then have he option to call out someone who has done it before.
The problem is that there is every chance that flexible mounts will have dropped, and probably the rear ones more than the front. If I were to do that, I think I would use a very sharp centre punch on the thread tight up against the bottom of the lower nuts.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 10, 2021 8:24:48 GMT
I have read the notes on Tony Brooks excellent web site, and a detailed answer he gave in response to a question in canal boat magazine. Whilst it sounds complicated in theory, I was hoping that the practice might be a bit easier. Apart from measuring the gap at the R&D type flexible coupling and inspecting the rubber engine mounts, I have done little more at this stage. My current thinking is that if I were to mark the engine mount adjustment bolts with either a dab of paint, or a centre punch indentation, and then note any adjustment I make, at the very worst, I can align it back as it is now if I don't improve the alignment. I would then have he option to call out someone who has done it before.
The problem is that there is every chance that flexible mounts will have dropped, and probably the rear ones more than the front. If I were to do that, I think I would use a very sharp centre punch on the thread tight up against the bottom of the lower nuts.
I don't know for sure, but visual inspection of the mounts certainly looks as if some are more compressed than others. Would you advise changing the flexible mounts prior to re-aligning it? Obviously its hard for you to say without having seen them. They have been in place, I would say for 10 years with little engine running time on them.
|
|
|
Post by peterboat on Oct 10, 2021 8:39:20 GMT
I have done this a few times recently, on my big boat and the bathtub, the results when done correctly do indeed make a difference to the smooth running. Its the ability to be able to work in 3D that counts, because altering one mount throws the others out, a little and often seemed the best for me. On the big boat lts easy as the electric motor is small and light, but when it had the diesel in it, it was more difficult climbing around it to get it right
|
|
|
Post by tonyb on Oct 10, 2021 8:41:51 GMT
The problem is that there is every chance that flexible mounts will have dropped, and probably the rear ones more than the front. If I were to do that, I think I would use a very sharp centre punch on the thread tight up against the bottom of the lower nuts.
I don't know for sure, but visual inspection of the mounts certainly looks as if some are more compressed than others. Would you advise changing the flexible mounts prior to re-aligning it? Obviously its hard for you to say without having seen them. They have been in place, I would say for 10 years with little engine running time on them.
They will compress to a degree just by engine weight, so it is hard to give an answer. The problem will come when either the radial misalignment causes so much vibration you need to do something, or metal parts below the rubber in the coupling hit the bed and cause noise and vibration.
I think that as long as there is no signs of oils degrading the rubber, I would just try realigning and see how it goes.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 10, 2021 8:45:38 GMT
I have done this a few times recently, on my big boat and the bathtub, the results when done correctly do indeed make a difference to the smooth running. Its the ability to be able to work in 3D that counts, because altering one mount throws the others out, a little and often seemed the best for me. On the big boat lts easy as the electric motor is small and light, but when it had the diesel in it, it was more difficult climbing around it to get it right As Tony B says, its sounds like it could be a frustrating process. I am torn between having a go, and just giving the job to someone else. Access isn't particularly good, and my knees aren't getting any younger.
|
|
|
Post by tonyb on Oct 10, 2021 8:50:35 GMT
Mark the studs, as discussed and have a go, you can't make it worse as long as you set everything back to the marks if you have to. You can also keep note of the flats you turn each bottom nut and which way, so that will help you put it back if needed. At least with that type of mount, you will not be trying to lever the engine feet up!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 10, 2021 8:51:02 GMT
I don't know for sure, but visual inspection of the mounts certainly looks as if some are more compressed than others. Would you advise changing the flexible mounts prior to re-aligning it? Obviously its hard for you to say without having seen them. They have been in place, I would say for 10 years with little engine running time on them.
They will compress to a degree just by engine weight, so it is hard to give an answer. The problem will come when either the radial misalignment causes so much vibration you need to do something, or metal parts below the rubber in the coupling hit the bed and cause noise and vibration.
I think that as long as there is no signs of oils degrading the rubber, I would just try realigning and see how it goes.
Thanks Tony. One last question. I have made the massive assumption that it is in fact the shaft misaligned, somewhat confirmed by the measurement made on the coupling, though the coupling may have been distorted. However to help diagnose the problem, I noticed that whilst I ran the engine in both forward and reverse gear,the vibration is definitely noticeable in forward gear, but increasing the revs reduces it to almost zero. There is barely any vibration when in reverse gear. So, could it be that the shaft itself is bent, or bent and misaligned. Again, I know its a hard question to answer without actually seeing it. Thanks
|
|
|
Post by Telemachus on Oct 10, 2021 8:51:10 GMT
I have done this a few times recently, on my big boat and the bathtub, the results when done correctly do indeed make a difference to the smooth running. Its the ability to be able to work in 3D that counts, because altering one mount throws the others out, a little and often seemed the best for me. On the big boat lts easy as the electric motor is small and light, but when it had the diesel in it, it was more difficult climbing around it to get it right As Tony B says, its sounds like it could be a frustrating process. I am torn between having a go, and just giving the job to someone else. Access isn't particularly good, and my knees aren't getting any younger. If you give the job to someone else, how will you determine whether they are going to be better at the job than you would be? Time is a big factor when getting a job done professionally. One advantage of DIY maintenance is that time is much less of an issue, so more time can be spent getting it right.
|
|
|
Post by Telemachus on Oct 10, 2021 8:53:14 GMT
They will compress to a degree just by engine weight, so it is hard to give an answer. The problem will come when either the radial misalignment causes so much vibration you need to do something, or metal parts below the rubber in the coupling hit the bed and cause noise and vibration.
I think that as long as there is no signs of oils degrading the rubber, I would just try realigning and see how it goes.
Thanks Tony. One last question. I have made the massive assumption that it is in fact the shaft misaligned, somewhat confirmed by the measurement made on the coupling, though the coupling may have been distorted. However to help diagnose the problem, I noticed that whilst I ran the engine in both forward and reverse gear,the vibration is definitely noticeable in forward gear, but increasing the revs reduces it to almost zero. There is barely any vibration when in reverse gear. So, could it be that the shaft itself is bent, or bent and misaligned. Again, I know its a hard question to answer without actually seeing it. Thanks If you just disconnect at the gearbox flange, it will be pretty obvious straight away if there is significant misalignment. You can always reconnect again without doing any adjustment if you think it’s too difficult. But you will know whether or not there is an alignment issue vs a mounting or drive plate problem.
|
|