Engine to prop shaft aligment

[nicknorman]

A Practical Guide To Shaft Alighment (pdf)

 

Any good?

 

cheers,

Pete.

Yes that looks interesting thanks. As luck has it I have just finished my current ebook and nothing else on the iPad to read, so this will make excellent bedtime reading. For several nights.

[WotEver]

http://www.youtube.com/watch?v=dHenV6qzX_M

So... what we gonna do then?

 

I dunno... what you wanna do?

[blackrose]

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...!!!

 

That advice is all fine if you really don't like tinkering and messing about with things, but it fails to recognise that for some people learning about their boat, making adjustments and their getting their hands dirty is all part of the fun. They are already getting on with it and enjoying life before they've even untied any ropes.

 

Anyway, I have a R&D flexible coupling and just check the alignment in 4 places turning the shaft 90 degrees each time and making sure there's no more than 0.25mm difference between the 4 measurements. Is that sufficient?

[RLWP]

That advice is all fine if you really don't like tinkering and messing about with things, but it fails to recognise that for some people learning about their boat, making adjustments and their getting their hands dirty is all part of the fun. They are already getting on with it and enjoying life before they've even untied any ropes.

 

Anyway, I have a R&D flexible coupling and just check the alignment in 4 places turning the shaft 90 degrees each time and making sure there's no more than 0.25mm difference between the 4 measurements. Is that sufficient?

 

Dunno. What does the specification document for the R&D coupling say?

 

Richard

[RobinJ]

Anyway, I have a R&D flexible coupling and just check the alignment in 4 places turning the shaft 90 degrees each time and making sure there's no more than 0.25mm difference between the 4 measurements. Is that sufficient?

I think R&D used to say between 8 and 12 thou, probably depending on the size of the coupling?

[RLWP]

As 1mm is approximately 0.040", sounds OK then.

 

Anyone got access to the datasheet so Mike can check?

 

Richard

Edited April 18, 2012 by RLWP

[RobinJ]

As 1mm is approximately 0.040", sounds OK then.

 

Anyone got access to the datasheet so Mike can check?

R&D

Any Good?

[nicknorman]

That advice is all fine if you really don't like tinkering and messing about with things, but it fails to recognise that for some people learning about their boat, making adjustments and their getting their hands dirty is all part of the fun. They are already getting on with it and enjoying life before they've even untied any ropes.

Thank you for that, at least there is someone out there on my wavelength! You would think that on a forum entitled "boat building and maintenance" that we wouldn't be in the minority! Oh and you get a greenie!

Edited April 18, 2012 by nicknorman

[RLWP]

R&D

Any Good?

 

Page 4:

 

4. If the gap is the same in all four positions, the engine is accurately aligned. Recommended

minimum to maximum gap difference: 0.25 mm / 0.010 inch.

 

Spot on then

 

Richard

 

<snip>

 

However, I have never done this before so any tips would be useful please...

 

<snip>

 

TIA

 

nick

 

 

Thank you for that, at least there is someone out there on my wavelength! You would think that on a forum entitled "boat building and maintenance" that we wouldn't be in the minority! Oh and you get a greenie!

 

Next time, when asking for tips, please consider accepting them graciously, even if you don't want to hear or act on them.

 

Richard

[nicknorman]

 

Next time, when asking for tips, please consider accepting them graciously, even if you don't want to hear or act on them.

 

Richard

 

As I asked, I wanted tips on how to do the job, not tips on whether to tackle the job since I had already decided to do it. The only tip you gave me was to not do it, plus in post #59 a list of what might be required, which was useful thanks since it confirmed pretty much what I thought. Anyway, I don't think I was that ungracious, just politely declined to agree. It would be rather difficult to say thanks for your advice I will follow it, and then expect the debate to continue with tips on how to actually do the job.

 

In future I will try to feign more gratitude for that which I didn't ask for (sounds like that knitted pullover Christmas present!) so to help me perhaps you could point me to the posts in question where I was insufficiently gracious? (without taking a phrase out of context please!). Is it just post #83?

 

I am driving down to the boat in the next few days to tinker (flights are too expensive for a last minute job) so fairly soon, one of us will be able to say to the other "told you so"!

Edited April 18, 2012 by nicknorman

[blackrose]

Dunno. What does the specification document for the R&D coupling say?

 

Richard

 

0.25mm

 

I only installed the coupling recently and was just wondering if that's all I need to do from now on?

Edited April 21, 2012 by blackrose

[RLWP]

0.25mm

 

I only installed the coupling recently and was just wondering if that's all I need to do from now on?

 

From the document, it seems that it is.

 

Richard

[Chris Pink]

As I asked, I wanted tips on how to do the job, not tips on whether to tackle the job since I had already decided to do it. The only tip you gave me was to not do it, plus in post #59 a list of what might be required, which was useful thanks since it confirmed pretty much what I thought. Anyway, I don't think I was that ungracious, just politely declined to agree. It would be rather difficult to say thanks for your advice I will follow it, and then expect the debate to continue with tips on how to actually do the job.

 

In future I will try to feign more gratitude for that which I didn't ask for (sounds like that knitted pullover Christmas present!) so to help me perhaps you could point me to the posts in question where I was insufficiently gracious? (without taking a phrase out of context please!). Is it just post #83?

 

I am driving down to the boat in the next few days to tinker (flights are too expensive for a last minute job) so fairly soon, one of us will be able to say to the other "told you so"!

 

I think it entirely to this forum's credit that one can be as obnoxious as this and still people offer their expertise and advice.

[nicknorman]

So, yesterday removed the centaflex to gbx flange bolts, slackened off all the sliding mounting bolts and the vertical adjuster top nuts. Access a bit of a fiddle but not too bad.

With flange bolts undone it was immediately obvious that, whilst the lateral and vertical parallel alignment was spot on, and angular alignment in both lateral and vertical axes was visually out - ie can see noticable daylight on one side of the flange joint, none on the other. Maybe 0.4mm but it is only a small flange. Clearance remains in the same absolute location regardless of rotating shaft. I suppose the centaflex and the flexi engine mounts can take angular error quite well (must be able to, since it is well out) however it seems sensible to bring it in as close as possible, so I adjusted the lateral position by quite a lot at the front of the engine - in fact it is now fully over in the slots - and by a small amount at the back so as to maintain the lateral parallel alignment. Ditto for the vertical - it had to be raised a fair bit at the front and just slightly at the back. Because there was no parallel offset I don't think the mounts have drooped, just that this aligment was considered "adequate" when the engine was installed by the professionals.

 

A quick cruise to check the alignment on the move was carried out. I found that provided my ear defenders were well fitted, the screeching noise was quite tolerable, and although initially the smoke from the stern bearing made it difficult to see where I was going, fortunately after a bend in the canal the wind became a crosswind thus blowing the smoke out to the side and clear vision was restored.

 

OK maybe not!

 

This job is quite simple, though like any other boat job always takes longer than one could imagine, mainly due to access. I am sure other types of mounting can be a lot harder, such as when shimming is required, but the Beta flexi mounts are a doddle to adjust. So to those who vigorously tried to dissuade me from doing this job, I suggest that you should try doing it yourself to see that it is not rocket science.

 

To those that gave words of encouragment and useful advice, Thank You.

Edited April 21, 2012 by nicknorman

[bizzard]

So, yesterday removed the centaflex to gbx flange bolts, slackened off all the sliding mounting bolts and the vertical adjuster top nuts. Access a bit of a fiddle but not too bad.

With flange bolts undone it was immediately obvious that, whilst the lateral and vertical parallel alignment was spot on, and angular alignment in both lateral and vertical axes was visually out - ie can see noticable daylight on one side of the flange joint, none on the other. Maybe 0.4mm but it is only a small flange. Clearance remains in the same absolute location regardless of rotating shaft. I suppose the centaflex and the flexi engine mounts can take angular error quite well (must be able to, since it is well out) however it seems sensible to bring it in as close as possible, so I adjusted the lateral position by quite a lot at the front of the engine - in fact it is now fully over in the slots - and by a small amount at the back so as to maintain the lateral parallel alignment. Ditto for the vertical - it had to be raised a fair bit at the front and just slightly at the back. Because there was no parallel offset I don't think the mounts have drooped, just that this aligment was considered "adequate" when the engine was installed by the professionals.

 

A quick cruise to check the alignment on the move was carried out. I found that provided my ear defenders were well fitted, the screeching noise was quite tolerable, and although initially the smoke from the stern bearing made it difficult to see where I was going, fortunately after a bend in the canal the wind became a crosswind thus blowing the smoke out to the side and clear vision was restored.

 

OK maybe not!

 

This job is quite simple, though like any other boat job always takes longer than one could imagine, mainly due to access. I am sure other types of mounting can be a lot harder, such as when shimming is required, but the Beta flexi mounts are a doddle to adjust. So to those who vigorously tried to dissuade me from doing this job, I suggest that you should try doing it yourself to see that it is not rocket science. Or maybe you are in the pay of marine engineers who would prefer to keep a sense of mysticism around this job so that unsuspecting DIYers will feel the need to pay them? To those that gave words of encouragment and useful advice, Thank You.

So now the only future adjustment required should only be to raise the engine slightly if and when the rubber mounts sink.The other angles should not or hardly alter now.

Now you've got the alignment correct i would as i suggested earlier and do the caliper measurement carefully under all four mounts and note them down. Then in future if the mounts sink a little just slacken top nuts and raise the which ever or all the mounts to compensate and bring them back up to the noted down figure. This will save going through the whole performance again.And i'd keep a check on the tightness of the G/box flange to Centaflex bolts as i've often found them lose.

[nicknorman]

So now the only future adjustment required should only be to raise the engine slightly if and when the rubber mounts sink.The other angles should not or hardly alter now.

Now you've got the alignment correct i would as i suggested earlier and do the caliper measurement carefully under all four mounts and note them down. Then in future if the mounts sink a little just slacken top nuts and raise the which ever or all the mounts to compensate and bring them back up to the noted down figure. This will save going through the whole performance again.And i'd keep a check on the tightness of the G/box flange to Centaflex bolts as i've often found them lose.

Thanks Biz I will do just that. The gbx to centaflex bolts have quite stiff spring washers, plus they were obviously chemically threadlocked so I shall add some threadlock when I refit and hopefully they will not come loose. However I will check from time to time since if a bolt did wind itself out, it would come into contact with the gearbox casing which could be a disaster!

 

Having read the manual (after doing the job of course!), Beta mention that the engine should not be mounted too high on the studs to keep vibration to a min and mount life to a max. In my case, the rear mounts are fairly well up, in fact the top of the studs is protruding through the nut only a little more than the flat bit of the stud. I am not sure how much of an issue this is, but perhaps for a later project I might consider adding packing under the mount as the manual suggests. So picking up on a point you made earlier, whilst I have maintained the evenness of load on the mounts by being careful to adjust each pair identically, if I remove a mount (and looks as though that could be done one at a time with engine supported on remaining 3 mounts) how do I re-establish a matched load on each pair of mounts?

[bizzard]

Thanks Biz I will do just that. The gbx to centaflex bolts have quite stiff spring washers, plus they were obviously chemically threadlocked so I shall add some threadlock when I refit and hopefully they will not come loose. However I will check from time to time since if a bolt did wind itself out, it would come into contact with the gearbox casing which could be a disaster!

 

Having read the manual (after doing the job of course!), Beta mention that the engine should not be mounted too high on the studs to keep vibration to a min and mount life to a max. In my case, the rear mounts are fairly well up, in fact the top of the studs is protruding through the nut only a little more than the flat bit of the stud. I am not sure how much of an issue this is, but perhaps for a later project I might consider adding packing under the mount as the manual suggests. So picking up on a point you made earlier, whilst I have maintained the evenness of load on the mounts by being careful to adjust each pair identically, if I remove a mount (and looks as though that could be done one at a time with engine supported on remaining 3 mounts) how do I re-establish a matched load on each pair of mounts?

To place packing under them i presume.Uncouple g/box flange from Centaflex. I'd do two at a time,with a hoist or jack in the tray to hold the engine and box up.The two rears first say.place the packing under the two mounts and then do the same to the front ones.Then back off the top adjusting nuts and then wind down the four underneath nuts equally,by counting all the turns or spanner flats precisely until realigned with the Centaflex and then just very minor tweaks to get them bang on.

[nicknorman]

To place packing under them i presume.Uncouple g/box flange from Centaflex. I'd do two at a time,with a hoist or jack in the tray to hold the engine and box up.The two rears first say.place the packing under the two mounts and then do the same to the front ones.Then back off the top adjusting nuts and then wind down the four underneath nuts equally,by counting all the turns or spanner flats precisely until realigned with the Centaflex and then just very minor tweaks to get them bang on.

Thanks but trouble is I don't have a hoist or suitable jack down at the boat. Whilst I can see that your way is the best way, do you think it is unfeasible to do it by replacing 1 mount at a time? I take it there is no easy way to determine the load on each mount - although it must have been set up in the first place. Or maybe it was done as accurately as the angular alignment was!

[Eeyore]

Having read the manual (after doing the job of course!), Beta mention that the engine should not be mounted too high on the studs to keep vibration to a min and mount life to a max. In my case, the rear mounts are fairly well up, in fact the top of the studs is protruding through the nut only a little more than the flat bit of the stud. I am not sure how much of an issue this is, but perhaps for a later project I might consider adding packing under the mount as the manual suggests. So picking up on a point you made earlier, whilst I have maintained the evenness of load on the mounts by being careful to adjust each pair identically, if I remove a mount (and looks as though that could be done one at a time with engine supported on remaining 3 mounts) how do I re-establish a matched load on each pair of mounts?

Hello Nick

You mentioned in an earlier post that the engine moved a lot when placed in gear, and you've found the answer.

The Beta 43 is usualy a fabulously smooth engine when instaled correctly; I think you already know the meaning of "profesional" in the context of your engine.

The static wieght bearing capacity of the mounts is largely unaffected by the height of the engine, but the longditudinal and transverse dynamic capacity is hugely compromised. Just look at the length of the adjuster below the nut and compare that to the depth of rubber it is effectively sitting in.

And finaly getting to the point:

a few days ago a bag containing four mounts appeared next to my desk at work; they all had approx 2" of adjuster left in them - they had all sheared off below the adjusted nut. There was evidece of bending on at least one, and a comment about minor prop damage. The engine was of similar wieght and power output to yours.

Worth thinking about?

Steve

Edited April 22, 2012 by Eeyore

[smileypete]

If you fancy a little project, why not monitor engine vibration by the mountings with an accelerometer module.

 

 

Might help show when the prop is getting fouled or the engine mounts are going. Also confirm if alignment adjustment is helping (or not! ).

 

cheers,

Pete.

[bizzard]

Of course you could remove all the rubber mounts and place four bathroom scales, one under each foot to discover the units differential in weight distribution.Or suspend the unit by four hefty Salter spring balances,on to each foot to do the same and note the differences.

I've often thought about fore and aft thrust on set ups with rubber mounts and no separate thrust block,

when not enough room for a double UJ and thrust block.A good plan would be to either fit a fore and aft torsion bar between say the engine and a bracket welded to the bulkhead or from the gearbox to something solid behind.The bar could be a vehicles torsion bar or Panhard rod, a bar of suitable length with an eye on each end with hard rubber bushes inserted.Or easier really, solidly bolt down four hard wood blocks,one on either side of both front or rear engine mounts with a hard rubber buffers between them and the mounts to prevent vibration and bolted down to the bearers hard up against the rubber mounts.

And indeed a side ''torque'' torsion bar could also be fitted too. Both these bars would take most of the stress off the rubber mounts leaving them almost free to just support the engine and gearbox.

[nicknorman]

Hello Nick

You mentioned in an earlier post that the engine moved a lot when placed in gear, and you've found the answer.

The Beta 43 is usualy a fabulously smooth engine when instaled correctly; I think you already know the meaning of "profesional" in the context of your engine.

The static wieght bearing capacity of the mounts is largely unaffected by the height of the engine, but the longditudinal and transverse dynamic capacity is hugely compromised. Just look at the length of the adjuster below the nut and compare that to the depth of rubber it is effectively sitting in.

And finaly getting to the point:

a few days ago a bag containing four mounts appeared next to my desk at work; they all had approx 2" of adjuster left in them - they had all sheared off below the adjusted nut. There was evidece of bending on at least one, and a comment about minor prop damage. The engine was of similar wieght and power output to yours.

Worth thinking about?

Steve

Thanks Steve, I can certainly see the point and I will move "adding packing under mounts" further up my to-do list! To be fair to the builder, he builds a half dozen or so of these boats a year with Beta 43s, and I have not heard of any owners having a problem with broken mounts, so I don't think imminent failure is likely, but clearly the installation is not optimal.

 

If you fancy a little project, why not monitor engine vibration by the mountings with an accelerometer module.

 

 

Might help show when the prop is getting fouled or the engine mounts are going. Also confirm if alignment adjustment is helping (or not! ).

 

cheers,

Pete.

Interesting, though sounds like some project though! You would probably need two sensors, one for each axis.

Our deep draft does seem to act like a magnet for poly bags lurking on the bottom and I have thought about some means to determine whether the prop is partially fouled or not. My initial idea was for a torque meter based on engine displacement in the rubber mounts - eg a linear position sensor mounted at left and right mounts to detect differential movement of the rubber feet in response to torque. One would then get an idea of normal torque for given rpm on type of canal, and if torque was too high prop fouling would be suspected.

 

Of course you could remove all the rubber mounts and place four bathroom scales, one under each foot to discover the units differential in weight distribution.Or suspend the unit by four hefty Salter spring balances,on to each foot to do the same and note the differences.

I've often thought about fore and aft thrust on set ups with rubber mounts and no separate thrust block,

when not enough room for a double UJ and thrust block.A good plan would be to either fit a fore and aft torsion bar between say the engine and a bracket welded to the bulkhead or from the gearbox to something solid behind.The bar could be a vehicles torsion bar or Panhard rod, a bar of suitable length with an eye on each end with hard rubber bushes inserted.Or easier really, solidly bolt down four hard wood blocks,one on either side of both front or rear engine mounts with a hard rubber buffers between them and the mounts to prevent vibration and bolted down to the bearers hard up against the rubber mounts.

And indeed a side ''torque'' torsion bar could also be fitted too. Both these bars would take most of the stress off the rubber mounts leaving them almost free to just support the engine and gearbox.

Hi Biz

 

Ii think the torsion bars would tend to transmit vibration and noise into the hull (sounding board effect)! On the feet weight distribution, I was thinking that it is probably incorrect to expect the same weight on each foot. That would presume that the centre of mass is in the middle of the engine mount footprint, something that I very much doubt is the case. As in the case of the rocking bar stool, 3 legs look after themselves, one just needs to pack the 4th leg to match the load on the diagonally opposite leg, therefore at worst it is only necessary to measure the load in a pair of diagonally opposite mounts.

[bizzard]

Thanks Steve, I can certainly see the point and I will move "adding packing under mounts" further up my to-do list! To be fair to the builder, he builds a half dozen or so of these boats a year with Beta 43s, and I have not heard of any owners having a problem with broken mounts, so I don't think imminent failure is likely, but clearly the installation is not optimal.

 

 

Interesting, though sounds like some project though! You would probably need two sensors, one for each axis.

Our deep draft does seem to act like a magnet for poly bags lurking on the bottom and I have thought about some means to determine whether the prop is partially fouled or not. My initial idea was for a torque meter based on engine displacement in the rubber mounts - eg a linear position sensor mounted at left and right mounts to detect differential movement of the rubber feet in response to torque. One would then get an idea of normal torque for given rpm on type of canal, and if torque was too high prop fouling would be suspected.

 

 

Hi Biz

 

Ii think the torsion bars would tend to transmit vibration and noise into the hull (sounding board effect)! On the feet weight distribution, I was thinking that it is probably incorrect to expect the same weight on each foot. That would presume that the centre of mass is in the middle of the engine mount footprint, something that I very much doubt is the case. As in the case of the rocking bar stool, 3 legs look after themselves, one just needs to pack the 4th leg to match the load on the diagonally opposite leg, therefore at worst it is only necessary to measure the load in a pair of diagonally opposite mounts.

The fore and aft thrust torsion bar would be the more important and would need to be fixed as low as possible,onto really solid things, any transmitted noise if any would be very low and would take an enormous strain off the mounts.

This is almost a wheeeeeze;- Four bathroom scales could be actually put into use AS engine mounts and do away with the rubber ones. You would then be able to keep a beady eye on all the four different engine torque pressure,propeller torque effects figures at different boat speeds and reverse. It would be fascinating.Wires could be brought from the scales to a 4 needle gauge on your dash panel too.And you could perhaps even inform the rubber mount makers of your findings so that they can make them more robust in the future.Or perhaps they could then provide you with four different densities of the rubber mounts,one for each different mount,this method would always ensure that all your mounts squashed down an identical amount.

[nicknorman]

Hello Nick

You mentioned in an earlier post that the engine moved a lot when placed in gear, and you've found the answer.

The Beta 43 is usualy a fabulously smooth engine when instaled correctly; I think you already know the meaning of "profesional" in the context of your engine.

The static wieght bearing capacity of the mounts is largely unaffected by the height of the engine, but the longditudinal and transverse dynamic capacity is hugely compromised. Just look at the length of the adjuster below the nut and compare that to the depth of rubber it is effectively sitting in.

And finaly getting to the point:

a few days ago a bag containing four mounts appeared next to my desk at work; they all had approx 2" of adjuster left in them - they had all sheared off below the adjusted nut. There was evidece of bending on at least one, and a comment about minor prop damage. The engine was of similar wieght and power output to yours.

Worth thinking about?

Steve

 

Photo of a rear mount (the higher ones) here. Perhaps not too bad though there is clearly room to pack the mounts up a bit. Note that when I took the pick, the top nuts had not been tightened hence loose looking spring washer. Lower nuts are nyloc as well.

[nicknorman]

The fore and aft thrust torsion bar would be the more important and would need to be fixed as low as possible,onto really solid things, any transmitted noise if any would be very low and would take an enormous strain off the mounts.

This is almost a wheeeeeze;- Four bathroom scales could be actually put into use AS engine mounts and do away with the rubber ones. You would then be able to keep a beady eye on all the four different engine torque pressure,propeller torque effects figures at different boat speeds and reverse. It would be fascinating.Wires could be brought from the scales to a 4 needle gauge on your dash panel too.And you could perhaps even inform the rubber mount makers of your findings so that they can make them more robust in the future.Or perhaps they could then provide you with four different densities of the rubber mounts,one for each different mount,this method would always ensure that all your mounts squashed down an identical amount.

OK I'll buy your wheeze if the scales are replaced by strain gauges! Also would need a microprocessor to analyse the current engine rpm and gps speed, and gps position against a database of canal depth to work out whether prop is fouled. In fact it could be a neural net type programme that learns canal "normal" torque vs rpm vs speed vs location and can then report if the matrix deviates from "normal"

Edited April 22, 2012 by nicknorman