Engine to prop shaft aligment

[Arthur Brown]

This could be an expensive and time consuming DIY project, so unless you have the tools and skills I'd suggest that you leave well (enough) alone! If you have real suspicions then a call to a respected engineer would give a safer result albeit at cost. In reality the labour cost could well be less than the damage cost incurred by failing a DIY task.

[nicknorman]

...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.

You are on my ingore list, but there is the button that says "view anyway" and the ignore list is just to remind me not to get drawn into an argument with you when the moon is in the wrong phase and you are in the "start an argument on any pretext, and make it personal" state. When you are in your more usual helpful state you get a gold star and who knows, enough gold stars and you might be taken off the list!

 

How long is your shaft?

 

See what I mean, there is just no need for personal remarks and if the argument gets down to the point of whose is bigger, it is back on the ignore list for you.

 

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

 

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

 

Its a fairly compact installation - trad stern with engine under boards in the "engine room" so I would say perhaps 3 feet from gearbox to stern gland. I don't quite understand what you mean, yes if you could remove the shaft and connect a shorter one to the engine that just about touched the stern gland that would help, but how can it be done with the prop shaft and prop in place?

 

Oh dear, is that the moon coming up now...

 

This could be an expensive and time consuming DIY project, so unless you have the tools and skills I'd suggest that you leave well (enough) alone! If you have real suspicions then a call to a respected engineer would give a safer result albeit at cost. In reality the labour cost could well be less than the damage cost incurred by failing a DIY task.

 

Thanks for the concern, but like I said I am not that sort of guy. At the very least, just removing the couplings to check the algnment, without actually adjusting the engine, surely can do no damage. I always service my own cars, motorbikes and aircraft so I see no reason why the boat should be different - I just need to learn the skills, issues and pitfalls and that is where this forum is so good.

[nicknorman]

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.

Yes I could check that, although with a new installation by a reputable builder, and me having been very careful to adjust both nuts equally, it should be pretty close. But even if the flanges are parallel, not sure that the precision of the studs etc is sufficient to warrant using the clearance around the pusher flange as the primary means of determining shaft alignment.

[bizzard]

If i had a set up like that with 3' between g/box output flange and sterntube,i Would do or have the job done properly.

You have enough room to instal a proper Double UJ and thrust-block like Python or Aqua-drive.It would take all the stress off the stern tube and also the thrust stress of the rubber engine mounts and no more keep checking alignment.

[nicknorman]

If i had a set up like that with 3' between g/box output flange and sterntube,i Would do or have the job done properly.

You have enough room to instal a proper Double UJ and thrust-block like Python or Aqua-drive.It would take all the stress off the stern tube and also the thrust stress of the rubber engine mounts and no more keep checking alignment.

Yes I do rather wish I had asked for a UJ type linkage during the build, at the time I didn't really understand the difference between a centaflex and a UJ type linkage. It is slightly alarming to see just how much the engine moves when engaging gear etc

 

However that would require welding a support for the thrust bearing and one thing I am totally crap at is welding.

 

I am hoping that after an intial possible requirement to adjust up the mounts to compensate for sagging, they will settle down and not need adjusting again until they are shagged.

[bizzard]

Yes I could check that, although with a new installation by a reputable builder, and me having been very careful to adjust both nuts equally, it should be pretty close. But even if the flanges are parallel, not sure that the precision of the studs etc is sufficient to warrant using the clearance around the pusher flange as the primary means of determining shaft alignment.

No not for alignment,just to ensure that the pusher which is part of the inboard stern bearing is perfectly true and square with the rest of the tube bearing.

 

Yes I do rather wish I had asked for a UJ type linkage during the build, at the time I didn't really understand the difference between a centaflex and a UJ type linkage. It is slightly alarming to see just how much the engine moves when engaging gear etc

 

However that would require welding a support for the thrust bearing and one thing I am totally crap at is welding.

 

I am hoping that after an intial possible requirement to adjust up the mounts to compensate for sagging, they will settle down and not need adjusting again until they are shagged.

And the stern-tube is shagged along with them.

You could cut out a cross brace from steel plate to the correct dimensions for your boat and an Aua-drive thrust block yourself.It wouldn't cost much for a welder to only weld it in if all was set up for him.

[nicknorman]

No not for alignment,just to ensure that the pusher which is part of the inboard stern bearing is perfectly true and square with the rest of the tube bearing.

I see, yes good idea and easy to do.

 

And the stern-tube is shagged along with them.

You could cut out a cross brace from steel plate to the correct dimensions for your boat and an Aua-drive thrust block yourself.It wouldn't cost much for a welder to only weld it in if all was set up for him.

Correct me if wrong but I think the majority of boats don't have a double UJ linkage so I don't feel too exposed. But I do see the advantage so I think that is probably a project for the future, in the mean time I still want to check the alignment of the current setup.

[RLWP]

An Aquadrive or a Python drive is a double 'UJ' linkage, they are pretty common. Tawny Owl has one

 

Richard

[bizzard]

I see, yes good idea and easy to do.

 

 

Correct me if wrong but I think the majority of boats don't have a double UJ linkage so I don't feel too exposed. But I do see the advantage so I think that is probably a project for the future, in the mean time I still want to check the alignment of the current setup.

The more modern method of non twin UJ's with rubber mounts is purely in order to stuff the engine and transmission as close up to the stern as possible in order to make internal cabin space as large as possible,a better attraction and selling point than a proper engine installation in non practical buyers eyes as most people seem to be these days.

The water lubricated Cutless type stern tube set up being a little flexible is more tolerant of this dodgy set up.

As Richard mentioned.--I think most hire boat builders did and still do do it properly.

In my opinion if the engine has to go close up in the stern there is no option but to go solid mounted and aligned spot on accurately.A little more transmitted noise and vibration but 100% reliable.Done properly and greased properly the tube bearings should last the life of the boat.

[by'eck]

Wonder if a cardan joint would work for you Nick.

 

 

They were extensively used on Moto Guzzi V twin motorcycle drivetrains. Constant velocity and very compact, basically being a double UJ system without the shaft between.

[bizzard]

Wonder if a cardan joint would work for you Nick.

 

 

They were extensively used on Moto Guzzi V twin motorcycle drivetrains. Constant velocity and very compact, basically being a double UJ system without the shaft between.

Better than a Centaflex but because the two UJ's are so close together would not allow a great amount of flexibility,i'd say and be rather nobbly if it ran at more than a a few degrees out of line,another few inches between the UJ's would make all the difference, this is why Aquadrive use the truly universal FWD vehicle type of Constant velocity joints.

[RLWP]

Better than a Centaflex but because the two UJ's are so close together would not allow a great amount of flexibility,i'd say and be rather nobbly if it ran at more than a a few degrees out of line,another few inches between the UJ's would make all the difference, this is why Aquadrive use the truly universal FWD vehicle type of Constant velocity joints.

 

From memory, the CV joint (Hardy Spicer?) is a lot more compact than the Hookes joint too, so an Aquadrive is shorter than the equivalent Cardan shaft

 

Richard

[bizzard]

What about twin Layrub joints on a shaft, the predecessor or the Hardy-Spicer style of UJ.

Or twin rubber Doughnuts on a shaft like some old type drive shafts cars had with IRS,Lotus Elan for one

Edited April 15, 2012 by bizzard

[Albion]

From memory, the CV joint (Hardy Spicer?) is a lot more compact than the Hookes joint too, so an Aquadrive is shorter than the equivalent Cardan shaft

 

Richard

Hardy Spicer was the old manufacturer's name term (bit like Biro and Hoover) for what is more correctly known as the Hooke's Joint or Universal Joint (UJ). The Python and Aquadrive (paired constant velocity joints) joints are an excellent bit of kit and they do have a very short shaft between them, it is just so short it is hardly visible. Another advantage is that they have a thrust bearing before the CV joints so that no thrust load is to the gearbox, engine and engine mounts. Well worth having if you have the space to be able to incorporate one as it allows more flexible engine mounts (for reduced engine vibration) with no side loading on the stern tube.

Roger

Edited April 15, 2012 by Albion

[bizzard]

From memory, the CV joint (Hardy Spicer?) is a lot more compact than the Hookes joint too, so an Aquadrive is shorter than the equivalent Cardan shaft

 

Richard

Yes they are more compact. The BMC Austin and Morris Mini cars were the first to use the ball type CVJoint in 1959 not very successfully at first but that was not a design fault but a metal fatigue fault which they eventually got right and now of course nearly all cars use them.

There is the sliding fork UJ which a lot of continental cars use for the inner drive shaft joint on FWD cars but is only a variant of the spider type Hardy Spicer UJ.

[RLWP]

<snip>

 

As Richard mentioned.--I think most hire boat builders did and still do do it properly.

 

<snip>

 

I had missed this. I guess that this is more to do with the ability to whip an engine out and drop a new one in as quickly as possible than anything else. Hire boats make money only when they are on hire

 

Most of Tawny Owl's kit is either very robust and/or easily accessible. You don't want hire boats hanging about with broken bits

 

Richard

[by'eck]

Yes they are more compact. The BMC Austin and Morris Mini cars were the first to use the ball type CVJoint in 1959 not very successfully at first but that was not a design fault but a metal fatigue fault which they eventually got right and now of course nearly all cars use them.

There is the sliding fork UJ which a lot of continental cars use for the inner drive shaft joint on FWD cars but is only a variant of the spider type Hardy Spicer UJ.

 

Yes I'd forgotten about the splined sliding sleeve/joint needed with UJ drivetrains.

 

A little off topic but a friend tuned Guzzi's for the Bear production bike race series in the 90's. Development had to cease though as over 130 bhp was reached on the dyno at the back wheel. The drive shaft was twisting so much whilst under power that the splines locked up, effectively locking the rear suspension as well.

[bizzard]

I had missed this. I guess that this is more to do with the ability to whip an engine out and drop a new one in as quickly as possible than anything else. Hire boats make money only when they are on hire

 

Most of Tawny Owl's kit is either very robust and/or easily accessible. You don't want hire boats hanging about with broken bits

 

Richard

Exactly i'm a great fan of ex hire boats for their robust, sensible and no nonsense arrangements of the fundamental things that matter. Most boat builders building for private owners tend to be coheresed into concentrating on more cosmetic internal features especially stupidly complicated electrical systems instead of making sure all the fundamentals like engine installations are done properly for proper reliable use.

[by'eck]

Exactly i'm a great fan of ex hire boats for their robust, sensible and no nonsense arrangements of the fundamental things that matter. Most boat builders building for private owners tend to be coheresed into concentrating on more cosmetic internal features especially stupidly complicated electrical systems instead of making sure all the fundamentals like engine installations are done properly for proper reliable use.

 

Yeh but its so much better than watching the telly, getting a stupidly complicated electrical system working

 

Both Nick & I know this only too well

[bizzard]

Yes I'd forgotten about the splined sliding sleeve/joint needed with UJ drivetrains.

 

A little off topic but a friend tuned Guzzi's for the Bear production bike race series in the 90's. Development had to cease though as over 130 bhp was reached on the dyno at the back wheel. The drive shaft was twisting so much whilst under power that the splines locked up, effectively locking the rear suspension as well.

I can imagine. I remember the old big Sunbeam's and Douglas Dragonfly had shaft drive too but i expect it was similar to BMW's

Edited April 15, 2012 by bizzard

[bizzard]

Yeh but its so much better than watching the telly, getting a stupidly complicated electrical system working

 

Both Nick & I know this only too well

Well electrical stuff is your hobby too i think Richard which you obviously enjoy very much and you are also are a very great help to many folks in distress with electrical faults on this forum. Door bells.

[nicknorman]

Wonder if a cardan joint would work for you Nick.

 

 

They were extensively used on Moto Guzzi V twin motorcycle drivetrains. Constant velocity and very compact, basically being a double UJ system without the shaft between.

Not sure it would take the torque and run for 1000s of hours. As Biz says you need a bit of shaft between the joints to allow lateral displacement. Anyway, as the former owner of a Lemon it was a bit of a tractor and my boat is far too elegant to have tractor parts...

 

 

( yes i know Kabota engine etc)

 

 

Anyway, trying to drag the debate on the history of flexible couplings back towards my issue!!!

 

 

How about this: just remove the Centaflex from both shafts (not sure how easy that is) then pull the long shaft and short shaft together. So now i have a short shaft rigidly connected to the engine and a long shaft rigidly connected to the prop. When they are butted up against each other I would like to see that a long straight edge can be lain across both shafts and touches all along. Or that it touches 1 shaft all along but there is a constant slight gap to the other shaft (lateral offset). Or that it touches both shafts but only makes point contact with each (angular offset).

 

Would that be a valid way to check alignment?

Edited April 15, 2012 by nicknorman

[RLWP]

The thing in the picture is a very short Cardan shaft with two Hookes joints. That's why it has 3 Zerks*. You would need one hell of a prop to generate enough torque to bother a thing that size

 

Richard

 

*They'm nipples, inn'ey

Edited April 15, 2012 by RLWP

[nicknorman]

The thing in the picture is a very short Cardan shaft with two Hookes joints. That's why it has 3 Zerks*. You would need one hell of a prop to generate enough torque to bother a thing that size

 

Richard

 

*They'm nipples, inn'ey

How can you tell the size from the photo? I thought it was from a Guzzi, so quite small. On the Guzzi it goes quite fast so fairly low torque. On the boat it would rotate slowly so lots and lots of torque

[RLWP]

How can you tell the size from the photo? I thought it was from a Guzzi, so quite small. On the Guzzi it goes quite fast so fairly low torque. On the boat it would rotate slowly so lots and lots of torque

 

Size of the circlips, the writing on the needle rollers, and so on

 

No way is that a bit of Italian engineering from a Guzzi. More like a bit of a lorry

 

You can't generate loads of torque with a canal boat propeller, it just isn't big enough

 

Richard