Metalastik coupling, large GU motors?

[Timleech]

I seem to remember someone looking for these prop shaft couplings and maybe getting a batch made. Was it the Fulbournes?

Anyway, I'm looking for one now (though I haven't told my customer yet!)

Any helpful suggestions gratefully received.

 

Thanks

Tim

Edited September 26, 2009 by Timleech

[rrt2]

I seem to remember someone looking for these prop shaft couplings and maybe getting a batch made. Was it the Fulbournes?

Anyway, I'm looking for one now (though I haven't told my customer yet!)

Any helpful suggestions gratefully received.

 

Thanks

Tim

 

 

B.M.W. cars use them on the gearbox to propshaft coupling although size might not be correct

[Timleech]

B.M.W. cars use them on the gearbox to propshaft coupling although size might not be correct

 

From what I remember the size used to be a standard Metalastik off-the-shelf product but is now obsolete, though they or their successors were willing to make small batches to order.

 

Tim

[paulcatchpole]

B.M.W. cars use them on the gearbox to propshaft coupling although size might not be correct

 

A Guibo?

 

Part 2 in the following diagram, as an example...

 

http://www.realoem.com/bmw/showparts.do?mo...hg=26&fg=10

 

 

PC

[Timleech]

A Guibo?

 

Part 2 in the following diagram, as an example...

 

I should think that's way too small.

The GU type is a disk with 6 bolt holes, so maybe the same basic principle, but that's about where the similarity ends

 

Roughly 9" dia., sandwiched between two cast iron flanges each of which has three 'clearance' bolt holes and three large holes to clear the heads of the 'other' three bolts. It carries propellor thrust in both directions, but over a large number of years the astern thrust pulls it out of shape.

 

I'm sure that makes no sense at all unless you already have a rough idea what |I'm talking about

 

Tim

Edited September 26, 2009 by Timleech

[Swallowman]

Hillman Imp drive shaft couplings? Should be available off the shelf at most motor factors.

[rrt2]

lotus elan "type 26" used them as did the ford gt40 on the drive shaft from the diff to the wheels

[paulcatchpole]

I should think that's way too small.

The GU type is a disk with 6 bolt holes, so maybe the same basic principle, but that's about where the similarity ends

 

Roughly 9" dia., sandwiched between two cast iron flanges each of which has three 'clearance' bolt holes and three large holes to clear the heads of the 'other' three bolts. It carries propellor thrust in both directions, but over a large number of years the astern thrust pulls it out of shape.

 

I'm sure that makes no sense at all unless you already have a rough idea what |I'm talking about

 

Tim

 

Aye, I get what you mean! My example is much too small, as you say! Same idea though.

 

PC

[Chris Pink]

I seem to remember someone looking for these prop shaft couplings and maybe getting a batch made. Was it the Fulbournes?

Anyway, I'm looking for one now (though I haven't told my customer yet!)

Any helpful suggestions gratefully received.

 

Thanks

Tim

 

if you find a surplus, let me know, i'm in the market for one too, though i was going to replace it with a tyre coupling.

 

Is there an advantage to using the original unit?

[Steve Priest]

I think that I've got a couple of spare ones as I have recently put a cardan shaft in Aquila. I just need some time to sort them out

[Arnot]

I should think that's way too small.

The GU type is a disk with 6 bolt holes, so maybe the same basic principle, but that's about where the similarity ends

 

Roughly 9" dia., sandwiched between two cast iron flanges each of which has three 'clearance' bolt holes and three large holes to clear the heads of the 'other' three bolts. It carries propellor thrust in both directions, but over a large number of years the astern thrust pulls it out of shape.

 

I'm sure that makes no sense at all unless you already have a rough idea what |I'm talking about

 

Tim

Would this help?

 

Regards

 

Arnot

[mick110]

Would/could a automotive .C.V. joint be suitable?.....accepting it would have to be adapted/welded to engine shaft with a splined flange fixed to prop side ???? may be too much of an egineering challenge? the original part @ 9" is way over any car part but check with plant/agricultural fitters I'm certain I've seen them ..dump trucks etc.????

[Guest User]

These sort of things ? ..... Techdrive couplings CLICKY ... or Teignbridge CLICKY & R&D Marine CLICKY

[Timleech]

I think that I've got a couple of spare ones as I have recently put a cardan shaft in Aquila. I just need some time to sort them out

 

Thanks Steve, that woud be appreciated.

 

Would this help?

 

Regards

 

Arnot

 

Unfortunately no, no capability for the astern thrust

 

Tim

[Timleech]

Would/could a automotive .C.V. joint be suitable?.....accepting it would have to be adapted/welded to engine shaft with a splined flange fixed to prop side ???? may be too much of an egineering challenge? the original part @ 9" is way over any car part but check with plant/agricultural fitters I'm certain I've seen them ..dump trucks etc.????

 

There are of course other ways to do the job, a wagon prop shaft (already mentioned) is a common and successful method if done properly.

The original setup though normal for these GU boats is a bit unusual. There's an intermediate shaft, I'll hazard a guess without going out in the dark to measure about 5' long, which is rigidly coupled to the gearbox output and has a support bearing towards its after end. Then this is coupled to the sterngear via the offending Metalastik coupling which allows for a small amount of angular misalignment between the two shafts.

The one I'm dealing with has had the Metalastik flanges bolted up solid, presumably the middle part failed in the past, and the resulting stress from misalignment has worked loose the half-couplings at either end of the intermediate shaft. The alternatives are to repair the existing shaft (bore out & bush the couplings, turn down the ends of the shaft etc) and fit a replacement flexible part, OR chuck out the whole lot, get a wagon prop shaft, alter its length to suit, move the support bearing back to behind the prop shaft flange, and make up adaptors between the universal joints and the two remaining half-couplings.

 

Tim

Edited September 26, 2009 by Timleech

[Arnot]

Unfortunately no, no capability for the astern thrust

 

Tim

I know they don't quote it (in fact they don't give very much away at all) but looking at the design I would have thought that it would take some thrust in either direction.

 

I will keep thinking about it though...

 

Do you have a piccy of the original? I can't bring it to mind.

 

Regards

 

Arnot

Edited September 26, 2009 by Arnot

[Timleech]

I know they don't quote it (in fact they don't give very much away at all) but looking at the design I would have thought that it would take some thrust in either direction.

 

I will keep thinking about it though...

 

Do you have a piccy of the original? I can't bring it to mind.

 

Regards

 

Arnot

 

From what I remember, those couplings just have pins into a flexible disc, nothing to stop it all falling apart.

 

The originals are the same in principle as the newer much-misused and abused R&D semi-flexible couplings. Maybe they make one that's big enough/could be adapted, I'll perhaps look into that tomorrow.

 

Tim

[Arnot]

From what I remember, those couplings just have pins into a flexible disc, nothing to stop it all falling apart.

I think that they actually bolt through like the old fashioned generator couplings...

 

Regards

 

Arnot

[Hairy-Neil]

When I was at tech college these were known as a Layrub Joint. A quick Google turned up this:- Layrub

[Timleech]

I think that they actually bolt through like the old fashioned generator couplings...

 

Regards

 

Arnot

 

I've used one, yonks ago (actually as a generator coupling), the best of my recollection backed up by what I can make out of the little pic on the Renold link is that they don't bolt through. I've been wrong before though

I wouldn't fancy transferring astern thrust though one of their discs, whatever the case.

 

Tim

 

When I was at tech college these were known as a Layrub Joint. A quick Google turned up this:- Layrub

 

Same general idea, likewise the old 'Hardy Spicer' 4-bolt flexible couplings, but those that I've seen like that have fairly soft rubber inserts which wouldn't last long with a substantial thrust loading (probably).

 

Tim

[Derek R.]

That Layrub coupling looks about as close to the metalastic that came out of Tycho than any of the others.

 

I seem to remember it appeared like a solid rubber disc sandwiched between two metal plates. Quite how exactly it was fixed to the plates was not clear, no bolt heads could be seen, and tough as new motocross boots, but then it was seven years ago I last set eyes on it. Not only would it take some misalignment, it had a very good ability to transmit thrust ahead and astern. Also would take some of the shock when the blades hit hard objects - and It was mounted just as Tim states. Whilst we had no problems with our block deteriorating, we have heard of other types of flexible couplings involving flexible plates bolted at the lugs alternately to one plate then the other, failing catastrophically. The Layrub that Neil refers to looks more substantial, though the ability to efficiently transmit thrust might be in question, and I'll expand out of interest (hopefully - though not experience of the Layrub).

 

It was the reverse/forward thrust issue that needed to be addressed when changing from our metalastic system to the lorry prop. The positioning of the plummer blocks mounted on the boats bottom in the previous setup meant that when on dock, the flexing that took place (bed'ole wouldn't close etc.) put stress on the shaft (depends where the stocks are of course). This in turn had worn the tailshaft and bearing prematurely - not that much flexing if any took place when afloat - but the shaft was not as well contained in its movement as would have been best for tail shaft alignment due to the distance from plummer block to tailshaft. The lorry shaft with its two UJ's is mounted between the reduction box output flange and the tailshaft flange and supported at the back by a new plummer block mounted on a cross web between the swim plates close to the tail shaft - and the reduction box output bearing at the front. This latter gave rise to showing up a problem that the previous set up had hidden:

 

The old plummer block was fairly close to the reduction box output and had the effect of supporting the short reduction box output shaft and flange thereby keeping it more or less well aligned in the casing. The thrust bearing mounted in the output had worn, and now with the length of the new shaft weighing on it, showed its failing in an 'orrible clankety clank from under the floor in astern. It started this half way up the Stockton flight after leaving the dock. Sounded like the blades were hitting something. Thought it was a bit of ballast touching the shaft coupling bolt heads. None of the above!

 

The drop in attitude of the reduction box output allowed due to the worn bearing, had tilted the larger pinion in the reduction box (3:1) and was allowing the cast web supports (four if I recall right) of the pinions face to contact one of the internal cast web supports of the reduction box casing. The sound was being amplified by the new hollow lorry shaft to frightening proportions. I soldiered on, and did a lot of strapping on that trip. I called Graeme, and he said there shouldn't be anything basically wrong with the set up, but to check that reduction box output bearing. Sure enough, it was at fault.

 

One other point to bring up with such changes. The old reduction box bearing was a double ball race thrust bearing, the old plummer block bearing, I believe was not. The new tailshaft is now mounted in its stern tube bearing and a plummer block about eighteen inches forward of it. This bearing is now the thrust bearing, and the replacement that went into the reduction box output is a non-thrust bearing. Noise gone - problem solved. Or is it?

 

The thought occurs to me, that such a length of steel in the form of prop shaft from rearmost plummer block to reduction box complete with two UJ's, that the expansion and contraction of the steel in the shaft, compared to the steel of the hull, will place 'some' load on that non-thrust bearing dependent upon tempaerature. The question is - how much, and will it have any detrimental effect? One solution to alleviate any such load through temperature change, might be to have the lorry prop machined and put a spline in place. The only problem with that (as I see it) is an additional introduction of a moving part prone to more wear and possible misalignment also. So it's staying as it is, with the aft most plummer block taking thrust. When not locked to the shaft, I can slide the tailshaft back and inch, and lift the lorry prop clear for access to ballast and bilge which was a lot harder with the old set up, and I know the tailshaft ain't moving out of alignment.

 

Sorry this has drifted away from metalastic Tim, but it seemed to be associated knowledge and experience that might aid decisions for those in a similar situation (nearly said 'same boat'!).

 

Derek

[Tim Lewis]

I seem to remember someone looking for these prop shaft couplings and maybe getting a batch made. Was it the Fulbournes?

Anyway, I'm looking for one now (though I haven't told my customer yet!)

Any helpful suggestions gratefully received.

 

Thanks

Tim

 

Yes it was Fulbourne, we had to get them direct from the manufacturer. I think we had to get three (minimum order) and they were on something like a six week delivery.

 

we still have one spare but after we shredded another one last year we would be loathe to give it up.

 

Tim

Edited September 27, 2009 by Tim Lewis

[Hairy-Neil]

Same general idea, likewise the old 'Hardy Spicer' 4-bolt flexible couplings, but those that I've seen like that have fairly soft rubber inserts which wouldn't last long with a substantial thrust loading (probably).

 

Tim

 

Agreed, the Layrub spec doesn't even mention thrust.....

 

The coupling specification inevitably has to meet numerous and sometimes conflicting requirements:

 

* Torque capacity

* Physical size

* Torsional stiffness

* Damping

* Mis-alignment capabilities

* Chemical immunity

 

I always associate Hardy Spicer with the cardan shaft type joint and Metalastic with lorry spring bushes, though I guess there was a mix and match overlap of designs once patents had expired. Have you noticed how Hilti now make a Sthil Saw and that JCB make workboots.....

 

Time I went and did the hoovering.......

Edited September 27, 2009 by Hairy-Neil

[Timleech]

<snip>

 

Sorry this has drifted away from metalastic Tim, but it seemed to be associated knowledge and experience that might aid decisions for those in a similar situation (nearly said 'same boat'!).

 

Derek

 

It's often said that ordinary vehicle prop-shaft UJs shouldn't be used to carry thrust. In practice so long as they are generously sized and not working through a large angle it's not a problem. Unfortunately, 'not working through a large angle' can shorten their life as the needles in the UJ bearings then don't get moved around enough so you can't win Use good big ones, grease them regularly & they'll last for years

 

The point about taking thrust elsewhere than the gearbox is a very valid one, some gearboxes don't like it, Parsons used to specifically refer to it in their manuals.

 

Tim

[Chris Pink]

Yes it was Fulbourne, we had to get them direct from the manufacturer. I think we had to get three (minimum order) and they were on something like a six week delivery.

 

we still have one spare but after we shredded another one last year we would be loathe to give it up.

 

Tim

 

Well if Tim Leech wants to get three, I'll definitely have one.

 

Although Trelleborg do not list it in their marine product range.