Thordon Shaft Bearings

[Fish 0]

Does anyone have experince with Thorndon shaft bearings?

 

They are supposed to last 2 to 3 times longer than conventional shaft bearings and cutless bearings (And cost the same).

The bit I can't get my head around, is that they have far greater tolerances than conventional bearings, i.e. even when new, the shaft is loose in them and slaps around. Generally, my test for when a bearing needs to be replaced is when there is significant play in it.

 

The supplier's story is that the bearing sets up a hydrostatic pressure, and the shaft actually rotates on a water film, rather than physically contacting the bearing.

 

1) Any using Thordon shaft bearings?

2) Is there any vibration issues in use (i.e are they smooth and quiet)?, and 

3) How do you check the engine alignment with the shaft half coupling if the shaft is slopping around loose in its bearings (cutless and stern tube bearings)?

[waikiore 399]

The reason why Thordon and Tufnol (Novasteen) have to be set up loose is they both swell quite a bit when immersed, and you dont want them to seize on to your shaft, thats why standard cutless or Vesconite are to be preferred, they all run on a laminar film of water if set up correctly.

[Steve Pope 243]

Slightly larger clearances on your prod, bearing, (s)  for "your" peace of mind wouldn't / shouldn't be an issue. If their recommendations were at all wrong we would have heard about it long ago. I used them on my prop shaft, and it rotates very nicely.

[Crazyhorse 47]

Spoke with Chatfield Engineering who supplied our vesconite cutlass after it wore a little since last year. The engineer (I use that term loosely now for him) machined and installed it with a perfect fit, no play at all and was told its normal to have the bearing seat in after a while where there is a little play in the shaft, no mention of the material swelling. We run a flexi link to allow for miss alignment of the donk but it is lined up perfectly so was confused that we had some play in the shaft when hauling out for winter. The engineer who shall remain nameless suggested it was not getting enough water up past the bearing and he could have put log cups in to scoups water up. Great, now he tells us. I don't think that's an issue as we can burp the gland easily enough so water flows through to the PSS seal and our maximum speed under prop is a tad over 6kts. Others who know this stuff in the yard like Kevin and Noel said the wear is not excessive but shouldn't get any worse of there is a problem. Find out next year.

[Island Time 1,235]

With Vesconite, there will not be an issue with the size bearings we are using. If you have huge bearings, the small clearances can be an issue, but Vesconite is extremely dimensionally stable, and wont swell to any appreciable extent when wet for yacht bearings. If anyone wants the actual specs for clearances, send me a PM with the details of your bearing requirements, and I can tell you the clearances specified by Vesconite. I have the Vesconite marine bearing design manual.

[waikiore 399]

KM  I would leave a reasonable clearance on the prod bearings just for ease of deployment , on your pintle ones go for 5 -6 thou .

[Island Time 1,235]

From vesconite:

Thordon has a grade which they supply called SXL. This material is an elastomer and elastomers such as this and rubber all does need bigger clearances to start off with due to moisture absorption.

Tufnol which would have probably been the Whale brand is produced with a phenolic cotton resin. This also absorbs moisture, but also has the chance of de-lamitation. De-lamination could occur immediately or after the material has been fully absorbed.

 

What does put Vesconite apart would be the structure of the material. This being both dimensionally stable as well internally lubricated with polymers that are all compounded together, meaning that you have the self-lubricating ability throughout the life of the material, even when wear takes place.

 

We use the water to lubricate and cool down the bearing - so no extra seals or oil required for the stern tube.

 

For the rudder we also use open ended bearings with no lubrication and this is an excellent application.

 

We do however do not recommend by putting a lubrication groove on the 6 o’ clock position. This is also the case with Thordon, Tufnol or any other bearing material. This just speeds up the wear of the material due to the groove present.

 

You can also use our design-a-bearing calculator on our website to size your bearings. This gives you a complete drawing of what the material needs to be final machined to. No need for extra machining after the material has been fitted.

 

We have a warehouse available in NZ and I myself would probably be available in NZ in the next couple of months to help the customers with their Vesconite requirements.

If you have any specific questions - please do not hesitate to ask.

 

Kind Regards

Eddie Swanepoel

eddie@vesconite.com

Cell: +27 82 384 6265

[Steve Pope 243]

There is an awful lot of abrasive stuff floating sea water, anywhere tidal keeps it in suspension, just look at the crap that attaches to the hull any time your boat is not being used. Even more noticeable now that antifoul has been dumbed down to almost being useless. Whangarei is an especially good example. Vesconite has to be in the top 1% of what is available.