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Charlatan

Thordon Shaft Bearings

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Does anyone have experince with Thorndon shaft bearings? Apparently the US Navy use them as standard, so I'm hoping there is some knowledge around here.

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.

For a 1 1/4 inch shaft.

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)?

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5 hours ago, Charlatan said:

Does anyone have experince with Thorndon shaft bearings? Apparently the US Navy use them as standard, so I'm hoping there is some knowledge around here.

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.

For a 1 1/4 inch shaft.

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)?

Can't give you any specifics on this particular brand, or the tolerances for them.  I will give you two general observations though:

1.  All cutlass and strut bearings rely on the shaft being supported by water essentially.  If the shaft rubs one area in use constantly the friction burns it off, so the question of  gap is relative, not absolute.

2.  for many cutlass bearings(especially larger ones, ie 2.5" shafts) we would either wrap the shaft carefully with a specific number of wraps of a hard tape(it was basically fiberglass cloth with thin adhesive from what I recall, no overlap on the wraps, butted up and seamed if the shaft was already out.    If they were already in place, long but narrow shims of a consistent thickness were pushed into the cutlass bearing at 12, 3, 6 and 9 oclock to position it.  You can feel the sides, and then split the difference and brace the shaft if you're in the water and can't access them but it is not as accurate. 

 

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They are very well regarded in commercial use. But I've never heard that the gap is supposed to be bigger. They come in many flavours; there's not just 1 type.

Here's one of their engineering manuals:

https://thordonbearings.com/docs/default-source/propeller-shaft-bearing-systems/design/engineering_manual.pdf?sfvrsn=59dc44c5_12

They swell probably more than rubber - page 15 says 1.3%. So perhaps initial gap has to be bigger. They also have very good technical support so reach out to them directly.

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Thanks for the info guys.

That engineering manual was just what I was after Zonker, I could only find sales brochures on their website for some reason.

 

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What?

You can make a living as an Internet smartass?

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I do it for the fame and the glory. Well somebody cooked me a nice dinner once when I dove on their hull and inspected it after it had bashed on a reef overnight.

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I used them on pleasure boats since the 80's, no issues, they are a great invention

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As an FYI, there are two giant Thordon pad bearings on each side of Mirabella V's enormous lifting keel, carrying all the side loads.  I believe they're still with the original ones put in by Vosper's.

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