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Old 30-07-2013, 06:17   #16
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Re: Oil Filled Prop Shaft

That seatorque thingo looks a bit dodgy to me, think this is more appropriate to a power boat that gets pulled out of the water 99% of time.

I guess I'm annoyed at the lack of info, its not clear how the design prevents water getting to the bearing, how many seals. We are talking about a system that is required to be reliable minimum 2 years or when you have to paint the hull.

You may have convinced me if the tube was fitted to the propeller hub but it looks like it stops at the strut (bit silly), it also lacks info about the thrust bearing and how the force is transmitted to the hull.

Type of lub is it oil or greese, the density is less than SW, what about getting the header tk above SW level.

I'm not completely negative, just yet to be convinced.
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Old 30-07-2013, 08:34   #17
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Re: Oil Filled Prop Shaft

another manufacturer: Nautical Specialties manufacturer of Lasdrop Shaft-Seals
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Old 31-07-2013, 04:00   #18
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Re: Oil Filled Prop Shaft

This Lasdrop is a shaft seal. What you need is another one of these on the SW side (without the bellows) as well as this one put a couple of bearings in and fill the space in between with oil and a header tk and hope for the best.
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Old 31-07-2013, 04:44   #19
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Re: Oil Filled Prop Shaft

The Seatorque system looks nice but very expensive and would be a problem to retrofit to existing sail boats.

Where you would go with this depends upon what you ultimately wish to achieve. The two more troublesome aspects of the old orthodox stern bearing and stuffing box are the need to regularly change out worn stern bearings and the continual problems with the consequences of salt water leakage thru the stern gland - even if your hull is non corrosive it still flings everywhere and causes things to go rusty.

Billdriver, what would you hope to achieve with an oil filled stern tube and would you prefer to design and build something yourself or fit an off-the-shelf system.
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Old 31-07-2013, 05:22   #20
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Re: Oil Filled Prop Shaft

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The Seatorque system looks nice but very expensive and would be a problem to retrofit to existing sail boats.

Where you would go with this depends upon what you ultimately wish to achieve. The two more troublesome aspects of the old orthodox stern bearing and stuffing box are the need to regularly change out worn stern bearings and the continual problems with the consequences of salt water leakage thru the stern gland - even if your hull is non corrosive it still flings everywhere and causes things to go rusty.

Billdriver, what would you hope to achieve with an oil filled stern tube and would you prefer to design and build something yourself or fit an off-the-shelf system.
Eliminate the need for stuffing box, cutlass bearing, reduce vibrations and remove thrust from the engine/transmission. Reduce almost all maintenance related to shaft and seals.
The only drawback seems to be the fabrication of the cross member to carry the thrust bearing in the space where it would have to be mounted.
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Old 31-07-2013, 15:01   #21
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Re: Oil Filled Prop Shaft

These are all very desirable outcomes and were also the reasons for my own plans to implement an oil filled system.

Since my stern tube is steel I intend to weld stainless steel flanges to both ends of it and mount the tapered roller bearings and seals in bolt on housings. The required pre-loading will be achieved by adjusting the length of the bushes on which the seals bear.

One of the problems I experienced with the predecessor to the gland arrangement illustrated above was that I used sealed, single row roller bearings and the shaft rotated inside them. This necessitated bearings with some sort of shaft locking arrangement. The Y bearings were the only ones available locally which have grub screws to lock onto the shaft.

I don't have a problem with transmitting the prop thrust through the gear box and engine mounts to the hull. Marine gearboxes and engine mounts are designed for this, although the system I propose with tapered roller bearings would do this directly via the stern tube - tapered roller bearings are designed for both radial and axial loading.

Should the shaft gland arrangement in the above image prove effective I may consider using just a miss-aligning spherical roller bearing on only the prop end of the shaft, these are supposed to allow shaft flexing without consequent damage to the bearing. You might consider this as a possible solution which would not need a thrust bearing.

I have a small lathe and mill aboard the vessel and enjoy mucking about in boats so doing and redoing these things to get them right is actually recreation for me. I don't mind doing them over a number of times and trying different things as I find it all interesting, it is a gainful way of filling my days at anchor when I am not cruising and there is a great deal of satisfaction to be gained from achieving a successful outcome without recourse to the excessively expensive marine supply organizations.
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Old 31-07-2013, 18:07   #22
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Re: Oil Filled Prop Shaft

RaymondR
If you fix the shaft at Sterntube and also at Gearbox, I would think you still need some flexibility somehow to allow for thermal expansion.
I would suggest that better to leave propshaft support only at Sterntube and thrust at gearbox.
Sorry I may have missed it, what seal arrangement have you decided on.
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Old 31-07-2013, 18:48   #23
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Re: Oil Filled Prop Shaft

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RaymondR
If you fix the shaft at Sterntube and also at Gearbox, I would think you still need some flexibility somehow to allow for thermal expansion.
I would suggest that better to leave propshaft support only at Sterntube and thrust at gearbox.
Sorry I may have missed it, what seal arrangement have you decided on.
RaymondR,

There is a flange on the exterior end of the tube that supports the tube. The interior end is also secured. The shaft then attaches to the thrust bearing assembly and proceed to a CV joint and spline assembly to the tranny. The seals are included in the shaft assembly along with the bearings that allow the shaft to rotate within the tube. Seatorque Control Systems, LLC will show how it works.
(Simple......uh hu! we'll see)
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Old 03-08-2013, 21:33   #24
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Re: Oil Filled Prop Shaft

My existing arrangement has a cutless bearing at the prop end and the engine end connects to the gearbox via a polyflex coupling. The thrust is transmitted to the hull via the gearbox and engine mounts. I think this is the commonest arrangement on sail boats.

I proposed two arrangements in this discussion:
Mounting tapered roller bearings on both ends of the stern tube with a short shaft with polyflex flexible couplings at both ends between the now fixed prop shaft and the gearbox to allow misalignment between the moving/vibrating, engine/gearbox and the fixed-to-hull stern tube.

or,

Retaining the present arrangement, single bearing with engine/gearbox movement/vibration allowed via a single flexible coupling at the gaearbox end, but replacing the cutless bearing with a seal and spherical roller bearing.

With the first proposal the prop shaft seals would retain the oil in the tube and with the second the existing gland and the seal for the spherical roller bearing would retain the oil in the tube.
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Old 04-08-2013, 00:23   #25
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Re: Oil Filled Prop Shaft

I am trying to upload sketches, not sure it is going to work.
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Old 04-08-2013, 00:30   #26
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Re: Oil Filled Prop Shaft

Dual Bearing.PDF
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