Strange stern gland update

[ZuidWester]

Thanks to those who offered advice already. I have made some progress as shown in the link below:
http://members.PhotoFun.com/zuidwester/boat

The seal is now out. It took me two days of buggering about and asking advice before I got the courage to use the club hammer to shift the case. A replacement seal cost Euros 3.50 at a local supplier.
I still have to remove the case that houses the bearing. It is extremely hard to access and is very tightly threaded onto the stern tube. The bearing race itself seems to consist of barrel-like bearings. There is no play in the prop shaft though, so I'm wondering if the bearings are really okay, but were insuficiently greased so that they produced a rumble when under full power! I live in hope.
Anyway, this seems to be a one-off stern seal arrangement, although one guy said that this is common on some ships (I guess he meant the 1000 - 2000 tonners that ply the Maas). The moral then is to check a boat CAREFULLY before you buy it...

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[david_bagshaw]

Sorry to say the rumble will definately mean both the inner & outer set & the outboard seal will need renewing., see my post on your other thread for a suggestion.

<hr width=100% size=1>David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[ongolo]

Hi Zuidwester,

I have designed a similar seal and bearing arrangement. I cannot see for sure on the pictures whether your bearing are cylindrical roller bearings or conical roller bearings. I almost suspect that they are conical which means they have to be adjusted for some play like a wheel bearing when you install them. This would also explain the presence of the grub screws to hold the assembly in position.

However, the bearings whatever they are shot. The seal is a simple industrial or automotive oil seal that is specified by its three dimensions d x D x w.

My system uses two seals inboard and three in tandem outboard side, I am also using self aligning spherical roller bearings on the out end and self alining ball bearing on the inner end. More expensive but no alingment problems or excessive wear ever.

I am also using adaptor sleeves to secure the bearings to make fitting and removing easier.

Lubrication was initially an oil bath system I suspect, which somebody out of ignorance filled with grease. The oil should be a sterntube oil which can emulsify in case you have a leakage from the outside.

The headertank with the oil feed should be at least 1.5m above the water line, so when a leak develops, oil runs OUT rather than water coming in.

A similar system using special oil seals and expensive like hell, which does not matter on ships, is called SIMPLEX SEALS. Why simplex I dont know as there are three or more in tandem. This system is used by the German Howaldt Ship Builder and by some Japanese Yards as well. That is where I got the idea from initially, I have also had drawings of a submarine shaft seal arrangement that is simlar. It is a good system and you should have a drip free installation.

To be safe, in an emergency, I could remove the bearing on the inside and install an ordinary gland and packing while in the water even when the outer seals are shot and let a little water in. Then I could replace the outer bearings and seals with either a teflon or vesconite bushing to leave me with a conventional installation.

As it has been mentioned, there must be a similar arrangement on the out end, probably with more than one seal. This means that to lubricate the outer seal initially, a lantern ring which must be filled with oil via a small screw, is located between the two or more outer seals. That lantern ring cannot be bought but must be turned to specs, so dont damage it. It is however not of critical dimensions and can be made from brass/bronxe or even steel.

good luck

ongolo


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