Stern gland greasing - why?

[vyv_cox]

That photo could almost have been taken on my boat. As can be seen from the photo, plenty of grease gets to (and through) the packing. I usually end up with a little pile of grease in the bilge under the gland. The stern tube also fills with grease though I have never noticed any exiting from the cutless bearing.

Same as mine was too. But the grease isn't injected through the packing, it goes astern of it. Maybe a bit of water pressure and rotation of the shaft helps but there's no direct mechanism for it to grease the packing rings.

 

[ironmaiden]

What you are describing is a lantern ring lubricator, common on some centrifugal pumps used for non-hazardous products. Years ago I had books that described these for stern glands but I've never come across one. The greaser on mine was located immediately astern of the packing rings, where grease injected may have reached the packing but probably not. No lantern ring though. Interested to know if you have come across any?

what I am discribing is a simple packing gland, what you are discribing is a high pressure gland which, while would work on a stern tube is not necessary, a lantern ring is placed into a pump gland as there are many more rings of packing.. 7 or even 9 rings it is placed in the middle of the rings to allow grease to spread evenly over the shaft, if it was not there then the grease would pool on top of the packing rings while the principle is the same, the type of gland you are discribing will take much higher speed and conciderably more pressure, 150/200 psi.

some packing glands do have grease entry abaft the packing, which will eventually fill the stern tube with grease if it is used over many years, grease is carried up the shaft on rotation to feed the packing, but I have found in my own experience that they are not as good as stuffing boxes that grease the packing directly.

regards rachel.

 

[vyv_cox]

Lantern rings are certainly not only used with high pressure pumps, nor with multiple packing rings. However, that's not my point.

You refer to packings in which the grease is supplied to, or through, the rings. Every one I have ever seen supplies it to the aft side, like this

I am asking whether you can show me a photo, drawing, link, etc of one as you describe.

Edit: I know it describes it as a bearing but we know it isn't. Not my drawing!

 

[alahol2]

Lantern rings are certainly not only used with high pressure pumps, nor with multiple packing rings. However, that's not my point.

You refer to packings in which the grease is supplied to, or through, the rings. Every one I have ever seen supplies it to the aft side, like this

I am asking whether you can show me a photo, drawing, link, etc of one as you describe.

Edit: I know it describes it as a bearing but we know it isn't. Not my drawing!

I have often wondered, is there an actual bearing inside the bit of the 'bearing' which is marked 'bearing'?
Actually, looking at that diagram, it seems to be going 'uphill' towards the stern?

 

[vyv_cox]

So is the text! I suspect somebody scanned it at an angle and posted it as it was. I only used it as a rough guide. I guess there could well be contact between that part and the shaft, so in that sense it is a bearing. Maybe that's why it's greased, nothing to do with the packing rings at all!

 

[NormanS]

Shaft packing, (and Lantern Rings)

After more years than I care to remember, being intimately involved in the installation and maintenance of all types of water pumps, I have, as they say, probably packed more pumps than you've had hot dinners.

Gland packing does NOT require grease to make a seal. It will, however not do any harm to the packing or sealing, but as previously stated, grease can harm a Cutless bearing.

Lantern rings are commonly used on the suction side of pumps. Air wants to get into the suction side of a pump, and often water is taken from the second stage of a multi-stage turbine pump, and introduced into the middle of the suction packing, by means of a Lantern Ring, in order to improve the seal, and to provide cooling and lubrication. I wouldn't have thought that lantern Rings would have any relevance in the propeller shaft packing on a boat.

Personally, I have a horror of packing glands mounted on bits of rubber hose, and would always recommend a rigid packing gland, properly fastened to the inboard end of the sterntube, but obviously using an Aquadrive, or similar coupling, if the engine is flexibly mounted. Incidentally, I feel that a properly lined-up engine solidly mounted on proper bearers is better, but it does require to be accurately lined up to the shaft. few people are prepared, or able, to take the trouble to do this.

 

[Tranona]

Personally, I have a horror of packing glands mounted on bits of rubber hose, and would always recommend a rigid packing gland, properly fastened to the inboard end of the sterntube, but obviously using an Aquadrive, or similar coupling, if the engine is flexibly mounted. Incidentally, I feel that a properly lined-up engine solidly mounted on proper bearers is better, but it does require to be accurately lined up to the shaft. few people are prepared, or able, to take the trouble to do this.

Think your horror may be misplaced. There are thousands of boats happily using flexibly mounted traditional style stuffing boxes. They came in when flexibly mounted engines became popular and often in installations using a P bracket, where the stern tube is in fact just an open ended tube with no bearing. The hose provides some support for the inboard end of the shaft though not as much as a full bearing. It does however allow the whole shaft to move with the engine. No grease is needed in this type because there is no white metal bearing to grease.

Defintely do not agree with solid mounts. Imagine a 1 GM on solid mounts! Would keep your dentist busy! The optimum set up for me, having been through all variations is flexible mounts, flexible coupling (Centaflex, or in my case Bullflex), Volvo seal, rigid shaft with cutless inboard and outboard bearings. Simple and minimal maintenance. Operated perfectly for the last 13 years with a Yanmar 1 GM and retained with my new Nanni 14. Agree totally with the need to line up properly, even though the Bullflex will tolerate 2 degrees out. Always satisfying when the coupling bolts slide in perfectly and the gap is the same at all 4 bolts!

 

[Neil_Y]

Spot on Norman, I'd love to find out who first started selling systems with grease as there are parts of the world where they are almost never seen with grease, I can't see what benefits grease offers in a properly set up packing gland as you say they lubricate, cool and seal in pumps as well as many stern glands without any grease. When greased systems have shown up it has been because the bearings have failed due to the grease preventing good water flow.

As far as bearings and flexible engine mounts are concerned I'd suggest a properly designed and fitted bearing system (not rubber) can support the shaft enough to prevent deflection even when the engine is rubber mounted. The fact that marine systems have become used to (in many cases) minimal support, rubber bearings and slim shafts that allow the shaft to deflect under thrust has meant there is a need in some designs for a simple thrust bearing set up to isolate the shaft from the engine.

Rigid close tolerance bearings properly aligned will keep a shaft in line under thrust and torque. Even if the engine bottoms on its mounts in heavy seas and the shaft touches the bearing surface momentarily, with dry running lubricants this is not a problem.

To give an idea of what sort of delection can happen, on a 50.00mm shaft there can be a deflection of 0.16mm over a bearing length of 200.00mm when the shaft touches the bearing, if you do the maths thats only 0.05 of a degree which in an adpator plate of 100.00mm diameter results in a gap 0.08mm or not much, so you can virtually assume the shaft is held rigid. When setting up alignment o.10mm is very good on a 100.00mm plate. So the shaft can not move this much however much the engine moves.

 

[LittleSister]

Re refilling remote greaser (if you have/want one) - a couple of people have mentioned this as a problem, but i haven't found it particularly so. I can't see the advantage of an icing dispenser.

My (probably rather amateur) method - unscrew the reservoir body from the base (not the cap from the body!). Your tin of grease will (almost certainly) have a thin metal plate with a hole in it sitting on top of the grease. Place the bottom of the reservoir body over the hole and push, while un-screwing (i.e. anti-clockwise) the reservoir greaser knob. (I find it easiest to do this starting by putting the grease can on its side on the companionway step, and having the reservoir horizontal. If you have the luxury of two people. one pushing the other screwing (as it were!) all the better.) The combination of the pressure on the grease in its tin, and suction into the reservoir body, more or less fills the reservoir by the time you've fully unwound the greaser knob. I probably wouldn't do this in my Sunday best, but i don't remember it being very messy.

Alternative potential method - try unscrewing the greaser knob fully before trying to get grease in, put the bottom of the reservoir body over the hole in the grease can 'inner cover', as before. Now turn it upside down (i.e. grease can mouth facing down, reservoir end opening facing up) and push on a low ceiling (cabin roof?) to force grease into reservoir. This latter method probably best restricted to those with a good sense of humour and without carpet underfoot, just in case!

 

[vyv_cox]

Lantern rings are commonly used on the suction side of pumps. Air wants to get into the suction side of a pump, and often water is taken from the second stage of a multi-stage turbine pump, and introduced into the middle of the suction packing, by means of a Lantern Ring, in order to improve the seal, and to provide cooling and lubrication. I wouldn't have thought that lantern Rings would have any relevance in the propeller shaft packing on a boat.

I'm not arguing. Many years ago I recall seeing a drawing of a device very like a lantern ring intended to take grease between the rings of a stern gland packing. I've often wondered whether any exist, as I have yet to see one.

A decent rubber-mounted packing gland doesn't depend upon the hose for torsional strength. You can see in this photo

that my stern tube has two lugs on its forward end. These mate with similar ones on the stuffing box. So the rubber hose does no more than any other hose, i.e. keeps the water out of the boat.