Stern Tube Lubrication

[derekwarner_decoy]

Hi PD's......I have moved this from another Folder.........

Castrol manufacture a product called........   forgotten the Trade name .....but is Rubber Grease...

"Castrol Girling Red Rubber Grease is a castor-lime based lubricant formulated for packing rubber dust covers in both hydraulic and mechanical braking systems. GRR is water and solvent resistant and may be used as a general-purpose non-injurious grease for components in contact with natural or synthetic rubbers"

......& this does not break down when in contact with water...so the model vessel does not leave those   tell tale OIL slick ....rings on the water.....

Now if some of our more technically enlightened members  .....could answer this VEXING question.....

If we consider the diametrical clearance between the propeller shaft & the gland bush under water......then relate this back to the diametrical clearance between the propeller shaft & the gland bush in the vessel.......with all things being equal & the pressure acting on both clearances being equal [1 atmosphere]...why does the oil leak out into the water in minute quantities?

1) is it the weight of the oil?
2) is it the fact that the inboard gland bush has marginally less pressure acting upon it due to actual height?
3) what is the relationship between the [1 atmosphere] acting on the depth of the water
between the water level & the immersed gland bush?.........
4) if oil has an SG of say 0.95...& water an SG of 1.0...why does the water not displace the oil back into the vessel bilge...... 

30 years ago I could not answer these questions so converted the model vessel's stern tube to Rubber Grease .....  .....this could be a good question for our members Sandy Campbell  or Moritz ......Derek

[towboatjoe]

I've always built my own stuffing tubes and used just plain black axle grease. I regrease once in the Spring each year and that does me.

[steamboatmodel]

I think(my wife disagrees) that the Oil/Grease being a lower SG floats on the water leaving a trail so we know where we have been. It works its way out of the stern tube due to a imperfect seal between the shaft and bearing, and the rotation of the shaft. Or there are demented microGremlins in the boat who pump it over board.
Regards,
Gerald

[andy]

Hm, I think, if you use a biological oil like olive oil, salad oil and so far, this was no problem. or use teflon bearings. Or if the brass bearings were in the perfect size, and the oil a stiffer one, between grease and oil, there will not come water into the hull. In all my models with propeller drive, I did nothing but a stiffer oil.

Andy

[derekwarner_decoy]

Hi PD's.....& Ken asks.... my shaft goes through a phosphor bronze bearing in the side of the hull. How would I stop water ingress please ?

Ken..both the real vessel & the 1/8 scale model have similar proportioned outboard bearing housings .......so you have a few options

1) manufacture two 'STERN TYPE TUBES'  ...now called SIDE TUBES complete with an oil/grease injection port & mount these in the sides of the hull..so the grease/oil stops the water entry...the only down side here is that the tubes may be say 1'' long...look at the recent posting by TBJ in Stern Tube Lubrication

2) I am sure Model shops have these pre built to suit the nominated shaft diameter & just require the actual tube length to be finalised prior to soft soldering in the second bronze bush

3) depending on weight concerns ...you could consider building a pair of outboard bearing block supports similar to the real vessel & the 1/8 scale model & manufacture similar set of side tubes......but extend the tube length from the inboard face of the hull to the outboard face of the bearing block....no one will know....& the closer the bearing to the load provides greater support.....you know what I mean 

4) one advantage of using the proprietry model shop tube sets [or make your own] is that the bushes are machined from solid brass/bronze...........stay away from sintered pre sized bronze bushes.......they are flooded with oil so are problematic  to LOCTITE or soft solder

5) another option is to use baby stainless steel ZZ sealed ball bearings  in the side tubes......if you purchase these from a Bearing supplier you will find the cost is LESS per unit than sintered bronze bushes.....another advantage here is ....they can be LOCTITED into that K&S thin wall brass tube from the hobby shop ......they are pre-lubricated for life & will not allow the ingress of water

6) the possibilities are endless.....but if you did consider any varient of the SIDE tubes......a tip is to soft solder an anti rotation lug or disk onto the OD of the tube in line with where it can be epoxied into the hull for construction......just  make sure you use a dummy axle shaft to line everything up prior to casting the final drops of cement 

7) oh ...will it ever end ?? Model shops also sell those little packets of DU-BRO model accessory components....you will find the range of small brass collars pre machined to suit 1/32"shaft increments.....these are drilled & tapped with a hollow pointed grub screw to fix & secure your paddle shaft ...so two of these can position the padle shaft so that it will never float......

  ......this may sound like radical dock yard surgery   ...but better happening this week than this time next year    

[derekwarner_decoy]

Hi PD's....as Andy notes......PTFE is OK for stern tube bearings & yes it is..... however 30 years ago I foolishly used glass filled nylon thinking  all would be OK  ..it swelled..it is also difficult to secure in any stern tube material.......here is a quotation from a NYLON manufacturer......

"Moisture absorption by nylon has been a source of great study for many years. Although all polymers absorb some amount of moisture, on none does it have such a significant effect as on nylons. Table 6.1 illustrates the moisture absorption levels of various types of nylons".

Virgin PTFE [poly tetra fluro etehelyene......something  ] has very low mechanical strength or resistance to abrasion...my best advice is to stick with bronze 

[bogstandard]

What really annoys me on this sort of debate, one drop of oil covers a very large surface of the lake, it looks a lot worse than it is. But the lake owners forget the background polution that they don't see, and ignore the pollution that they can. Pick on the minority.

My local lakes suffer very bad poisonous blue green algae (if we ever get more than a weeks sunshine), a lot of that is caused be the hundreds of lovely wild birds that populate the lake, geese, ducks, swans etc, just one of their droppings is more than equal to one drop of our oil. Don't forget the people that come to feed these lovely wild birds, tons of stale bread thrown into the water, a lot of it sinks, to go rancid on the bottom of the lake, more algae. Fishermen are just as bad, hundredweights of bottom fed ground bait (it sinks a lot quicker than the previously fed bread), most of it again, rots away in the depths, more algae.
Local yobs with their litter, beer bottles, coke cans, fag packets etc, all end up at the bottom of the lake, more algae.

And we are worried about one drop of oil.

The solution, go down at night and wring all the wild birds necks, if you find some fishermen there, wring theirs as well. Two thirds of the problem solved in one hit.

Wring the yobs necks during the day, you might find a lot of people wanting to help you on that one, and also any fishermen you missed on your night excursion.

The algae problem will dissappear very quickly, unless of course you have dumped all the carcasses in the lake, more algae.

John

[derekwarner_decoy]

Hi PD's .....& bogstandard asks.... "and we are worried about one drop of oil"........ well John....certainly I am not guilty  .....but those   nice Government Officers are

They are employed on 9.00 to 5.00 five days a week & are on overtime 9.00 to 5.00 on the weekend to catch some poor unsuspecting steam boat modeler depositing ONE drop of petroleum in their waterway

My thoughts & comments were simply to offer members a possible alternate to the Council fine..... Derek

[bogstandard]

Hi Derek,

Long time no speak.

I wasn't getting on your back Derek, just raising the point that a drop of oil, if you want to argue with the jobsworths and nazis, is nothing.

A few years ago there was a beautiful lake within a few miles of me. We hadn't sailed it for many a year, but the RSPCA decided it was a perfect place to release their rehabilitating swans. Very nice for about six months, but due to it being a country area, a lot of overhead wires, started to knock them off fairly regularly (great), then the wonderful swan watchers came, dumping huge quantities of stale bread in the lake. That got rid of a few more as they ended up with vitamin deficiency, through eating nothing but white bread (even more applause). It is now like an open sewer, to such a stage, the local council have put a large aeration pump in the middle, to try to rescue the lake, but it just makes the stench worse, it also annoys the residents because all this mist being projected into the air about 30ft, when the wind is in the wrong direction, covers their houses, cars and washing in this lovely ripe mixture.
I don't think the residents are worried about a drop of oil.

I could cure all their problems with a piece of rope and a shotgun.

The way around the problem is to tell the nazis that you are using something like peanut oil for lubrication, and it is full of vitamins and nutrients that does plant and wildlife the world of good.

Expect a big cheque through the post with an accompanying letter, asking you to sail as much as possible, plus you can and dump as much oil in there as you want.

They know not what they do.

BTW, I always use phos bronze bearings and multigrade (not peanut) oil.


John

[derekwarner_decoy]

Hi PD's........ ...John ..in a previous posting a few days ago ....I  said ..."God rest you merry gentleman"....& today you quote...."They know not what they do"....

...and then Andy notes "if you use a biological oil like olive oil, salad oil" ........so where is the GARLIC & red wine & 1/2 a loaf of bread & the two sardines to feed the masses?........ no ducks or geese or Kornal Saunders allowed ...... ...

PS....how are Bandit & Vinne coping in the new workshop?...........Derek

[steamboatmodel]

Hi John,
Don't try Peanut Oil, " all NUT products are hazardous " When my Son was in grade school, I not knowing of a Peanut Bane at his school sent him to school with a peanut butter sandwich for lunch. You would have thought I had sent him with poison from the reaction of the school, I was called to the school from work and told that by sending Peanut Products "I could have killed a child". I investigated the matter meanwhile sending the Lad off to school everyday with a Peanut Product in his lunch (Which was confiscated by the School and replaced by a cafeteria lunch at there expense), my investigation showed that the previous year there had been one child out of 600 at the school who had a slight peanut allergy, so the school instead of isolating that one child, banned peanuts for the whole school. But they would not bane the use of perfume, even though they had 17 children who were asthmatic and reacted to strong perfume. So watch out for the Peanut Nazis.
Regards,
Gerald
PS I have found that white lithium grease works well

[kno3]

White lithium grease is what I use in my stern tube. It's viscous (like a cream) and didn't seem to flow out through the bushing.

By the way, that peanut ban is incredible, sometimes I'm wondering if these people are still able to reason.

[Tug--Kenny]

Thank you for the information, Derek. Plenty to think about here.

Ken

[mjt60a]

I used vaseline in mine, only sailed it once so far (does the wind EVER stop blowing in southend? no wonder they put a wind farm just off shore...) but no problem with grease escaping or water entering, possibly helped by the fact it only gets 'splashed' by the paddles and not immersed like a prop tube...

[cosmic]

There are two good alternatives for this problem. Best: High Vacuum Silicon Grease (Dow Corning). Iy's used on petcocks for caustic fluid transmission. Won't wash out other than with strong acid, such as chromic. Next best: waterprood plumber's grease, used to lubricate faucet stems. The latter is available in the US at Home depot; I'm sure there's a source across the pond or down to Oz.