Stainless experts, please convene.

[Roger Long]

My wind vane got very "clacky" and loose sounding when I grabbed the tower and I found a lot of play in the bearings. Cape Horn sent me a new set of bearings at no cost and this is what I found when I took things apart.

All my dealings with Cape Horn incline me to believe Yves when he says that he has never seen anything like this and he is still using the same set of bearing that he put in 20 years and two Atlantic crossings ago. There's quite a bit of rust which turned into an abrasive that wore the bearings in just three short seasons of coastal sailing. The bearings are a self lubricating plastic and he has never used any lubricant on his.

My theory is that being in an urban environment and downwind from the city results in a lot of grit. I certainly see it on my decks. I think the grit wears away the oxide layer of the stainless and the rust then grinds away the bearings.

Do you think I'm on the right track or is there something else going on?

I'm going to polish the bearing surfaces and re-passivate with Spotless Stainless. Now that I'll be spending most of my time in cleaner environments, I expect the new bearings to last considerably longer.

 

[SEMIJim]

My theory is that being in an urban environment and downwind from the city results in a lot of grit. I certainly see it on my decks. I think the grit wears away the oxide layer of the stainless and the rust then grinds away the bearings.

Do you think I'm on the right track or is there something else going on?

I'm no "stainless expert," but, given what I know of how stainless steel works, that seems a perfectly viable theory to me.

Jim

 

[rpwillia]

Concur

We are 1/2 mile away from a power plant and rumor has it we have a lot of heavy metals in our air. If you are seeing grit on your decks, that stuff tends to get everywhere.

 

[Rick D]

How About All The Work On The Boat?

nm

 

[Fly_H23]

Wonder if you could affix some sort of boot over it to prevent dirt/grit from dropping down in the bearings?

 

[RichH]

Probably not a problem with the stainless (per se) but rather a problem of 'surface finish' vs. the plastic (Delrin/Acetal ?) bearing.
If surface roughness develops on the stainless, Delrin etc. will quickly abrade and 'transfer' to the shafting with the result of accelerate bearing wear (DO NOT 'LUBRICATE' Delrin/Acetal - or you risk swelling/softening).
(I'm not a happy camper with Delrin for bearings - transfers to shafting surfaces by micro abrasion and is subject to 'fretting'.)

Of course, development of surface roughness will accelerate surface corrosion and 'crevice corrosion' on a macromolecular scale along the 'grain boundaries' of the base metal, etc. and I 'think' thats what I'm seeing in your pic.
I would also make the guess that this component 'sat around' for a long time with no 'rotation' to keep the shafting polished .... this will accelerate the affect of increased surface roughness and in that regard (by Yves' apparent scantling history) this will not occur again if you USE the windvane.

Rx: re-polish the shafting to 'extra fine' surface finish (mirror polishing with extra fine "tripoli' compound, etc.). I'd also opt toward a surface roughness of ~5 micro-inches (Ra) surface roughness - hard to do by hand and to keep the normal bearing clearances (0.001" per inch of shaft diameter ??) accurate and true.

 

[Roger Long]

(DO NOT 'LUBRICATE' Delrin/Acetal - or you risk swelling/softening).

Does this include the synthetic Superlube Peggie recommends for head pumps and dry silicone sprays? The bearing material is UHMW polyethylene.

I hadn't thought about lack of use. The windvane has been used on daysails 2 - 6 times a week and 1 - 4 two week cruises since installation in 2007. With Maine's short season, that does translate into into a lot of sitting around though. I see a lot of these vanes on boat that don't get used much, perhaps they also have the problem and just haven't noticed. I should be moving pretty much constantly now so the vane should get plenty of exercise.

Polishing is going to be a real challenge since the other end of the shaft has a assymetrical weldment that precludes putting it in a lathe. The bearings are a fairly loose fit to start since it is an ultra low speed shaft. If I remove much metal, I'll be right back where I started.

The new bearings have a radial groove pattern on the inside. It looks a lot like a vinyl record surface but a bit finer. I would have expected a polished surface.

 

[Roger Long]

The bearing material is UHMW polyethylene.

 

[tommays]

UHWM is good because its water stable compared to other plastics BUT none of them deal well with grit

You cant really polish it other then a fine feed when its machined

 

[kloudie1]

Might be good to talk to some guys like these .. Self-lube bearings.. We used a lot of stuff like that in water pump repair at the refinery.. Works well.. When ya talk to 'em, they may suggest a better "engineered polymer" for that application.. There may be a need for a couple of "trash grooves" as in Cutless , to allow the grits (OK, that may be a southern problem) to flush out .. Rich H has the ticket on the stainless..
http://www.igus.com/iPro/iPro_02_0001_0000_USen.htm?c=US&l=en

 

[RichH]

Does this include the synthetic Superlube Peggie recommends for head pumps and dry silicone sprays? The bearing material is UHMW polyethylene.

Polyethylene is stable with most aggressive lubricants/chemicals; hwever, its not so good for 'abrasion' service .... so shaft surface finish becomes important

Polishing is going to be a real challenge since the other end of the shaft has a assymetrical weldment that precludes putting it in a lathe. The bearings are a fairly loose fit to start since it is an ultra low speed shaft. If I remove much metal, I'll be right back where I started.

Then youre going to have to do a 'hand job'

The new bearings have a radial groove pattern on the inside. It looks a lot like a vinyl record surface but a bit finer. I would have expected a polished surface.

The are probably only 'lathe cut', normal for 'polymer plain bearings' - not a problem as its the shaft surface roughness that causes the 'wear' problem

Ive seen this problem many times in chemical service with 'plain bearings and SS shafting, etc.' ... back in medieval times when I was engineering 'plastic bearings' ... back before the time of the steam engine. Proper clearance is important .... the installed clearance should be close to ~0.001"-0.002" / inch of shaft diameter, if more sloppy than that you get 'point to point' contact between the surfaces which tends to lead to accelerated wear; I state this so you dont 'hog down' the shaft diameter in an attempt to 'over-polish' it - just remove the pits, rust, scores/galling and put a 'bright' finish on the shaft.

 

[Allan12210]

Roger,

I would look into Rulon beaings. It is a composite of nylon and teflon. We used to use them in high load applications. More stable than UMHW and self lubricating. Check this link

http://www.tstar.com/rulon-plane-bearings

The grooves you saw in new bearings is to reduce contact area. If it is perfectly smooth, then the friction goes up.

Allan

 

[Roger Long]

Proper clearance is important ....

I think these have more than that. The new ones make a barely audible "click" when I wiggle them on the shaft. The worn ones make a loud "clack". I wish I could find my feel gauge. I may have to buy one this afternoon.

Cape Horn said they would make a set for me with tighter tolerances but there's a question of whether I want to wait for them. I may just give these a try and deal with it in a couple years if there is a problem. The vane works fine, the tower just rattles when you grab it (it doubles as a hand rail for going up and down the boarding ladder to the dinghy) and sometimes under power.

 

[Bill Roosa]

You can try heat treating the plastic to make it smooth. I've had some limited success ( and nasty failures too) with passing a propane tourch over the "well sanded" surface to get a polished look.

 

[OldCat]

I'm not a happy camper with Delrin for bearings - transfers to shafting surfaces by micro abrasion and is subject to 'fretting'..

How about Teflon filled Delrin AF? Delrin for stability, Teflon for lubricity. ??

OC

 

[kloudie1]

Roger, sounds like the bearings you have will be fine !! Some of the ID will disappear as the constrained bearing swells a bit with water/humidity absorption.

 

[OldCat]

Polishing is going to be a real challenge since the other end of the shaft has a assymetrical weldment that precludes putting it in a lathe. The bearings are a fairly loose fit to start since it is an ultra low speed shaft. If I remove much metal, I'll be right back where I started.

The lathes in the machine shop that I used to manage had holes through them. If the shaft is long enough & the stuff on the end not massive enough to create a vibration problem, then it can be chucked in the lathe by pushing it through "from the back" as it were.

Is the design such that you can remove metal and have a custom bushing made with a smaller bore?

Or, could a sleeve be pressed on the shaft? Guess I'd worry about corrosion in a marine environment for that, but could the joint be sealed? I would consider a Loctite product to seal a joint such as this & their recommendations regarding fit to seal the joint.

But, my experience on this is clean rooms, not salt water...

OC

 

[Roger Long]

I polished up the shaft and the bearings feel like a pretty good fit. There is some slight scoring on the bottom of the shaft that I can't get out but these are very, very, low speed and lightly loaded bearings so I'm not going to worry about it for now.

 

[CarlN]

Roger,

Whatever you end up with for bearings, have you tried this McLube product:

http://www.mclubemarine.com/onedrop/

I've been using it for a few years and bearings seem to stay cleaner. I started using it because I've been so happy with SailKote as a dry lube. I spray it all over the place. - sail tracks, companionway slides, etc. Not only is there no WD40 type petroleum stickiness but it is hydrophobic - so dirt and salt really don't have much to hold onto. I'm pretty new to their bearing lube but I figure it must have some similarities.

Carl

 

[Ron20324]

Take the tube to a muffler shop and have them put a pipe expander in the end. MAYBE it will open up the OD enough to bring it back to OEM size?