Delayed
A message from John Woodworth read, “Day before departure and I see Moli is missing her prop.”
Indeed, Mo is again on the hard at KKMI Boatyard where, on Thursday, I extracted her propeller, shaft, and thrust bearing two days before she was to sail under the Golden Gate Bridge.
New Figure 8 departure date: October 28.
What’s going on?
Here’s the back-story.
In August, when I hauled the boat to inspect her rudder and drivetrain, I found that the plain bearing that carries the after end of the propeller shaft had failed. The material, a soft metal alloy called Babbitt, had fractured in several places.
View of the inside of the old Babbitt bearing. Note fractures in the casing.
By today’s standards, Mo’s drivetrain is ancient technology. Instead of the standard stuffing box and water-cooled cutlass bearing arrangement, Mo’s propeller shaft passes through a long tube filled with grease. Two plain bearings (no moving parts) hold the shaft in place, and two lip seals at each end of the tube hold the grease in and the water out. This was cutting edge machinery when the Model-T came rolling off the line but is now only found on old fishboats.
How this shaft bearing had failed was unclear, but I decided to update the old Babbitt with a high-tech plastic called Vesconite, a product that is used as bearing material by the tugboats in the Bay Area.
While everything was apart, I also decided to replace the thrust bearing.
Once back in the water, problems with the drivetrain began immediately. The shaft tube spat its grease into the bilge after only a few hours of operation, and on one occasion, I heard the shaft squeak as it rotated. I also noted that the new thrust bearing wobbled slightly and got warmer (160 degrees Fahrenheit after several hours of hard motoring) than I thought warranted.
I’ve been working the problem with Mo in the water these last weeks. Did I damage the lip seals while installing the new shaft? Had I popped them by pumping too much grease in the tube? Had I used the wrong grease? Had I damaged the thrust bearing while pressing it in place; was the press a straight one? Most importantly, could I live with these issues for the duration of the Figure 8, including 5,000 miles of mostly motoring in the Arctic?
All this was happening in the run-up to departure. Food, water, and fuel were aboard; charts had been audited and augmented where necessary; new electronics were installed and tested. Mo was otherwise ready and the season, getting on; so, I decided to worry about this problem later. I bought great quantities of grease and explored places to haul the boat in New Foundland when I arrived in the spring of next year.
But the last straw was plucked from my confidence when I noted the new thrust bearing, a non-serviceable part, was spitting its own grease. I had another look at Figure 8 weather windows and, after a conference with Joanna, decided a two-week delay here carried less risk than a departure with such problems below the waterline.
So, we moved Mo’s sailing date from October 15 to October 28, and I hauled the boat last Wednesday.
As Mo slid into her slings, I thought I was looking to solve two problems, a leaky grease tube and a leaky thrust bearing. However, a third issue quickly made itself evident: the new plastic bearing had melted.
New Vesconite bearing going in back in August.
Vesconite bearing as found last week. Note scoring.
Thomas Merton never reached deeper into his soul than have I these last days. With so few moving parts, disassembled with the help of Caleb at KKMI and now laid out singularly on a table, one would think the problem to be as evident as a pot-hole on a country road.
It is not. Bent shaft? Nope. Misaligned shaft? Nope. Injured lip seals? Nope. Bearing swell due to exposure to grease and water? Nope. Wrong tolerances for the new bearing? Unlikely, as work was done by a professional shop. Wrong grease (Calcium-based axel grease)? Maybe, but unlikely to be the cause of such extreme failure.
Dave at The Prop Shop checking the shaft for true with a dial indicator.
Lacking a definitive culprit and with no time for further experimentation, I’ve decided to ditch the new technology in favor of the old. Though I have a spare Vesconite bearing, I’m having a new bearing machined from Babbitt. On Friday, I visited RotoMetals in San Leandro and bought nine-pounds of Babbitt ingots, and on Monday, Dave at the Propeller Shop will pour and then machine a new bearing to meet the exact specifications of the bearing that has worked in Mo for 30 years.
Nine pounds of Babbit ingots plus their elemental breakdown.
And with that done successfully, the Figure 8 will be back on schedule…
Aaaaargh…what a disaapointment and pain. See you in NFLd in the spring as we are soon to make the trek north albeit at a much more leisurely pace.
Dude!
Babbitt bearings didn’t stop working. Thousands of machines still run on them worldwide. Tried and true. Just old fashioned.
My shaft is also in a tube but instead of grease I use heavy transmission oil. There are two bearings, one is the thrust bearing towards the tranny and then at the other end of the tube is much smaller ball bearing assembly with an oil seal, then water seal and bolt on cap. That is how the Meta yard has been doing it for many years maybe even today although I think Gerd used something more modern on his build.
Are you solving the problem or did you uncover Mo’s archilles heel? https://en.m.wikipedia.org/wiki/Achilles%27_heel Do you really do surgery and leave on a Figure-8 voyage without running-in your ‘fix’ for a good length of time… at least there are haul outs in Mexico but will likely loose your voyage window… as always be safe… time is on your side with next year open to the voyage.
BTW – Did you note the 2017 NWP sea ice blockages in Victoria-Franklin Straits this season… expect more in 2018 with the cold vortex weather trend…
Voyage Adviser
Arcticnorthwestpassage.blogspot.com
It is a mistake to use any grease with water lubricated bearings. They rely on the water for cooling and the grease stops the water from flowing through the grooves in the bearing. They then start heating up, the plastic swells, and they quickly destroys itself. All I would use is a light wipe of synthetic grease for first start on the dry shaft. I would also make sure there is water at the shaft seal before you start spinning the shaft too hard. FWIW, you have to be careful any time you put any oil or grease on a plastic. Some plastics are damaged by greases or oils, since they are both petroleum products. I try to use synthetic based products after seeing some plastic plumbing and an autopilot destroyed by a spray of WD-40. There are warnings about this in aviation but for some reason people on boats don’t know about this problem and just spray petroleum based products like WD-40 on anything. Best of luck with your voyage. Moli looks great.
I just looked at the pictures again. On my boat, there is no lip seal where the shaft exits the tube at the prop. There is water is allowed to come in, filling the shaft tube. Some boats just let the water flow up from the bottom but on larger shafts, water may be injected near the shaft seal into the tube to assure no air, good water flow, and good cooling.
On point… the shaft on my 55′ has a small scoop to force cooling/lube seawater into the shaft tube… the seawater exits through the cutlass bearing grooves for cooling and lubrication…
The original babbit lasted for how many years? 30? The new plastic bearing for less than an oil change? Something drastically wrong with the plastic implementation… grease blocking the water grooves? Yabetcha… but even at that it should of lasted longer… I suspect a poly line wrapped around the prop melted into the bearing?
My original installation was similar with a small 1/2 inch hole in the side of the tube to allow water to flow to the old rubber grooved cutlass bearing. When I went to a higher tech plastic, I decided to go with direct water injection with a hose as they recommend with large diameter shafts. It is probably over-kill but I am glad I have done it. The more I think of it, I think using a lip seal on the bottom of the tube was a big mistake since it completely blocks the water from getting to the bearing. I am really surprised the boat yard would do this on something that is meant to be water cooled. IMO, they should have known better.
Wow! A lot of great info! Although you’ll be sailing alone, as long as you have connection, sounds like there’s a great team of sailors sharing the adventure. Sorry for your delay, but awesome that it happened in dock. Chapter one… 😁
Whewwww! Characters, problem, climax, resolution. All elements of a great story. And the low tech resolution calmed my racing heart and sweaty palms!!!
Low tech has seved me well over many a nautical mile. I believe it will.you as well.
Wow! what a journey you’ve travelled even before the voyage!! Well done on working through all the trials and getting it done. So interesting to follow. In your comments ” bent shaft? Nope. Misaligned shaft? Nope. Injured lip seal? Nope………..wrong tolerates for the new bearing? Unlikely”.
My experience with Vesconite is that is has performed admirably and I really think that the “unlikely” is probably the likely. The Vesconite I know has multiple approvals like American Bureau of Shipping, Germanscher Lloyd and others. To get these it must have done something right so I’m pretty sure that if ever you are faced with another bearing dilemma, give Vesconite another go. Happy sailing.
Question to Stunned Mullet: Why discuss water cooled bearings? I believe the author says: “Instead of the standard stuffing box and water-cooled cutlass bearing arrangement, Mo’s propeller shaft passes through a long tube filled with grease…[with] two lip seals at each end of the tube hold the grease in and the water out.” Sounds like Moli’s arrangement is not water cooled, but sealed, which would imply that lubricants are necessary. Am I missing something?
The boat has been out of the water many times… i question the original tube designed to be filled with grease lubricant in this small a boat.. what have the previous two owners done to the boat? Even if filled with grease, I cannot imagine a new poly bearing failing from short motoring time… how many hours of motoring since the babbet was replaced with a poly bearing? What advise did the poly bearing mfg give? Something is not being fully told.
Vesconite is good at 100C for continuous use… but note it is only moderately chemically resistant… “melt” was chemical attack by the lubricant makes the most sense to me.
What say others?
VA
It depends on Vesconite and it’s chemical resistance. There should be a data sheet on it from the manufacturer. I really think damage was caused due to no water in the bearing. It would start in only a few minutes. It is surprising how quickly something like this can heat up. The plastic would swell as it heats and just get tighter. I have had old style bronze grease shaft seals too tight in the past and they got hot to touch after only about 10 minutes running.
The long and the short of it:
1. Dont mix technologies. Vesconite is SELF lubricating for continuous service to 100C. Submerged in sea water never reaches boiling temps.
2. Its actually a dis-service to add a grease into the shaft tube coming into contact with vesconite – the grease chemically attacts the vesconite bearing.
3. The vesconite bearing was fabricated with lanes to allow sea water flow through to promote cooling and flushing of wastes.
Unless proper aligned, shafting true and non-resonate in operating rpm, not to mention secured in place… no bearing will have a good service life.
VA
Because the Vesconite bearing that was used is a water cooled bearing. It is mixing technologies to use a water cooled bearing in a non watercooled shaft arrangement.
Hm, well, yes and no. I agree that once it got too hot, a vicious spiral got going: tigher tolerances more friction. I’m technologically conservative, am very comfortable with babbitt, so I’m not the person to defend Vesconite. However, going through the literature, I see that Vesconite can be lubricated, or water cooled, or run dry; it’s a “water friendly” technology but not a “water only” technology. The vendor states that Vesconite is resistant to oils, petroleum, and organic solvents. Obviously, in hindsight, we’re *all* cheering for babbitt now.
October 28th has come and gone… double delayed? Whats up?
Hi – this is Randall’s support team. Departure happened yesterday as expected. We’re working out some kinks on communication updates and have a post organized to queue. You can see where he is on the tracker tab of the site.