PDA

View Full Version : Got my new vesconite prop shaft bushes



sdowney717
11-25-2005, 07:48 AM
installed.
Very nicely made and machined, a hard grey solid plastic with 6 water channels. I put them in the freezer overnight and pressed them in using a press.
If they live up to their claims about very low wear well worth the price, only paid $23 per bushing. They make vesconite and vesconite hi lube. It is important to freeze then in the freezer or use dry ice. They shrink and it is easier to install, when they warm up they lock in place.

http://www.vesconite.com/industry/marine/marine.htm

Aramas
11-25-2005, 08:03 AM
God I hate proprietry polymers. The section on the website following "What is Vesconite" should read: "We're not telling". It's a polymer. Whoopee. So is wood. So is lettuce, for that matter.

Just another PTFE bearing with some fruity filler? Or a non-Newtonian, pan-dimensional quantum probability field on a stick? Who can tell?

Ross M
11-25-2005, 11:11 AM
My bet is a polyimide like DuPont's Vespel or polyamide-imide similar (Amoco's?) Torlon.

In the right app, both are amazingly high performing materials...

sdowney717
11-25-2005, 11:37 AM
who knows what it is made of..
You can also have them machined for a sliding slip fit into the housing and use loctite or an epoxy to secure it, so you would never need to worry about finding a press again. With a press fit, the bushing actually shrinks its internal diameter ever so slightly, using a slip fit the internal bore would be machined for a tighter clearance. I estimate my clearance now at a little under .010 to the shaft

sdowney717
01-15-2016, 12:18 PM
Updating, so it has been about 10 years!! on these vesconite bushings.
They work just fine. They have not worn themself or the shaft.
They do have an issue though. IF a small rope like 1/4 inch nylon from a crab trap wraps your shaft, the vesconite can be melted away by frictional heat of rope rubbing the bushing. Last haulout 2015?, I dug out about 1/2 inch of nylon rope that had undercut into the bushing. I went back in without replacing the bushings. I think next haulout, I will get some new vesconite bushings made.
Before I went back in, I glued on a piece of PVC around the shaft in the space between prop and strut thinking it might keep a line away from the bushing.

Peerie Maa
01-15-2016, 12:29 PM
^ Then again there are things like this:
http://www.spursmarine.com/shaft-main.html

sdowney717
01-15-2016, 12:34 PM
I had a nice hard ball of nylon rope wrapped around the shaft.
It was extremely tight and very difficult to get off.
One advantage in my favor is vesconite is self lubricating, so even though water flow must have been compromised, everything survived ok. Not sure if rubber would have held up if water flow was blocked.

I do like the spur idea.

paulf
01-15-2016, 01:52 PM
It has unobtainium cryogenicly fused into the matrix.

Seriously, poly pro rope with sand in it will saw off a prop shaft.

Breakaway
01-15-2016, 02:07 PM
^ Then again there are things like this:
http://www.spursmarine.com/shaft-main.html

These work, but have their flaws. They create drag and may create bubbles flowing over the prop. You also need to increase the distance between the bearing and the prop hub to a dimension beyond accepted iimits ( ABYC--ymmv).

These are best on slower boats with big gear reductions and slow shaft rpm.

Kevin

sdowney717
01-15-2016, 02:58 PM
These work, but have their flaws. They create drag and may create bubbles flowing over the prop. You also need to increase the distance between the bearing and the prop hub to a dimension beyond accepted iimits ( ABYC--ymmv).

These are best on slower boats with big gear reductions and slow shaft rpm.

Kevin
I imagine the slower your shaft turns, the efficiency drag issues would be much lessened.
I have debated buying them in the past and have not simply due to I don't want to spend the money.BY:D
Having 2 props, It would cost me double.

I think I have about 1 inch between prop and the strut.

Neil_Y
01-23-2016, 12:41 PM
There is also the newer quicKutter rope cutter from Perth, these are used by the UK RNLI and Navy (they removed Spurs cutters) there are also two other companies in the UK making scissor cutters that operate in a similar way to Spurs, the Gator and the Stripper.

As far as I know Vesconite is very different to Vespel, Vespel is a a much higher temperature bearing that uses graphite as its friction reducer, Vesconite is a thermoplastic that melts and absorbs a similar percentages of water to other composite bearing materials. There are a number of more advanced composites with lubricants that have performed very well on marine shafts but I might be seen as biased on that subject.

sdowney717
02-02-2016, 03:54 PM
There is also the newer quicKutter rope cutter from Perth, these are used by the UK RNLI and Navy (they removed Spurs cutters) there are also two other companies in the UK making scissor cutters that operate in a similar way to Spurs, the Gator and the Stripper.

As far as I know Vesconite is very different to Vespel, Vespel is a a much higher temperature bearing that uses graphite as its friction reducer, Vesconite is a thermoplastic that melts and absorbs a similar percentages of water to other composite bearing materials. There are a number of more advanced composites with lubricants that have performed very well on marine shafts but I might be seen as biased on that subject.

Well, if you believe the company that makes Vesconite, they specifically say it does not absorb water and swell. They do mention nylon swells and can lock shafts. My shafts have never done that.
Vesconte can melt if it gets real hot, the rope rubbing nylon friction created enough heat to do that, anod or maybe it was high pressure wearing, I know that rope was wedged in extremely tightly and hard, and the thrust is forward into the bushing, however it was kind of unusual thing that happened. I have thought if you screwed a bronze washer onto the end of the strut tube, a rope could not work its way up against the Vesconite.

Neil_Y
02-02-2016, 04:24 PM
Well, if you believe the company that makes Vesconite, they specifically say it does not absorb water and swell. They do mention nylon swells and can lock shafts.

I know, it's confusing, they state in one place that it doesn't absorb water but if you read their own specification sheets on the same website it does absorb water and swell at 0.50% at 20C.

With the new range of composite bearings that are available the largest change in dimensions is now as a result of thermal expansion so this is far more important than moisture swell, and this will be the major factor in determining your clearances. There are also now non melting composites which don't get soft and sticky as they get hot.

Nylon when it was new was thought to be a miracle polymer but it has quite high moisture absorption and in the marine industry they learnt the hard way. The simple fact is no body should go near Nylon for a bearing where there is any moisture involved.

Most modern composite bearings will achieve 0.5% or less as a moisture absorption figure, but thermal swell over the working temperature range will probably be larger, but always best to check the specification sheets and ask the manufacturer what clearances to run.

sdowney717
02-02-2016, 04:35 PM
I know, it's confusing, they state in one place that it doesn't absorb water but if you read their own specification sheets on the same website it does absorb water and swell at 0.50% at 20C.

With the new range of composite bearings that are available the largest change in dimensions is now as a result of thermal expansion so this is far more important than moisture swell, and this will be the major factor in determining your clearances. There are also now non melting composites which don't get soft and sticky as they get hot.

Nylon when it was new was thought to be a miracle polymer but it has quite high moisture absorption and in the marine industry they learnt the hard way. The simple fact is no body should go near Nylon for a bearing where there is any moisture involved.

Most modern composite bearings will achieve 0.5% or less as a moisture absorption figure, but thermal swell over the working temperature range will probably be larger, but always best to check the specification sheets and ask the manufacturer what clearances to run.

Even at 0.5% swell, not enough swell to make any difference. I know that after almost 10 years in the water, when the boat came out there was no play in the bushing, and the prop turned freely.
There is always the question of cost, getting a bushing made from Vespel, I don't have a clue what that might cost. I sort of like the idea of screwing a bronze plate on the end just in case some rope wedged in there again. Before I went back in, I glued on some PVC pipe fittings around the shaft, close up to end of strut to prevent any rope getting down in there again.
I certainly know the much higher cost of a rubber lined bronze bush for myself, it is not worth the expense.