Now I've seen it all <G>

I come across some awful bodges perpetrated on boats from time to
time, and some bizarre uses of silicone sealer, but this was a new one
on me.
I'm renewing the 2" dia prop shaft & bearing on a 70 year old boat,
the old one had about 1/2" of play in the bearing. The bearing is
about 10" long, cast iron with a bronze bush.The shaft probably ran
originally directly in the cast iron, lubrication is by water or a bit
of grease if you're lucky.
I'd noticed a build up of crud at the inner end of the bush, where the
shaft isn't free to wave about as much as the outer end. A bit of
investigation found this to be RTV silicone - it seems that someone
had injected silicone sealer into the bearing to try to reduce the
play!! Maybe there's some fancy silicone sold for this sort of job?
I've no idea whether it had ever done any good, but it certainly
wasn't by the time it came to me. The bearing, judging by the state of
the retaining studs, hadn't been out for at least 15 years. The
silicone must have been injected via the greaser union!
There are 'rubber' prop shaft bearings available, but AFAIK they are
neoprene, and made with longitudinal flutes and arrangements to ensure
a flow of water from one end to the other. I'm not convinced about RTV
silicone as a bearing material, even under water.
A lot of boat repair can be described as bodging (doing the best you
can in the circumstances/with the money available), but I like to
think mine are of a better class than this
Cheers
Tim
Dutton Dry-Dock
Traditional & Modern canal craft repairs
Vintage diesel engine service
Reply to
Tim Leech
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That's what I was alluding to above (stictly it's cutlEss)
Perish the thought. Maybe the same cowboys have moved on to boats? You've got me thinking now. Bronze loaded body filler anyone?
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
Maybe you haven't seen it all yet? :)
A few companies already sell bronze loaded polyesters. Bronze loaded epoxies are quite common too. They are actually quite good for repairing lightly stressed bearings.
Reply to
Peter Fairbrother
I'd guessed that such things do exist, it was the concept of injecting them through the greaser which appealed as perhaps a bodge one degree better than the RTV silicone. Pewrhaps I should investigate further, New stern bearings fitted without drydocking, wonder miracle cure, etc
Some info on cutless type bearings, for those who may be interested, at
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I'm interested in this stuff
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Having tried oil bearing nylon some years ago, with poor results, It's very tempting to stick to the old technology which everyone knows & which works, but the blurb does make this stuff look promising.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
There are many thermoplastics suitable for bearings these days, with all sorts of additives. One we use at work is an acetal loaded with ptfe. Most of these materials are based on acetal, as it has very good frictional properties to start with.
Regards
Kevin
Reply to
Kevin Steele
I'm I've seen Tufnol used as bearing material in high performance boat apps - 1 inch prop shaft turning at 12000 rpm
That is to say I've seen it removed from such a boat looking a bit charred
Steve
Reply to
Steve
re plastic bearings
i used to work at a plastic bearing moulders they make plastic inners/outers and cages in different type of plastic ,in some instances using ground glass balls . injection moulding leave a hard durable skin on the tracks where the balls ru -
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-- willowkevi ----------------------------------------------------------------------- willowkevin's Profile:
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this thread:
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Reply to
willowkevin
Perhaps it was someone's idea of a cutlass bearing? :-)
As for introducing bearing media through the grease nipple, I've known of cowboys that have resurrected worn kingpin bushes, albeit temporarily, by injecting body filler with a grease gun. Most were refugees from northern hemisphere railway arch establishments..
Tom
Reply to
Tom
I was actually alluding to pirate version...Too deep? :-)
Tom
Reply to
Tom
In article , Steve writes
*boggle*
How the *hell* do they prevent cavitation at those speeds?
Reply to
Nigel Eaton
Is that from the "Deerhunter " ?
-- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:-
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Reply to
John Stevenson
In article , John Stevenson writes
Haven't you got a workshop to tidy, or a Reliant to burn, or something?
Reply to
Nigel Eaton
Ah, Knaresborough - where they have Dripping Wells. Never seen them, I imagine some association with Jam Butty mines?
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
Must be a *very* small propellor? I wonder why Tufnol? it swells in water (as does Nylon), clearances at that sort of speed must be fairly critical. Is it known as a bearing material (wet)?
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
Good point. Waiting to the stove the get the temperature up a tad and then go do some work. It's bloody cold in there with all that iron. The mercury dropped that low in the thermometer last night it trapped a rat on the floor.
-- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:-
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Reply to
John Stevenson
The boat has been officially clocked at 150mph+ over a two way run over 1km.
What is amazing is the drag of 1 sq inch of rudder at those speeds -
The motor is a V8 chevy tuned to 750 bhp IIRC
Steve
Reply to
Steve
If you're into fast boats take a look at this
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I had no idea this was going on until a couple of weeks ago, there doesn't seem to have been a lot of mainstream media coverage. It's good to see someone trying to bring another world speed record back to the UK.
Regards
Kevin
PS I don't think I'd fancy piloting this thing at those kind of speeds over a lake.
Reply to
Kevin Steele
Something strong in the tea this morning, John??? :-))
Peter
Reply to
Peter A Forbes

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