best material for rudder bearing

C

ColinR

Well-Known Member
Joined
23 Oct 2001
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www.victoriashadow.co.uk
I removed the bronze rudder heel fitting (thanks to this forum for advise; a hot air gun and long lever did it). The bearing looks like phospher bronze but the surveyer recommended using polypropolene. When I took it to the engineer (not a marine one) he said phospher bronze would be better and longer lasting. Any idea which to go for? Basically its a cup bearing which the bottom of the stainless steel rudder stock sits in.
thanks

Colin
 
Colin,

I guess a lot will depend on how much load this bearing takes, and since it is very open a metal fix might be preferred.

However modern plastic materials are used widely for just this situation, and come with loads of avdice, tolerances etc. Have a look at this site -

http://www.theplasticshop.co.uk/nylon-index-1729-0.html

The company is very good and has a wide range. If you choose plastics, acetyl not nylon may be your solution becasue of its performance in water. But talk with them first.

Be reassured, they sell boaty sized bits!

PWG
 
[ QUOTE ]
The only material for rubber and propshaft bearing in vesconite

www.vesconite.com

DO NOT USE NYLON it will swell and make your steering stiff.

[/ QUOTE ]Ooooh, rather sweeping statement that. I guess you never heard of Tufnol then, and in particular their "Bear Brand" product? /forums/images/graemlins/grin.gif
hammer.gif
Artificial Intelligence is no match for Natural Stupidity

[/ QUOTE ]
 
Straight Bronze is OK, but if it is a removable bearing then one of the water lubricated materials such as Delrin or Vesconite is perhaps better. I have a Delrin insert in my bronze heel fittting which I installed 16 years ago and it shows no sign of wear. I had a spare made at the same time which makes a nice ornament!

Do not use nylon or any material that absorbs water.
 
[ QUOTE ]
I guess you never heard of Tufnol then,

[/ QUOTE ]

Oh yes used to use it 30 odd years ago when I was designing conveying equipment and in particular equipment for factories producing explosives.

Vesconite has replaced almost all other "conventional" bush/bearing material in the dusty and wet environment of mines in South Africa
 
Very sweeping, as you say Cliff.

There are a huge range of composite and plastic bearing materials with vastly different properties.

The ones chosen for the most demanding jobs are often novolac Phenolic resins, these do not soften and become sticky with heat as Polyester based materials do. They can have lower static and dynamic friction properties than teflon.

At failure a bearing will suffer localised heat, a long lasting bearing resists this initial breakdown at a molecular level. Bearings that soften either delaminate or transfer material to the shaft. Phenolic bearings post cure and become harder with heat. At failure they are still hard and can mechanically support the shaft.

But for your application it depends what you want, many materials will work quite well under medium loads and limited heat ranges.

We supply bearings for everything fromcutless bearings to crane pulley blocks, as well as to a wide range of mining applications.
 
The problem is that by adding material to give low friction you will in most cases weaken the supporting structure. The bearing has a mechanical role and needs to keep its dimensions.

If you use a material which melts, it will start to soften and loose its mechanical properties long before its melting point. As it softens it is starting to fail.

That's the bearing lecture, back to the original question.

Most leisure boats will be fine with Delrin or something similar for the rudder, but if you want what's best you'll have to start to dig deeper and understand the variety of materials and properties available.
 
[ QUOTE ]
[ QUOTE ]
The only material for rubber and propshaft bearing in vesconite

www.vesconite.com

DO NOT USE NYLON it will swell and make your steering stiff.

[/ QUOTE ]Ooooh, rather sweeping statement that. I guess you never heard of Tufnol then, and in particular their "Bear Brand" product? /forums/images/graemlins/grin.gif
hammer.gif
Artificial Intelligence is no match for Natural Stupidity

[/ QUOTE ]

[/ QUOTE ]

Err;……………it's an advert
 
Whatever you use be aware that sitting on a drying mud mooring or leaving the helm untied will significantly reduce its life.
I have used bronze machined to fit as a press fit bushing, and made my own using Nylon 66 (worked just fine) at the lower end and latterly epoxy/graphite with overgenerous bearing area inside the actual rudder stock on a spade rudder, (details through WEST systems)..
Vesconite sounds good.
 
When building my Spray, I used oil-filled nylon for the bearings (and still have most of the metre I had to buy, if you're interested). Supplier was Nylonic Engineering who, going by what little they charged me for moulding a 1 metre length, are probably out of business now.
Were I doing it again, I would use acetal (Delrin is one trade-name for acetal).
Having said that, she's been afloat almost continuously for the last ten years, has been in a mud berth for the last four, and shows no wear or reduced clearance on the stock.
I have used Delrin for the bow rollers (no wear by the chain and rust-free) and for the halyard sheaves up the mast.
 
High molecular weight plastic can be used for rudder foot bearings. It has great resistance to wear, is inexpensive, radily available, and machinable.
 
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