Rudder Bushing Material

[kmacdonald]

What is the best rudder bushing material? The lower existing rudder bushing is bronze. There is a lot (1/4") of slop in it. I'm thinking of reaming the bronze female bushing and inserting a bushing to match the size of the pintle. Any suggestions?

[Chotu]

I used Delrin/acetal which is holding up fine, but bronze is longer lasting. Why not use more bronze?

[JoeRobertJr]

My father-in-law just made me a new bushing out of acetal on our home lathe.

[GordMay]

“Vesconite” ➥ https://www.vesconite.com/marine/

➥ https://www.vesconite.com/vesco/FAQ.htm

➥ https://www.vesconite.com/design-a-b...ator-imperial/

➥ https://www.hydro-watt.com/marine-bushings.html

[Fuss]

Delrin is the way to go, it wears V slowly and does not expand in water, mine is 15 years old.

[GordMay]

Delrin or POM-H (homopolymer acetal) is part of the POM material family, the other POM being copolymer acetal (POM-C).

How does Vesconite compare with Acetal (POM) ?
Vesconite has much higher wear resistance, higher load carrying capacity and higher surface speed limits than acetal, together with better dimensional stability and lower friction.

Vesconite can be used with much finer tolerances and clearances, owing to much better dimensional stability.

Vesconite's chemical resistance to acids and solvents is much better.

Vesconite machines more easily.

Some data on polyacetal (POM) vs Vesconite :

Tensile yield strength = acetal 65MPA / Vesconite 80

Design loading = acetal 25 MPa / Vesconite 30 MPa

Thermal expansion = acetal 10 mm/mm/oC x 10-5 / Vesconite 6 mm/mm/oC x 10-5

Water absorption (saturated) = acetal 0.8% / Vesconite 0.5%

Maximum operating temperature continuous = acetal 100oC / Vesconite 100oC

[Celestialsailor]

It should be noted that Acetal (Delrin) does absorb water and clearance should be taken into consideration.

[Searles]

Vesconite is the way to go ,stern bearings ,rudder bearings autopilot bearings ,nothing else comes close .⛵️⚓️

[JoeRobertJr]

I am hoping my newly-made acetal/Delrin bushing will outlast me, but if not, I'll definitely consider Vesconite next time. I'll note that a quick search of suppliers showed me that Vesconite is about 2.5 times more expensive than Delrin.
A 3-inch diameter, 12-inch length cylinder of white acetal from Grainger: $83 with tax and shipping.
The same size cylinder of Vesconite from Gallagher Fluid Seals (in my home state of PA, USA) is listed at $212 before tax and shipping.

[dlj]

Just a FYI, Vesconite is a trade name. Not a material specification. Delrin is also a trade name, not a material specification.

Manufacturers tend to use specific materials and may make some specific adjustments to then give their produced product a "twist" and then give it a "trade name". Or they may just use a commercially available material and sell it under their trade name....

The marine industry is littered with this kind of thing. Polymers are particularly prone to this kind of marketing, although it happens in metallic alloys also. The reality is, there is no such thing as a specific "marine grade" material. All materials are made to industry standards and the materials selected within a given industry have been shown to perform well in that industry.

Acetal is a good material for what you need. You could also use UHMWPE if your bearing has no UV exposure. Both are easy to machine.

Bronze would also be a good choice. But you would do well to know what bronze alloy you are sleeving and get that same alloy or a compatible alloy for your sleeve. That may be more difficult than it's worth so going with acetal is an easy solution. Depending upon your pintle, gudgeon and rudder design, the "best" (In my opinion no such thing actually exists) would be to match bronzes and sleeve with the correct bronze (likely) alloy.

dj

[Chotu]

Originally Posted by JoeRobertJr

I am hoping my newly-made acetal/Delrin bushing will outlast me, but if not, I'll definitely consider Vesconite next time. I'll note that a quick search of suppliers showed me that Vesconite is about 2.5 times more expensive than Delrin.
A 3-inch diameter, 12-inch length cylinder of white acetal from Grainger: $83 with tax and shipping.
The same size cylinder of Vesconite from Gallagher Fluid Seals (in my home state of PA, USA) is listed at $212 before tax and shipping.

I think you (we) be fine. It’s not like we are talking about supporting a shaft on a motor here. A rudder post just doesn’t complete that many revolutions per year in total travel distance.

Also, due to different rates of expansion and contraction with heat and cold, I agree with dlj. Using the same material as the rest of everything will give better results.

[dlj]

The chart has a technical error - you can't do Shore D hardness on Bronze. It's a worthless number. Additionally, the "friction wear rate" is also a worthless number - don't even get me started on that one... That one is pure marketing at it's finest!

dj

[Chotu]

Originally Posted by dlj

The chart has a technical error - you can't do Shore D hardness on Bronze. It's a worthless number. Additionally, the "friction wear rate" is also a worthless number - don't even get me started on that one... That one is pure marketing at it's finest!

dj

Good thing there was still a window to edit. Ha ha

[dlj]

Originally Posted by Chotu

Good thing there was still a window to edit. Ha ha

Yeah - the Shore D shot me in the eye, then I went back and looked at that idiotic wear rate column.... bring in the marketing team we need to sell product!!!! I've sat in those meetings... I was usually asked to either leave, or be a team player... Something I'm not so good at...

dj

p.s. - I just realized you were talking about removing the table from your post... hahahahahah... Somehow I thought you saw me edit my post addig in the part about the wear...