Rudder Bushes

Clyde_Wanderer

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Has any of you had any bushes made from Vesconite, or maybe that should be Vescomite.
I was given a sample a few years ago by someone who contacted me through this forum, and I am now thinking of getting a bush machined from it.
It is claimed not to swell when submerged in salt water.
C_W
 

Neil_Y

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All plastics / composites swell in water just some more than others. Delrin and polyacetal has relatively low swell rates but they are also materials which melt and hence soften and expand as they get hot. They have a significantly lower moisture absorption than Nylon, but similar or more than some of the latest composites.

Clearances should still detail an allowance for moisture swell, thermal swell and running clearance.

We give a breakdown of clearances in our calculator, http://www.h4marine.com/Downloads/Maritex AQUARIUS General Calculator REV 20100519.xls this sort of information should be checked before you machine the bush to suit your rudder. Maritex is probably too good for what you need.
 

Clyde_Wanderer

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Neil Thanks for that, you, or your company appear to have quite a knowledge of Bush materials, but you havent exactly answered my question on Vesconite have you, or have your company not come across this one?
It is used extensively in commercial shipping industry apparently.
http://www.vesconite.com/industry/applications/marine/3ships.htm
http://www.vesconite.com/vesco/self_service/downloads/vesconite_general.htm
http://www.vesconite.com/vesco/self_service/downloads/marine_brochure.htm
Thanks,
C_W
 
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Bobobolinsky

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Hi Visconite, can be used anywhere below the waterline, most commonly used as a water cooled propshaft bearing, but I've used it to replace rudder bearings before. It comes normally as a tube, you buy slightly larger od slightly smaller id and machine to fit. It's about twice the price of Nylon 66.
 

shaxi

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It's about twice the price of Nylon 66
if it is good as you post above , i think that it worthy of the expense !:)
thanks !
g.php
 

rogerthebodger

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Has any of you had any bushes made from Vesconite, or maybe that should be Vescomite.
I was given a sample a few years ago by someone who contacted me through this forum, and I am now thinking of getting a bush machined from it.
It is claimed not to swell when submerged in salt water.
C_W

Yes all my prop shaft and rudder bearings are Vesconite and I have had no problems.

This material is used in he mines where there is a lot of water and dust around (water spray keeps the dust out of the air) with not problems.
 

Neil_Y

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I know it quite well, make sure you allow the correct clearances, it does absorb sea water at 0.5% other data and clearances are on their website. Thermal expansion in most composite, resin and plastic bearings is usually a bigger issue than moisture. Moisture is always brought up as there were some issues when Nylon was used, but most bearing people have moved on to better materials now.

I tend to think of it as an alternative to Delrin as its performance is quite similar, you can compare data here.
http://www.machinist-materials.com/comparison_table_for_plastics.htm
 

Scotty_Tradewind

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one thing to consider when making new rudder bushes ...........
Does the rudder run exactly true in its bushes when turned?.... I doubt it.
Therefore to make the bushes with too tight/close a tolerance/clearance may be the first thing to consider avoiding.
If it's an easy case of putting it together and taking apart again with the % expansion tolerance allowed for then it could always be adjusted afterwards..... if the expansion of the material due to immersion hasn't seized it! :(
 
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