savageseadog
Well-Known Member
I need to make some replacement rollers for my rudder bearings. I've found the ones I've already made are prone to wear. There are at least 800 grades of Acetal any idea which one to use?
Acetal/Delrin Grades Any Experts?
- Thread starter savageseadog
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DinghyMan
Well-Known Member
I buy and use loads of Acetal but other than bulk sales I don't think I've ever seen anyone quoting the grade or even offering what grade they supply, and most places use acetal and delrin names interchangeably even though they are different materials
There are better plastics for bearings, for example Vesconite, but smooth surface to acetal or delrin bearing you should be getting decent life.
vyv_cox
Well-Known Member
When I had my rudder shoe rebushed with Acetal there was no suggestion of the grade to be used. Your post is the first time I have heard that alternatives existed.
Google finds this and others. https://www.curbellplastics.com/Research-Solutions/Materials/Acetal
Google finds this and others. https://www.curbellplastics.com/Research-Solutions/Materials/Acetal
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Jaguar 25
Well-Known Member
The two main grades of acetal are acetal copolymer and acetal homopolymer. The copolymer version is often used for plastic springs and I have used this application in the design of a switch for a hairdryer (many years ago!). Not sure which would make the better bearing material. You could also consider nylon and you can get this with a graphite filler. IGUS do plain plastic bearings that include a lubricant of some sort. They don't specify the polymer used.
vyv_cox
Well-Known Member
Never use nylon for immersed bearings. It swells in water up to 11% with some grades.
Daydream believer
Well-Known Member
Have you considered Oilon i have been machining bearings from this for the last couple of years to good effect
try plastcs direct online. They have an excellent technical advice service
try plastcs direct online. They have an excellent technical advice service
Dipper
Well-Known Member
I've made a rudder bearing and bow roller from ultra-high-molecular-weight polyethelene (UHMWPE). It's used extensively in the gravel industry due to its abrasion resistance and is the most commonly used plastic for artificial joints. It has extremely low water absorption. Have a look here.
savageseadog
Well-Known Member
I've considered Torlon and something I've never come across called Peek. The basic diameter of the rollers is 10mm by 60mm long, the ends are turned down to about 3.5mm diameter by 3mm long. The ends run in alloy rings to form an approximately 6inch diameter race with 38 rollers, it's a beast! The problem is that the ends don't have a lot of contact area and either the rollers wear or the rings do. I've already increased the diameter of the ends to 3.5mm from 3mm due to wear in the alloy.
Dipper
Well-Known Member
Sounds complex! Mine was just a simple bush.
savageseadog
Well-Known Member
38ft racing boat. There are two races, the top one is smaller but doesn't wear. The bottom one is partly submerged. I bought a mini lathe to do the job.
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Daydream believer
Well-Known Member
still think oilon but tuffnol whale is good in water. I use it in my ambassador rope cutter
vyv_cox
Well-Known Member
PEEK (poly ether ether ketone) has excellent properties in air, it is one of the top engineering plastics. High strength and excellent wear resistance. You may have seen it as tiny self lubricating gears in electric drills, for example. Very high cost but unfortunately I know nothing about its performance in water.
Torlon is another engineering plastic, poly imide-amide if I remember correctly. Used as balls in high spec furling gear and also as shaft (plain) bearings. Not quite the performance of PEEK but well proven under water.
Torlon is another engineering plastic, poly imide-amide if I remember correctly. Used as balls in high spec furling gear and also as shaft (plain) bearings. Not quite the performance of PEEK but well proven under water.