Acetal trailer rollers

[richardabeattie]

What is the advantage over the rubber ones?

 

[pawl]

hi, I don't know if there is any advantage. Acetal is a good deal harder than rubber, although there are various grades of rubber hardness. However, acetal is much easier to machine, if I were making my own I would use acetal.

 

[richardabeattie]

The story is that these harder rollers turn more easily than rubber and make winching the boat onto the trailer much easier. But is that right?

 

[Graham_Wright]

hi, I don't know if there is any advantage. Acetal is a good deal harder than rubber, although there are various grades of rubber hardness. However, acetal is much easier to machine, if I were making my own I would use acetal.

It is also quite brittle.

 

[pawl]

Well, acetal does have certain self lubricating properties, so that might be an advantage. However, it depends on what you're comparing it with. I doubt that all the so called rubber ones are made of rubber, probably PU or a number of other synthetic materials. Also a lot would depend on how the roller system is designed and maintained. I rather suspect that, in practice, that amongst all the other factors that conspire against you when trying to get a boat onto a trailer, you wouldn't really notice any difference in the types of rollers, providing they all turned freely. As for acetal being "brittle" this is not the case, acetal will only be brittle if it is poorly moulded or extruded, or if it is of substandard quality.

 

[lw395]

Rubber is good if you've got GRP running over it, acetal would be too rigid I suspect and point load the gelcoat?

If I needed rollers for my RIB trailer, I'd buy rubber ones, or work with combinations of rubber tyred castor wheels.

My dinghy combi trailer has a steel tube roller which a steel trolley rolls on. That could do with being rubber or plastic IMHO.

Depends what you want from the individual roller.

 

[richardabeattie]

Thanks - I'll stick to what I've got but make sure they turn easily. That's probably the most important factor.

 

[lw395]

Thanks - I'll stick to what I've got but make sure they turn easily. That's probably the most important factor.

The rubber ones generally turn their axle with them, so the bearing is steel-on-steel.

 

[rogerthebodger]

The rubber ones generally turn their axle with them, so the bearing is steel-on-steel.

The steel shaft should be prevented from turning in its steel mounting.

An Acetal bush should be pressed into the hole through the roller to reduce the friction on the shaft, but thi costs more so no one does this.

 

[Graham_Wright]

As for acetal being "brittle" this is not the case, acetal will only be brittle if it is poorly moulded or extruded, or if it is of substandard quality.

Oh yes it is! I have machined many components in it and, believe me, you don't drop it! (I have to admit they were thin sections but not that thin.)

 

[lw395]

The steel shaft should be prevented from turning in its steel mounting.

An Acetal bush should be pressed into the hole through the roller to reduce the friction on the shaft, but thi costs more so no one does this.

Nobody does it because most people have better things to do than fiddle with something which works quite adequately.
The crude nature of the bearings for the rollers are generally the least of your worries with a RIB trailer.

 

[pawl]

Oh yes it is! I have machined many components in it and, believe me, you don't drop it! (I have to admit they were thin sections but not that thin.)

If you are having those sort of problems then you should consult your supplier. Although I'm now retired I have spent my entire working life in the plastics industry, supplying and processing engineering materials, such as acetal, to the car, aircraft, medical and business machine sectors. Acetal is widely used where the part is required to act as a spring or bearing of some sort. It should not be brittle. It is also widely used in cigarette lighter casings and zip fasteners, I don't think it would be used in these applications if it were.

 

[DinghyMan]

If you are having those sort of problems then you should consult your supplier. Although I'm now retired I have spent my entire working life in the plastics industry, supplying and processing engineering materials, such as acetal, to the car, aircraft, medical and business machine sectors. Acetal is widely used where the part is required to act as a spring or bearing of some sort. It should not be brittle. It is also widely used in cigarette lighter casings and zip fasteners, I don't think it would be used in these applications if it were.

We use loads of it and I've dropped plenty on the floor when I've left the saw running or just knocked it off the bench - it bounces nicely, marks up, but, as you say, certainly doesnt shatter or crack.

I've had parts back for repair that look like someone has used them as a hammer and never seen any signs of cracking.

 

[vyv_cox]

Every description of Acetal I see uses the word 'tough', which is just about the opposite to 'brittle'. My experience of it, as rudder bushes, is that it takes plenty of hard knocks.

 

[seumask]

Recent replacement of some rollers on old rib trailer ( Indespension) appeared to be acetyl hubs with a rubber tyre on them, so the best of both worlds? Old ones lost when retaining clips dissolved (galvanised steel through Aluminum axles)

 

[Graham_Wright]

Every description of Acetal I see uses the word 'tough', which is just about the opposite to 'brittle'. My experience of it, as rudder bushes, is that it takes plenty of hard knocks.

Perhaps I introduced stresses in machining. Complex parts, thin sections.