Replacing Torlon Balls In Sheaves?

[Tim Good]

I heard that replacing the 15 year old torlon balls in sheaves at the mast foot can make a huge difference to friction.

A few Q's

Difference between delrin and torlon?
How do I know if they need replacing?
If they look perfectly fine might they still need replacing?
If they measure 5.47mm are like likely to have worn down from 6mm or might they be 5.5mm new?

 

[vyv_cox]

Can only answer one with any authority. Torlon is an engineering plastic, a mixture of polyimide and polyamide to reduce the cost of the former, which is incredibly expensive. Quite remarkable stuff that outperforms many metals in bearings, gears etc. Engineering plastics are polymers based on aromatic chemicals, hence heavily cross-linked, giving great strength and other useful properties.

Delrin is an acetal, quite a good aliphatic polymer but not in the same league where engineering properties are concerned. Its big advantage is that it does not swell in water, hence its application in rudder (plain) bearings.

I would have thought that if the balls are round there would be little benefit in replacing them.

 

[Border Terrier]

Give a thoughr for the Torlons.

 

[William_H]

I don't think you will get much advantage in terms of less friction by replacing the balls unless you really have a problem with the sheave bearing. I would have thought you would have to replace the sheave with bearing as usually the frame that holds the balls in place are molded or pressed into place.
However if you have such an accurate measure of the ball diameter I guess you must have been able to remove the balls. Or maybe not.
Anyway as said if they are round and not apparently too small from wear and if the cups that the balls sit in are smooth you would not be able to improve on the bearing.
If you have too much friction in halyard then check the top sheave. good luck olewill

 

[wklein]

It's pretty unlikely you have torlon balls in mast Base blocks. They will likely be delrin side load balls. Or torlon rollers. Torlon balls are used more for rcb cars. If they still work I would leave them alone

 

[rotrax]

I recently replaced some on a set of double blocks on the traveller on our boat.

The balls on the two top blocks were exposed to UV rays and had gone literaly to dust.

After shaking the remains out it was possible to press the double inner track out and remove the worn but un UV'ed ones from the bottom blocks.

They were a nominal 5mm and some new ones were sourced through ebay at modest cost.

I filed a small notch in the edge of the track of the upper part of the inner race so as to be able to insert the new balls through the gap-assembly would have been impossible otherwise. I am still working out how they did it at the manufacturing stage!

A small piece of plastic cut from a food container was superglued over the notch to stop the possible exit of balls through the gap.

Been working fine for three seasons now, and saved over a hundred quid for two new blocks.

 

[Tim Good]

It's pretty unlikely you have torlon balls in mast Base blocks. They will likely be delrin side load balls. Or torlon rollers. Torlon balls are used more for rcb cars. If they still work I would leave them alone

Yes I think you are right.

The balls that came out I think are Delrin but measure 4.9mm... So maybe they were once 5mm. I can find plenty of 5mm bearing online but Harken and Lewmar do the black UV stable ones. However, they are imperial and so measure 4.75mm (even though Harken advertise them as 5mm).

Would a 4.75mm ball in a sheave designed for a 5mm ball be a problem? Is so then I''ll probably just resort to more non UV stable 5mm ones from ebay.