How to free a sheave that is seized to its spindle

This issue has indeed been a nightmare for my boom which I have had for about 8 years. For the reefing lines a total of 4 sheaves had completely locked/seized and which is hard to comprehend when one waggles the free ones and which shake in the breeze as normally they are super rattly loose. I soaked the boom ends in diesel for months and this did not help. I doused in boiling hot water many a time and this did not help. In the end with the help of 2 screwdrivers I applied twisting forces to the sheave edges and bit by bit some movement was gleaned. After probably an hour or so a rope around the seized sheave did allow slight rotational movement and then eventually freeing of the locked sheaves. It is hard to understand that the rod spindle would get furry enough up against the inside of the plastic/nylon sheave, but I guess the corrosion must grow like a mushroom! Would expect better from Selden considering the high price paid for their bits and pieces and for it to be A1 in the first place.
 
Tegan148 said:
This issue has indeed been a nightmare for my boom which I have had for about 8 years. For the reefing lines a total of 4 sheaves had completely locked/seized and which is hard to comprehend when one waggles the free ones and which shake in the breeze as normally they are super rattly loose. I soaked the boom ends in diesel for months and this did not help. I doused in boiling hot water many a time and this did not help. In the end with the help of 2 screwdrivers I applied twisting forces to the sheave edges and bit by bit some movement was gleaned. After probably an hour or so a rope around the seized sheave did allow slight rotational movement and then eventually freeing of the locked sheaves. It is hard to understand that the rod spindle would get furry enough up against the inside of the plastic/nylon sheave, but I guess the corrosion must grow like a mushroom! Would expect better from Selden considering the high price paid for their bits and pieces and for it to be A1 in the first place.
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If yours are like mine the cause is that nylon bushes in the sheaves swell in water, eventually seizing on the spindles. I knocked the spindles through and ran a drill through the nylon, taking them back to the original bore. That was years ago and they have been free ever since.
 
vyv_cox said:
If yours are like mine the cause is that nylon bushes in the sheaves swell in water, eventually seizing on the spindles. I knocked the spindles through and ran a drill through the nylon, taking them back to the original bore. That was years ago and they have been free ever since.
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Ok thanks and very interesting... I could not see any easy way of extracting the pins but may well have to pursue that soon. So what you are saying is no corrosion as such but just swollen nylon?
 
Albert Ross said:
Sorted!

Sorted at last!

The following didn't work:
1. Winding a rope around each seized sheave, tying off the ends, twisting and cranking both ropes with a long screw driver (effectively putting a tourniquet around each sheave) and using this to turn each sheave in opposite directions.
and 2. Heating all with a hairdryer for 2 hours
and 3. Hitting the end of the spindle with a punch and a heavy hammer
and 4. levering the sheaves apart by forcing screwdrivers between them and then twisting them
and 5. soaking the components with best quality (screwfix) 3 in 1 releasing spray
and 6. all the of the above together

The following did work:
Drilling holes into the plastic (nylon?) sheaves down to the spindle sufficient to ruin middle of the sheave where the spindle was stuck, then knocking the spindle out with a hammer and punch.

Replacement sheaves cost over £8 each .. for a plastic wheel 45 mm in diameter.
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Find someone with a lathe and ask them to turn you some sheaves in Delrin instead of nylon. Delrin doesn't expand in water.
 
Tegan148 said:
Ok thanks and very interesting... I could not see any easy way of extracting the pins but may well have to pursue that soon. So what you are saying is no corrosion as such but just swollen nylon?
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That's true of mine, Selden mast and boom have aluminium sheaves with nylon bushes. Only need to drill out once and they are good for ever.
 
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