How to free a sheave that is seized to its spindle

A

Albert Ross

Well-Known Member
Joined
14 Oct 2004
Messages
230
Location
Troon and beyond
Visit site
Some of the sheaves in the end of my boom have seized up.
The sheaves are made of some sort of plastic and should run on a metal axle or spindle. I can't get the sheaves to turn on their spindles.

I've tried knocking out the spindle .. it wont budge.
I've tried forcing the sheave to rotate .. it wont turn
I've tried a kettle of hot water .. it didn't free it.
I've tried oil ..no good

Any ideas, please?
 
flat1 said:
Some of the sheaves in the end of my boom have seized up.
The sheaves are made of some sort of plastic and should run on a metal axle or spindle. I can't get the sheaves to turn on their spindles.

I've tried knocking out the spindle .. it wont budge.
I've tried forcing the sheave to rotate .. it wont turn
I've tried a kettle of hot water .. it didn't free it.
I've tried oil ..no good

Any ideas, please?
Click to expand...

If you can show a picture of the boom end or which company made the boom it may help. I guess if the sheaves are plastic possibly Z spars or Sparcraft?
 
I guess you have tried putting on top of a vice with the pin going down the gap but not being gripped, hitting with a hammer may shift them, you won't damage the pin and I presume if need be new sheaves are available from a Selden agent. If you damage the sheave just post here and someone will have a sheave that will fit.
 
Have you tried leaving the whole end of the boom to soak in a container of vinegar for a few days??

This has worked a treat for me in the past with spinnaker pole piston ends and seized shackles.
 
Thank you ..
Will try soaking in vinegar .. but will need quite big vat of the stuff ..
am reluctant to hit it too hard with a punch and hammer for fear of cracking the alloy end of the boom .. difficult to get the boom end into a vice.

any more suggestions please?
your ideas are all much appreciated, thanks.
 
You don't say whether the spindle is S/S or aluminium. Most likely stainless, with most of the spars I've seen. There may be some corrosion on the pin as can happen in areas deprived of oxygen. It's unlikely that a quick squirt of anything will shift it, it'll need time to soak in, perhaps a week and a little brute force to get things moving. Bring the boom home and up-end it in a can of diesel, vinegar or your own preferred liquid for a week and then try again.

Rob.
 
Pretty sure you will find the pin is held in with a circlip on one end. Look very carefully at (probably) the port side and you will see the split of the clip. Usually the problem is wear of the sheaves rather than seizing, so they won't turn under load.
 
flat1 said:
Will try soaking in vinegar .. but will need quite big vat of the stuff ..
.
Click to expand...

if you go down this line try you can reduce the volume of vinegar you need by filling up any voids in your container or boom with something else.

Also, rather than a solid container you could just use a polythene bag that is taped or strapped to the profile of the boom.

Best of luck!
 
Sheaves

The best way to get a really good grip on a sheave is to wrap a turn of rope around it. Full circle then tighten the rope perhaps witha G clamp or in a vice squeezing the ends of the rope together. This will get a good grip without damaging the sheave and you can then try to force a rotation.
I have reeplaced many plastic sheaves in my pulleys etc over the years. They are good but don't last that long. good luck olewill
 
I was presuming the pin was out of the boom end! As has been mentioned the pin is held with a C clip on one side, I guess this has been removed? Be careful with knocking the pin to hard as if the boom end is old it may not be possible to replace if you damage it. This I think has been mentioned before.
Also not sure if you are doing this on the boat or in a workshop, the boom on a bench and held will make it easier. Good luck, it will be good for the forum if you can let us know the outcome.
 
expansion

Sheave is plastic? spindle S/S?

Plasic sheaves are often made from Nylon or Delrin. These do expand when absorbing liquid / moisture. Expansion => sheave hole smaller. Process takes a very long time, but is inevitable.

Might be some oxide on the spindle, which might be attacked by vinegar but also this does take time. If boom end (spindle + sheave ) are soaked in vinegar, then sheave will absorb more liquid.

Spindle is probably removable, look into that as proposed earlier. Try not to use a hammer, can damage the spindle - seen this happened with s/s spindle to a folding prop.
If the spindle is connected to Alu and there is a lot of oxide around ("white powder") this can be difficult. Careful heating will expand the Alu (more than the s/s) and it should be possible to press out the spindle, but do look out for locking rings etc.

When spindle is freed it is easy: clean, if necessary increase slightly the hole in the sheave. Slightly = parts of mm, just with a smooth sandpaper.

/J
 
Jaramaz said:
Sheave is plastic? spindle S/S?

Plasic sheaves are often made from Nylon or Delrin. These do expand when absorbing liquid / moisture. Expansion => sheave hole smaller. Process takes a very long time, but is inevitable.

Might be some oxide on the spindle, which might be attacked by vinegar but also this does take time. If boom end (spindle + sheave ) are soaked in vinegar, then sheave will absorb more liquid.

Spindle is probably removable, look into that as proposed earlier. Try not to use a hammer, can damage the spindle - seen this happened with s/s spindle to a folding prop.
If the spindle is connected to Alu and there is a lot of oxide around ("white powder") this can be difficult. Careful heating will expand the Alu (more than the s/s) and it should be possible to press out the spindle, but do look out for locking rings etc.

When spindle is freed it is easy: clean, if necessary increase slightly the hole in the sheave. Slightly = parts of mm, just with a smooth sandpaper.

/J
Click to expand...

Exactly right. the sheaves in my Selden boom and mast have done exactly that. I managed to drive the spindle out and ream the holes slightly larger. That was many years ago and they remain free to rotate.
 
Many thanks for all your suggestions and advice.

The spindle is steel. The sheave is nylon, I think. (perhaps the nylon has taken in water and expanded? .. .. can this water uptake be reversed?)
There is no retaining clip (well, there were none on any of the other spindles in the boom ends).
The spindle and sheave cant be removed from the boom end until the spindle has been removed from the sheave.

There is a lot of "white dust" around. I think this is corrosion of the steel spindle.

As there are 2 sheaves stuck on this spindle, I will try to clamp some rope around each of them and the turn them in opposite directions (that may free one of them). Many thanks for this suggestion William_H.

Do penetrating oils work?

If and when sorted I will, of course, feed it back to you.
 
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.
 
Spray shaft liberally with silicone lubricant. Attach an oil-filter removal tool around the sheave and apply alternative clockwise and anticlockwise effort.
 
flat1 said:
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.
Click to expand...
I think you gave up and resorted to violence too soon! I've freed quite a few siezed sheaves and found the most difficult bit was getting the first bit of movement. Once you can sense the slightest 'give', you're nearly there. I use the penetrating oil and rope (no 1) trick but think the suggestion of using an oil filter clamp sounds good.
 
You must log in or register to reply here.

Share this page

Top