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neuronz

replacing sheaves

20 posts in this topic

we need to replace the sheaves in our mast and boom.

the rollers are pretty much done and one has already fallen apart.

I don't know the manufacturer of the sheaves and a search (harken, ronstan, antal) hasn't returned any results.

anybody know the manufacturer?

sheave diameter: 50mm

pin diameter: 8mm

width: 15mm

the body is aluminium and the rollers are torlon afaik.

post-6362-049601800 1332008103_thumb.gif

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Custom sheaves are available from zephyrwerks.com. You might check there.

 

Thanks for this link. Exactly what I needed.

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Thanks for the answers.

I would like to stay with the sheaves I have, because their slots where designed around the sheaves.

I also believe that these sheaves are not custom made and therefore I expect them to be cheaper plus I like the roller bearing. Right now we don't need a mast man for setting sails and I would like to keep it that way.

anyone else having an idea?

Are there more hardware manufacturers besides the ones mentioned selling sheaves?

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You wont find a ball bearing or roller bearing sheave strong enough for hi load halyard sheaves; we make a ton of custom sheaves, and always with either a delrin or sintered bronze bushing. Harken uses a sophisticated journal bearing for their purpose built halyard sheaves.

 

Keep in mind that your halyards move a lot for a few seconds, then never rotate for 95% of the time while they are in use. A little friction can always be overcome with a winch when highly loaded.

 

BTW, fit is a huge part of the job, an extra .015 of an inch doesn't seem like much, but will greatly effect the way the sheave rolls on the axle, which should be polished to a mirror finish. Make sure whoever makes the sheave scores them properly for the material; we use a universal scoring on ours. This will greatly extend the life of your halyards.

 

Bam Miller

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You wont find a ball bearing or roller bearing sheave strong enough for hi load halyard sheaves; we make a ton of custom sheaves, and always with either a delrin or sintered bronze bushing. Harken uses a sophisticated journal bearing for their purpose built halyard sheaves.

 

Keep in mind that your halyards move a lot for a few seconds, then never rotate for 95% of the time while they are in use. A little friction can always be overcome with a winch when highly loaded.

 

BTW, fit is a huge part of the job, an extra .015 of an inch doesn't seem like much, but will greatly effect the way the sheave rolls on the axle, which should be polished to a mirror finish. Make sure whoever makes the sheave scores them properly for the material; we use a universal scoring on ours. This will greatly extend the life of your halyards.

 

Bam Miller

 

Well I think there is a lot more load on my backstay sheaves (6:1) which are ball bearing and holding up fine. So it would be possible. But the sheaves are biggger and don't fit the rig.

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You wont find a ball bearing or roller bearing sheave strong enough for hi load halyard sheaves; we make a ton of custom sheaves, and always with either a delrin or sintered bronze bushing. Harken uses a sophisticated journal bearing for their purpose built halyard sheaves.

 

Keep in mind that your halyards move a lot for a few seconds, then never rotate for 95% of the time while they are in use. A little friction can always be overcome with a winch when highly loaded.

 

BTW, fit is a huge part of the job, an extra .015 of an inch doesn't seem like much, but will greatly effect the way the sheave rolls on the axle, which should be polished to a mirror finish. Make sure whoever makes the sheave scores them properly for the material; we use a universal scoring on ours. This will greatly extend the life of your halyards.

 

Bam Miller

 

Well I think there is a lot more load on my backstay sheaves (6:1) which are ball bearing and holding up fine. So it would be possible. But the sheaves are biggger and don't fit the rig.

Oh, so you have 3 sheaves (6:1) sharing the load, so each sheave is only seeing 1/3 of the total load, which might actually work, where as your halyard sheave is 1:1 and is seeing 100% of the load. Why do you think that you havent been able to find any ball bearing or roller bearing mast sheaves?

 

Bam Miller

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Bam, wouldn't a 1:1 halyard sheave be seeing 200% of the load?

 

Quasi Expert, this type of sheave is normally plain bearing for good reason, for a reference, please see your old sheaves. Also, any roller bearing replacement is going to be way more expensive than a custom plastic or al sheave with a bronze bushing.

 

I would take the expert opinions being offered and replace with plain sheaves. You will not need to hire a mastman.

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You wont find a ball bearing or roller bearing sheave strong enough for hi load halyard sheaves; we make a ton of custom sheaves, and always with either a delrin or sintered bronze bushing. Harken uses a sophisticated journal bearing for their purpose built halyard sheaves.

 

Keep in mind that your halyards move a lot for a few seconds, then never rotate for 95% of the time while they are in use. A little friction can always be overcome with a winch when highly loaded.

 

BTW, fit is a huge part of the job, an extra .015 of an inch doesn't seem like much, but will greatly effect the way the sheave rolls on the axle, which should be polished to a mirror finish. Make sure whoever makes the sheave scores them properly for the material; we use a universal scoring on ours. This will greatly extend the life of your halyards.

 

Bam Miller

 

Well I think there is a lot more load on my backstay sheaves (6:1) which are ball bearing and holding up fine. So it would be possible. But the sheaves are biggger and don't fit the rig.

Oh, so you have 3 sheaves (6:1) sharing the load, so each sheave is only seeing 1/3 of the total load, which might actually work, where as your halyard sheave is 1:1 and is seeing 100% of the load. Why do you think that you havent been able to find any ball bearing or roller bearing mast sheaves?

 

Bam Miller

 

Well actually this doesn't matter, but my backstay is setup on each side with the sheaves I referred to being the turning sheaves in the back of the boat (so each getting 50% of the load which is still more than on the halyards IMO)

Maybe I should mention that the boat is ~8m long and weighs roughly 1300kg. I seldom have to tension the halyards with a winch so the loads cannot be that high. IMO it would be possible to have roller bearing mast sheaves (the one shown is 10+ years old). I want to add that I would be totally fine with replacing them every 3-5 years. The only thing that keeps me from buying new ones is that all manufacturers I looked at do not have (high load) sheaves that fit my mast slots, either their diameter is too big or they are too wide/too narrow.

The next problem I see with plain bearings is that as mentioned above the pin diameter and pin hole diameter need to be adjusted to each other precisely, otherwise the sheave won't turn. So I will have to buy new custom sheaves and pins in order to get it right the first time. simply exchanging the sheaves would be way easier, faster and probably cheaper.

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we need to replace the sheaves in our mast and boom.

the rollers are pretty much done and one has already fallen apart.

I don't know the manufacturer of the sheaves and a search (harken, ronstan, antal) hasn't returned any results.

anybody know the manufacturer?

sheave diameter: 50mm

pin diameter: 8mm

width: 15mm

the body is aluminium and the rollers are torlon afaik.

post-6362-049601800 1332008103_thumb.gif

 

 

That looks like an old FREDERIKSEN Sheve. Quite popular in the 90's. They were Taken over by Ronstan a while back, if yoyu just want a replacment give them a try.

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we need to replace the sheaves in our mast and boom.

the rollers are pretty much done and one has already fallen apart.

I don't know the manufacturer of the sheaves and a search (harken, ronstan, antal) hasn't returned any results.

anybody know the manufacturer?

sheave diameter: 50mm

pin diameter: 8mm

width: 15mm

the body is aluminium and the rollers are torlon afaik.

post-6362-049601800 1332008103_thumb.gif

 

 

That looks like an old FREDERIKSEN Sheve. Quite popular in the 90's. They were Taken over by Ronstan a while back, if yoyu just want a replacment give them a try.

 

I think you are right. It looked familiar, I have several of these.

 

I also think it should be replaced with a sleeve bearing, rather than ball bearings. You need to add a lot of weight to size up to a ball bearing sheave over the sleeve bearing sheave to handle the load. You don't need that weight for the minimal reduction in friction.

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Thanks for all your input so far. I appreciate it, although I hoped to get different advice.

I am pretty sure now that these are (better say were) Frederiksen sheaves, but I think they are not available anymore.

So now I need new custom sheaves with plain bearing made (probably during the season). I already know someone who can make them.

Obviously getting the pin and hole diameters is important. Anything else I have to look for?

What materials should/could be used? Stainless stell for the pin, bronze for the bearing surface and delrin for the sheave? what about aluminium?

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Thanks for all your input so far. I appreciate it, although I hoped to get different advice.

I am pretty sure now that these are (better say were) Frederiksen sheaves, but I think they are not available anymore.

So now I need new custom sheaves with plain bearing made (probably during the season). I already know someone who can make them.

Obviously getting the pin and hole diameters is important. Anything else I have to look for?

What materials should/could be used? Stainless stell for the pin, bronze for the bearing surface and delrin for the sheave? what about aluminium?

 

On a 8m long boat, and unless you are using wire for halyards, delrin throughout is perfectly fine; you really dont need a bronze bushing.

 

I would suggest that you try and use UV stabilized Delrin, as opposed to acetyl, which is very similar, but not quite as good a material for mast sheaves. Black, I think, is the most UV stable. I would also suggest that you get the sheaves sizes as perfectly as possible; we turn our sheaves to a .005 precision - the better the fit, the better the performance. Also make sure that the axle pin is smooth and polished and round; a bolt wont really cut it and will chew up the new sheave in no time. Made sure the outer edges are radiused nicely, or it will beat the hell out of your halyards in no time, if the pull is slightly off axis. Try to mimic the scoring from a current Harken black magic block; the shape is parabolic (called Universal Scoring) and ensures that the line is evenly supported, regardless of size.

 

Finally, if your machinist is a clever guy, he can sculpt the extra material from the sides, making the sheave lighter and with less area for contact in the sheave box, which will reduce friction as well.

 

Oh, one last thing, we get $45.00 a sheave, up to 3", so you don't wind up paying too much.

 

Bam Miller

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Thanks for all your input so far. I appreciate it, although I hoped to get different advice.

I am pretty sure now that these are (better say were) Frederiksen sheaves, but I think they are not available anymore.

So now I need new custom sheaves with plain bearing made (probably during the season). I already know someone who can make them.

Obviously getting the pin and hole diameters is important. Anything else I have to look for?

What materials should/could be used? Stainless stell for the pin, bronze for the bearing surface and delrin for the sheave? what about aluminium?

 

On a 8m long boat, and unless you are using wire for halyards, delrin throughout is perfectly fine; you really dont need a bronze bushing.

 

I would suggest that you try and use UV stabilized Delrin, as opposed to acetyl, which is very similar, but not quite as good a material for mast sheaves. Black, I think, is the most UV stable. I would also suggest that you get the sheaves sizes as perfectly as possible; we turn our sheaves to a .005 precision - the better the fit, the better the performance. Also make sure that the axle pin is smooth and polished and round; a bolt wont really cut it and will chew up the new sheave in no time. Made sure the outer edges are radiused nicely, or it will beat the hell out of your halyards in no time, if the pull is slightly off axis. Try to mimic the scoring from a current Harken black magic block; the shape is parabolic (called Universal Scoring) and ensures that the line is evenly supported, regardless of size.

 

Finally, if your machinist is a clever guy, he can sculpt the extra material from the sides, making the sheave lighter and with less area for contact in the sheave box, which will reduce friction as well.

 

Oh, one last thing, we get $45.00 a sheave, up to 3", so you don't wind up paying too much.

 

Bam Miller

 

Really good info! Thank you very much.

shouldn't be much of a problem to design a sheave and have it machined to the needed precision.

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Just a guess, but I think you've found someone who can do it.

 

;)

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Just a guess, but I think you've found someone who can do it.

 

;)

 

Although I believe mr. miller would make a wonderful set of sheaves with his knowledge and skills, I prefer a local solution for various reasons.

I know someone who can do it who has already built other stuff for the boat which works great and has always delivered good quality for very competitive prices.

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Why not just replace the rollers?

 

Or maybe you want one of these:

RF1767

http://www.apsltd.com/c-1008-ronstanreplacementsheaves.aspx

 

we need to replace the sheaves in our mast and boom.

the rollers are pretty much done and one has already fallen apart.

I don't know the manufacturer of the sheaves and a search (harken, ronstan, antal) hasn't returned any results.

anybody know the manufacturer?

sheave diameter: 50mm

pin diameter: 8mm

width: 15mm

the body is aluminium and the rollers are torlon afaik.

post-6362-049601800 1332008103_thumb.gif

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Why not just replace the rollers?

 

Or maybe you want one of these:

RF1767

http://www.apsltd.com/c-1008-ronstanreplacementsheaves.aspx

 

we need to replace the sheaves in our mast and boom.

the rollers are pretty much done and one has already fallen apart.

I don't know the manufacturer of the sheaves and a search (harken, ronstan, antal) hasn't returned any results.

anybody know the manufacturer?

sheave diameter: 50mm

pin diameter: 8mm

width: 15mm

the body is aluminium and the rollers are torlon afaik.

post-6362-049601800 1332008103_thumb.gif

 

First of all I don't know the exact diameter of the rollers as they are all deformed. Then I have tried to reassemble a sheave that already fall apart and it is quite difficult to do. Last reason is they didn't last that long.

 

I guess the RF 1767 is the successor to my sheaves, but they have ball bearings so I expect them to have even less working load than the roller bearings.

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