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Low Friction Rings and Sheaves Anarchy


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I'll start with the observation that low friction rings, sheaves and shockblocks are fantastic, particularly with slippery lines like dyneema. Having said that, they are ridiculously expensive.

I'm rigging small boats with lines in the 2mm-4mm range, and just a setup of 6 blocks costs a pretty penny. 

Do you have a supplier with good pricing for - say - a bag of 10 rings/sheaves/shockblocks for small diameter line? 

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20 hours ago, martin.langhoff said:

I'll start with the observation that low friction rings, sheaves and shockblocks are fantastic, particularly with slippery lines like dyneema. Having said that, they are ridiculously expensive.

I'm rigging small boats with lines in the 2mm-4mm range, and just a setup of 6 blocks costs a pretty penny. 

Do you have a supplier with good pricing for - say - a bag of 10 rings/sheaves/shockblocks for small diameter line? 

climbing rings from REI  ... i paid about $4-5  apiece ...  

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13 hours ago, Max Rockatansky said:

They do but it's an expensive game. $10 apiece for the smallest ones. I get similar pricing on tylaska rings from Amazon. 

The climbing/rappelling rings are a great find. Cost about half but don't have the open profile (at least they I can see), so it's not quite the same. For some uses it'll be fine, for others it won't work.

Ah well. When I discovered rings and shockblocks, couple years ago, they looked so straightforward that I imagined that, while expensive bought individually, they'd eventually be something you buy a bag of, 10 for $20. At least the small ones.

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8 hours ago, Grande Mastere Dreade said:

i've used the fat maroon ones for jib tweekers and a larger grey one on my vang...  20' boat..  i've have not seen any distortion or failure of any type.. 

Ditto. Mine have a interesting oval section (radial width is smaller than the axial width). They work great in cascades, but don't have the hollowed outer diameter to hold in a spliced eye.

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1 hour ago, Alcatraz5768 said:

What about stainless sailmakers thimbles. 

These are perfect, I use them all over on the I14, but they are still $5 a piece. Come on, we're looking for cheap here!  Even McMaster is $5/each

 

Closed-End Light Duty Wire
Rope Thimbles—Not for Lifting

3634t74c1-e01j-digital-master1562013994-
 

Smooth rounded edges and an endless design protect wire rope from snagging. Made of 316 stainless steel, these thimbles have excellent resistance to salt water and chemicals.

Warning: Do not use with coated rope unless the coating is removed.

 
Loop
   
For Wire
Rope Dia.
Inside
Lg.
Inside
Wd.
  Each
316 Stainless Steel
1/8" 5/8" 3/8" 3634T71 $5.94
3/16" 1 1/16" 11/16" 3634T73 7.33
1/4" 1 5/16" 13/16" 3634T74 8.48
5/16" 1 9/16" 1" 3634T75 14.57
3634t74c1-e01j-digital-master1562013994-p9@1x_636975958036165337.png?ver=ImageNotFound
 
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You can get them on alibaba down to less than $1... but for 500-1000.

I'm sure I'd be able to offload at cost some to mates and such, but I wouldn't be happy reselling further afield in case someone starts using them somewhere critical. 

It would be nice to get batches of 20-30 at less than $5 so do a complete switch out of the boat. But, I'm not paying $9-15 to replace blocks which are still working. 

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1 hour ago, Mozzy Sails said:

You can get them on alibaba down to less than $1... but for 500-1000.

I'm sure I'd be able to offload at cost some to mates and such, but I wouldn't be happy reselling further afield in case someone starts using them somewhere critical. 

It would be nice to get batches of 20-30 at less than $5 so do a complete switch out of the boat. But, I'm not paying $9-15 to replace blocks which are still working. 

ok, I saw a "closed loop rope thimble" on Amazon, $62 for $25

No idea what level of quality.

 

DuraBrite 316 Stainless Steel Super HD Thimble - 5/16” Wire Rope (Pack of 25)

by DuraBrite

 

 
 
 
 
 

Price: $61.99 & FREE Shipping
 
 
 
Note: Not eligible for Amazon Prime.
 
 
 
 
 
 
 
 
 
 
 
 
 
Size: 5/16" Wire Rope - Pack of 25
  • 1/2" Wire Rope - Pack of 5
    $64.99
  •  
  • 3/4" Wire Rope - Pack of 2
    $41.99
  •  
  • 3/8" Wire Rope - Pack of 25
    $79.99
  •  
  • 5/8" Wire Rope - Pack of 5
    $73.99
  •  
  • 5/16" Wire Rope - Pack of 25
    $61.99
  •  
  • 7/16" Wire Rope - Pack of 10
    $62.99
 
 
 
 
 
 
 
 
 
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2 hours ago, martin.langhoff said:

The thimbles linked by @weightless and @Raz'r look more like classic thimbles. No promises about friction.

Do the low friction rings make any specific promises about friction? Allen of L-36.com has done some testing eg. https://l-36.com/low_friction_rings.php I'm not sure if any difference would be meaningful in typical applicants. Polished stainless thimbles are used for tweakers even on some big boats. For small deflections they're fine. If you need very low friction on a big deflection maybe a block is a better solution than a "low friction" ring?

 

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For many years the marketing department told us that we had to have extremely expensive blocks that used complex bearings crafted from exotic materials. We all remember the advertising graphics.

 

Now the same marketing departments tell us we need low friction rings.  These are very strong, at the time we were never told how pathetically weak our expensive blocks were.  These magic rings are expensive, but not very expensive, and cost pennies to produce. That's the magic part.   The expensive bit is the snake oil, but that washes off, so you have to buy more.

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16 hours ago, weightless said:

Do the low friction rings make any specific promises about friction? Allen of L-36.com has done some testing eg. https://l-36.com/low_friction_rings.php I'm not sure if any difference would be meaningful in typical applicants. Polished stainless thimbles are used for tweakers even on some big boats. For small deflections they're fine. If you need very low friction on a big deflection maybe a block is a better solution than a "low friction" ring?

 

The way L-36 tested does seem to be the most common arrangement for low friction rings, but is it the most efficient? It seems better to use dyneema as the bearing surface through the centre of the doughnut and have the ring rotate with the moving line. To make this work better, as seen in Ropeye and Ino blocks, you need something to deflect the bearing dyeema above the ring, so that it doesn't pinch on the sides of the friction ring, but runs at a more oblique angle through the centre. The downside here, is the moving line can fall off the outer grove of the ring when not under load, so it also helps if whatever is deflecting the dyneema bearing line above the block also wraps around the side and acts as a keeper.

8c384ded-9643-4be1-b9d1-055db6b51175.png

I'd be interested to see a comparison of friction rings used in this way to ball bearing blocks at the sorts of loads we more typically see on dinghies. 

Currently, I see use for low friction rings at the two ends of turning point requirements on a dinghy.

-Firstly are turning points which are low importance and have low loads and where friction isn't too important. Things like take up elastics and routing for continuous control lines across the deck.  Here they probably add more friction than a standard block, but the benefit is low weight and easier maintenance. 

-Secondly are the very high load turning points which don't see much movement, like the top block in kicker purchase systems, or rig (jib wire) tension if that's applied by any pulley system. In most dinghies you're still at the threshold of whether a block is better in terms of friction, but the rings are better from a weight and maintenance point of view, plus they tend to fail safe if you have enclosed splices. I wonder if using friction rings as turning sheaves like described above would bring the benefit of these further down the cascade? 

But, everything in between the two scenarios above is better served with a decent ball bearing block. Basically any sheet or line which is being moved regularly with 1:1 loading from the crews hand, then the friction will pretty always be lower with a ball bearing block. 

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I'll accept that they're light, and in some applications they fail safe.  That said they never used to tell us how unsafe all their previous blocks were.  It's the price where they take us for fucking mugs and we lap it up.

For example;

Harken 8mm lube anodised (whatever the fuck that means) ring.  £21.21 to you on the Purple marine website.

Then take the equivalent small block.  Harken Micro single block, £11.75 on the same site.

Lube anodised ring.  Taken roughly from behind by the marketing team without lube more like.

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On 11/18/2019 at 10:39 PM, martin.langhoff said:

Ah well. When I discovered rings and shockblocks, couple years ago, they looked so straightforward that I imagined that, while expensive bought individually, they'd eventually be something you buy a bag of, 10 for $20. At least the small ones.

It sounds like you've identified a real inefficiency in the market. You should open a business to take advantage of this opportunity!

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6 hours ago, European Bloke said:

Harken 8mm lube anodised (whatever the fuck that means) ring.

FWIW, Antal and, I presume, Harken do fill the anodized surface with something that feels slick. They are very nicely made. That said, when the hard coat wears through they're toast. Polished SS surfaces should be more durable until the the whole fitting breaks into little bits because of crevasse corrosion.

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3 hours ago, DDW said:

true hard anodize will wear far better than SS

 I don't doubt that but I've seen anodizing wear though. Looking at chafe patterns on fittings suggests to me that stainless hardness varies considerably even within the same brands of the same vintage.  So, I'm not sure how valid a general comparison is likely to be. If you do get down to the substrate the SS is is going to be a lot harder than the Al.

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One problem is that all anodizing is not the same. You can get something anodized to make it look black, but it will be type I or II ornamental anodize, a few tenths thick and not very hard. Then are are places doing "hard anodize" but cheating on the process so the oxide isn't very hard. True MIL-A-8625 Type III hard anodize will be around 0.002" thick, done in an acid bath chilled to near freezing temperature. If you try to machine this off with carbide tooling it will ruin the carbide tool. It is very hard, difficult even to grind through. Now it is only 2 thousandths thick, so you can deform the underlying aluminum and destroy the coating. Also it is porous (especially if not either nickel acetate or DI sealed) and can corrode underneath. The anodizing I've seen from Harken has been pretty good, from Antal it seems to vary a lot (like the dimensions on their parts). Some other vendors don't do hard anodize at all. 

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It is a messy process - probably better off taking it to a commercial enterprise. I note that the chiller required for true Type III is not included in that system. There is a certain amount of art involved and considerable process control if you want consistent results. 

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14 hours ago, DDW said:

The anodizing I've seen from Harken has been pretty good, from Antal it seems to vary a lot

Right. I assume it's a tricky industrial process, where scale is what'll bring costs down. So for low volume items, you're either paying for the fact that they manufactured just a handful (with awful per unit costs) or for risk / stocking of a big lot made at good per-unit cost.

If any manufacturer made a big lot, they'll want to start pushing them in larger bundles & better pricing into the market. It either hasn't happened, or everyone's still gun-shy.

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It is true that the machining costs for something like this are pretty modest. I ran into this same problem with the Tylaska spool shackle. They are pretty proud of them, and would not replace one of these "flog proof" shackles when I lost one to flogging off of Cape Ann. Also the sizes offered did not meet my requirements. I made replacements myself for about $0.50 in aluminum and $2 anodizing. I consider the $50K or so cost of the machinery to do so sunk cost. :)

On the right machine you can knock out the rings at probably one every 30 seconds or so. The material costs almost nothing. It takes them longer to etch or machine all the logos in the side than the machining itself. But then there is marketing, 3 tier distribution, etc. A lot of people are keeping their kids in private school on the profits. 

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  • 2 weeks later...
34 minutes ago, crankcall said:

have a look at the Viadana thread, on there website are low friction rings at an affordable price.

They have confusing naming that doesn't line up with anyone else's, but once you get past that they don't seem much cheaper.  

https://www.velasailingsupply.com/viadana-low-friction-aluminum-ring-19mm/

https://www.velasailingsupply.com/antal-low-friction-ring-7-x-5mm/

It's about 20% off of the Antal in this size, the discount is a little bigger with the larger rings.  The Viadana surface finish and shape don't look very good (it stands out more in the 35mm one at https://www.velasailingsupply.com/viadana-low-friction-aluminum-ring-35mm/).

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^^ I think this may be unfair. Although I've not used Vela rings, Nautos rings have a similar finish and shape, and they work and wear just fine. The different shape can increase the number of rigging options (larger groove).

[I've used rings by Antal, Harken, Nautos, Ronstan, and Scheafer. They all work. A like Antal for the smooth finish and Nautos for the deep, wide groove.]

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  • 3 weeks later...

I've had a quantity of low friction rings made for a project som 2-3 years ago. Machined from AL7075 T6 and hard-teflon anodized. Anodize color "bronze-ish" and black.

the shape is somewhat different from the classic LFR; that is because I used these rings in several more creative ways. For anyone interested I have some quantity available still. 

sizes/ price

80x17mm for 13mm line: $18
60x14mm for 11mm line: $14
52x11mm for 8mm line: $11
45x9mm for 7mm line: $10

 

C5720356-68D1-405D-9227-D6630C421703.jpeg

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On 11/23/2019 at 3:32 PM, DDW said:

It is true that the machining costs for something like this are pretty modest. I ran into this same problem with the Tylaska spool shackle. They are pretty proud of them, and would not replace one of these "flog proof" shackles when I lost one to flogging off of Cape Ann. Also the sizes offered did not meet my requirements. I made replacements myself for about $0.50 in aluminum and $2 anodizing. I consider the $50K or so cost of the machinery to do so sunk cost. :)

On the right machine you can knock out the rings at probably one every 30 seconds or so. The material costs almost nothing. It takes them longer to etch or machine all the logos in the side than the machining itself. But then there is marketing, 3 tier distribution, etc. A lot of people are keeping their kids in private school on the profits. 

I’m not sure if it’s possible to turn it in 30 seconds because it requires a pick off for the back side. I understand you have a machine shop, how would you process this part?  

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I would not use 7075 for this purpose - nice material but very corrosion prone in salt water. 6061 OK, 6013 is ideal.

To machine the part efficiently you'd need a lathe with a sub spindle and a bar puller. The bar goes through the spindle and main chuck. Turn the front side and groove, chuck it in the sub spindle, cut off and turn the backside on the sub spindle, drop it in the parts catcher, pull the bar and to it again. There are automatic bar feeders that will load another 6' bar when you go through the first one. It can be a "lights out" operation, no operator intervention is required. 

I don't have that equipment, for me I'd have to machine the front side, cut it off, re-chuck it flipped over and machine the back as a second op. And manually pull the bar. I'd have more time loosening and tightening the chuck than machining. I make sheaves for my headboard all the time this way, takes longer though because machining the thrust ball track is slow. 

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11 hours ago, DDW said:

I would not use 7075 for this purpose - nice material but very corrosion prone in salt water. 6061 OK, 6013 is ideal.

To machine the part efficiently you'd need a lathe with a sub spindle and a bar puller. The bar goes through the spindle and main chuck. Turn the front side and groove, chuck it in the sub spindle, cut off and turn the backside on the sub spindle, drop it in the parts catcher, pull the bar and to it again. There are automatic bar feeders that will load another 6' bar when you go through the first one. It can be a "lights out" operation, no operator intervention is required. 

I don't have that equipment, for me I'd have to machine the front side, cut it off, re-chuck it flipped over and machine the back as a second op. And manually pull the bar. I'd have more time loosening and tightening the chuck than machining. I make sheaves for my headboard all the time this way, takes longer though because machining the thrust ball track is slow. 

Sure, some sort of Swiss, not a multi spindle Swiss like a Torno, that’s not needed but something that can do the pick off for the back side work.  I don’t know what equipment is out there today but certainly it exists.   You would want a high speed machine with the feeds backed off for a good finish so secondary finishing could be eliminated.  

I don’t know that the pricing for these rings are really that far out of line.  

Just kind of musing here. 

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Not a Swiss process lathe, just a dual spindle or one with a sub and a big enough spindle bore for the bar size. Not that expensive as machines are priced these days. You aren't going to pay for it making rings, but you could make them when it's otherwise idle very quickly. It really isn't the material or machining costs that make these expensive, its the relatively low volume and expensive distribution. 1 minute each would be a very long time on the right machine, and you can get that machine run for $60/hr even here in the US. That's $1 each machining costs, probably much less. 

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  • 3 weeks later...

If you're looking for cheap thimbles Allen does Stainless steel rings https://www.allenbrothers.co.uk/product/a-82-10-stainless-steel-thimble/ 

You could also look at their range of plain bearing blocks, they will offer less friction than the stainless steel thimbles and are actually slightly stronger. Pretty cheap for what you're getting too.  https://www.allenbrothers.co.uk/product/plain-bearing-single/

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