Anchor Roller Refurbishment?

Good idea! :)

I'm not a bolt expert, by any means - but I assume you are using 'real' bolts only threaded at the end with a long unthreaded portion. At the back of my mind I have an idea there are fixed ratios of thread to unthreaded and getting the unthreaded portion to match the roller (or anything else) can be a real challenge. But the threaded portion, o.d., is usually smaller than the unthreaded - which can offer other challenges!

Jonathan
 
Neeves said:
Good idea! :)

I'm not a bolt expert, by any means - but I assume you are using 'real' bolts only threaded at the end with a long unthreaded portion. At the back of my mind I have an idea there are fixed ratios of thread to unthreaded and getting the unthreaded portion to match the roller (or anything else) can be a real challenge. But the threaded portion, o.d., is usually smaller than the unthreaded - which can offer other challenges!

Jonathan
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Why not get 316 rod and have threads cut on each end? I've had that done often. (They did it for my anchor roller)

The young fitter & turner who did mine drilled a small hole down the center of the shaft and tapped a grease nipple in each end. (A bit over the top!)
 
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coopec said:
I have no knowledge of the characteristics of different types of "plastics"but why not use nylon
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Some nylon grades swell more than 10% in water, others maybe a little less. My mast sheaves had nylon bearings that swelled and seized solid. I had to get the axles out and ream the nylon to fit. This is why nylon is never recommended for rudder bearings.
 
From experience I can recommend Kev at A2A4.com

http://www.a2a4.com/acatalog/A2A4_M10_Hexagon_Head_Bolt__A4_PART_THREADED_847.html

The chart at the top of this link shows threaded length per diameter, makes calculating the blind shank length a doddle!

Neeves said:
Good idea! :)

I'm not a bolt expert, by any means - but I assume you are using 'real' bolts only threaded at the end with a long unthreaded portion. At the back of my mind I have an idea there are fixed ratios of thread to unthreaded and getting the unthreaded portion to match the roller (or anything else) can be a real challenge. But the threaded portion, o.d., is usually smaller than the unthreaded - which can offer other challenges!

Jonathan
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vyv_cox said:
Some nylon grades swell more than 10% in water, others maybe a little less...
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Indeed, but it would be so much easier :)

Vyv, I'm glad you are reading this. I've decided to buy some 16mm A4 rod to make new axles, replacing the 12mm. This means I can use M8 screws in the ends, so closer to the original 10mm that protruded through as a rivet.

I'm considering making the whole assembly slightly narrower, so I don't need to countersink the axle screws completely. I could put a washer either side on the main swivel.

Does everyone understand what I'm doing, or do I need to explain better?
 
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nigelmercier said:
Indeed, but it would be so much easier :)

Vyv, I'm glad you are reading this. I've decided to buy some 16mm A4 rod to make new axles, replacing the 12mm. This means I can use M8 screws in the ends, so closer to the original 10mm that protruded through as a rivet.

I'm considering making the whole assembly slightly narrower, so I don't need to countersink the axle screws completely. I could put a washer either side on the main swivel.

Does everyone understand what I'm doing, or do I need to explain better?
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I understand and I think 16mm dia axle is great as it is the size of mine axle, The captive pin (upper pin to retain the chain ) is also 16mm with a drop nose to retain the top pin. My 16mm axle is retained with a keep plate welded to the end of the 16mm axle and then having a 6 mm hole offset with a M6 csk set screw tapped into the side plate. This retains the axle in both lateral directions and prevents the axle from rotating which is also important to prevent the hole in the side plate waring oval over time.
 
I didn't know that nylon can absorb water but I suppose anything including fiberglass resins can absorb water.
I wonder how much a nylon anchor roller would absorb since it is not permanently in water?

An interesting comment regarding rudder bearings but I'll follow that up in another thread.
 
coopec said:
I didn't know that nylon can absorb water but I suppose anything including fiberglass resins can absorb water.
I wonder how much a nylon anchor roller would absorb since it is not permanently in water?

An interesting comment regarding rudder bearings but I'll follow that up in another thread.
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As VyV says it can absorb up to 10% water and it can do this from the humidity in the atmosphere. This is from my days of designing all kind of plastic molded engineering components.

The moisture absorption also effect the dimensional stability.

When machineering nylon the base material has been in the atmosphere without a lot of heat unlike injection molding so the nylon may already become normalized (which is the term used)

This is what I use Vesconite and why

http://www.vesconite.com/prod/vesconite/DimenStable.htm

acording to vesconite manufacturer nylon absorbs up to 9% by weight and can increase in dimensions by 3 %
 
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I just did a google on vesconite and obviously they make bearings out of it: something I will have to think about for the bottom rudder bearing on my yacht.

I suspect we might have a problem buying "round bar"?
 
coopec said:
I just did a google on vesconite and obviously they make bearings out of it: something I will have to think about for the bottom rudder bearing on my yacht.

I suspect we might have a problem buying "round bar"?
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Round bar and thick wall tube not a problem.

My rudder bushes, stern shaft bearings, ware plate on my stem head fitting (under the anchor chain). Mast head and foot pulleys are all machined from vesconite.

There is a toll free number from Australia if you look at the bottom of this page

http://www.vesconite.com/vesco/finishpt.htm

If you are cheeky you could ask for a sample if you don't need too much.
 
Rogershaw said:
Round bar and thick wall tube not a problem.

There is a toll free number from Australia if you look at the bottom of this page

http://www.vesconite.com/vesco/finishpt.htm

If you are cheeky you could ask for a sample if you don't need too much.
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OMG! No!

I'm the sort of guy who is feeling bad because I bought that SS Ball valve valued at $115 on eBay for $13.50 (plus postage). The poor guy is just trying to make a living: how must he feel?

Actually you've got me thinking because there are a number of places where I could use "wear plates". I made my chain pipe out of very heavy High Density Polyethylene Pipe (?) industrial piping so hopefully that will be kind to the galvanizing on the chain
 
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As I said above, I've decided to upgrade the axles to 16mm to allow an M8 countersunk screw either end. It worries me slightly that this will require a much deeper countersink cut into the side plate, so I need advice from someone who has a similar roller...

Looking at tit again, I'm wondering if I need to be concerned about making the screw heads flush at all! The main swivel is central between the axles, and roughly half way up the box fixed to the bow. Can the ends of the axles pass inside the box when swivelled either way? In other words, do they go further than the red lines?

Bow-Roller-Arc.png
 
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nigelmercier said:
As I said above, I've decided to upgrade the axles to 16mm to allow an M8 countersunk screw either end. It worries me slightly that this will require a much deeper countersink cut into the side plate, so I need advice from someone who has a similar roller...

Looking at tit again, I'm wondering if I need to be concerned about making the screw heads flush at all! The main swivel is central between the axles, and roughly half way up the box fixed to the bow. Can the ends of the axles pass inside the box when swivelled either way? In other words, do they go further than the red lines?

Bow-Roller-Arc.png
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That's somewhat dependent on your anchor, but on mine they certainly do (or did, as I modified it somewhat and moved the main swivel forward to allow for stowing a roller bar anchor). The two rollers are aligned with the shank and both travel inside the bracket. The top bar (without a roller) does not. This bar ends up at the top, so you'd have to have a very strange anchor indeed if they don't on yours.

I'm watching this thread with interest, as I have the same bow fitting :)
 
Yngmar said:
... The top bar (without a roller) ... ends up at the top...
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So with the chain on, the whole lot swivels anticlockwise? I should have taken more pictures!

[Edit] found one, on left below. So you are quite right, the bar ends up at the top when stowed, so that scuppers that plan.

However, I did find a picture of a similar roller on another boat. This had about a 10mm gap either side of the swivelling part and the fixed box, and no spacers! Any reason I can't make the whole lot narrower?

Dolcetto-019a.png
Other-Bow-Roller-(3).png
 
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nigelmercier said:
So with the chain on, the whole lot swivels anticlockwise? I should have taken more pictures!
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Err, with the anchor stowed on it, yes. With the chain running through it, a bit too. Here's an old photo from mine pre anchor upgrade and bow fitting modification:

anchor_swivel.jpg


As you can see, both roller axles are well inside the bracket. No easy way out of that one I'm afraid.
 
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