Rocna Size

[marinextreme]

Originally Posted by Auspicious

I have two Rocna 25 anchors, a 2006 Canadian one and a 2008 NZ one. I'm happy to have them tested NON-DESTRUCTIVELY if someone can point to a independent lab that can generate meaningful results somewhere close to Annapolis MD.

I would not be concerned at all about the Canadian or NZ made ones.

[captain58sailin]

Very interesting thread.

[Pete7]

Originally Posted by Delfin

The Canadian and NZ anchors are probably made to spec, or at least there isn't any information I am aware of that would indicate they aren't. The easy and cheap test is a hardness test, which should show the shank to be Rockwell 63 or Brinell 255 hardness if it is 800 MPa steel. This just involves pressing a dimple into the metal. Not sure where to get it done in Maryland, but there would likely be someplace close since this is a pretty common test.

Probably at a local technical college. If I remember rightly (and it was 3 decades ago) the test involves a small hardened steel weight dropped from a known height and the bounce measured which gives the hardness value of the sample tested. A very simple mechanical rig.

Peter

[GordMay]

There are three principal standard test methods for expressing the relationship between hardness and the size of the impression, these being Brinell, Vickers, and Rockwell. Since the definitions of metallurgic ultimate strength and hardness are rather similar, it can generally be assumed that a strong metal is also a hard metal.

The Brinell hardness test method consists of indenting the test material with a 10 mm diameter hardened steel or carbide ball subjected to a load of 3000 kg. For softer materials the load can be reduced to 1500 kg or 500 kg to avoid excessive indentation. The full load is normally applied for 10 to 15 seconds in the case of iron and steel and for at least 30 seconds in the case of other metals. The diameter of the indentation left in the test material is measured with a low powered microscope. The Brinell harness number is calculated by dividing the load applied by the surface area of the indentation.

The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load F0 usually 10 kgf. When equilibrium has been reached, an indicating device, which follows the movements of the indenter and so responds to changes in depth of penetration of the indenter is set to a datum position. While the preliminary minor load is still applied an additional major load is applied with resulting increase in penetration. When equilibrium has again been reach, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration. The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

The Vickers hardness test method consists of indenting the test material with a diamond indenter, in the form of a right pyramid with a square base and an angle of 136 degrees between opposite faces subjected to a load of 1 to 100 kgf. The full load is normally applied for 10 to 15 seconds. The two diagonals of the indentation left in the surface of the material after removal of the load are measured using a microscope and their average calculated. The area of the sloping surface of the indentation is calculated. The Vickers hardness is the quotient obtained by dividing the kgf load by the square mm area of indentation.

For additional important information,
See also ➥ Hardness Testing

Hardness Testers ➥ Hardness Testers for Rockwell and Brinell | Newage Testing Instruments

[Pete7]

I was thinking of the Scleroscope test which doesn't mark the surface of a product. This would be useful for testing a steel anchor becuase if it met the required spec then the anchor could be returned to service.

EngNet - Engineering Directory - Engineering Dictionary)

Pete

[Hydra]

The indentation made by a Rockwell hardness test is very small indeed and doesn't prevent using the object. I own a knife with such a mark on the blade, it is about 1mm wide.

So, such a test wouldn't prevent using the anchor. You would just have to paint the test area over, to avoid corrosion.

Alain

[Singleprop]

So how do the current owners or prospective buyers of the Rocna's know if the anchor is made in China and when it was produced?

Is there a "Made in China" stamp on them, or a date maybe?

[skipmac]

Originally Posted by Singleprop

So how do the current owners or prospective buyers of the Rocna's know if the anchor is made in China and when it was produced?

Is there a "Made in China" stamp on them, or a date maybe?

Previous posts in this thread state that the Chinese made Rocnas have the company name molded in the base of the fluke. Look back in the thread and there is a photo.

[Delfin]

Rocna hasn't made any anchors outside of China for a few years, so I think it's fair to say that any retail product you buy today would have been made in China. As noted, all Chinese Rocnas have stampings on the base of the flukes stating that it is a "Genuine Rocna", meaning it is a cheap knock off of the original, by design.

[S/V Alchemy]

By design and as per analysis!

[Exile]

Hard to miss the "Made In China" stamp on the underside.

As of yesterday, the regional WM rep for Charleston, SC had not heard all the commotion. The one I bought a month ago but have yet to use is getting replaced by WM for a Manson. Not sure I'm totally convinced but, with all the analysis & questions raised (and yet unanswered), it seems prudent to be cautious.

[Dockhead]

Originally Posted by Delfin

As noted, all Chinese Rocnas have stampings on the base of the flukes stating that it is a "Genuine Rocna" . . .

Not all of them -- all of the Chinese Rocna wihth cast flukes. The "Genuine Rocna" letters are cast, not stamped.

My 55kg Chinese Rocna has a brake-pressed plate fluke, not a cast one, so lacks the letters even though it was made in China. I'm itching to get to the boat with a hammer and center punch to see what the shank if made of.

[Shawn67]

Originally Posted by Dockhead

Not all of them -- all of the Chinese Rocna wihth cast flukes. The "Genuine Rocna" letters are cast, not stamped.

My 55kg Chinese Rocna has a brake-pressed plate fluke, not a cast one, so lacks the letters even though it was made in China. I'm itching to get to the boat with a hammer and center punch to see what the shank if made of.

I think Grant posted on the YBW forum that the 55kg and above Chinese Rocnas all have the plate fluke because the castings were not strong enough in those sizes.

Shawn

[marinextreme]

Originally Posted by Shawn67

I think Grant posted on the YBW forum that the 55kg and above Chinese Rocnas all have the plate fluke because the castings were not strong enough in those sizes.

Shawn

Thats correct, the 4kg-40kg have a cast fluke with the raised embossed name and size across the rear underside of the fluke.

The 55kg and above are welded plate.

They all have very smooth radiused edges on the shanks for all sizes on the Chinese ones where the NZ and Canadian ones have a chamfered edge that is distinctly sharp by comparison.

The last NZ ones were made in early 2009 and the last Canada ones around the same time.

[s/v 'Faith']

Originally Posted by Shawn67

I think Grant posted on the YBW forum that the 55kg and above Chinese Rocnas all have the plate fluke because the castings were not strong enough in those sizes.

Shawn

I think it would be 'fair' and probably overly 'charitable' to say
that Rocna has at least raised some doubt over their credibility in
determining what is indeed 'strong enough'.