Need thickness of Rocna 25kg(55lb) shank?

[Bill O]

I measured our 40kg shank, it is 3/4" thick. Your shank isn't going to any larger than that and from 5/8" that is only 0.125" difference.

How much wiggle room do you need? Too tight of a tolerance and it will not work correctly all the time.

[flightlead404]

Originally Posted by Dsanduril

The fact that it scales up nicely to 5/8" and 16mm (within some very small scaling changes) gives me some confidence, but I don't know if that is confirmation bias. Sometimes questionable when math works out perfectly.

Using the same technique on the 40 template yields 0.74-0.79" (depending on exactly where I place endpoints) which matches well with Bill O's report.

I appreciate it, I'll use 16mm for the sample run and see how it goes. I'm doing 2 or 3 models with different groove depths and a different shape to the concave side sections.

[flightlead404]

Originally Posted by Dsanduril

FWIW we have a groove similar to your description on our roller and it does function quite well for our anchor as you describe. I've seen some comments here on CF about the unnecessary-ness of them, but we like ours, rolls the anchor properly every time.

That's great feedback, thanks. That's exactly what I was hoping to achieve. It will be especially important when I start having my other anchor on the bow roller as well to prevent any interference.

[flightlead404]

Originally Posted by Bill O

I measured our 40kg shank, it is 3/4" thick. Your shank isn't going to any larger than that and from 5/8" that is only 0.125" difference.

How much wiggle room do you need? Too tight of a tolerance and it will not work correctly all the time.

Thanks Bill. As far as "how tight" I just don't know. That's why I want to 3d print a test model or two or three before I spend the $ to have someone CNC it.

It will need to be tight enough to hold the shank, the ratio of depth to width needs to be such that it doesn't get cocked over or slip out of the groove, and not so tight that some sand etc doesn't prevent it functioning.

[flightlead404]

Originally Posted by Dsanduril

FWIW we have a groove similar to your description on our roller a...

What material are you using?

I am mostly thinking Delrin, but Rocna mentions using aluminum, but I don't often see aluminum anchor roller sheaves.

Any feedback on material?

[Dsanduril]

Ours in plastic, I believe Delrin/Acetal, but would have to see if I can find the paperwork. Made about 5 years ago in NZ and still going (after continuous live-aboard at anchor use).

[flightlead404]

Thanks

[Drennan]

My c.2015 Roc 25 happens to be (sadly) under the house. Just measured with 16’ Stanley “Contractor Grade”: the measurement is 11/16” — 3/4” would be safe.

[ventu]

The width of the Rocna 25 kg shank is 16.5 mm. I measured it to build a bowroller on my HR36.

[Rod Headlee]

Originally Posted by flightlead404

I'm whipping up a 3D model for a new anchor sheave I'm going to have made.

I need the thickness of the shank (side to side, not vertical width) of a Rocna 25kg/55lb. Can't find it anywhere on the web even Rocna site.

If anyone is near their anchor and can measure this for me I'd appreciate it.

Thanks

Mine measures .675 =or-

[Dougtiff]

I have that anchor, it's 11/16" .

[contrail]

Originally Posted by flightlead404

Thanks Bill. As far as "how tight" I just don't know. That's why I want to 3d print a test model or two or three before I spend the $ to have someone CNC it.

It will need to be tight enough to hold the shank, the ratio of depth to width needs to be such that it doesn't get cocked over or slip out of the groove, and not so tight that some sand etc doesn't prevent it functioning.

Not to mention a barnacle or two, or when some galvanizing wears off, the fact that rust is thicker....I honestly think you are trying to be too precise.



A very easy way to avoid all of this is to stop when the anchor is right at the surface, and then drive the boat in reverse for a few feet. The anchor flips right over, and if it is dirty, gets a bit of a wash, as well.

[Flatswing]

[QUOTE The design with have a center groove to aid self-righting as it comes aboard. This is an issue with my current roller as it always comes aboard rotated 90' and then does a wild fling. The groove needs to be wide enough to accommodate the shank with a small amount of "wiggle", but not so wide that it allows the shank to flip over[/QUOTE]

The “wild fling”is the best part of anchor retrieval-you should try it with a 100lb Spade -always exciting! Seriously though, anchors sometimes come up rotated 180 deg. (Mine does 20% of the time) but with a sloppy roller groove, the anchor will rotate on it’s own-wild, yes but not dangerous once you learn to let it happen.

I would be concerned that your fine tolerances, though well intended, may prohibit the proper & desirable rotation. Check out Steve Goodwin’s (SV Panope) “lab” retrieval vids. Self rotating is one of the positive aspects of the new generation of anchors for many of us.

Good luck & let us know what you settle on.

[flightlead404]

Originally Posted by contrail

I honestly think you are trying to be too precise.

Originally Posted by Flatswing

I would be concerned that your fine tolerances,....

Its a character flaw

[Nicholson58]

Originally Posted by flightlead404

I'm whipping up a 3D model for a new anchor sheave I'm going to have made.

I need the thickness of the shank (side to side, not vertical width) of a Rocna 25kg/55lb. Can't find it anywhere on the web even Rocna site.

If anyone is near their anchor and can measure this for me I'd appreciate it.

Thanks

Rocna site has CAD full size models you can download. I made a cardboard copy before selecting mine.