Mechanics Of Anchor Roller

[tkeithlu]

Could someone explain to me the mechanics of anchor bow rollers? I built one - a roller and a constraining hoop on an extension of the bow. It's a 44# claw. Once the end of the shaft comes to the roller, the load necessary to lever the shaft up onto the bed of the roller is more than I, the roller, or my anchor winch can handle. What's the secret here? Somehow, all those anchors I see lying in stainless steel troughs got up and around the corner at the roller, but as I see it, there is no lever arm with which to pry the weight of the anchor up over the roller. Help?

[a64pilot]

Inertia, known as a running start? Before my windlass, that was the only way I could do it manually.

[FSMike]

Two rollers, the forward roller being lower than the aft roller?

[tkeithlu]

Both good additions to my understanding, and I thank you. I did test with a running start, holding the welded up roller rig in a vise, and i was able to pull the 44# claw over the top. Adding a lower second roller to establish an angle in the shaft would also help. Thank you both.

[sy_gilana]

Larger diameter roller will fix it.

[Cheechako]

Most of mine would always come over the roller. How small diameter is your roller?

[tkeithlu]

Another excellent bit of advice. I used an appoximately 1 1/2 inch poly trailer roller, and I could change it out for a larger diameter. Thank you.

[bobofthenorth]

I built a pivoting receiver with a roller on each end of it. The pivot point is about 80% of the way to the windlass. On retrieval the receiver hangs more or less vertical, depending how hard the chain is pulling but when the stock reaches the 2nd roller it pivots up and the anchor gets lifted by what was until then the lower roller. It works slick but it took 1 false start to get the pivot in the right place.

R.J.(Bob) Evans
www.bobandmarilyn.ca

[leftbrainstuff]

As the anchor goes from vertical to horizontal over the roller you have a very small lever arm attempting to rotate the anchor 90 deg.

The angular acceleration increases from 0 to a maximum in a short space of time. Because the process is not smooth the anchor experiences a very rapid change in angular acceleration. This results in a very high peak load on the shackle and a violent motion.

Using a dual roller pivot in place of the original roller is an excellent idea. The dual roller pivot provides the following benefits:

1) It allows you to choose a grooved lower roller to align the anchor shank before you rotate it to the horizontal.
2) As the anchor shank reaches the second, upper, roller you then have a longer lever arm acting to rotate the anchor. This will reduce the violent rotation.

Without seeing a pic or dimensioned drawing of your pivot its difficult to comment. However you want 1 above to occur before 2.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Cheechako]

Yes, they've been making various forms of pivoting bow rollers for years. Short, or long like this one. Never felt I needed one, but I imagine they work well. Lewmar 66840007 | Fisheries Supply

[mitiempo]

Originally Posted by tkeithlu

I used an appoximately 1 1/2 inch poly trailer roller, and I could change it out for a larger diameter. Thank you.

A larger roller always works well. My anchor roller was lathe turned to the sane radius as the anchor - 1 33 lb Rocna. It is several inches larger than yours.

Delrin is a better material than the softer trailer rollers, which do not last long in this application.