Making an anchor roller

[rallyveteran]

I need a new anchor roller to hold my Rocna snugly and am planning to by a cylinder of Delrin from theplasticshop .
I know I need to get a hole drilled for the spindle, and a slot to hold the shaft of the Rocna, but do you think I can leave the sides of the cylinder parallel, or do they need to be curved?
I'm thinking the reason most rollers are curved is to ensure there are no sharp edges to foul rope, but I'll only ever put chain over this roller.

 

[oldsaltoz]

Rounding the outer edge will not only reduce the cutting 'you or rope' but also reduce damage leaving sharp edges.

Any engineering shop will turn this up on a lathe in no time at all, hardly worth doing it yourself, just tell them what size hole and the required profile.

Avagoodweekend......

 

[homa]

Seascrew sell the finished product for a few pounds, may be cheaper than making your own.

 

[vyv_cox]

The lower two from Seascrew are the shape you want for a Rocna plus chain. Almost exactly what I have, with the same anchor.

It's not quite obvious in the photos whether these are solid or moulded with internal cavities. Plastimo ones are made with cavities, which cause the roller to collapse after a while, especially if you trap the anchor in rocks. If the Seascrew ones are solid I would buy one of them, rather than making one.

 

[rallyveteran]

I've got a Rocna 25, so I need the slot in the roller to be about 20mm wide. Seascrew don't have all the dimensions on their website, but their largest roller is only 53 mm wide, so the slot looks to be less than 20mm. If the anchor shank doesn't fit in the slot, I'm worried that the anchor will wobble when waves hit it, unless it has a lashing. This is what happens at present so is the main reason for changing the roller. After one rough trip (without a lashing) the anchor had been hitting the forestay so much that the split pin holding the clevis pin had come under severe pressure! I've used a lashing since, but it is a nuisance to put on and take off each time the anchor is deployed.

 

[vyv_cox]

Right, you are clearly looking for something rather bigger. Your plan in the original question seems to be OK, I would select the largest diameter you can fit in the cheek plates and make the roller very much like the ones in the Seascrew photos. Mine looks very like them but is clearly smaller than yours will be. That apart, it holds the Rocna very well and we have had none of the sliding from side to side that we used to experience before changing to the present one.

You will find that the groove in the roller will also guide the chain, and will largely hold it centrally at anchor, cutting down the noise of it slapping from cheek plate to cheek plate. The shape of the roller's intermediate diameter needs to accommodate the width of the chain links on their side.

 

[Dipper]

You can buy shorter lengths and have a greater choice of diameter from Direct Plastics. I have bought nylon, delrin and PVC rods from them in the past.