delrin sheave

PabloPicasso

PabloPicasso

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I need two new delrin sheaves. Only supplier is in NZ and doesn't seem to be able to supply in time.

Anyone know a sheave manufacturer/turner?
 
Neil_Y said:
What's the application? load, rope/wire size, shaft diameter, Outside diameter.
Why did the old one fail?
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Two sheaves needed for a benateau 47. Vang sheave is approx 50mm diameter, 12mm wide, 10mm hole.

Reefing line sheave in aft end opf boom is (approx) 85mm diameter, 12mm wide, 15mm hole.

Perhaps delrin would be the material of choice.

Certainly a nylon sheave in the vang did not last. if you can help it would be appreciated. I can measure more accurately if you know someone who can manufacture
 
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Being a dedicated bodger, I have in the past, considered making some sheaves from sheet tufnol. You could cut the disc using a hole saw, then profile the edge by spinning the disc with an electric drill mounted in a vice, while shaping the edge with a file or possibly a dremel.

On the whole, I would think it easier to see if Selden have something that could be bored or bushed to fit.
Also phone around a few riggers, they may have a few spares in stock or even be able to find something serviceable in a broken mast.

You might find it's cheaper to buy a plain bearing Barton pulley and take the sheave from it?
That's what I did in the end!
 
I think that boat has a Z spar mast, the ones they provide are rubbish injection moulded nylon affairs. A solid delrin one would be fine. Teak would not work particularly well, would swell around the pin. Most metal workers would be able to make you some. Selden ones wouldn't be much better.
 
PabloPicasso said:
yes that would be strong. It is finding someone to do it that is the problem. If I had a lathe and some delrin i could probably do it myself, but haven't:(
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Versatile Marine, who advertise on ebay, and whose link is given above, will make sheaves in bronze for you made to order.

You would need to make a drawing giving dimensions:

a. thickness.
b. overall diameter.
c. diameter of rope to be used so they can cut the semicircular groove for it.
d. diameter of hole in middle.
and e...
if you are concerned with weight, this could be reduced by undercutting on both sides.
f. probably, they may even cut the pin in stainless to go through the centre, and prepared so you could rivet one end to secure in pulley housing.

I hope this helps.
 
Looks like Delrin will be ok for the lighter loads lower speeds, we just do bearing bushes for other materials. I'm surprised that Delrin doesn't deform as it is quite soft, but it's used by a few spar people as sheave material, and was probably on my old

@ IW395 be very careful machining tufnol the fumes and dust are quite nasty. Free phenol (the acrid smell) and very fine cotton fragments.
 
The limitations of UHMWPE and Delrin and many similar materials is thermal expansion and that they are ultimately a melting material so they will soften as friction produces heat. If they stay cool they can cope with quite high loads (bow/anchor roller) but add speed/friction and heat and they will deform which then adds to the friction and ultimate failure.
 
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