Where can I get new sheave made?

[tudorsailor]

One of the sheaves in the boom (a very old Hood/Formula rig) needs replacing. I have removed it and 3D printed a temporary replacement. So I have the original to be copied. Its quite big being a diameter or 150mm
Can anyone suggest someone who might make a replacement? I have had a quote of £152 + vat + shipping from a riggers in Southampton which seems a lot - or am I unrealistic
Thanks
Tudorsailor

 

[ash2020]

I have had some success printing sheaves in nylon. You say you've printed one, nylon would be a good permanent solution. If not, I'm sure you could find a local engineer who would turn you one out of aluminium, a 15 minute job. I think your mistake is going to someone in the marine industry!

 

[Rum Run]

The

I have had some success printing sheaves in nylon. You say you've printed one, nylon would be a good permanent solution. If not, I'm sure you could find a local engineer who would turn you one out of aluminium, a 15 minute job. I think your mistake is going to someone in the marine industry!

The bought item in aluminium would be anodised, protecting against wear and corrosion. A local engineer probably would not offer that cheaply.
If it's just an outhaul one of the engineering plastics probably would be sufficient - I'd worry about the pin deforming the hole in nylon but if you have done it and it works that's useful to know.

 

[B27]

there are a couple of people on ebay who will turn delrin sheaves.
You could try your local model engineering club?

3D printing in ABS might be a good answer?
A metal bush or even ball race in the centre is a possible way forwards.

Maybe you could modify the boom to take a smaller sheave?
Or find a secondhand block you can take the sheave from?

If it's the centre of the sheave that's worn, it can probably be bushed.

 

[AntarcticPilot]

The

The bought item in aluminium would be anodised, protecting against wear and corrosion. A local engineer probably would not offer that cheaply.
If it's just an outhaul one of the engineering plastics probably would be sufficient - I'd worry about the pin deforming the hole in nylon but if you have done it and it works that's useful to know.

Anyone who could turn one up out of aluminium could do it in another metal - bronze comes to mind, or stainless steel. That would avoid the coating issue.

 

[Rum Run]

Anyone who could turn one up out of aluminium could do it in another metal - bronze comes to mind, or stainless steel. That would avoid the coating issue.

Very true but both materials are more costly both as billet cost and machine time, and much heavier than the original.

 

[tudorsailor]

I could print in ASA which is UV resistant, but I am not so confident that it would withstand the stress if actually used for the outhaul. However at present it could be put in the centre of the 3 sheaves that is unused - so that is an option
TudorSailor

 

[Neeves]

The anodising on sheaves does not last very long, lots of marine components are made from the 5083 alloy - and they, dinghies, are not anodised.

Its unusual that the weight of a sheave would be a concern for excessive weight (I have noted that the sheave is quite large, if not enormous) unless you have a weight fetish.

These are cheap as chips, which puts the quote you have into context, but about 10cm diameter

Winch Snatch Recovery Ring 45000 Lbs Winch Snatch Block - Temu Australia

but the shaft would be an issue

I have used them as sheaves but no shaft, simply suspending them with soft shackles.

Jonathan

 

[AntarcticPilot]

Very true but both materials are more costly both as billet cost and machine time, and much heavier than the original.

Of course, the sheave could have holes drilled in it to reduce the weight, and if it's on a lathe anyway, the metal could be thinned away from the hub and the perimeter. I'm not up on metal costs, but I'd have thought that the small amount needed would be an insignificant part of the overall cost. After all, you only need a piece 150mm square and perhaps 10-15mm thick. Stainless steel isn't that expensive and would be lighter and cheaper than bronze.

 

[DinghyMan]

Of course, the sheave could have holes drilled in it to reduce the weight, and if it's on a lathe anyway, the metal could be thinned away from the hub and the perimeter. I'm not up on metal costs, but I'd have thought that the small amount needed would be an insignificant part of the overall cost. After all, you only need a piece 150mm square and perhaps 10-15mm thick. Stainless steel isn't that expensive and would be lighter and cheaper than bronze.

Material costs roughly - 316 would be about £40 for 25mm, bronze about £55 for 25mm, Acetal £77 for 100mm, Nylon £67 for 100mm, Aluminium £30 for 25mm

So £152 + VAT looks a good price, doubt that that includes anodising if its aluminium though

 

[Rum Run]

Material costs roughly - 316 would be about £40 for 25mm, bronze about £55 for 25mm, Acetal £77 for 100mm, Nylon £67 for 100mm, Aluminium £30 for 25mm

So £152 + VAT looks a good price, doubt that that includes anodising if its aluminium though

Hi DinghyMan, for future reference, where did you get the price for bronze from?

 

[thinwater]

If you had a lathe and the skill and the material (no, no, and no) how long would it take from unboxing the one to copy to getting the replacement to the post? Yup, time is worth money and one-off should have a price. The quoted price seemed fair, the machinist needs to eat, and you would be done.

A smaller size could probably be sourced. But that is big.

Me, I'd have gone in the basement shop and knocked it out from scraps on hand, but that requires a good bit of shop, scrap, and learning. If 3D printing is going to be how you make parts, it sounds like upgrading the filiment and the printer might make sense for you.

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Also it helps to think about how old and why did it fail. It should help decide what materials are suitable. The load, for example, may not be that high. They just wanted a low-friction run.

 

[DinghyMan]

Hi DinghyMan, for future reference, where did you get the price for bronze from?

https://www.m-machine-metals.co.uk/downloads/Metals catalogue.pdf page 19

Diameter Brass CZ121 6 1/2" D £45.00 inch/25mm £54.00 inc. VAT plus shipping

About the best supplier there is currently, particularly for obscure sizes

 

[tudorsailor]

The sheave is 23 years old and was the one that the outhaul ran around. Being in mast furling, the outhaul goes in and out regularly. It failed from a combination of ultraviolet exposure and maybe some eccentric load when the boom is out to one side. Being the outhaul, the load is high. I wonder if the sheave actually spun on the spindle which might be part of the problem.
THanks for all the input
TS

 

[thinwater]

The sheave is 23 years old and was the one that the outhaul ran around. Being in mast furling, the outhaul goes in and out regularly. It failed from a combination of ultraviolet exposure and maybe some eccentric load when the boom is out to one side. Being the outhaul, the load is high. I wonder if the sheave actually spun on the spindle which might be part of the problem.
THanks for all the input
TS

Hard to say without a photo, but perhaps a bronze bearing insert would help spread the load (if it was the bearing that failed).

If it was UV on the plastic, covering it is the solution. With conventional on-boom sails that pulley would be under the sailcover, not exposed.

If you didn't have a lathe but had a drill press and a scrap of the correct material, you cut a circle with a center hole and chuck it with a bolt through the center. Then turn using a stiff bolt through the table as a tool rest. Not difficult if you have any hand turning skills. Then re-drill the center. Probably faster than designing the CAD file. But you have to have the scrap.

 

[tudorsailor]

The sheave is failing along the edge of the trough. It lives on the underside of the boom so not really in direct sunlight

I have had a better price from Wyvern Technical Services Ltd so will probably use their services

TS

 

[thinwater]

Thanks for the photos. I've had very similar failures. Nigh identical, but halyard sheaves.

Yes, there is obviously a bearing problem. But rubbing on the side from an eccentric load would exacerbate that sticking. Of course, bearing wear would exacerbate the rubbing.

I think a better bearing would help by keeping it straight. Think about an insert. I think you are right, that UV plays only a minor part.

 

[Copious]

Try Cliff Mogridge at Whitlock Steering at Emsworth. Can produce sheaves, normally for steering systems, but may be able to help out.

 

[chris-s]

EBay seller ‘bushes2u’. Have had several bushes and sheaves made up by him.

 

[justanothersailboat]

I looked at turning bronze sheaves myself and almost fell out of my chair when I saw the prices of short lengths of large diameter bronze bar stock, as opposed to brass. Thick sheet is hard to get. Delrin seems a good choice for sheaves and is fairly easy to get as thick sheets in offcut sizes that are perfect for one or two sheaves.

That said, it is a reasonable amount of work to do a one-off and nobody good will be super-cheap.