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Old 17-10-2018, 01:36   #1
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Sheaves for yacht cable steering

I am working on the cable steering of a 43 ft yacht I am building and currently making up the pulley blocks.

The sheaves are cast iron with brass bushes and ss shaft. I currently have a ss washer between the sheave and the arm of the pulley block. But I'm now wondering what for? Surely it would make more sense to have a washer between the cotter pin (split pin) and the sheave carrier for a bit of protection in case the shaft started spinning. (Gee I hope that never happens....)

I tend to overkill but yacht steering is something I would never compromise on.

I'd appreciate thoughts on the matter from the experts!

Clive
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Old 17-10-2018, 02:59   #2
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Re: Sheaves for yacht cable steering

Why not both if there is space
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Old 17-10-2018, 03:36   #3
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Re: Sheaves for yacht cable steering

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Originally Posted by admiralslater View Post
Why not both if there is space
That's the problem, there is not the space in some of them!

Sadly I asked my Son (who welded the pulley blocks up for me) to put a sheave and two washers between the posts as the spacer but he knew better.

I can't imagine washers would be all that necessary as the sheaves will not do that many revolutions in their lifetime. It is not as if they are to be used in an industrial situation where they are constantly revolving.

Thanks for your response.

Clive
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Old 17-10-2018, 03:49   #4
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Re: Sheaves for yacht cable steering

There is a chance that you might be over thinking this one , but under the cotter pin would make sense to me . It seems you may not have a choice.
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Old 17-10-2018, 03:50   #5
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Re: Sheaves for yacht cable steering

It would be better if you eliminate as much space as possible between the sheave and the sheave box/mount. In any event, make sure your cables are adjusted to eliminate slack so it can't jump the sheave.

The image shows a sheave from a friend's boat -- the steering cable should run where the blue/white messenger string is. Note the groove in the sheave box that was cut by the steering cable after it hopped out of the sheave groove. The box caused the cable to fray and it severed at 1am while sailing about 40 miles offshore from Cape Fear. (Fun night. We made our way to the Cape Fear River using the emergency tiller in ~7 foot seas.)


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Old 17-10-2018, 04:33   #6
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Re: Sheaves for yacht cable steering

[QUOTE=SailFastTri;2743278] Note the groove in the sheave box that was cut by the steering cable after it hopped out of the sheave groove. The box caused the cable to fray and it severed at 1am while sailing about 40 miles offshore from Cape Fear. (Fun night. We made our way to the Cape Fear River using the emergency tiller in ~7 foot seas.)

I am routing the cable where it can easily be inspected and it will be kept taut. On most sheaves the cable will traverse 90°. I'm going to use 240V electrical cable as a guide to ensure everything is lined up perfectly. (That is about the 8 mm thickness of the steering cable)

I have yet to build the furniture in the aft cabin but I will ensure the furniture over the quadrant can easily be removed in a panic stricken instant. The top of the rudder post (above the quadrant) has been machined square to take emergency steering fitting. Then I suppose I'll take a couple of ropes through the bulkhead at the rear of the center cockpit via screw cap covers and then to the sheet winches? That is something to think about down the track.

Thanks

Clive
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Old 17-10-2018, 04:47   #7
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Re: Sheaves for yacht cable steering

When I bought my boat, my surveyor noticed that the sheaves did not have outside washers and the cotter pin failed (causing the clevis pin to slide and jammed the sheave resulting in wearing it out). I asked the yard to install washers and they installed them on the inside causing the sheaves to have extreme friction. Fortunately I heard a small noise when steering and caught the issue. Now the washers are between the cotter / clevis pins and the arms and all is working great. So for me - washers outside for sure, inside only if you need to fill excess space.
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Old 17-10-2018, 05:07   #8
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Re: Sheaves for yacht cable steering

Look what Edson does: https://edsonmarine.com/products/sai...es-assemblies/
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Old 17-10-2018, 05:49   #9
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Re: Sheaves for yacht cable steering

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Originally Posted by kmacdonald View Post
Have you had a look at their prices! All my X12 sheaves cost around AUD 300.
The two adjustable Edson idlers (that go directly under the steering wheel) cost around $500!!


"The Aluminum Sheaves are ideal for the performance boat that requires sensitive, lightweight steering"

Great on a high performance yacht but not a cruising yacht.
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Old 17-10-2018, 06:03   #10
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Re: Sheaves for yacht cable steering

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Originally Posted by coopec43 View Post
Have you had a look at their prices! All my X12 sheaves cost around AUD 300.
The two adjustable Edson idlers (that go directly under the steering wheel) cost around $500!!


"The Aluminum Sheaves are ideal for the performance boat that requires sensitive, lightweight steering"

Great on a high performance yacht but not a cruising yacht.
Their prices are crazy high. You can get equivalent or better sheaves for a lot less elsewhere. Suncor Stainless has sheaves in 316 SS with bushings or bearings at a much better price point as do several other companies. The same can be said for steering cable and chain.
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Old 17-10-2018, 07:20   #11
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Re: Sheaves for yacht cable steering

I have a Edson 6" adjustable idler kicking around in the garage that is available for less than any of the above. Brass shives, new pins and bushing, steel adjustment plate. Good condition.
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Old 17-10-2018, 07:29   #12
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Re: Sheaves for yacht cable steering

I think the Edson comment was for how they solved it
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Old 17-10-2018, 08:23   #13
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Re: Sheaves for yacht cable steering

If the sheaves do not have an anti friction bearing washer between them and their mounts there will be friction and wear. The best material for these bearing washers is one of the self lubricating bearing plastics. Rulon, UHMW, moly filled nylon will all work. These are available from McMaster Carr.

A self lubricating bearing for the sheaves is also superior to the brass/bronze you are using. The best of these are teflon/fiberglass bushings. They have very low friction, withstand very high loads, have no galvanic issues and are good in wet environments.

As regards fitting a washer under the cotter pin, again there is a large selection from McMaster. If there isn't room then buy a longer pin, also available from McMaster.
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Old 17-10-2018, 08:30   #14
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Re: Sheaves for yacht cable steering

Leave the washers in place to reduce the sheave from wandering and then go to McMastercarr.com and order thin stainless shim washers for the outside. You just need to prevent the split pins from rubbing against the frame.

And you are correct it is a very slow system. As is it would be a very long time before you saw any significant warring unless there was another problem with alignment.
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Old 17-10-2018, 09:05   #15
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Re: Sheaves for yacht cable steering

Quote:
Originally Posted by SailFastTri View Post
It would be better if you eliminate as much space as possible between the sheave and the sheave box/mount. In any event, make sure your cables are adjusted to eliminate slack so it can't jump the sheave.

The image shows a sheave from a friend's boat -- the steering cable should run where the blue/white messenger string is. Note the groove in the sheave box that was cut by the steering cable after it hopped out of the sheave groove. The box caused the cable to fray and it severed at 1am while sailing about 40 miles offshore from Cape Fear. (Fun night. We made our way to the Cape Fear River using the emergency tiller in ~7 foot seas.)


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If the cable actually follows that messenger string, that sheave is VERY misaligned. The centerline of the sheave needs to be aligned with the cable--on both sides.
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