Sheave Replacement

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marno
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Joined: Sat Dec 06, 2008 6:21 pm

Sheave Replacement

Post by marno »

I need to replace some of the sheaves in my boom. I am not 100% sure how to remove the pin holding them in place, so I thought I'd ask. I have removed the screw.
Image
Thanks
Marno
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GeoffSchultz
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Re: Sheave Replacement

Post by GeoffSchultz »

I don't have any answers for you, but I have some questions:

1) Does the other side of the boom look just like the side in the photo?
2) How are the sheaves pins (if that's the correct verbage) attached to these plates?

-- Geoff
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1997 Freedom 40/40
http://www.GeoffSchultz.org

marno
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Re: Sheave Replacement

Post by marno »

Gday Geoff,
The other side of the boom is blank (you cant see anything, so the other end of the pin is fastened internally somehow)
It looks like the pins are welded to the plates.
Thanks
Marno
GeoffSchultz wrote:I don't have any answers for you, but I have some questions:

1) Does the other side of the boom look just like the side in the photo?
2) How are the sheaves pins (if that's the correct verbage) attached to these plates?

-- Geoff
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Castaway
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Re: Sheave Replacement

Post by Castaway »

The logical attachment would be that the plate held in place with the screw carries the pin to a blind socket within the boom, forming the axis of the sheave. In this case, the plate, with pin attached, ought just to slide out when pulled. One assumes this is not the case, but could it be threaded, and thus come out if the plate is rotated? Perhaps some heating ( or freezing ) cycles and then a light blow with a percussive maintenance instrument would free it up. However, an stainless pin in an alloy socket may be more than just a little recalcitrant.

Good luck!

Gerald
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland

AlanK
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Location: Freedom 33 Boston, MA USA

Re: Sheave Replacement

Post by AlanK »

I have an F-33 with isomat booms. I don't recognize your picture so its probably a different arrangement but in case there's some similarity...
I replaced the sheaves in mine. I expected to find some sort of screw but the shafts just sit in slots. I loosened the lines to remove compression and popped the shift and sheaves out with a screw driver. Was quite simple except on the aft end of my mizzen where there must be some corrosion where the pin was stuck.

Mike Holibar
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Re: Sheave Replacement

Post by Mike Holibar »

Alan, as the sheaves simply rotate there is no end thrust on the pin. So all that is required to hold the pin in place is the small screw in that welded flange. The chances are it is locked up with corrosion, it doesn't seem to take much with ss and al. I would be careful of damaging the boom with levers under the flange. To loosen the pins I would try the following
1) Spray penetrating oil on all points you can see where the pin is in contact with the boom.
2) With a flat bar drift, tap the flange up and down at the screw end.
3) If you can get some movement, try working a lever (screw driver) under the flange from the gooseneck end and alternate with 2 above.
4) If no movement you can try tapping a bit harder but try not to distort the flange.
5) if still no movement, try heating the aluminium at the points where the pin passes through. Aluminium expands faster than ss. Aside from the obvious that any lines will have to be kept away from the heat, be careful not to overheat the aluminium as it will melt without warning. A small propane torch rather than oxy/acetelene would be better. Keep on with 1,2 and 3 above, and hopefully the pin will come out. Regards,
Mike Holibar
S/V Fyne Spirit of Plymouth (Freedom 39PHS-1989)
Lyttelton
New Zealand

marno
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Re: Sheave Replacement

Post by marno »

Gday Guys,
I got my first one out. I had someone describe to me what they found on their F39 (Thanks Pete). He solved the problem by drilling a hole on the opposite side of the boom to the pin and use a drift to tap it through.
I thought I would try the brute strength approach now that I had an idea of what I would find. I got a set of vice grips and grap the flange thing, and after a couple of false starts found that I could slowly work the pin out. When I got it out, I found that the pin was aluminium, so it was tight, but not corroded in.
I'll post a pic when I get a chance.
Thanks for the help
Marno

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marno
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Re: Sheave Replacement

Post by marno »

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Brian Duff
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Re: Sheave Replacement

Post by Brian Duff »

oy guys -

Like your buddy said, you just drill a hole on the other side of the boom and use a punch. this should have been done when the sheavebox was made.

get new sheaves from ed at http://www.zephyrwerks.com

they are the best you can get, and cheap too!

that pin is not aluminum- i can see itst stainless steel.
Brian Duff
yacht rigger

Southbound Cruising Services, LLC
Annapolis, MD

marno
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Re: Sheave Replacement

Post by marno »

Gday Brian,
I have already bought my sheaves from Rigrite, they were half the price but don't look anywhere near as good. If I was doing it again I would think quite strongly about getting them from Zephyrwerks, although what I should have done was get one of my customers who made my solar panel mounts out of Delrin make them for me, but I didn't think of it till I had already ordered them. Incidentally, I got the impression from the rigrite website that the sheaves I was getting would be the solid type but they are the vaned ones.
Thanks
Marno
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