Mast Base sheave problem ...

[aitchw]

Re: Forum advice...

Another thing I have used in the past is to drill a hole into the sheave to just short of the pin to match a suitable small diameter tommy bar ( or any convenient dia. bolt). With the that in place you can tap the bar up and down to try to break the seal. The bar needs to be a good fit ideally. If you have a blow lamp with a fine flame that you can play on the sheave that might expand it a bit as well.

 

[Guest]

Re: Forum advice...

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Hello Nigel my guess is that you have 2 corrosion problems one being the pin into the casting and the other being the sheave onto the pin. Apologies if I have got it wrong.

Also of course you will have the base fitting corroded into the mast. The latter being best left well alone. If you decide to remove the casting the best bet is to decide to sacrifice a few inches of mast and basically cut the mast off then cut through the mast material attached to the fitting and try to peel away the mast material.

I think I read that you can't get a piece of rope around the sheave. If you could a rope will give a good grip on the sheave if it is twisted tight to make a good grip the twist could be spoken to with a large hammer to possibly break the corrion of the sheave onto the axle. it is worth trying if possible cos it would solve the problem easily.

Anyway assuming you decide to leave the fitting in the mast and you want the shaft pin out then I would suggest you need to destroy the sheaves by drilling and chiselling. Actually a cold chisel (I gather everything is cold) on the edge of the sheave may get some turning and if not may well be the beginjning of smashing the sheave. If you don't get the sheave out of the way you will have a corrosive join of the pin into the sheave as well as the pin into the casting and as the sheave is virtually joined to the casting you will have little chance of breaking all corrosion joins at once. Once the sheave is out of the way then you have a corrosion join at each end of the pin where it fits in the casting. You may even be able and willing to cut the pin in half so you are only dealing with one corrosion join at a time. Heat on the casting may be the best way to get movement.

I would think that the hammer bash would be as good as hydraulics however you should try to warm the casting before you bash the pin. You may have access to that chalk or pencil used on aluminium to indicate temperature when welding ie before it goes too soft which would allow you to get a good high temperature confidently.

Old age is a bugger for sailors and for masts so good luck olewill

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I don't think you are far wrong !! /forums/images/graemlins/frown.gif

I have considered :

Cutting the sheaves through with the pins and removing - leaving the pin ends to sort. Replace with bolts (unthreaded main stock part) and standard sheaves from split apart blocks. But that's a last resort.

As Cliff suggests - grind down a hacksaw blade to clear between sheave and casting ... then plenty of Plus-Gas etc. ... time and patience tapping away at it etc. (Most likely action I think I will take when weather warms up a bit).

Removal of whole casting - but think that is really a no-no for the same reason as you say - probably corroded in ... and will do more damage ...

Cliff has put fwd the ground down hacksaw blade - which seems about the best way so far ... the razor blade which is similar idea - I feel the blade will not have the strength to take the extent of crud to remove ...

The acetic acid I applied previously hasn't worked - basically because I think it froze before it had time to do anything !!

mmmmmmm /forums/images/graemlins/tongue.gif