Sloppy pintles and gudgeons

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Garry R

Sloppy pintles and gudgeons

Post by Garry R » Thu Aug 07, 2008 9:03 am

Has anyone ever tried to take the wear out of phosphor bronze pintles and gudgeons by for example getting a metal works fill up the holes and re-drilling. The rudder on Vivette is sloppy to say the least!!

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Brookesy
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Re: Sloppy pintles and gudgeons

Post by Brookesy » Thu Aug 07, 2008 9:57 am

Welding of Phosphor bronze is a very specialized process and there are not many places that will undertake it. However all is not lost, some years ago I had a gear selector broken on a classic race car and after chasing all over the country to try and find someone who would attempt it , found a company here in Cornwall who did a marvellous job, and then proceeded to do all the other broken Moss box selectors for other people around the country with a similar problem.
They can be found at Wheal Honey, Menheniot, Cornwall and trade as Weldspray Engineering tel.01579 342299. There may be others about who can do the process known as eutectic welding but I was not able to find any at the time.
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Ed
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Re: Sloppy pintles and gudgeons

Post by Ed » Thu Aug 07, 2008 12:27 pm

Not such a nice fix.....

but I got a piece of 15mm copper pipe and cut out a slice and then hammered into a lipped collar that sat inside the female half. Then araldited it into place.

I only did the bottom one....as that was the one that was giving me a problem, but it worked fine.

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eib
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Re: Sloppy pintles and gudgeons

Post by Ian Malcolm » Thu Aug 07, 2008 1:23 pm

T. Norris (Isleworth, London) machined a new gudgeon for us from bar stock using an old one for a pattern when I needed a replacement for a previously broken and bodged one on our Contessa 26. The price was acceptable and the quality excellent. There is no significant difference apart from size between it and the ones on my Albacore so I'll be taking them to T. Norris when I get fed up with the slop.

Other options include silver soldering a suitable sleeve into the gudgeon or if its got thick enough walls, machining it out and pressing in either a phosphor bronze bush or a bush of Molybdenum Disulphide loaded Nylon.

It shoud also be possible to babbet the bearing surface of the gudgeon but babbet bearings are obsolete techology and few companys do it now so unless you know a model steam enthusiast, its probably cheaper to get a complete new part machined.
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Re: Sloppy pintles and gudgeons

Post by Ed » Thu Aug 07, 2008 1:31 pm

you say:

It shoud also be possible to babbet the bearing surface of the gudgeon but babbet bearings are obsolete techology

Can you tell me more about this process?

cheers

eib
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Re: Sloppy pintles and gudgeons

Post by Ian Malcolm » Thu Aug 07, 2008 2:33 pm

Babbit or white metal bearings cast in place were the standard for all machinary before ball/roller bearings and shell bearings came into use. Shell bearings are still made with a babbit alloy surface. There are lots of Babbit alloys, roughly divided into two categories - Tin based or leads based. The basic process is tin the inside surface of the bearing housing. For a tin based babbit alloy, use a lead free solder. Flux the tinned surface. Plug the lower end of the housing with something heat resistant so that its absolutely liquid metal tight. (I understand that asbestos string and fireclay used to be commonly used - glassfiber string would be a better modern choice and many silicone caulks are surprisingly heat resistant). Either use the well sooted shaft as the core (steel shaft, housing packed out at its shims to allow for scraping the bearing) or use a wooden core or for a small bearing re-drill the hole after casting.
Melt the babbit metal and pre-heat the bearing housing if possible and pour it in to cast the babbit in place.
When cool, knock out the core, remove the plug and clean up the ends of the babbet. If a core other than the shaft was used, ream to a snug fit. If its a split bearing split the babbit (or cast as two halves) . Then blue and scrape to correct fit for the shaft. If possible burnish in place with heavy oil turning the shaft at about 10% of running speed and nipping up the bearing cap progressively so the bearing runs hot, just short of smoking then shim for the correct running clearance.


We'd just be getting the pintle machined true, cleaning up the gudgeon, tinning and casting in babbet and drilling to size. I doubt it would even need reaming for the sort of clearances appropriate for a dinghy rudder. Add a good smear of marine grease, assemble and use. Anyone who's ever done any metal casting *AND* can solder properly with experience of wiped joints etc. could handle it. The problem is sourcing the alloy in less than 10Kg quantities!
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Re: Sloppy pintles and gudgeons

Post by roger » Thu Aug 07, 2008 2:47 pm

Fascinating... the things you learn on this website.
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Re: Sloppy pintles and gudgeons

Post by Brookesy » Thu Aug 07, 2008 3:16 pm

To lower the tone with a bodgers fix, there is alway JB weld, a cheap epoxy/metal mix which could be used to fill the gugeon as if using araldite, and then drill to size.
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Garry R

Re: Sloppy pintles and gudgeons

Post by Garry R » Thu Aug 07, 2008 3:24 pm

Not such a bodge possibly, as epoxy is often used to fill the worn hole in a centreboard pivot point and then drilled to size. I suppose there is a lot more wear in a rudder hanging though.

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Re: Sloppy pintles and gudgeons

Post by Ed » Thu Aug 07, 2008 5:27 pm

Wonderful Ian,

good to know.

Would love to have a go at that, maybe I shall sometime.....

How hard is the babbet metal.

It may be bit of a bodge, but could you tin the inside of the gudgeon and then fill with a molten plumbers solder, then drill out?

A rudder does not get a 'vast' amount of use, but does I agree come under a fair amount of pressure.

Since we have brought up the idea of using an araldite.....you could also try casting in situ an epoxy graphite bush.

this might work, although the problem would be getting a really good adhesion between the epoxy and the bronze. Not easy, but by no means impossible.

cheers

eib
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Re: Sloppy pintles and gudgeons

Post by Ian Malcolm » Thu Aug 07, 2008 10:59 pm

Babbitt is soft enough to scrape with a knife but is considerably harder than soft solder. If one wanted to get close to an accepted lead containing white metal bearing composition, speaking theoretically, 8 parts of Savbit solder (used for its high copper content - no substitute) to 1 of soft lead and 1 of Antimony (available as a mineral sample on Ebay) would come pretty close. The main defect would be only 1.2% copper instead of the intended 1.5% and some extra Savbit would be needed to allow for the flux in it. I dont have the facilities to do my own alloying so wont be trying it.

I share your pessimism about getting epoxy to stick to bronze! You'd probably need to wet sand with mixed epoxy to get a result, also the Graphite may well cause a serious electrolysis problem in salt water. Both molybdenum disuulphide and PTFE powder can be obtained with some difficulty from USA suppliers and I suspect that epoxy heavily loaded them and a fair bit of copper powder would prove to be superior.
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Re: Sloppy pintles and gudgeons

Post by Ed » Fri Aug 08, 2008 10:03 am

All good points!

copper and bronze powder are both easily available too.

cheers

eib
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