I have broken off a small piece of cylinder cooling fin. It is cast iron so am reluctant to get it welded / brazed. Does anyone have any knowledge or experience in 'glueing' a fin shard back on with epoxy please?
Thank you, Vinnie.
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why bother? it won't make any difference unless you want it to look smarter? there is a puty we use at work and you roll it into a ball get it warm and attatch it to metal parts like a patch not ideal but does work.
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I agree, don't bother unless it is for cosmetic reasons.
But if you want to, araldite, quicksteel or any similar epoxy resin that is suitable for high temperatures and metal.
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I tend to agree, the themal resistance of even a thin layer of epoxy will render the fin thermally useless, and the only reason for glueing it back on is for the sake of appearance.
Number_Cruncher
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sorry mate but the epoxy idea wont work only short term..
the cast iron and the epoxy expand at different rates as the engine heats up and this causes a crack to appear and the epoxy bit falls off..
even welding a small part on is a tricky one with cast.
Sorry TJ
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I agree with "tewby", you're on a hiding to nothing with cast iron.
If it was aluminium, it would be possible for someone who is handy with a TIG to repair it, but not cast iron, I would think the risk of further (un-repairable) damage is too great. But before you give-up, why not look for a British or American vintage bike forum and ask the question on there.
Just as a matter of interest, what bike is it on?
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I would be inclined to file it smooth, it might then even then look ast hough it is supposed to be like that.
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There is some good info here tinyurl.com/9h9pm about welding cast iron.
Brazing may work also.
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Dear Nick, thanks for replying. The repair I need has to look right as it is on a 1926 250cc Raleigh Model 14 which I am restoring to concours condition. There are only 6 others of this model left in existence.
Years ago I stripped the thread in a alloy head used by the big finned circular nut to hold an exhaust pipe to the head. I bored out the port and shrunk in a stainless threaded collar along with epoxy (belt & bracers!). That held fine but I can't say that epoxy alone would have held.
Be nice to know what temperature fins get up to in normal use so I could them check it against the epoxy spec.
Thanks again, Vinnie.
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Without someone measuring the temperature of a similar machine during operation, I think finding the fin temperature will be difficult.
Also, the fin temperature will depend where on the engine the fin is. Is it near the top of the cylinder, or lower down?
The fin temperature also varis along the fin, there is a gradient, with the hottest part being close to the cylinder, while the free tip is the coolest part. Is the fracture closer to the cylinder, or the tip?
Number_Cruncher
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Dear Nick, thanks for replying. The repair I need has to look right as it is on a 1926 250cc Raleigh Model 14 which I am restoring to concours condition. There are only 6 others of this model left in existence.
So my sugestion of filing it smooth is clearly a non starter, I have just looked at the spec sheet with my tube of Loctite Chemical Metal (an epoxy compond) and it says that it can withstand temps up to 160 deg C though should not be used with constant temps over 100 deg C, I have used it before to cosmetically fill a gouge in a m/cycle crankcase/oilpan though I fear tempertaure might rule out it's use on a cylinder head or barrel.
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Just an idea.
How about carefully drilling small holes sideways in barrel and broken piece and inserting pins to provide mechanical retention as well as using the plastic metal to fill the gap. Thinking of sewing pin size.
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I wasna fu but just had plenty.
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jbweld.net/
Try this from Halfords, has high metal content.
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Dear Ashok,
Thanks for telling me about 'Jb weld'. Had a look at their site and its spec is 500 deg F (300C) which I think will be adequate.
Tried Halfords & they discontinued it nationally 1 month ago and replaced it with a 160 deg C Loctite !!
Have now ordered some from www.revolutionmodels.co.uk so should be OK now.
Many thanks to all who joined in, great place this forum isn't it?
Best wishes, Vinnie.
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They used to sell JBWELD in Wilkos(wilkinsons).
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Good luck Vinnie, it is somewhat water soluble when first mixed if required, and you can make it hotter to make it runnier, or cold to make it more viscous. You can also use hot melt glue to hold the item in place until the JB sets the hot melt glue peels off easily afterwards.
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JBweld is available from www.westfalia.net
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