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Permanently bonding Aluminium

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mick18/12/2011 16:43:58
421 forum posts
49 photos
Time to scratch the collective gray matter again. I'm building another IC engine, scaled up by 50% so the entire crank case and cylinder blocks have to be fabricated from solid billits, which in the case of the main crank case, is in two halves so I can hollow it out for crank rotation, as the casting for the standard size is in one piece. There are only a couple of points where I can use long M5 socket heads to clamp the two halves together, so I need a strong and permanent bond between the two halves. Does any one know of an industrial bonding agent that would do the job?
Regards.
Mick
Ramon Wilson18/12/2011 18:55:41
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1655 forum posts
617 photos
Hi Mick,
I haven't used it in the application you refer too but JB weld has great tenacity and is very strong. With two 5mm bolts in situ it would probablly be near indistructible. It also is tolerant to a fair degree of heat if you use the standard version and not the rapid stuff. When I was flying control line I made most of my own silencers which where purely held together with this product. Never had one come apart and glow exhaust gets pretty hot as I'm sure you are aware.
 
Only thing is it has a dark grey finish which may not fit in with your ali crankcase appearance but if you could incorporate a small rebate between halves that would not only improve surface area but probably disguse the join line too.
 
Just a thought
 
Regards - Ramon

Roderick Jenkins18/12/2011 23:09:05
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2376 forum posts
800 photos
We've been looking at metal to metal bond strengths as part of the day job. It turns out that the original blue packaged Araldite is about as strong as you can get. However, as with most adhesives, surface preparation is the most important factor in achieving a good bond.
 
Rod
Martin W18/12/2011 23:36:35
940 forum posts
30 photos
Mick
 
Have you thought about using something like Techno Weld or the Durafix equivalent product to join the two parts. It is very much like soldering but forms a low temperature weld between the parts.
 
I tried the Techno Weld product on some thin walled aluminium tube and it produced a nice fillet between the tubes with no sign of penetration on the inside. Admittedly you have to get the temperature up to about 380/400 deg C but that is well below the normal melting point of aluminium. One advantage is that it can be machined, drilled, tapped etc just like aluminium though there may be a colour difference between it and the base metal aluminium.
 
Cheers
 
Martin
Chris Trice18/12/2011 23:40:49
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1376 forum posts
10 photos
Araldite, or to be more precise, epoxy resin adhesive, which is what it is, tends to soften and let go under hot conditions likely to be encountered on an IC engine. I don't think there's very many adhesives that hold up to high temperatures although some are better than others. Devcon and R&G both do an epoxy mixed with metal powders which is designed to form plastic injection moulding moulds but you need to fully cure it in an oven at increasingly high temperatures. You might want to look at some of the specialist aluminium solders like Technoweld.
Bill Pudney19/12/2011 02:10:09
622 forum posts
24 photos
I second Ramons suggestion of JB Weld. I have a 2.5cc diesel engine with a piston held together with JB Weld. It has a claimed max operating temp of something like 250degrees C. My motor has been in use with its epoxied piston for about 4 years now with absolutely no problems.
cheers
Bill Pudney
Windy19/12/2011 02:25:10
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910 forum posts
197 photos
I have used Techno Weld to build up and repair damage on my early flash steamer crankcases and pumps.
The downside it becamet a dark colour after a while which in my case did not matter.
There was also some large pieces of ally that I tinned with it and sweated them together.
It will probably anneal the ally as well.
There is another similar product I have used (Swedish I think) that is a better colour match.
I was after some high temp epoxy myself and a friend gave me an old cataloque with many differant high temp adhesives some with ceramics in it but the firm no longer trades.
The aerospace industry no doubt will have something but at a price.
 
Windy
Michael Gilligan19/12/2011 08:37:29
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23121 forum posts
1360 photos
If I recall correctly ... the Aircraft repair technique demands a Phosphoric Acid etch and dry, immediately before applying the Epoxy.
Phosphoric Acid is [or was?] the active ingredient in Rust Removers, like Jenolite, so that may be worth a try.
Simply abrading the surface is not really effective ... the Epoxy will eventually de-bond.


An alternative approach might be to use a few screws and a layer of Loctite 638, or similar. ... This acts more like a gasket than a true adhesive, but we had excellent results on vibration test fixtures.

MichaelG.
peter walton19/12/2011 09:49:08
84 forum posts
You used to be able to get a hot set Araldite, looked like astick of wax.

Just heat the part to be joined and apply till enough was melted, not seen it lately.


Mind you it was 30yrs ago!

Link to Araldite surface prep http://www.google.co.uk/url?sa=t&rct=j&q=hot%20set%20araldite&source=web&cd=27&ved=0CIQBEBYwBjgU&url=http%3A%2F%2Fwww.cad.sun.ac.za%2Fcatalogs%2FNonMetal%2FAralditeBonding.pdf&ei=5AjvTuJ61J3yA8Ow0IUK&usg=AFQjCNEn_7SftDPUXNrZcsAhHICIFCDMlA

 


Peter

Edited By peter walton on 19/12/2011 09:53:59

Ian S C19/12/2011 12:11:58
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7468 forum posts
230 photos
I think it was called Redux, Vickers used it to stick the Viscount together back in the 50s, don't think any of them fell to bits. Ian S C
Michael Gilligan19/12/2011 15:25:13
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23121 forum posts
1360 photos
Further to Ian's post ...
There is an excellent wikipedia article about Redux:

http://en.wikipedia.org/wiki/Redux_(adhesive)

MichaelG.
mick19/12/2011 17:51:14
421 forum posts
49 photos
Thanks to all. Just ordered some JB weld. Just goes to show you can learn something new every day.
Regards.
Mick

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