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PostPosted: Sun Oct 20, 2013 7:03 pm 
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Joined: Tue Dec 21, 2010 6:31 pm
Posts: 1111
Evening,

I was recently offered an Alan aluminium frame.

When I went to see it, I found cracks in the top and bottom head tube lugs.

The top lug has a crack coming down from the headset cup, and another one coming up from
the head tube.

The bottom lug has a crack coming up from the bottom headset cup.

The owner said he hadn't noticed these, and said I could have the frame for half the original price he was asking. He also let me take it away (without paying) so I could ask about having it repaired.

It's really a shame because for the rest the frame's in decent condition. I wonder if the cracks were caused by poor installation of the headset cups.

What do people think? Is it possible and worthwhile to repair the cracks?

I've read stuff about having these frames glued with aerospace glue, or having a reinforcement ring welded onto the lugs. I also wondered if it's possible to just reweld the aluminium.

I've also read that it could be possible to just drill a hole at the end of the cracks, which could prevent them spreading.

I want to build the frame up to ride (if it can be rescued) so I'm not so bothered if the repair looks a bit ugly, as long as it's solid. So could any of the above repairs work, and would they be cheaper than just finding another frame in better condition?

Thanks for looking,

Johnny


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PostPosted: Sun Oct 20, 2013 7:08 pm 
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Joined: Sun Mar 17, 2013 10:25 pm
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It's a common problem with these frames and I've often wondered if it is caused by poor headset cup installation.

As for repairing them, not an easy task, I do wonder if the crack could be opened up with a grinder and then Tig welded, although you would have to find out exactly what type of aluminium allot the lugs were made from


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PostPosted: Sun Oct 20, 2013 7:54 pm 
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Joined: Mon Feb 01, 2010 8:57 pm
Posts: 774
Radial stress failure - probably a combination of poor machining tolerances and lack of material. Aluminium alloy has poor elastic properties, so press-fitting is not a good idea. Repair would involve ungluing the lugs, welding and then regluing and getting the alignment correct...


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PostPosted: Mon Oct 21, 2013 8:54 am 
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Joined: Tue Dec 21, 2010 6:31 pm
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monty dog wrote:
Radial stress failure - probably a combination of poor machining tolerances and lack of material. Aluminium alloy has poor elastic properties, so press-fitting is not a good idea. Repair would involve ungluing the lugs, welding and then regluing and getting the alignment correct...


Thanks for the replies.

Monty, that all sounds very expensive and not guaranteed to succeed :(

I think I could probably sell on the parts from the frame (the fork seems in good condition).

Johnny


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PostPosted: Mon Oct 21, 2013 9:12 am 
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Joined: Wed Apr 25, 2012 2:08 pm
Posts: 2185
Location: Shrewsbury
That's a shame ALAN are nice frames. It does look like its the headset install that's caused the cracks. It could be the photo but the bottom cup doesn't look to be all the way in or straight? I know a guy in Cheshire who would weld it but because its over the engraving it will be an obvious repair.


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PostPosted: Mon Oct 21, 2013 9:29 am 
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Joined: Tue Dec 21, 2010 6:31 pm
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I think you're right about the headset cup Robbie, it's not just the photo.


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PostPosted: Mon Oct 21, 2013 11:22 am 
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Joined: Mon Jan 15, 2007 12:12 am
Posts: 1513
Location: Gold Coast Australia
I wonder if it's cracked in retaliation for having a Japanese headset fitted ?


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PostPosted: Mon Oct 21, 2013 2:28 pm 
r.B.o.T.M. & P.o.T.M. Winner
r.B.o.T.M. & P.o.T.M. Winner
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Joined: Thu Nov 22, 2007 10:51 am
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Location: Camel Land
Fit for the Bin I'm afraid


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PostPosted: Mon Oct 21, 2013 2:41 pm 
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Joined: Mon Jan 15, 2007 12:12 am
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Location: Gold Coast Australia
I think it can be ridden till the bottom crack gets bigger , but its worth nearly nothing now IMO


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PostPosted: Tue Oct 22, 2013 11:09 pm 
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Joined: Sat May 22, 2010 10:33 pm
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Location: Suffolk
Don't pay a penny for it. This is why I am not taking the headset out of my ALAN. Before fitting a new headset to these you must ensure the press fit is 0.1mm or less. If the difference between the headtube ID and cup OD is 0.15mm or greater the cups will require a lot of force to go in and this could lead tot he cracks observed.


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