cracked aluminum frame

Discuss light weight issues concerning road bikes & parts.
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spud
Posts: 675
Joined: Sat Feb 07, 2009 5:52 am

by spud

I've attached a pic of an old standby aluminum frame that got a crack on the seat lug. My view is that I should cut the lug off, drill a new stress releaver hole at the back of the seattube, slot the tube and use a collar. I suppose it might be possible to weld the lug/rub shut, but I think this will entail higher expense, along with a possibility of the crack reopening later.

Any alternative ideas?
IMG_0140.JPG

flying
Posts: 1530
Joined: Mon Dec 19, 2005 9:16 am

by flying

Your method sounds like a good option & will likely be fine

I guess the only question is that the remaining section is fairly short & close to a big weld
so might not flex enough when clamped to tighten. But if you slot as you say I imagine it would.

by Weenie


NiFTY
Posts: 1222
Joined: Sat May 26, 2012 11:26 pm

by NiFTY

I would do as you propose.
Evo 4.9kg SL3 6.64kg Slice RS 8.89kg viewtopic.php?f=10&t=110579" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

alcatraz
Posts: 1298
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

What's the outer diameter of that seat tube?

/a

mattr
Posts: 3831
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

NiFTY wrote:
Mon May 28, 2018 4:05 am
I would do as you propose.
I have done as you propose. ;)

Cleaning up the top of the new seat tube was probably the most time consuming job.
Have seen it done several times, Even seen a sculpted clamp to clear a weld.......

alcatraz
Posts: 1298
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Before cutting I'd probably try to dremel away the ears and clean up the seat tube. Then I'd try to fit a clamp over it. If there is a big tube piece missing I'd try to fit something there.

The reasons for this are:
1. weak clamping force near a huge weld
2. hard to find clamps that are the right diameter and can provide enough clamping force to hold the seat tube
3. it looks better (personal) when the clamp isn't slammed

by Weenie


Bridgeman
Posts: 665
Joined: Wed Jan 12, 2005 6:04 am
Location: USA
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by Bridgeman

alcatraz wrote:
Mon May 28, 2018 3:58 pm
Before cutting I'd probably try to dremel away the ears and clean up the seat tube. Then I'd try to fit a clamp over it. If there is a big tube piece missing I'd try to fit something there.

The reasons for this are:
1. weak clamping force near a huge weld
2. hard to find clamps that are the right diameter and can provide enough clamping force to hold the seat tube
3. it looks better (personal) when the clamp isn't slammed
Great advice. I would also add that it would be wise to lengthen the relief slot and include a new hole at the end of it. I've experienced a similar issue and this slot length increasement solved the cracking problem so well that the manufacturer adopted the modification.

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