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PostPosted: Tue Sep 01, 2020 3:48 pm 
Old School Grand Master
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Joined: Mon Nov 20, 2006 10:12 pm
Posts: 5571
Location: Barry
Anyone have an idea how to fix this? Should I leave it to a professional?


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Koga Ti.jpg
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 Post subject: Re:
PostPosted: Tue Sep 01, 2020 6:31 pm 
Gold Trader
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Joined: Fri Jan 23, 2009 2:30 pm
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Location: Surrey
Personally I'd leave that to a professional unless you have the skills to do it. I give most things a go but draw the line at frame repair.


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 Post subject: Re:
PostPosted: Thu Sep 03, 2020 4:49 pm 
Old School Hero

Joined: Tue Jan 06, 2009 9:44 pm
Posts: 193
Location: bristol
You don't mention how the frame is constructed , it looks as if it might have titanium tubes
resin bonded into alloy lugs ? in which case it is probably game over unless you want to
get into frame building ! It looks like the bond has failed , and you won't be able to
re-activate the resin by heating it . Its a question of heating all the joints until they
weaken sufficiently to pull the frame apart , followed by a thorough clean up and
re-bond ( preferably in a frame jig ) Good luck


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PostPosted: Fri Sep 18, 2020 10:22 am 
Old School Grand Master
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Joined: Mon Nov 20, 2006 10:12 pm
Posts: 5571
Location: Barry
Thanks chaps yep if in doubt go pro! on its way to Danson67.


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Miyata Ti 2.jpg
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PostPosted: Tue Sep 22, 2020 7:40 pm 
Devout Dirtbag

Joined: Fri Oct 12, 2018 6:28 pm
Posts: 149
I would think that if you can get the 2 tubes apart then you could use an epoxy adhesive that they use for joining golf club heads to shafts as they must suffer more stress than a bike frame .It would not cost very much to try.


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PostPosted: Tue Sep 22, 2020 10:58 pm 
retrobike rider
retrobike rider
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Joined: Tue Jan 29, 2008 11:04 pm
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Location: A wretched hive of scum and villainy...
Quote:
if you can get the 2 tubes apart then you could use an epoxy adhesive

That's the plan.. Frame received.

All the best,


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PostPosted: Wed Sep 23, 2020 8:06 am 
Retro Guru

Joined: Sun Apr 25, 2010 10:07 pm
Posts: 2354
danson67 wrote:
Quote:
if you can get the 2 tubes apart then you could use an epoxy adhesive

That's the plan.. Frame received.

All the best,

Any chance of a few pics of the repair process?


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PostPosted: Thu Sep 24, 2020 11:26 am 
Old School Grand Master
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Joined: Mon Nov 20, 2006 10:12 pm
Posts: 5571
Location: Barry
Damn handsome frame if I do say so myself! Looking forward to getting it back. NB I am not in a rush Dan 8)


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PostPosted: Wed Nov 25, 2020 7:00 pm 
retrobike rider
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Location: A wretched hive of scum and villainy...
OK, all done...here's the process.

Inspected the other joints first, moving and pulling by hand, to see if there was any sign of failure.
All OK, so tap RH dropout rearwards with a soft mallet to open the joint.
The joint moves easily enough, but there is too much spring in the Ti frame tubes and the plug is too long to exit the tube.
So, I undo the top bolt of the seatstay yoke. It's just like a seat clamp bolt. This creates a longer, less stiff, structural length to gain some flex:

Attachment:
Top bolt undone.jpg
Top bolt undone.jpg [ 389.74 KiB | Viewed 173 times ]


This works fine, and the joint can now be pulled apart by hand.
The plug is an impressively long, but very smooth forging, and the bonding surface to the aluminium appears to have failed, rather than a deterioration of the adhesive itself.

Attachment:
Plug pulled.jpg
Plug pulled.jpg [ 288.17 KiB | Viewed 173 times ]


Old adhesive residue and corrosion fur removed from plug with emery cloth, surface roughed up to aid adhesion:

Attachment:
Plug cleaned.jpg
Plug cleaned.jpg [ 350.46 KiB | Viewed 173 times ]


Chip and scrape out as much of the old adhesive as possible from the inside of the tube.
The chainstay is too narrow to fit a sanding drum inside, so emery wrapped around fat round file to clean back to the metal surface and abrade.
Small wooden block fitted to temporarily spring the frame enough to get good clearance into the end of the tube:

Attachment:
Tube cleaned.jpg
Tube cleaned.jpg [ 284.68 KiB | Viewed 173 times ]


Clean all surfaces with acetone and apply adhesive (3M 490, 2-part structural epoxy) to inside of tube and outside of plug:

Attachment:
Adhesive applied.jpg
Adhesive applied.jpg [ 240.38 KiB | Viewed 173 times ]


This epoxy is usable a few hours, so no need to hurry, but it does mean that it needs to be well fixtured while it cures (6hrs+).
So, spring the plug back into the chainstay, press home, refit the top bolt, and clean off the excess adhesive with 70% alchohol while still wet.
Then fit a 135mm x 10mm dummy axle to hold dropout in alignment, and put the whole frame in my jig overnight:

Attachment:
Held in fixture.jpg
Held in fixture.jpg [ 357.47 KiB | Viewed 173 times ]


Finished :D

Attachment:
All done.jpg
All done.jpg [ 319.78 KiB | Viewed 173 times ]


All the best,


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 Post subject: Re:
PostPosted: Wed Nov 25, 2020 7:13 pm 
Feature Bike
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Joined: Fri Aug 11, 2006 8:13 pm
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Location: York-ish UK
Lovely work and a v. Satisfying read.


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