Fork fail caught (just) in time - but how to repair?
05-24-15, 07:07 PM
#26
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I see 26.2 ~ 26.22 mm at different points around the circumference, that's using a standard vernier that will provide an overestimate as standard, suspect it's 26.2mm
05-24-15, 08:09 PM
#28
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05-25-15, 03:36 AM
#30
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I am a mechanical engineer, own a lathe, manual and CNC mill and much of the ancillary measurement devices and fittings that makes the gear actually usable, also have done a bit of welding (mostly MIG and TIG). I think given three phase power, a shop with my gear on a desert island I reckon I could get the fork working and safe. 
That being said, I'm still keen to send it off.
I don't know what I don't know and I'm not willing to risk the fork or my teeth in learning
I am keen if possible to be over the shoulders of the people doing the work though, as long as I'm not hindering them even by simply my presence, it'd be really interesting watching.
That being said, I'm still keen to send it off.
I don't know what I don't know and I'm not willing to risk the fork or my teeth in learning
I am keen if possible to be over the shoulders of the people doing the work though, as long as I'm not hindering them even by simply my presence, it'd be really interesting watching.
Notice the integral shoulder at the top of these stamped, cast or forged fork crowns:
After the steerer is brazed into the crown and the blades attached, the shoulder at the top of the fork crown is machined down to ~26.4mm or 27mm. The steerer is 1" diameter which is 25.4mm.
When the fork is finished and ready for assembly the crown race is forced over the machined shoulder with an interference fit.
The crown can be machined on a lathe but on production frames they were usually cut with special multi tooth cutters.
The 26.4mm shoulder on your fork has broken off of the crown. Then the fork is repaired, it will need to have a build up of brazing material to re-machine.
Trying to TIG, Arc or gas weld a part that has been previously brazed will create a real mess because of the differences in melting temperature between the brass and steel.
verktyg
Chas.
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Don't believe everything you think! History is written by those who weren't there....
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Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
05-25-15, 03:51 AM
#31
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I've seen them! Yip, but the fork in person is a bit more instructive
I got the race off earlier today - a better measurement of the actual seat area shows an OD of ~26.4mm and the ID of the race ~26.4mm which makes more sense, the previous measurement must have been in an area ramped ever so slightly so as to allow easier installation, or just bad measurement.
I'm in touch with a builder at the moment who appears to be quite knowledgeable - I linked him to this thread also.
It's off to the electroplaters next, just need to find one that is sensitive to vintage ('vintage' to me at least) bike parts.
I got the race off earlier today - a better measurement of the actual seat area shows an OD of ~26.4mm and the ID of the race ~26.4mm which makes more sense, the previous measurement must have been in an area ramped ever so slightly so as to allow easier installation, or just bad measurement.
I'm in touch with a builder at the moment who appears to be quite knowledgeable - I linked him to this thread also.
It's off to the electroplaters next, just need to find one that is sensitive to vintage ('vintage' to me at least) bike parts.
05-25-15, 01:09 PM
#32
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You would need to remove the plating, clean the crown's ID and braze a new steer tube in along with a ring to accept the crown race. You need a jig to ensure the proper alignment of the steer tube. That being said, seeing how poorly the joint was done, and how potentially catastrophic a fork failure is, I wouldn't trust the fork blade brazing to be sound.
05-25-15, 01:32 PM
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that's a good point, it's a lot harder to do those blades than the steerer
05-28-15, 12:15 PM
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I don't see anything wrong with reusing the steerer. After all, it hasn't been brazed before
05-29-15, 07:23 AM
#37
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Well it was heated enough to temper it, it's chrome plated, and a new steer tube costs $10...
05-29-15, 09:44 AM
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you're right, best to replace it. I wouldn't really worry about the re-heat cycle so much, but the chrome isn't a good thing
06-24-15, 10:16 PM
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Hello all, an update:
Found a builder who could do all required but then strangely enough after months and months of looking on ebay I found an unbranded NOS late 80's columbus fork with the cinelli crown (the design I like the most) on ebay with a huge steerer. Pretty much ideal.
Although gawd-awful expensive it still worked out cheaper than the re-build.
I'll keep the Battaglin as a conversation piece - (need to find some people who find that kind of thing interesting first).
Still, it's interesting to discuss it, so thanks for all the info
Found a builder who could do all required but then strangely enough after months and months of looking on ebay I found an unbranded NOS late 80's columbus fork with the cinelli crown (the design I like the most) on ebay with a huge steerer. Pretty much ideal.
Although gawd-awful expensive it still worked out cheaper than the re-build.
I'll keep the Battaglin as a conversation piece - (need to find some people who find that kind of thing interesting first).
Still, it's interesting to discuss it, so thanks for all the info
06-25-15, 10:45 AM
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good deal, I certainly could get 15 minutes of conversation out of it if there was beer involved
08-03-15, 04:12 PM
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It IS fixable, but the details and trouble all add up to making a new fork a much less expensive and practical choice.
What with the unplating - polishing - replating - crown race machining - rebrazing, aligning, etc. you could be looking at spending $800 to save a $250 fork.
Why not try and contact Battaglin in Italy if they are still in business ? The frame and fork was probably subcontracted to Billato or a similiar contract builder.
What with the unplating - polishing - replating - crown race machining - rebrazing, aligning, etc. you could be looking at spending $800 to save a $250 fork.
Why not try and contact Battaglin in Italy if they are still in business ? The frame and fork was probably subcontracted to Billato or a similiar contract builder.
08-06-15, 09:21 AM
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As a first time fork builder the lesson I'm taking from this thread is that the brake mounting bolt can prevent this type of failure from being truly "catastrophic"!
William Chitham.
William Chitham.
08-06-15, 09:47 PM
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that's true, but it's really not hard to tell if you have good filler penetration. Just pull the filler through from the crown race side to the bottom. I braze the crown on the steerer first, and a lot of crowns have an area where you can see the filler in through the fork legs sockets. There should be a fillet of filler visible there
