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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 04-22-14, 10:23 PM   #1
Andrew R Stewart 
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Top Tube Replacement

https://www.flickr.com/photos/731955...7644238503485/

Here's a link to an 8 shot album of a practice TT replacement I did recently. I chose to grind out the tube from the lug, opposed to replacing the lugs too. Things went well enough but it's easy to grind too much out and end up with a loose fitting new tube... I was concerned about the brazing in the new tube. The old was done with silver as was the seat cluster. In the long ago past i'd had problems with heat control and remelt when doing mulitple brazing steps on top of previous ones. This time the brazing went very well. No remelt of existing filler. Good fill and lug lines. Clean up went fast.

Now that this is behind me I will say that I was very focused during the grinding, prep and brazing steps. I took my time and played out the process in my mind over and over before moving on to the next step. Once again i find that you learn more doing a repair then a full up build. Andy.
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Old 04-23-14, 07:24 AM   #2
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Very good -

Is there is reason you chose to grind the tube out instead of heating it to liquify the filler and slip it out? I've never tried grind one out.

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Old 04-23-14, 07:57 AM   #3
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Dave- I was nervous about damaging the seat cluster, remelting the existing filler (remember it's silver for the SS caps and attachment). The reason I ground out the head lug was to not have to duplicate the OE lug's shape. But the next time I feel like experimenting I'll consider pulling the tube with heat. I have done this many times with drop outs and crowns. Since I don't do this for a job i don't have the heat control chops that some have. Andy.
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Old 04-23-14, 08:25 AM   #4
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Cool -

I think you would find it's easier than it might seem to slip the tube out.

The seat lug is thick as are the stay caps and it will take a good bit of heat to get that stuff to fall apart. If you focus most of the heat on the tube to be pulled (no worries about cooking it for obvious reasons) and let that heat soften the silver I think you'll find you can pull that tube without worry of dropping the stays off.

You can also put a heat sink in the seat tube (a crap post is perfect) and this will pull a lot of the heat away from the stays.

Best of luck to you - keep up the good work.

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Old 01-26-16, 12:33 PM   #5
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Quote:
Originally Posted by Andrew R Stewart View Post
https://www.flickr.com/photos/73195587@N00/sets/72157644238503485/.... Once again i find that you learn more doing a repair then a full up build. Andy.
Hey Andy, thanks for posting this thread, I'm planning to do a tt replacement myself and I'm particularly interested in way that you have run the new tt through the seat tube wall. Was this how it was made originally? If not I can see how it makes the grind out and clean up a lot easier. Did you do it at the ht end as well?

William.
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Old 01-26-16, 08:11 PM   #6
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William- The frame was made in a conventional manor with both the ST and HT being only vented with small holes at the ends of the TT. I chose to do the prep for new TT in the way I did for a few reasons. First was that I had done one many years ago the same way and therefore had some idea what I needed to do. Second was that in my past I had some issues with silver bleeding out of previously brazed joints when I did a second hotter (brass) joining involving the same joint. So I wanted to avoid the number of heat cycles that would be greater then silver's first melt point. Third was the matter of mitering the TT to butt up against the ST and HT if they were to not be ground out. Fourth was the issue of cleaning out the sockets with the blind bottoms if the tube stubs were just pulled out. I don't have a sand blaster and was concerned about the cleanliness prep for the silvering in the new TT. Last was the flow depth I might get when brazing in the new TT. I thought about drilling a few small holes near the socket's root to confirm the fill depth but in the end decided that a through tube brazing would be easier to confirm full filler fill.

So I ground out both the HT and ST to let the TT pass through completely. I mitered the TT a couple of MMs longer then needed and ground it down at the ST end to allow the post to slide past after brazing. I confirmed that the silver was flowed over onto the ST and HT a bit. I used a Dremel and die grinder to grind out the lugs.

This is where I had the challenges. I didn't pay as much attention to the amount of TT removal within the lugs. They ended up a bit conical with the tight fit being the shorelines and the loose fit being the roots. But not so loose that the silver didn't flow fully. To do again I would likely repeat but look for the tell tale sign of tube removal and the OEM filler showing. Perhaps around this point I might consider reaming the last bit of new tube fit within the sockets.

Before I did this job I did a bunch of thinking and what on line research I could do. I did talk with a couple of confidents who have vastly more experience than I have. both said that I have to do use the method I think I can pull off and that there's a few ways to skin this cat. Andy.
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Old 01-27-16, 04:17 AM   #7
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Thanks Andy, you've described all the poblems I've been worrying about and this seems like a great solution.

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