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Builder's Corner Restoration and preservation. Keep them running in perfect shape. What size is your bottom bracket?

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Old March 28th, 2015, 7:02 AM   #1
billkillohill
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Default Brazed or welded?

OK Fat community, whadaya think? Is this frame brazed or welded?

Thanks!
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Old March 28th, 2015, 7:44 AM   #2
mainlyfats
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Brazed
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Old March 28th, 2015, 8:35 AM   #3
tvcreative
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looks like it's wazed and brelded. My understanding of fillet brazing is that you can keep adding material until you are happy - and then file it off for a smoother joint. There are some builders like Engin, that will give you a choice of smooth brazing or sloppy. Why someone would want sloppy is beyond me. But these look like sloppy brazes with a sh@t ton of paint over.
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Old March 28th, 2015, 8:49 AM   #4
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Quote:
Originally Posted by tvcreative View Post
looks like it's wazed and brelded. My understanding of fillet brazing is that you can keep adding material until you are happy - and then file it off for a smoother joint. There are some builders like Engin, that will give you a choice of smooth brazing or sloppy. Why someone would want sloppy is beyond me. But these look like sloppy brazes with a sh@t ton of paint over.
Less finish work for the builder = lower cost to the buyer. Man, that work is tough on the hands... Coconino offers the option too.
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Old March 28th, 2015, 11:21 AM   #5
yo-Nate-y
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Aha, here are further pics I!

I'd agree with everyone's sentiments above.
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Old March 28th, 2015, 4:37 PM   #6
billkillohill
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OK, so what I'm hearing is that it's brazed but sloppy. Interesting. The brazed Fat frames are only the early one's right? When was the first year they were in production?
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Old April 3rd, 2015, 11:40 AM   #7
I-ROBOT
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What is the serial number? That would hold a clue. The bottom bracket area appears to be welded and unfinished. The seat stays appear to be brazed which is how I think Chris did them when Gary Helfrich was getting started with TIG / Plasma welding around '84. When I showed up near the end of '86, Gary had already switched back to conventional TIG. While I mean no disrespect, Gary's steel TIG welds were not the smoothest I've ever seen. Also, by then, Gary was committed to titanium and striking out on his own with Kestrel (later Merlin) so his head was not in the same place.

After I got things going, I discovered how to use a pulsed current technique that yielded a significantly smoother weld and the bead width could be held to about +/- .010" (0.3 mm). That also helped making the heat input much more consistent which gives manual TIG a big advantage over manual fillet brazing. We also were able to drastically reduce our finishing time since the welds now required very little filing or sanding.

The reasons brazed fillets are finished are appearance and reduction of abrupt changes in direction and cross-sectional area. That helps the fatigue life of the frame which is more important for mountain bikes that tend to be ridden much more harshly.

So, my guess is that the bike is an '84 with a TIG welded main triangle and brazed seatstays.

All the best
Scott
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Old April 3rd, 2015, 5:29 PM   #8
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Ok, il admit it, I have a fetish for top welding but just look at the workmanship on this Fat Ti. I Know a chap who welded in F1 for years and even he said there is nobody that good ! I have a collection of F1 Ti exhausts and components etc, nothing is Tig welded even close to IROBOT's standard and the F1 parts cost crazy money to make.
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Old April 12th, 2015, 8:16 PM   #9
MikeyNYC
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This is the seat cluster area of my 1983 fully fillet brazed Fat, I'd agree with I-Robot (obviously he knows what he's talking about...) it's got some Brazed as well as welded joints.



I also have another '83 that seems to have a few brazed areas but it's mostly welded.

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