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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 February 18th, 2010, 2:57 PM   #1
chainline
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Default bo1 with a twist

hey all picked up this bo1 a while ago. this has no steerer has campy dropouts and has a nice patina to it now.... lol the question is what is the oval piece for? Im kinda thinking it was for? it does appear to be silver soldered
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Old February 18th, 2010, 7:07 PM   #2
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Where did you find this treasure?

I guess I-ROBOT (Scott Bengtson) can answer more precise than me. I belive it's a reinforsment to withstand the tensile stress that appears on that side of the fork legs. The fork offset (caster angle) gives this area a fair amount of forces, mainly bending moment (round the fork crown) which results in very high local tensile stress in the outer surface (fibers in the steel). Rear side is exposed to tensile- and front side to compression stress (simplified consideration - circular cross section) . That plate is a local increaser of the wall thickness.

Also this could be a Heat Affected Zone (HAZ) from welding. I have a BOI with large cracks in this area, but diagonal (left lef rear, and right leg front) between the two legs. Reason? HARD USE...

Will post pics later..

-bns
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Old February 18th, 2010, 7:19 PM   #3
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Sorry, I know about the tress tab's if you look up by where the steer tube goes there is a 1 mm band that go's around. you kinda have to look real close I will try to post a better pic when I'm in the shop tomorrow
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Old February 19th, 2010, 2:38 AM   #4
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Sorry, did'nt get that yesterday.. I'm slow.

I've never seen that 1mm band or the cylindrical hub (threaded fender support?) in the center there before. Mabye some add-on from the previous owner..?

Nice patina, yeah! Are you going for a restore?




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Sorry, I know about the tress tab's if you look up by where the steer tube goes there is a 1 mm band that go's around. you kinda have to look real close I will try to post a better pic when I'm in the shop tomorrow
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Old February 19th, 2010, 7:45 AM   #5
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I think they have to do with production, but not really sure, this is 1 of 2. I guess you could call this unfinished NOS. I might just leave it like this ,unsure though, it is very tempting to finnish it but in the spirit of what it is might be best left alone like this. it is the highest level of what i call NOS.
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Old February 19th, 2010, 9:27 AM   #6
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I think that, with the patina, the fork is probably OOS, not NOS.

If you've got two I bet you could make some neat art. Alternatively, a BOI table or chair would be cool
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Old February 19th, 2010, 10:26 AM   #7
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hahah, I think your on to something.
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Old February 19th, 2010, 12:57 PM   #8
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Those gusset tabs are silver brazed. When we were fatigue-testing, we found cracking in the HAZ was occuring where the short tube from the steerer connected to the fork leg. The gussets added extra material and also help temper the HAZ from the weld. They performed significantly better on the fatigue tester. I believe we had some early production units break during riding. Reducing the fork legs to 1" really pushed the liability envelope. Many builders were hit with lawsuits from failed forks, so most opted to purchase forks manufactured by a large company and shift the liability. We did not want that to happen.

The gusset tabs were laser-cut from same-diameter 4130 tube material.

Its a shame the steerer tube was cut off. It is possible that you found a reject fork that was discarded. We would cut the steerer tubes off of any fork that could not be accepted and we had several that would get all the way through only to not make alignment tolerances and could not be straightened acceptably. Chris didn't want any to get trash-picked and wind up on some bike and then failing. We did not serialize forks so it would have been impossible to trace whether it was a reject or not.

Nice museum piece but don't try to fix it.
Sorry
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Old February 19th, 2010, 1:00 PM   #9
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I just noticed that this fork had laser-welded brake mounts. Those were pretty cool but were expensive compared to the machined pieces that had the spring perch plates that were had in place by the threaded mounts.

It was not unusual to put a fender mount on these either. There's probably not a lot of them that got a mount but I know some were done with them.

Scott
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Old February 19th, 2010, 2:31 PM   #10
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I spent this morning imagining a BOI-legged narrow side table. You could weld a platform on top, or use some nicely weathered/stained wood. Do it, man!
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Old February 19th, 2010, 3:19 PM   #11
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What about having Iglebike to replace the fork crown and re-use the fork legs..? Ah, it is more work than to build a new BOI, but it does'nt hurt to ask.

Pretty cool to save a gem like this, eyh?
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Old February 19th, 2010, 4:41 PM   #12
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I understand Scott's concerns for sure. there are also vertical line's inside the ( the steer tube area ) who knows. But it does make ! hell of a conversation piece for sure GOD I LOVE THE HISTORY OF FCC. HERE IS ANOTHER PIC FROM THE TOP SHOWING THE VERTICAL LINES ON THE INSIDE OF WHERE THE STEERER WOULD BE & THE 1 MM BAND. WICTH IM STILL KINDA PUZZLED ABOUT IT'S PURPOSE.
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Old February 19th, 2010, 4:43 PM   #13
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Quote:
Originally Posted by yo-nate-y View Post
i spent this morning imagining a boi-legged narrow side table. You could weld a platform on top, or use some nicely weathered/stained wood. Do it, man!
you gonna buy it? 1,000,000 should do just fine.hahahaha
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Old February 19th, 2010, 5:23 PM   #14
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Naw, but if I had those forks that's what I would do with 'em

Coolest Fat schwag ever.
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Old February 19th, 2010, 5:44 PM   #15
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LOL i hear ya
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Old February 21st, 2010, 6:28 AM   #16
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Default BOI with a twist - 2

Here is another condemned BOI.. Don't know if it's anything to fix?
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Old February 21st, 2010, 6:32 AM   #17
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Oh, forgot the back side..
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Old February 21st, 2010, 7:04 AM   #18
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It is funny ow they break thu the stress tab, just goes to show how strong the silver solder is
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Old February 21st, 2010, 8:02 AM   #19
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Yeah, for sure! That joining method makes it "homogeneous"..

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It is funny ow they break thu the stress tab, just goes to show how strong the silver solder is
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Old February 21st, 2010, 11:45 AM   #20
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I'm kinda interested, can you tip the fork upside down and take a really good photo of the bottom of the steer tube
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Old February 21st, 2010, 9:49 PM   #21
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WOW
That is a catastophic failure for sure!! It could be rebuilt but that cracked tube would have to be cut out and replaced. I'm not sure I would trust a repair weld there.

I always thought forks were small enough that it would make sense to heat-treat them but Chris didn't think the expense would be justified.

If I was building segmented welded forks now, I would not sell them without being quenched and tempered. There's no other way to make 4130 last in a light-weight application. There's just too many different microstructures and stress raisers going on in that design not to do heat treating. There are vibratory stress relief machines but I don't know how effective they would be for a small fab like a fork.

I have no clue what that ring (?) is that's around the top of the short tubes. Never saw anything like it before.

Let me know if you find out.
Scott
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Old February 22nd, 2010, 8:16 AM   #22
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Will do.
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